Taxonomy and quantitativebiochronology of Guadalupian brachiopods from the Khuff Formation, Southeastern Oman

TAXONOMY AND QUANTITATIVE BIOCHRONOLOGY OF GUADALUPIAN BRACHIOPODS FROM THE KHUFF FORMATION, SOUTHEASTERN OMAN LUCIA A N G I O L I N I & HUGO B U C H E R ANGIOLINI L. & BUCHER H. 1999. Taxonomy and quantitative biochronology of Guadalupian brachiopods from the Khuff Formation, Southeastern Oman. [Taxonomie et biochronologie quantitative des brachiopodes guadalupiens de la Formation Khuff, Sud-Est de l'Oman]. GEOBIOS, 32, 5: 665-699. Villeurbanne, le 31.10.1999. Manuscrit d6pos6 le 06.07.1998; acceptg d~finitivement le 14.09.1998. ABSTRACT - The Guadalupian Khuff Formation of the Huqf area (Sultanate of Oman) is composed of marine marls and bioclastic limestones which yield a rich brachiopod fauna associated with conodonts, foraminifers, ostracods, bivalves, gastropods, and cephalopods. The brachiopod fauna of the Khuff Fm. includes Perigeyerella raffaellae nov. sp., Derbyia sp. cf. D. diversa REED, 1944, Neochonetes (Sommeriella) arabicus (HuDsON& SUDBURY,1959), Celebetes manarollai nov. sp., Haydenella sp., Chonetellini ? gen. and sp. indet., Dyschrestia rugosa nov. sp., Kozlowskia tescorum (HuDsON & SUDBURY,1959), Calliprotonia sp., Juresania omanensis HUDSON& SUDBURY,1959, Bilotina yanagidai nov. sp., Linoproductus sp. aff. L. kaseti GRANT,1976, Grandaurispina ghabaensis nov. sp., Magniplicatina sp., Cyclacantharia sp., Acritosia sp., Orthotichia sp. cf. O. bistriata REED, 1944, Cleiothyridina sp. cf. C. seriata GRANT, 1976, Pennospiriferinoidea genus and species undetermined, Dielasma sp. A, Dielasma sp. B, Dielasma sp. C, D. sp. aff. D. minor WAAGEN,1882 and Hemiptychina sp. This fauna shows strong affinities with that of the Arab Fro. (Salt Range, Pakistan) and that of the Rat Buri Limenstone of southern Thailand. Analysis of the brachiopod data of the Khuff Fm by means of the Unitary Association method (Guex 1991) leads to the construction of a local biochronological sequence of eight faunal associations. Strictly based on a bed rock-controlled sampling, this result provides a firm basis and a first step for future correlations with other Guadalupian brachiopod sequences. It also suggests that species diversity and rates of faunal turnovers are only partly controlled by the vertical succession of depositional environments, which reflects an intra-Khuff asymmetric transgressive-regressive cycle. A full evaluation of the biochronologic component of the Guadalupian brachiopod faunas still requires further tests against other similarly well-documented sequences. KEYWORDS:

OMAN,

KHUFF

FM., BRACHIOPODS,

PALEOECOLOGY,

UNITARY

ASSOCIATIONS.

RI~SUM]~ - D a n s la rdgion du Huqf (Sultanat d'Oman), la formation Khuff dage Guadalupien est reprdsentde par des d6p6ts marins transgressifs qui contiennent une tr6s riche faune de brachiopodes associ6e ~ des conodontes, foraminif6res, ostracodes, bivalves, gast6ropodes et c6phalopodes. La faune de brachiopodes de la Formation Khuff comprend Perigeyerella raffaellae nov. sp., Derbyia sp. cf. D. diversa REED, 1944, Neochonetes (Sommeriella) arabicus (HuDsON & SUDBURY,1959), Celebetes manarollai nov. sp., Haydenella sp., Chonetellini ? gen. et sp. indet., Dyschrestia rugosa nov. sp., Kozlowskia tescorum (HUDSON& SUDBURY,1959), Calliprotonia sp., Juresania omanensis HUDSON SUDBURY, 1959, Bilotina yanagidai nov. sp., Linoproductus sp. aff. L. kaseti GRANT,1976, Grandaurispina ghabaensis nov. sp., Magniplicatina sp., Cyclacantharia sp., Acritosia sp., Orthotichia sp. cf. O. bistriata REED, 1944, Cleiothyridina sp. cf. C. seriata GRANT,1976, Pennospiriferinoidea gen. et sp. indet., Dielasma sp. A, Dielasma sp. B, Dielasma sp. C, D. sp. aff. D. minor WAAGEN,1882 and Hemiptychina sp. Cette faune est tr~s semblable ~ celle de la Formation Amb (Salt Range, Pakistan) et ~ celle des calcaires de Rat Buri (Tha~lande mgridionale). Le traitement de ces donn6es biostratigraphiques par la m6thode des associations unitaires (Guex 1991) permet d'~tablir une succession chronologiqne locale comprenant huit associations. Basge sur un ~chantillonnage banc par banc, ce r6sultat fournit une base fiable et constitue une premiere gtape pour de futures corr61ations avec d'autres sgquences de brachiopdes du Guadalupien, malgr~ Ie fait que la diversitg et les taux de renouvellements fauniques soient en pattie contrSl~s par l'enchainement des facies organis~s dans un cycle transgressif-regressif interne/t la Formation Khuff. La composante biochronologique des faunes de brachiopdes du Guadalupien ne pourra ~tre pleinement 6valu6e que par comparaison avec d'autres s6quences guadalupiennes bien document~es.

MOTS-CLI~S: OMAN, KHUFF

FM., BRACHIOPODES,

PERMIEN,

PALI~OI~COLOGIE,

ASSOCIATIONS

UNITAIRES.

666 INTRODUCTION This p a p e r deals with the description of Guadalupian brachiopods of the Khuff Formation from the H u q f area in southeastern Oman (Fig. 1). Most of the studied material was collected in 1995 by a team (L. Angiolini, A. Baud, J. Broutin, H. Bucher, H. A1 Hashmi, J. Marcoux, J-P. Platel and J. Roger) supported by the Peri-T~thys Program; additional material was collected by A. Pillevuit, J-P. Platel and J. Roger during 1991 in the course of field mapping. Permian brachiopod faunas from southeastern Oman (Haushi and Wadi Lusaba) were first described by H u d s o n & S u d b u r y (1959). These authors distinguished two faunas with a limited number of common species [i.e. Asyrinx haushiensis HUDSON & SUDBU~Y, Callispirina ornata W~GEN, Spiriferellina cristata (ScHLOTHEIM)]:the Haushi fauna from the Haushi Formation (i.e. Saiwan Formation in Broutin et al. 1995, with brachiopods described by Angiolini et al. 1997) and the overlying Lusaba fauna from the Lusaba Limestone (i.e. Khuff Formation in Broutin et al. 1995). However, accurate sampling of the Saiwan and Khuff Fms. does not confirm the occurrence of long ranging taxa common to both formations (Angiolini et al. 1997), as stated by Hudson and Sudbury (1959). Moreover, the revision of the material collected by Hudson and Sudbury (1959) housed in the Natural History Museum of London revealed that the lithology (coarse-grained calcareous sandstones) of the matrix embedding all the specimens ofA. haushiensis (revised as ? Cyrtella aff. nagmargensis (BIoN) and Subansiria sp. in Angiolini et al. 1997) is diagnostic of the Saiwan Fm. and clearly differs from that of the Khuff Fm. The occurrence ofA. haushiensis (sensu Hudson & Sudbury 1959) is thus restricted to the Saiwan Fm. The fauna studied here can be referred to as the Lusaba Fauna of Hudson & Sudbury (1959). A brief account on the fauna of the Khuff Fm. has been recently published by Angiolini et al. (1996) and Angiolini et al. (1998). Guadalupian brachiopods from the Oman Mountains (northern Oman) described by Yanagida & Pillevuit (1994) share only few taxa with the fauna studied here. DEPOSITIONAL SETTING The Huqf area is located on the southeastern margin of the Arabian Plate, in the Sultanate of Oman (Fig. 1). According to Dubreuilh et al. (1992), Roger et al. (1992), Le M~tour et al. (1994) and Broutin et al. (1995), the autochthonous Carboniferous to Permian succession of the H u q f a r e a consists of two mega-sequences separated by a regional unconformity:

Miocene to Quaternary

] Triassicto Cenomanian

Paleocene - Eocene

Late Paleozoic

Campanian Maastrichtian

Proterozoic to Early Palaeozoic

FIGURE 1 - Geologic s k e t c h m a p of t h e H a u s h i - H u q f area, sout h e a s t e r n O m a n . (Modified from B r o u t i n et al. 1995). Carte gdo-

logique simplifige de la r@ion du Haushi-Huqf, sud-est de l'Oman (d'aprgs Broutin et al. 1995, modifig).

- the first mega-sequence consists of the Lower Permian glacial-lacustrine deposits of the A1 Khlata Fm. overlained by the transgressive marine Saiwan Fm. of Sakmarian age (Angiolini et al. 1997); - the unconformable second mega-sequence consists of the fluvial terrigenous Gharif Fm., overlained by marine marls and bioclastic limestones of the Khuff Fm. The age of this megasequence spans the ?Roadian to Wordian time interval (Broutin et al. 1995; Angiolini et al. 1998). Exposures of the Khuff Fm. in the H u q f area amount to a total stratigraphic thickness of 30 to 40 m. The Khuff Fm. is composed of sandstones, marls and bioclastic limestones which contain a rich fauna of brachiopods, conodonts, foraminifers, crinoids, bryozoans, cephalopods, gastropods and

667

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bivalves (described by Dickins, 1999) and ostracods (described by Crasquin-Soleau et al. 1999). It has been subdivided into four members (Angiolini et al. 1998), as illustrated in Fig. 2;

- the first member (Mb. 1) comprises two contrasted subunits. The lower subunit is characterized by cross-bedded, pebbly, bioclastic quartzarenites interpreted as a barrier beach complex separating

668 the open marine deposits of the upper subunit from the underlying organic rich, marsh-alluvial environments of the Gharif Fm. This interpretation is also supported by the fact that highly abraded marine bioclasts have their lowest occurrence in the middle part of this subunit. The upper subunit is made of thin-bedded, cross-bedded, coarse to medium quartzarenites alternating with bioclastic limestone, resting with a sharp transition upon the lower subunit. The quartzarenite sheets display frequent burrows closely allied to Zoophycos. This subunit may reflect a mixed sand-mud shoreface environment; - the second member (Mb. 2) is composed of laminated marls and marly limestones, most of which suggest deposition below storm wave base. The middle part of the member typically contains closely packed, early diagenetic carbonate concretions and displays numerous subvertical burrows. This member records the most offshore deposition of the Khuff. It rests with a sharp transition on the first member but shows a gradational transition to the third member with progressive increase of the carbonate content and intercalation of thin tempestites;

the third member (Mb. 3) consists of marls, marly limestones and cross-bedded bioclastic limestones. It contains numerous tempestites which suggest deposition in an upper offshore setting, above storm wave base; -

- the fourth member (Mb. 4) chiefly consists of coarse, cross-bedded bioclastic limestones interbedded with silty and quartzose marls, suggesting deposition near the lower shoreface. This return of clastic input is also accompanied by the occurrence of Zoophycos-type traces. The top of this member is unconformably truncated by the continental sandstones and siltstones of the Triassic to Jurassic Minjur Fm. To summarize, the depositional settings of the Khuff Fm. in the H u q f area represent an asymmetric transgressive-regressive cycle. The transgressive sequence shows abrupt transitions between the depositional environments and culminates with the most offshore deposits of the base of the second member. Progressive filling of the available space can thus proceed until the platform returns to a shoreface setting. The fauna described here was collected in the Khuff Fm. along several sections: 28 brachiopod specimens were collected by A. Pillevuit (Institut de G~ologie, Universit~ de Lausanne) in nodular marls and bioclastic limestones of the Khuff Fm. (section HUQF1, samples 1284 and 1281), 8 km south-west of the Saiwan 1 oil well, along the trail to Ghaba; - 47 brachiopod specimens were collected by J-P.

Platel (BRGM, Pessac) and J. Roger (BRGM, Orleans) along section TBQ2392 (sample JPP392A) in gray marls of the Khuff Fm., 90 km south of Saiwan; along section AJZ2347 (sampleJPP347B) in bioclastic limestones about 32 m above the base of the Khuff Fm., 12 km south; along section HS2526 (samples JPP526E, I, B) near section 1 (see below); - over 1000 brachiopod specimens were collected during the 1995 fieldwork along five sections located in a small area b e t w e e n 21°00'37"N 57°39'35"E and 21°02'06"N-57°41'23"E, along the n o r t h w e s t e r n flank of the H a u s h i uplift (for details see figure 2 in Angiolini et al. 1998). Five of these sections are correlated by means of conspicuous lithological markers (e.g. tempestites) and contribute to the construction of the composite section shown in figure 2. B R A C H I O P O D

F A U N A

The brachiopod fauna of the Khuff Fm. is highly diversified and is numerically dominated by the productids Celebetes manarollai nov. sp., Dyschrestia rugosa nov. sp., Juresania omanensis HUDSON & SUDBUR¥,1959 and Linoproductus sp. aff. L. kaseti GRANT, 1976. The terebratulid Dielasma sp. A is also common. The productids Kozlowskia tescorum (HuDsON & SUDBURY,1959), Bilotina yanagidai nov. sp. and Grandaurispina ghabaensis nov. sp., the orthid Orthotichia sp. cf. O. bistriata REED, 1944, the strophomenids Perigeyerella raffaellae nov. sp. and Derbyia sp. cf. D. diversa REED, 1944 and the chonetid Neochonetes (Sommeriella) arabicus (HUDSON & SUDBURY,1959) are subordinated. Rare components of the brachiopod fauna are: Haydenella sp., Calliprotonia sp., Magniplicatina sp., Cyclacantharia sp., Acritosia sp., Chonetellini ? gen. and sp. indet., Cleiothyridina sp. cf. C. seriata GaANT, 1976, Pennospiriferinoidea gen. and sp. indet., Dielasma sp. B, Dielasma sp. C, D. sp. aff. D. minor WAAGEN,1882 and Hemiptychina sp. Among the Khuff fauna, cosmopolitan, Tethyan, Gondwanan and endemic genera may be distinguished: - Orthotichia, Derbyia, Linoproductus, Cleiothyridina, and Dielasma are wide ranging, cosmopolitan genera; - Perigeyerella, Haydenella, Kozlowskia, Calliprotonia, Grandaurispina, Cyclacantharia, Acritosia are Tethyan genera; Sommeriella and Dyschrestia are Gondwanan genera; - Celebetes and Bilotina are endemic genera of southeastern Oman, Salt Range and southern Thailand. -

The Tethyan genera amount to 44% of the fauna, the cosmopolitan are 31%, whereas Gondwanan and endemic represent 12.5% each.

669 The Khuff fauna is thus a mixed/transitional fauna (sensu Shi et al. 1995), with a dominance of Tethyan genera suggesting warm subtropical climate conditions. The mixed character of the fauna is also suggested by the conodonts assemblages, which record a mixing of cool water and Tethyan taxa (Angiolini et al. 1998). A marked shift in the composition of the southeastern Oman brachiopod faunas can be observed when comparing the Khuff fauna to the Saiwan fauna of Sakmarian age (Angiolini et al. 1997), the latter being less diversified, dominated by spiriferids and indicating lower water temperatures. PALAEOECOLOGY OF THE BRACItIOPOD FAUNA According to general ecological classifications (Muir-Wood & Cooper 1960; Rudwick 1970; Grant 1971, 1976; Brunton & Mundy 1988), brachiopods may be subdivided into attached forms and freeliving forms. The first group may be subdivided into shelly-attached forms, which if permanently attached represent a significant component of the reef fauna (i.e. reef dwellers), and pedicle-attached forms which are ubiquitous. The free-living group comprises surface-living species and quasi-infaunal forms, the ibrmer lying on the substrate and the latter sitting partially buried in soft substrate, pedicle-attached shelly-attached 12% 4%

a

free-living 84% pedicle-attached 35%

shelly-attached 13%

both using shell shape and/or spine patterns for stabilization. The free-living adult stage may be preceded by an initial attachment to the substrate by umbonal cementation or clasping spines in early stages. The Khuff fauna comprises two rigidly cemented richthofenioids and a coralliform enteletoid which are shelly-attached forms, the pedicle-attached genera Dielasma, Hemiptychina and Cleiothyridina and a significant component of free-living forms, comprising the surface-living Derbyia and Neochonetes (Sommeriella) and the quasi-infaunal productids. The Khuff Fm. thus contains 52% free-living species, 35% pedicle-attached species and 13% shellyattached species. Examining the Khuff fauna at the level of the individual, 84% of the fauna is represented by free-living forms, 12% by pedicleattached forms and only 4% by rigidly cemented individuals. Comparison of the two sets of data (Fig. 3) shows that the Khufffauna is clearly dominated by free-living forms, especially at individual level, indicating the preponderant role of the open substrate habitats and the absence of bioherms. A detailed analysis of the shelly-attached, pedicle attached and free-living forms in each member of the Khuff Fro. shows that the pedicle attached forms are as frequent as the free-living species in the first member, decreasing gradually upward to reach a minimum (14.3%) in the third member, where 71.4% are free-living species. In the fourth member the free living species decrease to 57%, whereas the attached forms slightly increase (Fig. 4). More specifically the second and third members are numerically dominated by quasi-infaunal spiny productids (i.e. Juresania omanensis) and by linoproductids suggesting a deeper and soft substrate occasionally affected by storm waves. The articulation/disarticulation ratio is quite low throughout the Khuff Fm., varying from 0.25 in

12

fliiiii!iiiiiiiiiili!i:

41 b

free-living 52%

Fx~w~ 3a,b - Distributions of the ecological characteristics of the brachiopod fauna at the individual (a) and species (b) levels. The brachiopod fauna of the Khuff Fm. is clearly dominated by free-living forms, especially at individual level. Rgpartition des caractdristiques dcologiques de la faune de brachiopodes au niveau des individus (a) et au niveau des espdces (b). La faune de brachiopdes de la Formation K h u f f est nettement dominde par les [brmes libres.

21 0

Mb.1 Mb.2 Mb.3 Mb.4 [] shelly-attached[]pedicle-attached [] free-living F[GUI~ 4 - Distribution of the shelly-attached,pedicle-attached and free-living forms in each of the four members of the Khuff Fm. Distribution des formes fixdes par la coquilIe, par Ie pddoncule ¢t libres dans chacun des quatre membres de la Formation Khuff

670 the first member to 0.03 in the second member, increasing again to 0.27 in the third member and finally decreasing to 0.09 in the fourth member. The abrupt decrease of this ratio from the first to the second member is probably due to an increase in energy of the wave regime (storm wave) and to the disappearance of species with higher hydrodynamic stability and stronger hinge (i.e.O. sp. cf. O. bistriata). In the third member, the higher ratio of a r t i c u l a t e d to disarticulated specimens is congruent with the occurrence of articulated specimens of J. o m a n e n s i s in fine muds, suggesting quieter waters. Finally the very low ratio of the fourth member is not congruent with the concomitant increase in terebratulid shells, characterized by cyrtomatodont hinge and high hydrodynamic stability (Alexander & Gibson 1993), suggesting a remarkable increase in the energy of the environment. The brachiopod palaeoecology is in good agreement with the palaeoenvironmental evolution inferred from the facies as discussed above. The upper subunit of the first member, which is interpreted as a transgressive shoreface environment, is characterized by a great abundance of smallsized chonetids (N. (S.) arabicus). The second and third member, dominated by quasi-infaunal productids adapted to live on soft bottoms, suggest rather deep m u d d y bottoms, occasionally affected by storm action as indicated by the sporadic occurrences oftempestites; the fourth member, with low

if'.

Non-oriented Graph

articulation/disarticulation ratio and increase of attached forms, is diagnostic of shallow water, turbulent sandy bottom environment. Furthermore, the occurrence of few shelly attached genera,, even if very rare and subordinate with respect to the quasi-infaunal forms, suggests the presence of nearby hard surface niches: a shallow water coarse substratum surrounding an exposed land located eastward (see Fig. 24 in Le M~tour et al. 1995). Both facies and palaeoecological analysis are in agreement with the palaeogeographic reconstruction by Al-Aswad (1997), where an inner carbonate shelf covers most of the Saudi Arabia, an outer shelf is recorded in southern Oman and a reef margin and a slope are recorded in the allochthonous of the Oman Mountains (Hawasina nappes) and Iran. BIOCI-IRONOLOGICAL ANALYSIS OF THE B R A C t t I O P O D F A U N A ANALYSIS OF THE DATA The brachiopod succession obtained from bedrockcontrolled samples is analyzed by means of the Unitary Associations (UA) method of Guex (1991) to which the reader is referred to for an exhaustive methodological description. P r i m a r y data from the Khuff Fm. include 21 taxa distributed in 7 sections (section AJZ2347 is not included here because it does not constitute a maximal horizon; sec-

"9

Oriented Graph

FIGURE 5 - Graphic representation of biostratigraphic raw data derived from the 7 partial sections (vertices correspond to species whose codes are given in Appendix 1). The biostratigraphic graph is composed of two parts. Associations are represented by edges linking the vertices in the non-oriented part of the graph. Superpositions are represented by arcs linking the vertices in the oriented part of the graph. Repr6sentation graphique des donn6es biostratigraphiques brutes provenant des 7 sections partielles (les sommets correspondent aux esp~ces dont les codes sont donnds dans l'appendice 1). Le graphe se compose de deux parties. Les relations d'association sont reprgsentges par les ar~tes reliant les sommets clans la partie non orientge du graphe. Les relations de superposition sont reprdsent6es p a r les arcs reliant les sommets dans la partie orientde du graphe.

671

tion TBQ2392 will be discussed separately at the end of this chapter). These 7 sections represent superpositional sequences of highly variable scope, some of the sections being more comprehensive t h a n others (see Appendix 1). The data are processed in a series of successive runs with the BioGraph Program (Savary & Guex 1991) and the BioGraph Tools (Savary & Guex unpublished). Confiietual superpositional relationships between the maximal cliques of each processed data set are in t u r n analyzed. These generally originate from either insufficient sampling (i.e. undocumented or "missing" occurrences) or local ecological exclusions. Other common causes include u n n a t u r a l samples (condensed beds or mixed samples), disjunctive reworking or misidentifications. These contradictions also generate non transitive or non transitively orientable subgraphs of the biostratigraphic graph (Fig. 5). Once the most plausible causes responsible for generating contradictory arcs are evaluated, the data set can be modified either by adding occurrences for locally undocum e n t e d occurrences if known from other sections, or by removing suspect occurrences (reworked and mixed samples) in order to eliminate the most frequently involved contradictory arcs. Contradictory arcs resulting from insufficient sampling are typically replaced by virtual edges (i.e. virtual cooccurrences) in the biostratigraphic graph, thereby destroying some of the forbidden generated subgraphs. This process is repeated until an optimal result, i.e. a minimal number of contradictions, can been reached. Coding of taxa is given in Appendix 1. Composition of the Unitary Associations 12345678

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A first r u n of raw data (i.e. with the 7 unmodified partial sections) highlights the general good quality of the data because no cycles (C3 & C4) are detected in the oriented part of the biostratigraphic graph (Fig. 5). However, none of the 8 UAs obtained from the non-oriented part of the biostratigraphic graph (Fig. 5) has a lateral reproducibility greater t h a n 3 as shown in the reproducibility matrix of Fig. 6. UA6 is characterized by two pairs of species (02PRA,08KTE) and (02PRA, 13GGH), none of which is documented in any of the sections (see UA s matrix and reproducibility matrix of Fig. 6). However, as can be seen in sections 7 and 7bis (Appendix 1), 02PRA shows contradictory superpositions with respect to both 8KTE and 13GGH, thus making these two pairs virtual pairs. Such virtual associations are generated by the automatic replacement of contradictory arcs (i.e. 02PRA=>08kte in section 7 and 08KTE=>02PRA in section 7bis) by the virtual edge 02pra=08kte. This data set also includes 11 contradictions between the m a x i m a l cliques, which correspond to 17 forbidden subgenerated subgraphs (3S'3 and 14S'4) of the biostratigraphic graph (Fig. 6). With the exception of the disconnected virtual UA6, the graph of superposition of the 8 UAs (Gk' in Fig. 6) shows 3 maximal paths, the longest of which contains UAs 1, 4, 5, 7 and 8, in ascending order. In a second run, a crucial step in lowering the number of contradictions is achieved with the construction of a composite section (see Appendix 1). In the Khuff Fm. the facies succession appears Composition of the Unitary Associations 23456

Number of Contradictions beh','ean Maximal Cliques: 5

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FIGURE 7 - Main results of the third run (composite section, HS2526 and Huqfl). These include the Unitary Associations matrix, the reproducibilty matrix and the superposition graph of the UAs (Gk'). The number of contradictions between the maximal cliques, the number of forbidden generated subgraphs and the most frequent arcs involved in these subgraphs are also listed. Principaux r6sultats de la troisigrne gx4cution (composite section, HS2526 and Huq[1). Ceux-ci comprennent la matrice d'associations unitaires~ la matrice de reproductibilt~ et le graphe de superposition des A U (GM). Le nombre de contradictions entre les cliques maximales, le nombre de sous-graphes induits interdits et les arcs les phts souvent impliqugs clans ces sous-graphes sont @alernent indiqu6s.

672 to be laterally fairly continuous and displays conspicuous storm layers which provide excellent synchronous markers for constructing a composite section. Based exclusively on lithology, a composite section including 44 successive fossiliferous levels is constructed with 5 out of 7 initial partial sections (Fig. 2). Only sections H u q f l and HS2526 cannot be safely correlated with the composite. The second run processes exclusively this composite section as a new data set comprising 19 of the 22 initial taxa. It yields a sequence of 7 UAs and has obviously no contradictions. The numerical ranges of the 19 taxa across the 7 new UAs is then converted into a new section comprising 7 levels or samples corresponding to the 7 UAs. F u r t h e r runs will then examine how the step by step addition of the remaining sections will alter this result. The third run processes a data file made of the converted composite, sections H u q f l and HS2526, with all of the initial 21 taxa. It yields 8 UAs, with a number of contradictions as low as 5 and only 9 forbidden generated subgraphs, all of which are of the S'4 type (Fig. 7). A detailed list of these contradictions and forbidden subgraphs is given in Fig. 8. It shows t h a t contradictions between the maxireal cliques result from the presence of opposite arcs between them. Indeterminations between the maximal cliques may occur either when there is an equal n u m b e r of opposite arcs, or when there are no arcs at all (e.g. "pure indetermination" between cliques K3.9" and K2.1). The arcs most frequently involved in the 9 forbidden generated sub-

=-- ® ® e ® ® @ ® l

.,Ioo@eel

K1.1

K3.9"

SuperpositJonal con~adicions between the maximal cliques

HHHHH Forbidden generated subgraphs [S'4)

FIGURE 8 - Graphic representations of the superpositional contradictions (arcs) between the maximal cliques of the third r u n (composite section, HS2526 and Huqfl) and detailed list of t h e forbidden g e n e r a t e d subgraphs. Reprgsentations graphiques des relations de superposition (arcs) contradictoires entre les cliques maximales de la troisi~me ~xdcution (section composite, HS2526 and Huqfl).

graphs S'4 are 03DDI<=09CAL (4 times), 09CAL=>10JOM (4 times), and 04NAR=>18DIA (3 times). In this data file, 09CAL has its unique occurrence in level 3 of section HS2526, and shares with 18DIA the highest implication frequency (9 times) in the contradictory arcs. On one hand, this unique occurrence of 09CAL would appear suspect but on the other hand, its identification is firmly established. Hence, this species cannot be removed from the data set and another cause must be searched for. A close look at the composite section shows t h a t 03DDI ranges from level 3 to level 42, t h a t 10JOM ranges from level 5 to level 42 and t h a t 18DIA ranges from level 14 to level 43. It thus appears from the composite (a very robust subset of the data file integrating 5 partial sections) t h a t 03DDI, 10JOM and 18DIA cooccur from level 14 to level 42, i.e. throughout an interval of significant length within the 44 level succession. Turning to section HS2526, one can see t h a t if 18DIA ranges through its 3 levels, 03DDI is only documented in level 2 and 10JOM in level 3. This suggests t h a t the record of section HS2526 is rather incomplete when compared with t h a t of the composite section. Hence, the new alternative consist in modifying the data file by adding 03DDI and 10JOM in level 1 of section HS2526, a modification which is in agreement with the cooccurrence of the three species in the composite section. As section HS2526 is located in the same geographic area and because its facies does not indicate any particular changes in depositional environments, possible local ecological controls can reasonably be ruled out and insufficient documentation appears as the most plausible cause for the contradictory arcs. The fourth run processes a data file composed of the composite, Huqfl, and HS2526 modified as explained above. It yields 7 UAs and an ideal, single maximal path in Gk' (Fig. 9). The number of contradictions between the maximal cliques drops down to 3, one of which is a pure indetermination (no arcs at all), the two others having each the same pair of opposite arcs: 04NAR=>18DIA and 09CAL=>12LKA. These arcs generate the single S'4 left in this data set. The arc 04NAR=>18DIA is found in the composite section, and the arc 09CAL=>12LKA in section HS2526.12LKA is restricted to level 3 in section HS2526 whereas it ranges from level 15 to level 42 in the composite, a range almost identical with that of 18DIA (levels 14 to 43). Here again, section HS2526 can be regarded as insufficiently documented and the data file is modified in adding 12LKA to its level 1. This modification is supported by the near-perfect cooccurrence of 12LKA and 18DIA in the composite. The fifth run takes this last modification into account. It yields 8 UAs, only one of which (UA4)

673

is not incorporated into the longest maximal path of Gk' (Fig. 10). The obvious reason for this is that it is the unique occurrence of 09CAL in section HS2526 which generates an UA restricted to this section (see the UA matrix and reproducibility matrix in Fig. 10). All of the 4 contradictions between the maximal cliques result from pure indeterminations, which leads to an optimal result with no forbidden generated subgraphs at all. Hence, it is the 8 [/As obtained in this run (Fig. 10) that are used for the biochronologic subdivision of the Khuff Fm (Fig. 2). Some of the samples of the fourth member of the composite do not contain characteristic species or pair of species and therefore cannot be attributed to a definite UA. UAs 1, 2 and 3 form a coherent group, differing only by the sequence of short ranging species such as 21DIC, 19MIN and 14MAG, in ascending order. The main change in composition occurs with UAs 4 and 5 where 09CAL, 18DIA, 20DIB, l l B Y A and 07DRU first appear in the succession. UA6 is characterized by appearance of 06HAY, 08KTE, 15CYC and last occurrence of 16ACR. UAs 7 and 8 differ only by the last occurrences of l l B Y A and 15CYC in UA7 and by the occurrence of 22HEM which is restricted to UA8. Finally, a sixth run with section TBQ2392 added to the preceding data file leads to a surprisingly high number of contradictions (11) which create many new forbidden generated subgraphs (21 Z"4, 6 $3, and 2 S'4). As the analysis of these new contradictions with the help of the composite does

not significantly reduces the number of forbidden subgraphs and since section TBQ2392 corresponds to a single level (see Appendix 1), the natural character of this assemblage m u s t be questioned. This problem was quickly solved when we learnt that this sample was collected during a rapid survey and that it does obviously not correspond to the sampling of a single bed. Hence, this mixed sample must be excluded 9rein the biochronological analysis. RATES OF FAUNAL CHANGES AND FACIES CONTROL Figure 2 illustrates the relatively good coincidence between facies changes and UA boundaries. Rates of local faunal turnover are illustrated in Fig. 11. Slopes less than 45 ° indicate diversification and slopes more than 45 ° indicate extinction. Rates between UA1 and UA2 as well as between UA7 and UA8 are meaningless because cumulative counts are highly biased at both ends. However, the main feature that clearly emerges is a protracted diversification from UA2 to UA6 at a nearly constant rate, followed by a reversed trend between UA6 and UAS. However, the turnover rate between UAs 2 and 3 should be treated with caution because of a high value of the gap ratio or dissimilarity between them (Fig. 11). Despite the fact that facies has a clear influence on quantitative distributions of the brachiopod Composffion of the Unitary Associations

Number of Contradictions between Maximal Cliques: 4

Number of S'4:0

Reproducibility Matrix

Graph of Suparpostion Gk'

12345678

Composition of the Unitary Associations

Number of ContradictJoee between Maximal Cliques: 3

21DIC • ~

•

Reproducibility Matrix

01OBI 04NAR

.• • 05Ct¢~ . 02PRA ' I I I I I I I 03DDI ' 1 1 1 1 1 1 1 , 10JOM . I I I I l i l -

22ITEM

I I • I

• I

01OgI

04NAR->I 8DIA

Graph of Suparpostion Gk'

.

14MAG 16ACR 12LKA IBDIA 20DIB lIBYA 07DRU 15CYC 06HAY 08KTE 13GGH

Number of S'4:1 Most frequent Arcs in S'4: 09CAL->I2LKA

123456

16ACR 12LKA

g

18DIA

5QT

2 FE HA

n

61

05CMA 02PBA 03DDI 10JOM lgMIN

C O M

SIfS 2[/I I I -

o,~

1

~ 1

FIGURE 9 - Main results of the fourth run (composite section, Huqfl and HS2526 with 03DDI and 10JOM added in level 1). These include the Unitary Associations matrix, the reproducibilty matrix and the superposition graph of the UAs (Gk'). The number of contradictions between the maximal cliques, the number of forbidden generated subgraphs and the most frequent arcs involved in these subgraphs are also listed. Principaux Hsultats de la quatri~me dx~cution (section composite, Huqfl et HS2526 avec 03DDI et 10JOM rajoutds dans le niveau 1). Ceuxci comprennent la matrice d'assocaitions unitaires, la matrice de reproductibiltd et le graphe de superposition des A U (Gk'). Le nombre de contradictions entre les cliques maximales, le nombre de sous-graphes induits interdits et les arcs los plus souvent impliqugs dans cos sous-graphes sent ggalement indiqads.

lIBYA 07DRU 15CYC 06HAY 08KTE 13GGH Z2HLM

.,.,~ •

C o

-• -IlnIIIII. .IlnIiiI I . "IIIIIIII. , , , , i

B

O

SHS

2 UI I I I • I

FE 0A

n

611

I • • • • • • I I I I •

1

~

FIGURE 10 - Main results of the fifth run (composite, Huqfl and HS2526 with 03DDI, 10JOM and 12 LKA added in level 1). These include the Unitary Associations matrix, the reproducibilty matrix and the superposition graph of the UAs (Gk'). The 4 contradictions between the maximal cliques correspond pure indeterminations, which leads the absence of any forbidden generated subgraphs. This optimal result is used for identification of the 8 UAs in the composite section (see Fig. 2). Principaux rgsaltats de la cinqui~me dxdcution (section composite, Huqfl et HS2526 avec 03DDI, IOJOM et 12 LKA rajoutds dons le niveau 1). Ceux-ci comprennent la matrice d'assocaitions unitaires, la matrice de reproductibiltg et le graphe de superposition des A U (Gk '). Le nombre de contradictions entre les cliques maximales, le nombre de sous-graphes induits interdits e t l e s arcs les plus souvent impliquds dans ces sous-graphes sent ~galement indiqu~s. Ce rdsultat optimal est utilisg pour identifier los 8 associations unitaires dans la section composite (voir Fig. 2).

674 dian corresponding to the Roadian, the Murgabian (restricted to the Neoshwagerina craticulifera Zone) to part of the Wordian, the Midian to the latest Wordian-Capitanian, the Dzhulfian to the Wuchiapingian, and the D o r a s h a m i a n to the Changhsingian (see Tabl. i in Angiolini et al. 1998).

assemblages (see preceding chapter on palaeoecology) as well as on species diversity (Fig. 11), it is nevertheless interesting to consider facies control in terms of presence and absence of taxa in order to better assess their biochronological potential value for future long distance correlations. With its late r e t u r n to shoreface environments, the asymmetrical transgressive-regressive cycle of the Khuff Fro. provides a good opportunity for such evaluation. P. raffaellae nov. sp., D. sp. cf. D. diversa and J. omanensis are the only species that range throughout the 8 UAs. P. raffaellae nov. sp. and D. sp. cf. D. diversa are both absent from the more distal second member, but J. omanensis is recorded from all four members. O. sp. cf. O. bistriata and N. (S.) arabicus are restricted to the shoreface deposits of the first member and do not reappear in the shoreface deposits of the fourth member, thus conferring a potential chronological value to their last appearances. C. manarollai nov. sp. occurs in the most contrasted facies of the first and second members, but do not range higher in the section, which can hardly be explained by pure ecological control. Both D. rugosa nov. sp. and B. yanagidai nov. sp. cooccur in members 2, 3 and 4 but are not recorded from the first member whose facies is close from that of the fourth member. Their first occurrences may thus be potential biochronological markers. Ultimate distinction between any real biochronologic components and facies control in the distribution of these brachiopods requires further comparison of this well-established regional sequence of the Khuff Fm. with other bed-rock controlled successions from other basins.

The brachiopod fauna of the Khuff Fm. of southeastern Oman, generally considered Early Permian by previous authors (e.g. Hudson & Sudbury 1959; Archbold & Burrett 1990; Grant 1976; Shi et al. 1995), has been dated as Guadalupian and more specifically as Wordian by Angiolini et al. (1998) on the basis of conodonts and brachiopods. This age assignment is also supported by the associated bivalves (Dickins 1999). CORRELATION WITH NORTHERN OMAN Brachiopods from the Oman Mountains (northern Oman) have been described by Yanagida & Pillevuit (1994), who suggested an Artinskian age for the faunules from Jebel Qamar South (Asfar Fro. in the allochthonous) and Quryat (Saiq Fm. in the autochthonous). The faunule from locality 753, Batain Melange is compared to the Arab and Wargal Fins. of Salt Range and ascribed to the Late ArtinskianEarly Guadalupian (Yanagida & Pillevuit 1994). However the accompanying foraminifers in loc. 753 (Yanagida & Pillevuit 1994, p. 95, Fig. 16) are Codonofusiella sp. and Ognibella sp. [figured as Boultonia by Yanagida & Pillevuit 1994, according to Vachard (pers. com. 1998)] and thus suggest a younger age (Capitanian-Wuchiapingian). The brachiopods of the Khuff Fro. of southeastern Oman share at least 2 species with the Jebel Qamar South faunule, whose age is younger than Artinskian.

AGE A N D CORRELATION

In the present paper, ages are referred to the Permian time scale approved by the Subcommission on Permian Stratigraphy of ICS and published by Jin et al. (1997). According to Kotlyar & Pronina (1995), Kozur (1995), Leven (1996), Jin et al. (1997), a tentative correlation with the Tethyan scale of Leven (1980) modified by Kotlyar and Pronina (1995) is here suggested with the Kubergan12 - Species Diversity

CORRELATION WITH SALT RANGE, PAKISTAN The age of the Arab Fm. of Salt Range (Pakistan), which contains a rich brachiopod fauna very similar to that of the Khuff Fm. of southeastern Oman, was considered A r t i n s k i a n by most authors (e.g. Balme 1970; Grant 1976; PakistaniJapanese Research Group 1985; Shi et al. 1995; 0,7

25 - Rates ol FaunalTurnover I 20-

11

"~ 10

UA8

0,6 0,5

-315-

"6 9

Z

~<

~~uA3UA4 ''''J UA5 UA6

5

7

a

MOUA7

g 10-

0,4

~c 0,3 0,2

UA10/-" UA2 i 2

i i i ! 3 4 5 6 Unitary Associations

i 7

i 8

0

,

0

5

,

~

,

10 15 20 Cumulated Fads

.

25

0,I

i

2

=

i

l

J

3 4 5 6 Unitary Associations

i

7

FIGURE 11 - Species diversity, r a t e s of f a u n a l t u r n o v e r and gap ratio calculated from the optimal solution given in Fig. 10. Diuersitd

spdcifique, taux de renouvellement faunique et dissimilarit6 calcul6s pour la solution optimale donnde dans la Fig. 10.

675 Archbold & Shi 1995). However, some authors (Kotlyar pers. com. 1998; Wardlaw & Pogue 1995; Baud et al. 1996) have recently changed its age to the Guadalupian. More specifically, Wardlaw & Pogue (1995) and Wardlaw (pers. com.) have dated the Amb. Fro. as Roadian-Wordian, chiefly on the basis of conodont data. Moreover the Wargal Fm., which lies disconformably above the Arab Fm., contains Capitanian to Wuchiapingian foraminifers and conodonts (Wardlaw & Pogue 1995). The southeastern Oman brachiopods are very similar to the fauna from the Arab Fm (Waagen 1882-1885). In fact the two faunas share 11 genera and 4 species. In addition, the Oman Bilotina, Dielasma and Hemiptychina are close specifically to those of the Amb Fm. The link between the Amb Fm. and the Khuff Fm. is enhanced also by the conodonts: in fact a species of Hindeodus and Merillina praedivergens have been found in both formations (Angiolini et al. 1998). CORRELATION WITH KARAKORUM, NORTH PAKISTAN The brachiopod fauna of the Khuff Fm. is significantly different from the Middle Permian brachiopod assemblages of Karakorum, Pakistan (Angiolini 1995, 1996). In fact the only genera in common between the southeastern Oman and Karakorum faunas are Neochonetes (Sommeriella), Magniplicatina, Linoproductus, Derbyia, and Dielasma, the first being a Gondwanan genus, the second an antitropical genus, whereas the last three are widespread genera. In any case the two Guadalupian faunas from Karakorum have a different age from the Khuff fauna, one being older (Roadian) and the other younger (Capitanian). CORRELATION WITH SOUTHERN THAILAND Brachiopods of the basal part of the Rat Buri Lmst. in the southern area of western Thailand (Rat Buri area) have been extensively studied by Yanagida (1970), Waterhouse & Piyasin (1970), Grant (1976), Waterhouse et al. (1981). Yanagida (1970) suggested a Late Artinskian to Early Guadalupian age, Waterhouse & Piyasin (1970) a Wordian age, whereas Grant (1976) indicated Late Artinskian age for the brachiopod fauna. In a general revision, Waterhouse et al. (1981) suggested a Kungurian age for these brachiopods beds. Fontaine et al. (1988) considered all the fauna of Rat Buri Lmst. in southern Thailand and diol not exclude a Kubergandian (= Roadian) age for the brachiopods at the base of the Rat Buri Lmst. which is mainly Murgabian-Dzhulfian (= WordianWuchiapingian). Finally Archbold & Shi (1995)

indicates again a Late Artinskian-Kungurian age for the Rat Buri brachiopods. However, most of the authors correlate the Rat Buri fauna with that of the Salt Range, so a Roadian-Wordian age is here preferred for the Rat Buri brachiopods. The brachiopods of the Khuff Fm. of southeastern Oman are very similar to those of Rat Buri, having 14 genera and 2 species in common. Furthermore, the Oman species of Dielasma are similar to the Thai ones.

Celebetes is also known to occur only in southern Thailand and in southeastern Oman, whereas Bilotina has been found only in the Arab Fm., Rat Buri Lmst. and now in the Khuff Fm., providing a strong link between the formations. CORRELATION WITH WESTERN TEXAS Correlations with the Guadalupian standard sections of western Texas are hampered by the extreme diversity of the North American faunas. According to Grant (1976), each formation in the Permian sequence of western Texas contains an average of 80 genera, largely exceeding the 21 Oman genera. The different size of the two faunas can thus strongly influence the percentage of common genera. However, a comparison at the genus level between the Khuff fauna and that of the Word Formation of the Glass Mountains, Texas (Cooper & Grant 19751976) shows seven common genera (Derbya, Acri-

tosia, Cyclacantharia, Linoproductus, Grandaurispina, Cleiothyridina, Die!asma), four of which are cosmopolitan. But at the species level the faunas of the Word Fro. and of the KhuffFm. do not share any common taxa. B R A C H I O P O D SYSTEMATIC S (L. A N G I O L I N D All the described specimens are housed in the Geological Museum of Lausanne, Switzerland (MGL numbers) and in the Palaeontological Museum of the University of Milan, Italy (MPUM numbers). Field numbers of single fossiliferous beds ( e L prefixed) are reported along with catalogue numbers. The systematic study follows the supra-ordinal classification of Williams et al. (1996) and the classifications of Williams & Brunton (1993) for the orthotetidines, Brunton et al. (1995) for the productids, Carter et al. (1994) for the spiriferids and of the Treatise on Invertebrate Palaeontology, pt. H (Williams et al. 1965) for the terebratulids. In the systematic descriptions, catalogue numbers are given for figured specimens only. For each spe-

676 cies, the amount of available specimens is given in brackets following each bed number. For example, OL60 (2 art., 4 v.v., 2 d.v.) means that two articulated shells, four ventral valves and two dorsal valves are available from bed OL60. Class STROPHOMENATAWilliams, Carlson, Brunton, Holmer & Popov, 1996 Order ORTHOTETIDAWaagen, 1884 Suborder ORTHOTETIDINAWaagen, 1884 Superfamily ORTHOTETOIDEAWaagen, 1884 Family MEEKELLIDAE Stehli, 1954 Subfamily MEEKELLINAE Stehli, 1954 Genus Perigeyerella WANG, 1955 T y p e s p e c i e s - Perigeyerella costelIata WANG, 1955. R e m a r k s - The genus Perigeyerella is characterized by its v e n t r a l interior with dental plates umbonally forming an elev a t e d spondylium, passing anteriorly to a sessil spondylium and extending parallel along the floor of the valve. Interior of dorsal valve with high cardinal process.

Perigeyerella raffaellae nov. sp. Fig. 12.1-6; Table 1

OL6-3 OL39-15 OL39-18 OL39-24 OL39-36 OL30-1 OL39-25 OL39-35

Width

Length

W. Int.

24.6 13.2 17.6 16.9 16.2 28.9 18.4 19.2

18.2 9.5 16.9 15.5 15.5 23.7 16.5 16

13.1 6.1 8.7

H.Int. 8

5.8

TABLE 1 - Perigeyerella raffaellae nov. sp.W.Int.: width of interarea. H.Int.: height of interarea. All dimensions are in mm.

Interior of ventral valve with slender dental plates joined in a low spondylium at the apex and extending anteriorly as separate subparallel plates up to 1/3 the length of the valve. Interior of dorsal valve with wide, posteriorly curved, bilobed cardinal process, each lobe being cut ventrally for muscle insertion; small socket plates fused to the cardinal process; adminicula diverging along the floor of the valve. D i m e n s i o n s (in ram) - see Tabl. 1. - The specimens from North Oman described as PerigeyereUa sp. by Yanagida & Pillevuit (1994) are here included in Perigeyerella raffaellae nov. sp. due to their strong similarity. Perigeyerella raffaellae nov. sp. resembles Perigeyerella tricosa Gt~ANT,1976 by its short and low elevated stage of the spondylium, but differs in its higher interarea, its coarser and less numerous costellae and its more convex dorsal valve. P. costellata WANG, 1955 and P. magna (GRECO, 1938) have higher spondylia and different external shapes. Discussion

1994 PerigeyereUa sp.: Yanagida & Pillevuit, p. 80, pl. 4, P1. 16. E t y m o l o g y - Species n a m e d for Raffaella Vecchi. H o l o t y p e - MPUM 8401 (OL6-3), v e n t r a l valve. T y p e l o c a l i t y a n d a g e - S o u t h e a s t e r n Oman, Huqf, Khuff Fm., section 1, bed OL6. Wordian. O c c u r r e n c e a n d a g e - Section 1 : O L 4 (1 art. ), OL6 (2 v.v.); section 7 : O L 3 0 (1 d.v.), OL34 (1 v.v.), OL39 (13 v.v., 8 d.v.), OL48 (1 v.v.); section 7bis: OL52 (1 v.v.). Khuff Fm. Wordian. Diagnosis - Representative of Perigeyerella with flabellate ventral valve, very convex dorsal valve, coarse and not very numerous costellae, short and low elevated stage of the spondylium. - Biconvex shell with rectimarginate anterior commissure. Maximum width at midlength. Ventral valve conical, flabellate, with deformed beak. Interarea high with delthyrium closed by a convex pseudodeltidium with a median monticulus. Dorsal valve very convex with subcircular outline. Chilidium small. A median flattening or a very shallow depression may occur in the anterior part of the valve. Ornamentation of costellae increasing in number by intercalation and bifurcation up to 14-18 per 5 mm at the anterior margin. Few irregular rugae may be present.

Description

O t h e r o c c u r r e n c e s - In North Oman Perigeyerella raffaellae nov. sp. occurs in the the Jebel Qamar South faunule (Yanagida & Pillevuit 1994).

Family DERBYIIDAEStehli, 1954 Subfamily DERBYIINAEStehli, 1954 Genus Derbyia WAAGEN,1884 T y p e s p e c i e s - Derbyia regularis WAAGEN, 1884.

Derbyia sp. cf. D. diversa REED, 1944 Fig. 12.7-14; Table 2 O c c u r r e n c e a n d a g e - Section 1:OL6 (1 d.v.), OL22 (2 d.v.), OL24 (2 v.v.); section 5:OL13 (1 v.v., 1 d.v.), OL20 (1 v.v., 1 d.v.); section 7:OL30 (1 v.v.), OL35 (1 v.v.), OL37 (3 d.v.); section 7bis: OL51(2 v.v., 2 d.v.), OL52 (1 d.v.), OL53 (1 d.v.); section 9:OL57 (16 v.v.); section HS2526: JPP526I (2 d.v.); sectionTBQ2392: JPP392A (1 v.v., 2 d.v.). Khuff Fro. Wordian.

FIGURE 12 - 1-6. PerigeyereIla raffaellae nov. sp. 1, postero-ventral view of ventral valve, holotype, MPUM 8401 (OL6-3) x 1,5.2, partially decerticated ventral valve showing spondylium, MPUM 8402 (OL39-22). 3, ventral valve, MPUM 8403 (OL39-18). 4,5, dorsal valves, MPUM 8404 (OL39-35) (4), MPUM 8405 (OL39-34) (%) x 1,5.6, detail of the cardinal process, MPUM 8405 (OL39-34) x 4,15. 7-14. Derbyia sp. cf. D. diversa (REED). 7,8, ventral valves, MPUM 8406 (OL13-30) (7), MPUM 8407 (OL57-37) (8). 9-10, dorsal valves, MPUM 8408 (OL37-1) (9), MPUM 8409 (OL37-12) (10). 11-12, internal (11) and external (12) view of a ventral valve (partially decorticated) showing spondylium, MPUM 8410 (OL57-39). 13-14, ventral and dorsal view of a v e n t r a l valve, MPUM 8411 (OL51-1). 1521. Neochonetes (SommerieUa) arabicus (HuDsON & SUDBUR¥). 15, interior of dorsal valve, MPUM 8412 (OL26-31). 16-17: ventral valves, MPUM 8413 (OL26-23) (16), MPUM 8414 (OL26-9) (17). 18-21, dorsal and ventral views of two articulated shells, MPUM 8415 (OL21-4) (18-19), MPUM 8416 (OL26-25) (20-21), x 2. All figures n a t u r a l size, unless otherwise indicated.

677

5

14

15

16

17

678 - C o n v e x - p l a n a r to convex-concave, l a r g e sized shell. M a x i m u m w i d t h a n t e r i o r to t h e hinge. Shell s u b s t a n c e p s e u d o p u n c t a t e . V e n t r a l v a l v e flat, concave anteriorly, w i t h subcirc u l a r outline. U m b o v e r y low; i n t e r a r e a low a n d w i d e w i t h large, convex, h o r i z o n t a l l y s t r i a t e d p s e u d o d e l t i d i u m a n d l a r g e p e r i d e l t i d i a l areas. D o r s a l v a l v e l o n g i t u d i n a l l y v e r y convex w i t h t r a n s v e r s a l l y elliptical outline. O r n a m e n t a t i o n of costae a n d costellae a r i s i n g by i n t e r c a l a t i o n at one f o u r t h a n d at h a l f t h e l e n g t h of t h e valve. T h e costellae a r e t h i n n e r b u t r e a c h t h e w i d t h of t h e p r i m a r y costae anteriorly. T h e n u m b e r of costae a n d costellae is 5-6 p e r 5 m m at t h e a n t e r i o r m a r g i n . T h e i n t e r c o s t a l t h r o u g h s are a b o u t twice t h e w i d t h of t h e ribs. F e w coarse a n d i r r e g u l a r r u g a e m a y be p r e s e n t on t h e v e n t r a l valve. G r o w t h lines a n d l a m e l l a e are also p r e s e n t . I n t e r i o r of v e n t r a l v a l v e w i t h d e n t a l p l a t e s apically f u s e d to t h e m e d i a n s e p t u m , w h i c h is v e r y t h i c k a n d s h o w s a m e d i a n line of j u n c t i o n as if it r e s u l t s f r o m t h e fusion of two plates. V e n t r a l m u s c l e field wide, s t r i a t e d , w i t h a lobed a n d r a i s e d a n t e r i o r m a r g i n a l ridge, e s p e c i a l l y t h i c k w h e r e it m e e t s t h e m e d i a n s e p t u m . Valve floor d e n s e l y t u b e r c u l a t e . I n t e r i o r of dorsal v a l v e w i t h bilobed, e x t e r n a l l y q u a d r i f i d c a r d i n a l process, e a c h lobe b e i n g divided b y a d i d u c t o r m u s c l e groove. Socket p l a t e s u n i t i n g to t h e c a r d i n a l process a n d d e l i m i t e d by low i n n e r socket ridges. C r u r a l p l a t e s s u p p o r t e d b y a p a i r of d i v e r g e n t plates, e x t e n d i n g f o r w a r d a l o n g t h e floor of t h e valve. Description

D i m e n s i o n s (in ram) - see Tabl. 2. Discussion - T h e a v a i l a b l e m a t e r i a l is a s s i g n e d to Derbyia diversa REED, 1944 b e c a u s e of its general shape, ornamentation and internal characters, n o t w i t h s t a n d i n g its f r a g m e n t a t i o n a n d s t a t e of preservation. Derbyia sp. cf. D. diversa differs f r o m Derbyia haribi ANGIOLINI, 1996 f r o m t h e S a i w a n Fm. of sout h e a s t e r n O m a n b y its c o a r s e r a n d u n e q u a l ornamentation, larger intercostal throughs and shorter median septum.

Other occurrences - Derbyia diversa Reed has been described by Reed (1944) from the Amb Fm. of Salt Range.

OL13-30 OL30-2 OL57-37 OL57-39 OL37-12

Width

Length

H.Int.

64 60 67.9 52.2 53.8

10.8

57

58 46.7 36.1

W. Int.

F a m i l y RUGOSOCHONETIDAE Muir-Wood, 1962 S u b f a m i l y RUGOSOCHONETINAE Muir-Wood, 1962 G e n u s N e o c h o n e t e s MUIR-WooD, 1962 (=Quadranetes SADLICK, 1963) S u b g e n u s Sommeriella ARCHBOLD,1982 (=Sommeria ARCHBOLD,1981) Type species - Chonetes prattii DAVIDSON,1859. Remarks - The subgenus Sommeriella has been introduced by Archbold (1981, 1982) for a group of species of Neochonetes (the Neochonetes pratti stock) characterized by large size, a deep sulcus, ventral hinge spines at moderate angle (40°-45°) and maximum width anterior to the hinge. According to Archbold (1981), the separate stocks which can be identified within Neochonetes show morphological overlap, making difficult to give them full generic status.

Neochonetes (Sommeriella) arabicus (HuDsON SUDBURY, 1959) Fig. 12.15-21; Table 3 1959 Chonetes arabicus HUDSON• SUDBURY,p. 26-28, pl. 3, figs. 6-16; P1.6, figs. 14-18. 1990 Neochonetes (Sommeriella) arabicus: Archbold & Burret, p. 121, Fig. 1A-C. Occurrence and age - Section HUQF 1:1281(2 v.v.), 1284 (1 v.v., 1 d.v.); section 1:OL1 (10 v.v., 3 d.v.), OL2 (1 art., 6 v.v.), OL4 (4 v.v., 2 d.v.), OL5 (1 v.v., 1 d.v.), OL21 (1 art.); section 7: OL26 (1 art., 15 v.v., 8 d.v.). Khuff Fm. Wordian. D e s c r i p t i o n - Concavo convex shell, w i t h semicirc u l a r o u t l i n e , s m a l l s i z e d for t h e s u b g e n u s . M a x i m u m w i d t h a n t e r i o r to hinge. C a r d i n a l extrem i t i e s rounded. V e n t r a l v a l v e m o d e r a t e l y convex, w i t h s m a l l ears. I n the m e d i a n p a r t of t h e v a l v e a s h a l l o w m e d i a n sulcus occurs, b r o a d e n i n g a n d s h a l l o w i n g a n t e riorly. I n few s p e c i m e n s t h e m e d i a n sulcus is v e r y shallow. D o r s a l v a l v e concave w i t h low m e d i a n fold. O r n a m e n t a t i o n of fine ribs i n c r e a s i n g by bifurcation, n u m b e r i n g 5-7 p e r 1 m m at t h e a n t e rior m a r g i n . G r o w t h l a m e l l a e occur at t h e a n t e r i o r m a r g i n . C a r d i n a l spines are p r e s e n t , n u m b e r i n g at l e a s t 5 at e a c h side of t h e u m b o . I n t e r i o r of v e n t r a l v a l v e w i t h a v e r y s h o r t m e d i a n s e p t u m a n d r a d i a l r o w s of papillae. I n t e r i o r of dorsal v a l v e w i t h a low q u a d r i f i d c a r d i n a l process w i t h pit, s u p p o r t e d b y socket ridges a n d w i t h a low median septum. Adductor scars thickened. Radial rows of coarse p a p i l l a e are also p r e s e n t . D i m e n s i o n s (in mm) - see Tabl. 3. Discussion

- Neochonetes (Sommeriella) arabicus

(HusDSON & SUDBURY,1959) is s i m i l a r to N. (S.) 9.8

36.6

TABLE2 - Derbyia sp. cf. D. diversa. O r d e r PRODUCTIDA S a r y t c h e v a & S o k o l s k a y a , 1959 S u b o r d e r CHONETIDINA Muir-Wood, 1955

baroghilensis (REED, 1925) f r o m K a r a k o r u m , differ i n g f r o m it b y its s m a l l e r size, t h e s h a l l o w e r m e d i a n sulcus a n d t h e a b s e n c e of c o a r s e r p a p i l l a e on t h e i n n e r surface t h e ears. A t t r i b u t i o n of the species to t h e s u b g e n u s Sommeriella w a s discussed by Archbold & B u r r e t t (1990), w h o i n c l u d e d it in Sommeriella n o t w i t h s t a n d i n g its s m a l l size. I n fact, according to Archbold (1981) K u n g u r i a n a n d

679 Width OL21-4 OL26-25 OL1-3 OL1-5 OL2-2 OL2-7 0L4-35 0L26-8 0L26-18 OL26-23 0L26-30 OL26-33 MGL 63197 OL1-12 OL26-14 OL26-20 OL26-29 MGL 69433

Length

11.6 10.3 8.7 9.4 8.6 10.1 6.7 8.9 6.9 11.8 7.5 9.2 10.5 9.7 8.4 10.8 7.6 7.7

8.7 7.5 6.8 6.6 7 7.3 5.2 6.6 5 8.9 4.8 5.9 8.8 6.9 6.4 7.3 5.1 5.2

TABLE 3 - Neochonetes (Sommeriella) arabicus.

Late Permian representatives of Neochonetes are characterized by small size. Suborder PRODUCTIDIDINAWaagen, 1883 Superfamily PRODUCTOIDEAGray, 1840 Family PRODUCTELLIDAESchuchert in Schuchert & Le Vene, 1929 Subfamily PRODUCTININAEMuir-Wood & Cooper, 1960 Tribe CHONETELLINI Likharev, 1960 Genus Celebetes GRANT, 1976 T y p e s p e c i e s - Celebetes g y m n u s GRANT~1976. - The ordinal position of the genera Celebetes GRANT, 1976, Bibatiola GRANT, 1976 and Chonetella WAAGEN,1884 was discussed at length by Grant (1976, p. 138-141). The three genera share chonetiform characters, such as the great number of internal tubercles, the dorsal muscle field and the cardinal spines. Nevertheless the features of the order Productida, such as the knob-like or trifid cardinal process, the lack of teeth and sockets, the cardinal spines placed anteriorly to the hinge edge and the great convexity, are dominating. According to Grant (1976, p. 143) the narrow cardinal process, which has two small lateral lobes only in adults, suggests affinity with the Linoproductidae. However, its shallow corpus cavity and lack of radial ornamentation suggest affinity to the Productellidae. Celebetes differs from Chonetella from the Salt Range by its smooth shell and lack of a ginglymus and nasute anterior margin. Remarks

Celebetes manarollai nov. sp. Fig. 13.1-8; Table 4 1959 Productina ? acinosa: Hudson & Sudbury, p. 37, P1. 12, Fig. 6, non Fig. 5. E t y m o l o g y - Species n a m e d for Dr. Luca Manarolla of Dipartimento Scienze della Terra, Milano. H o l o t y p e - MPUM 8418 (OL22-2), articulated shell. T y p e l o c a l i t y a n d a g e - Southeastern Oman, Huqf, Khuff Fro., section 1, bed OL22. Wordian. O c c u r r e n c e a n d age - HUQF 1 section: 1281 (1 v.v.), 1284 (1 v.v.); section 1:OL2 (1 v.v.), OL4 (20 v.v.), OL7 (13 v.v., 2 d.v.), OL22 (1 art., i v.v.), OL24 (1 v.v.); section 5:OL13 (1 v.v.); section

7:0L26 (1 art., 3 v.v.), 0L27 (43 v.v., 11 d.v.), 0L28 (1art., t v.v.). - Representative of Celebetes characterized by a strongly concavo-convex shell, by the occurrence of 3 pair of cardinal spines and by the spreading lateral lobes of the cardinal process. Diagnosis

- Concavo-convex shell with subcircular to slightly transverse outline. Maximum width at the hinge; ears extended. Shell substance strongly pseudopunctate. Corpus cavity shallow. Ventral valve very convex; umbo short, notched for lophidium. A low ginglymus occurs; teeth a r e absent. Dorsal valve deeply concave, with subcircu!ar outline. Surface smooth, with few spines on the venter of one specimen. Three coarse and long cardinal spines occur on each side of the ventral umbo, equally spaced and with their bases located anterior to hinge edge: the first near the umbo, the second at midwidth and the third near the cardinal extremities, all projecting laterally at low angle. Growth lines are dense on both valves. Interior of mature dorsal valves with long shafted, trifid cardinal process with large central lobe and two spreading lateral protuberances; lateral ridges low and short. A very low median septum starts from the shaft. Tubercles are numerous anteriorly on visceral disc. Description

D i m e n s i o n s (in ram) - see Tabl. 4.

The new species is similar to Celebetes leptus GRANT, 1976, differing in its larger size, the occurrence of three pair of cardinal spines, the presence of endospines in the dorsal valve and the spreading lateral lobes of the cardihal process. Cetebetes manarollai nov. sp. is chaDiscussion

OL22-2 OL26-1 OL4-10 OL4-18 OL4-31 OL7-5 OL7-11 0L7-12 0L13-12 0L26-2 0L27-32 0L27-37 0L27-41 0L27-42 0L27-58 0L27-66 0L27-78 OL27-79 0L27-31 0L27-33 OL27-59 0L27-71 0L27-73

Width

Length

13.4 15.7 13.2 6.4 6.1 13.2 12.3 10.8 12.8 14.7 9.4 11.7 13.4 10.7 13.4 12.9 11.9 11.2 12.7 11.2 12.8 12.7 12.1

12.6 15.5 :[2 6.1 5.5 :[1.8 11.9 9.9 11.9 14.3 7.9 !1.5 12.9 9.7 12.3 12 11.5 10.4 12.2

TABLE 4 - Celebetes manarollai nov. sp.

10.8

12.1 11.6 11.2

680 racterized also by a deeply convex ventral valve and a strongly concave dorsal valve. Genus Haydenella REED, 1944 T y p e s p e c i e s - Productus kiangsiensis KAYSER,1883. R e m a r k s - The diagnosis provided by G r a n t (1976) is here enlarged to include specimens with thick and layered shell and w i t h o r n a m e n t a t i o n of indistinct costeIlae and dense concentric filae. F u r t h e r m o r e the v e n t r a l spines along the hinge described by G r a n t (1976, p. 159) are not truly on the hinge line b u t s o m e w h a t anterior to it, as in Celebetes. Due to the absence of knowledge on the shape of the cardinal process, the taxonomic position of the genus HaydeneUa was uncertain and it was placed in the family Marginiferidae by most authors (Sarycheva 1960; Yanagida 1964; Ruzhentsev & Sarycheva 1965; Muir-Wood & Cooper 1960; Muir-Wood in Treatise 1965). G r a n t (1976) studied the cardinal process of two species of Haydenella from the Salt Range (Pakistan) and of a species from southern Thailand, revealing its linoproductide affinity. The inclusion of the genus Haydenella in the subfamily Linoproductinae was also supported by Archbold (1983). B r u n t o n (pers. comm.) assignes this genus to the tribe Chonetellini Likharev 1960 because of its shallow corpus cavity and ribs starting after a short distance from the smooth umbo. The genus Haydenella has been found in the Amb, Wargal and C h h i d r u Fms. of Salt Range (Pakistan) (Waagen 1884; Reed 1944; G r a n t 1976) and in the Late P e r m i a n of South and E a s t Asia (Diener 1915; Yanagida 1964; Fantini Sestini 1965; Ruzhentsev & Sarycheva 1965; G r a n t 1976).

Haydenella sp. Fig. 13.9-10 O c c u r r e n c e a n d a g e - Section 7bis: OL57 (4 v.v.); section 7: OL45 (3 v.v.). K_huff Fm. Wordian.

D e s c r i p t i o n - Convex ventral valve with subovate outline. Shell thick, layered, lustrous. Maximum width about 25 mm; corresponding lenght about 29 mm. A low ginglymus seems to be present. Ornamentation of indistinct, rather sinuous costellae numbering 8-9 per 5 mm starting at a short distance from the umbo; of dense concentric filae, which are more prominent in the inner shell layer; of spines in row slightly anteriorly to the hinge line, on the ears and on the venter. D i s c u s s i o n - The state of preservation of the few specimens from southeastern Oman prevents a specific determination. However, the specimens from southeastern Oman differ from Haydenella buravasi GRANT,1976 from the Rat Buri Limestone of southern Thailand by their subovate outline and ornamentation. In fact they are more similar

to the specimens of H. salinaria REED, 1944 from the Amb Fm. of Salt Range (Pakistan) figured by Grant (1976, p. 159, pl. 42, figs. 25-28). C h o n e t e l l i n i ? genus and species unidentified O c c u r r e n c e a n d a g e - Section T B Q 2 3 9 2 : J P P 3 9 2 A (2 v.v.). Khuff Fro. Wordian.

D e s c r i p t i o n - Strongly convex ventral valve with circular outline. Maximum width of 15.3 mm at the hinge; corresponding length 13.4 ram. Anterior margin slightly protruding. Ornamentation of fine ribs numbering about 7 per 5 mm at the anterior margin. A row of 4-5 spines occurs along the cardinal margin and across the ears at each side of the umbo. D i s c u s s i o n - The general shape and ornamentation of these two specimens recall Bibatiola GRANT, 1976. However, the state of preservation and the lack of details on internal characters and on the dorsal valve prevent a generic attribution. Subfamily OVERTONIINAE Muir-Wood & Cooper, 1960 Tribe COSTISPINIFERINIMuir-Wood & Cooper, 1960 Genus Dyschrestia GRANT, 1976 T y p e s p e c i e s - Dyschrestia spodia GRANT,1976. R e m a r k s - The genus Dyschrestia was introduced by G r a n t (1976) and discussed by Archbold (1984). Both the authors discussed the relationships between Dyschrestia and the allied genera Krotovia FREDERICKS, 1928, Lethamia WATERHOUSE, 1973, Stictozoster GRANT,1976, Comuquia GRANT,1976 and the linoproductids Grandaurispina MUIR-WOOD • COOPER, 1960 and Holotricharina COOPER & GRANT, 1975. However these authors did not compare Dyschrestia to Echinauris MumWOOD & COOPER, 1960 which is externally similar. Dyschrestia however does not possess the b r u s h e s of spines on the ears and on the lateral slopes which are characteristic of Echinauris, has fewer spines and different dorsal i n t e r n a l characters.

Dyschrestia rugosa nov. sp. Fig. 13.11-17; Table 5 ? 1959 Marginifera spinosocostata: Hudson & Sudbury, p. 34, PI. 2, Fig. 10 a-c. E t y m o l o g y - After the rugose ornamentation. t t o l o t y p e - MPUM 8427 (OL38-5), v e n t r a l valve. T y p e l o c a l i t y a n d a g e - S o u t h e a s t e r n Oman, Huqf, Khuff Fm., section 7, bed OL38. Wordian.

FIGURE 13 - 1-8. Celebetes manaroUai nov. sp. 1.5, ventral view of articulated shells, MPUM 8417 (OL26-1) (1) x 1,5, holotype MPUM 8418 (OL 22-2) (5) x 1,5.2-4,6,8, ventral valves, MPUM 8419 (OL7-2) (2) x 1,5, MPUM 8420 (OL7-11) (3), MPUM 8421 (OL27-58) (4), MPUM 8422 (OL27-66) (6), MPUM 8423 (OL27-72) (8) x 1,5.7, interior of dorsal valve, MPUM 8424 (OL27-73) x 2,4. 9-10. Haydenella sp.: v e n t r a l valves, MPUM 8425 (57-21) (9), MPUM 8426 (OL57-20) (10). 11-17. Dyschrestia rugusa nov. sp. 11-12, 14-17: v e n t r a l valves, holotype MPUM 8427 (OL38-5) (11), MPUM 8428 (OL28-9)(12), MPUM 8429 (OL12-7) (14), MPUM 8430 (392A-8) (15), MPUM 8431 (OL38-13) (16). 13: dorsal valve, MPUM 8432 (OL12-153) x 1,5. 18-21. Kozlowskia tescorum (HUDSON• SUDBURY).18, interior of dorsal valve, MPUM 8433 (OL51-12) x 1,5.19-21, v e n t r a l valves, MPUM 8434 (OL57-16) x 1,5 (19), MPUM 8435 (OL51-10) (20), MPUM 8436 (OL51-8) (21). 22-26. Calliprotonia sp. 22-23, v e n t r a l (22) and dorsal (23) view of a n articulated shell MPUM 8432 (526E2-2). 24, ventral view of a n articulated shell, MPUM 8438 (526E2-1). 25, interior of dorsal valve, MPUM 8439 (OL13-8). 26, dorsal valve, MPUM 8440 (OLD-4) x 1,5.27-28. Magniplicatina sp. 27, v e n t r a l valve, MGL63175. 28, dorsal valve, MGL63193. All figures n a t u r a l size, unless otherwise indicated.

681

3 2

,5

4 ,.

9

21

2;

!7

28

682 O c c u r r e n c e a n d a g e - Section 1:OL9 (1 v.v.), OL22 (1 art.), 0L24 (1 v.v.), 0L25 (1 v.v.); section 5:OL12 (29 v.v., 1 d.v.), OL13 (1 v.v.), OL19 (30 v.v., 1 d.v.); section 7 : 0 L 2 7 (12 v.v.),

Width OL22-4 392A-8 OL12-148 OL12-164 OL12-166 OL12-172 OL19-6 OL19-7 OL19-8 OL19-11 OL19-18 OL19-29 0L24-5 0L27-12 0L28-9 0L28-II OL31-1 0L31-3 0L38-5 0L38-6 0138-7 0L38-8 0L38-13 0L12-153 0L28-21

OL28 (13 v.v.,2 d.v.),OL31 (3 v.v.,),OL37 (1 v.v.),OL38 (17 v.v.), OL47 (1 v.v.); section 7bis: OL52 (2 v.v.); section TBQ2392: JPP392A (1 art., 1 v.v.).KhuffFm. Wordian. Diagnosis - Representative of Dyschrestia characterized by large size and prominent concentric ornamentation. The larger specimens of the new species show interrupted ribs and an anterior slightly protruding fold in the ventral valve.

- Shallow, large sized, concavoconvex shell with subovate outline. Maximum width anterior to the hinge. Shell substance pseudopunctate. Ventral valve convex with spiral profile, without geniculation. Trail enroled. Ventral umbo small, slightly recurved. Ears small, acute. Ventral sulcus absent. The larger specimens show a slightly protruding fold in the anterior part of the ventral valve. Dorsal valve very concave and thin shelled with gently concave and pointed ears. Ornamentation of ventral valve of irregular rugae on the visceral disc and spines with rather swollen bases. Spines are: i) in one curved row of 9 delimiting the ears, becoming double anteriorly; ii) irregularly scattered on the visceral disc and on the trail, at least 50 in number and of two distinct sizes. The ventral spines connect to the mantle cavity by anteriorly opening canals. All the preserved spines are slender and long. Growth lines are also distinct. The gerontic specimens show indistinct, interrupted ridges extending anterior from the bases of spines. Dorsal valve ornamented by concentric rugae, stronger than those of the ventral valve, dimples and few spines (detected only in specimen OL22-4). Interior of dorsal valve with crenulated ear baffles continuing h a l f way towards the anterior margin as a low marginal ridge. Cardinal process short, bilobed, with "w" shape in posterior view. Internal surface with endospines. Description

Dimensions

(in mm) - see Tabl. 5.

Diagnostic characters of the new species are the large size and the strong concentric o r n a m e n t a t i o n . This species probably lived in soft m u d s supported by the long lateral spines. A t t a c h m e n t was lost in the early stage of growth, indicating a short period of juvenile attachment. Dyschrestia rugosa nov. sp. differs from the other species of the genus by its unusually prominent concentric ornamentation and by its large size. However it clearly possesses the diagnostic features of the genus, i.e. the double row of lateral spines, the ventral spines of two sizes, the stronger concentric ornamentation on the dorsal valve and the spiral profile. Discussion

-

14.7 23.1 18.5 19.8 23.7 17.2 21.8 15.8 18.3 16.9 18.9 11 18.4 22.2 1].6 18.1 17.6 18.2 19 9.8 19.1 21.9 24.3 22.7 10.4

Length 13.9 25.2 20.9 20 25.1 12.7 22.3 18.8 18.8 19.3 20.4 11.5 19.7 22.3 12.4 20.1 17.9 18.8 18.2 10.2 18.2 16 25.5 20.1 9

TABLE 5 Dyschrestia rugosa nov. sp. -

Family PRODUCTIDAE Gray, 1840 Subfamily PRODUCTINAE Gray, 1840 Tribe KOZLOWSKIINIBrunton, Lazarev & Grant, 1995 Genus K o z l o w s k i a FREDERICKS, 1933 T y p e s p e c i e s - Productus capacii D'ORBIGNY~ 1842. R e m a r k s - As pointed out by Cooper & Grant (1975) the diagnostic character of the genus Kozlowskia FREDERICKS is the band of overlapping trails extending from the dorsal marginal ridge to close the anterior gap with the ventral valve. However, due to the weakness of the anterior trails, it is very rare to find all of them preserved on specimens (see also Cooper & Grant 1975, p. 970). Kozlowskia differs from Marginifera WAAGENby means of its overlapping trails and by the a r r a n g m e n t of spines. In fact the spines of Marginifera are more numerous with the lateral ones typically arranged in rows up the lateral flanks.

Kozlowskia tescorum (HuDsoN • SUDBURY, 1959) Fig. 13.18-21; Table 6 1959 Marginifera tescorurn HUDSON • SUDBURY,p. 35 , pl. 3, Fig. 1-5, Text-fig. 6. O c c u r r e n c e a n d age - Section 7:OL45 (1 v.v.); section 7bis: OL51 (4 v.v., 6 d.v.), OL57 (2 v.v., 1 d.v.). Khuff. Fm. Wordian.

- Small sized, concavo-convex, alate shell. Maximum width at the hinge. Shell substance pseudopunctate. Ventral valve deeply convex, with long trail. Ears alate, convex, smooth. Ventral sulcus narrow and rather deep. Ornamentation of costae: 3 slightly converging in the sulcus and 6 on each flank; of very weak rugae on the visceral disc; of spines arranged in a row of 2 along the hinge at each side of the umbo and in 2 transverse rows, each of few Description

683

spines, on t h e trail. Few small spines are s c a t t e r e d on the visceral disc. G r o w t h lines and g r o w t h l a m e l l a e are present. Dorsal valve s h a r p l y geniculated, with t r a n s v e r s e outline a n d Mate ears. A low m e d i a n fold occurs on the trail. I n t e r i o r of dorsal valve w i t h sessile, bilobed, trifid c a r d i n a l process; ear baffles strong, crenulated, c o n t i n u e d a n t e r i o r l y as a strong and b r o a d marginal ridge; m e d i a n s e p t u m present; elongate adductor pads; dorsal ridges forming pair of r a i s e d lobes. Multiple o v e r l a p p i n g trails are shown on specim e n OL51-15. Dimensions

Calliprotonia sp. Fig. 13.22-26 and age - Section HS2526: JPP526E (2 art.); section 5:OL13 (1 d.v.);scree: OLD (1 d.v.). Khuff Fro. Wordian.

Occurrence

- M e d i u m sized, piano-convex w i t h geniculate trails; outline s u b - q u a d r a t e . M a x i m u m w i d t h a n t e r i o r to t h e hinge, a b o u t 34.4-35 mm; corresponding l e n g t h (30.9-33.8 mm). Corpus cavit y deep. Shell s u b s t a n c e p s e u d o p u n c t a t e . Ventral valve strongly convex; v e n t r a l u m b o recurved w i t h cicatrix of a t t a c h m e n t . T r a i l long, curved w i t h a shallow m e d i a n sulcus. Dorsal disk almost flat, geniculated w i t h s h o r t trail. A low m e d i a n fold occurs anteriorly. O r n a m e n t a t i o n of 8-9 low concentric bands, becoming lamellose anteriorly. E a c h b a n d b e a r s regularly a r r a n g e d rows of r e c u m b e n t spines of two size: the coarser p o s t e r i o r l y in two rows and t h e finer a n t e r i o r l y in t w o - t h r e e rows. T h e spines show elongated bases. T h e b a n d s of t h e dorsal valves are n a r r o w e r and m o r e closely' spaced, the spines are finer and in f e w e r rows. Interior of dorsal valve with trifid, slightly dorsally recurved cardinal process; raised, dendritic posterior adductor scars; m e d i a n septum extending to 2/3 the length of visceral disc; lateral ridges extending among the lateral margin to join a thickened marginal ridge delimiting anteriorly the visceral disc. Description

(in ram) - see Tabl. 6.

- H u d s o n & S u d b u r y (1959) described 8 specimens f r o m the L u s a b a Lmst. of Haushi, s o u t h e a s t e r n O m a n as Marginifera tescorum HUDSON • SUDBURY,1959. However, in the discussion t h e y s t a t e d t h a t the a r r a n g e m e n t of spines was not typical of Marginifera; at the same time, t h e y c o n s i d e r e d t h a t the l a m e l l a r thickenings in the dorsal valve w e r e only occasional and did not j u s t i f y a n a t t r i b u t i o n to the genus Kozlowskia. The description a n d the illustrations of H u d s o n & S u d b u r y (1959) and the s t u d y of the new m a t e r i a l from s o u t h e a s t e r n O m a n confirm the a s s i g n m e n t of the species tescorum to the genus Kozlowskia, on t h e basis of t h e a r r a n g m e n t of spines, the internal c h a r a c t e r s a n d the p r e s e n c e of overlapping dorsal trails. In fact the l a t t e r can be seen only on the best p r e s e r v e d specimens (Cooper & G r a n t 1975, p. 970). Kozlowskia tescorum differs from Kozlowskia cornuta GRANT, 1976 and K. opipara GRANT, 1976 from the Rat Buri Lmst. of southern Thailand because of its less t r a n s v e r s e outline, the occurrence of a ventral sulcus and its ornamentation. Kozlowskia tescorum differs from Kozlowskia capaci (D'ORBIGNY, 1842) and from the species of the Carboniferous and E a r l y P e r m i a n of the United States by its much larger size, outline and details of ornamentation. Discussion

TABLE 6 -

- The genus Calliprotonia differs f¥om Echinoconchus WELLER,1914 by its more numerous rows of spines with longer bases, lower and more lametlose bands, longer lateral ridges and occurrence of an anterior marginal ridge inside the dorsal valve. Furthermore the dorsal posterior adductors are dendritic in Calliprotonia, whereas they are smooth in Echinoconchus. It occurs in the Late Carboniferous to Early Permian of Texas and in the Early Permian of Peru.

Remarks

Width

Length

OL51-10 0L57-16 0L51-12

12.8 12.3 16.8

11.2 10.9 9.8

OL51-13

13.4

8.8

Kozlowskia t e s c o r u m .

- The i n t e r n a l a n d e x t e r n a l characters suggest t h e a t t r i b u t i o n of t h e s e specimens to the genus Calliprotonia. The specimens from s o u t h e a s t e r n O m a n differ from the L o w e r P e r m i a n Texas species b y being l a r g e r w i t h a different outline a n d o r n a m e n t a t i o n . Discussion

S u b f a m i l y JURESANIINAE Muir-Wood & Cooper, 1960 T r i b e JURESANIINI Muir-Wood & Cooper, 1960 G e n u s J u r e s a n i a FREDERICKS,1928 Type species -Productus juresanensis TSCHERNYSCHEW~ 1902. - Juresania is not a well known genus and its typespecies has not been described in detail. As pointed out by Muir-Wood & Cooper (1960), Juresania differs from Buxtonia by means of its more subquadrate outline, more convex renter, ornamentation of spine ridges and prostrate spines of two series, absence of costae, bilobed cardinal process not elongated or curved dorsally at steep angle. Furthermore Juresania has no true buttress plates, but two parallel and separated ridges connecting the cardinal process to the adductor scars. Remarks

S u p e r f a m i l y ECHINOCONCHOIDEA Stehli, 1954 F a m i l y ECHINOCONCHIDAE Stehli, 1954 S u b f a m i l y ECHINOCONCHINAE Stehli, 1954 T r i b e CALLIPROTONIINI Lazarev, 1985 G e n u s C a l l i p r o t o n i a MUIR-WOoD & COOPER, 1960 Type species - Calliprotonia renfrarum MUIR-WOOD & COOPER~ 1 9 6 0 .

684 According to Muir-Wood & Cooper (1960) and to Cooper & Grant (1975) Juresania differs from Rhamnaria MUIR-WOOD& COOPER, 1960 by its buxtoniid, posteriorly projecting cardinal process, by its parallel plates connecting the cardinal process to the adductor scars and by the absence of the ventral median septum. Furthermore Rhamnaria has a variably developed ventral interarea, whereas Juresania has only an impersistent ginglymus.

Juresania omanensis HUDSON • SUDBURY, 1959 Fig. 14.1-16; Tabl. 7 1959 Juresania omanensis HUDSON & SUDBURY,p. 29, pl. 1, figS. 1-4. 1959 Juresania sp. - Hudson & Sudbury, p. 31, pl. 2, figs. 1-3, O c c u r r e n c e a n d a g e - Section HUQF 1:1281 (2 art., 7 v.v., 1 d.v.), 1284 (2 v.v.); section 1:OL4 (2 v.v.), 0L23 (7 art., 3 v.v.); section 5:OL13 (1 art., 5 v.v., 2 d.v.); section 7:OL27 (1 art., 13 v.v.), 0L32 (6 art., 9 v.v., 2 d.v.), OL33 (1 art.), 0L34 (1 v.v.), OL36 (3 v.v., 1 d.v.), 0L37 (1 d.v.), OL38 (5 art., 9 v.v.), 0L39 (3 art., 11 v.v.), OL40 (1 v.v., 1 d.v.), OL41 (12 art., 19 v.v.), OL42 (1 art., 52 v.v.), OL44 (1 v.v.), 0L47 (2 art., 6 v.v., 1 d.v.), 0L49 (2 art., 1 v.v.); section 7bis: OL51 (2 d.v.), 0L52 (1 v.v.), 0L53 (1 d.v.), OL54 (1 v.v.), OL56 (1 art, 1 v.v.), OL60 (10 d.v.); section 9:OL57 (4 v.v., 15 d.v.); section HS2526: 526B (3 art.); section TBQ2392: JPP392A (4 art); scree: OLD (1 art., 2 d.v.). Khuff Fm. Wordian.

Description Medium sized, concavo-convex, geniculated shell, with subquadrate to subrectangular outline; maximum width anterior to midlength. Corpus cavity deep. Ventral valve convex, with long recurved trail; umbo small, acute, recurved with a rounded and concave cicatrix of attachment; a low ginglymus m a y be present; ears small, convex. Trail with shallow sulcus or only a slight flattening in its middle part. Dorsal valve with flat visceral disc and short trail. Ornamentation of ventral valve of short spine ridges, concentrically arranged posteriorly; long and in two series on the trail: i) finer and more numerous spine ridges and ii) coarser and fewer ones. The latter bear anteriorly directed spines which form an higher angle (up to 30-40 °) to the valve surface than the finer spines. Anteriorly the two kinds of spines are roughly concentrically arranged. Suberect and closely packed spines occur in tufts on the ears and along the hinge, postero-laterally directed. They are intermediate in size between the larger and the smaller spines of the trail. Concentric bands and lamellae occur anteriorly to mid-length. Ornamentation of dorsal valve of dimples and of two series of spines ridges, with finer ridges much more numerous than the

corser ones; the fine ridges are radially aligned and bear prostrate spines. Concentric bands occur on the surface of the valve. Interior of dorsal valve with bilobed cardinal process slightly recurved dorsally or parallel to the valve surface, projecting posteriorly. The cardinal process is trifld posteriorly with a strongly rugose median lobe; two strong lateral ridges extend to the ears, where they curve anteriorly; from the junction between the lateral ridges and the cardinal process, two parallel ridges extend anteriorly to reach the posterior ends of the muscle scars and of the breviseptum; these parallel ridges and the cardinal process pit are best exposed in juvenile specimens, whereas in the adults they are covered by a callus. The breviseptum extends to the ante-

MGL 63188 MGL 63189 OL38-21 OL38-30 OL38-31 OL41-20 OL41-24 OL41-26 OL41-28 OL47-1 OL47-2 392A-1 392A-3 392A-4 MGL 63171 MGL 63177 OL27-16 OL27-17 OL27-23 OL34-2 OL41-3 OL41-11 OL42-5 OL42-17 OL42-20 OL42-29 OL42-34 OL42-43 OL42-49 OL42-50 OL57-5 0L57-6 OL60-2 OL60-6 OL60-9

Width

Length

>41 29.8 34.4 25.7 35.8 33.9 30.9 32.1 29.7 39.9 34.1 38.6 37.1 40 38 41.2 39.9 35.2 36.3 38.1 33.1 34.2 26.2 28.4 26.5 26.2 21.2 36.4 34.3 26 26.9 27.8 31.2 30 28.6

43.7 31.1 29.7 23.4 30.2 30.1 28.1 31.7 25 37.1 33.5 37.7 38 38.7 >33 43.2 37.8 32.2 33.5 33.1 32 30.3 25.1 26.4 26.2 25.1 19.7 33.8 32.9 24.3 25.1 24.4 27.2 26 24.5

TABLE7 - Juresania ornanensis.

FIGURE 14 - 1-16. Juresania omanensis HUDSON • SUDBURY. 1,8, ventral valves, MPUM 8441 (OL41-4) (1), MPUM 8442 (OL41-5) (8). 2-4,7, ventral view of articulated shells, MPUM 8443 (OL41-22) (2), MPUM 8444 (OL41-20) (3), MPUM 8445 (OL41-21) (4), MPUM 8446 (OL41-19) (7). 5-6, ventral (5) and dorsal (6) view of an articulated shell, MPUM 8447 (OL41-26). 9-10, dorsal view of articulated shells, MPUM 8448 (OL41-29), MPUM 8449 (OL38-21). 11,14, ventral (11) x 1,5 and dorsal (14) view of a dorsal valve, MPUM 8450 (OL57-15). 12: dorsal view of an articulated shell, MPUM 8451 (OL47-2). 13, dorsal view of a dorsal valve, MPUM 8452 (OL602). 15-16, interior of dorsal valves, MPUM 8453 (OL51-4) (15), MPUM 8454 (OL57-6) (16). 17-22. Bilotina yanagidai nov. sp. 17-22, ventral valves, MPUM 8455 (OL37-7) (17) x 1,5, MPUM 8456 (OL20-7) (18), MPUM 8457 (OL28-2) holotype (19), MPUM 8458 (OL379) (20), MPUM 8459 (OL12-179) (21), MPUM 8460 (OL46-1) (22). 23-29. Grandaurispina ghabaensis nov. sp. 23-24, dorsal (23) x 1,5 and ventral (24) view of an articulated shell, MPUM 8461 (392A9). 25-26, dorsal (25) x 1,5 and ventral (26) view of an articulated shell, MPUM 8462 (OL51-17) holotype. 27-28, dorsal (27) x 1,5 and ventral (28) view of an articulated shell, MPUM 8463 (OL51-18) x 1,5.29, ventral view of an articulated shell, MPUM 8464 (OL51-19). All figures natural size, unless otherwise indicated.

685

2

o

7 v

•i

"i~

v I

1U

6

14

24

3 1'1

~ 6 18

19 ~

28 ~

~i~

~

29

686 r i o r m a r g i n of t h e v i s c e r a l disc, b e c o m i n g h i g h e r a n d b l a d e - l i k e anteriorly. T h e a d d u c t o r s c a r s a r e s l i g h t l y r a i s e d a n d dendritic. T h e i n t e r i o r o f t h e t r a i l is s t r o n g l y p u s t u l o s e . Dimensions

(in mm) - see Tabl. 7.

O n t o g e n e t i c v a r i a t i o n - The juveniles show a more regularly arranged ornamentation and more distinct vertical ridges connecting the cardinal process to the muscle scars. These prominent vertical ridges in the young stage could be reminescent of the buttress plates present in the Carboniferous but lost in the Permian genera of the subfamily. - T h e o r i g i n a l d e s c r i p t i o n of H u d s o n & S u d b u r y (1959) is h e r e i m p r o v e d , especially concern i n g t h e o r n a m e n t a t i o n of t h e v e n t r a l valve. T h e s p e c i m e n s u n d e r e x a m i n a t i o n fit quite well into t h e r a n g e of v a r i a t i o n of Juresania ornanensis. Discussion

G e n u s B i l o t i n a REED, 1944 Type species - Strophalosia (Bilotina) subtecta REED,1944. - The diagnosis provided by Grant (1976) is here followed. However, in the discussion of the genus, Grant (1976, p. 147) considered buttress plates stemming from the cardinal process as diagnostic for the genus. According to Brunton et al. (1995) true buttress plates die out after Early Carboniferous and the plates diagnostic of Bilotina are in fact ridges connecting to the raised muscle platform (Brunton, pers. comm.). These ridges were called lateral septa by Waterhouse and Piyasin (1970, p. 121). The genus Bilotina REED,1944 was based on a single species from the Amb Fm. of Kishor Range, Pakistan (Reed 1944) and it was redescribed by Muir-Wood and Cooper (1960) and by Grant (1976). The recognition of a new species in the Rat Buri Lmst. in southern Thailand (Grant 1976) and the presence of the genus in southeastern Oman and in North Oman enhances its importance as a marker for the Wordian of the southern margin of the Neotethys. Bilotina is characterized by the internal characters of the dorsal valve, consisting of a bilobed cardinal process with ridges connected to raised adductor platforms and of a long and low median septum. Another feature of the genus is that the ribs which seem to ornament the ventral trail are in fact long bases of spines. According to Grant (1976) Septasteges WATERHOUSE& PIYASIN, 1970 is a younger synonym of Bilotina. Remarks

w i t h t r a n s v e r s e outline. D o r s a l v a l v e w i t h fiat visc e r a l disc a n d s h a r p l y g e n i c u l a t e d trail. O r n a m e n t a t i o n of v e n t r a l v a l v e of s p i n e s , w i t h s h o r t b a s e s r a d i a l l y a r r a n g e d on t h e v i s c e r a l disc a n d v e r y l o n g b a s e s , e x t e n d e d to f o r m ribs on t h e trail; t h e s p i n e s on t h e v e n t e r p r o j e c t a n t e r i o r l y at low angle, w h e r e a s t h e l a t e r a l s p i n e s a r e s u b e r e c t . T h e b a s e s o f s p i n e s on t h e t r a i l a r e 0.5-0.7 m m w i d e a n d u p to 9.5 m m long. T h e s p i n e s on t h e visc e r a l disc a r e w o r n , s h o w i n g i n t e r n a l t u b u l a r traces. B r u s h e s of c o a r s e s p i n e s o c c u r o n t h e e a r s a n d a r o w o f s p i n e s is p r e s e n t n e a r t h e c a r d i n a l m a r g i n . G r o w t h lines a r e d e n s e on t h e v i s c e r a l disc a n d on t h e t r a i l a n d d e n s e g r o w t h l a m e l l a e o c c u r at t h e a n t e r i o r m a r g i n . O r n a m e n t a t i o n o f d o r s a l v a l v e n o t c l e a r l y o b s e r v e d , b u t s e e m s to be s i m i l a r to t h a t of v e n t r a l one. I n t e r i o r of d o r s a l v a l v e w i t h v i s c e r a l disc e d g e d b y a b r o a d a n d flat m a r g i n a l ridge, c o n t i n u i n g i n t h e p l a n e of v i s c e r a l disc. C a r d i n a l p r o c e s s bilobed, w i t h d i v e r g i n g p l a t e s c o n n e c t i n g to r a i s e d a d d u c t o r p l a t f o r m s . L a t e r a l r i d g e s e x t e n d f r o m t h e card i n a l p r o c e s s to t h e m a r g i n a l ridge. Dimensions

Discussion - Bilotina yanagidai nov. sp. differs f r o m Bilotina acantha WATERHOUSE • PIYASIN, 1970 b y its t r a n s v e r s e outline, t h e n o n - s u l c a t e u m b o n a l r e g i o n a n d f e w e r spines, w h i c h h a v e s l i g h t l y s h o r t e r a n d m o r e w i d e l y s p a c e d bases. Bilotina yanagidai nov. sp. is also d i f f e r e n t f r o m Bilotina subtecta REED, 1944 b y its s h o r t e r t r a i l a n d f e w e r b u t c o a r s e r spines. T h e s p e c i m e n s d e s c r i b e d as B. aff. acantha b y Y a n a g i d a & P i l l e v u i t f r o m N o r t h O m a n (locality 753 of " B a t a i n M e l a n g e " ) differ f r o m Bilotina yanagidai nov. sp. b y f i n e r s p i n e s a n d m o r e n u m e r o u s a n d closer ribs on t h e trail.

OL12-176 OL12-177 OL12-179 OL20-7 OL25-7 OL28-2 OL37-7 OL37-10 OL46-1 OL49-2

Bilotina yanagidai nov. sp. Fig. 14.17-22; Tabl. 8 Etymology - Species named for Prof. J. Yanagida. I-Iolotype - MPUM 8457 (OL28-2), ventral valve. Type locality a n d a g e - Southeastern Oman, Huqf, Khuff Fm., section 7, bed OL28. Wordian. a n d a g e - Section 1:OL7 (1 v.v.), OL24 (1 v.v.), OL25 (5 v.v.); section 5:OL12 (4 v.v.), OL20 (1 v.v.); section 7: OL27 (1 v.v.), OL28 (1 v.v.), OL35 (1 d.v.), OL37 (4 v.v.), OL45 (1 d.v.), OL46 (1 v.v.), OL49 (1 v.v.). KhuffFm. Wordian.

Occurrence

- C o n c a v o - c o n v e x , g e n i c u l a t e d shell; maximum width at mid-length. Ears sligthly convex, e x t e n d e d . S h e l l s u b s t a n c e p s e u d o p u n c t a t e . V e n t r a l v a l v e v e r y convex, s t r o n g l y g e n i c u l a t e d , Description

(in mm) - see Tabl. 8.

Width

Length

17.1 15.5 13.3 15.3 14.1 15.1 15.5 13.4 14.4 10.2

14.2 12.2 10.7 12.3 12.1 13.9 13.9 12.1 11.7 10

TABLE8 - BiIotina yanagidai nov. sp. S u p e r f a m i l y LINOPRODUCTOIDEA S t e h l i , 1954 F a m i l y LINOPRODUCTIDAE S t e h l i , 1 9 5 4 S u b f a m i l y LINOPRODUCTINAE Stehli, 1954 G e n u s L i n o p r o d u c t u s CHAO, 1927 Type species -Productus c o r a D'ORBIGNY, 1842. Remarks

-

Linoproductus is a well known, cosmopolitan and

widely discussed genus.

687 The genus is distributed world-wide, occurring from Late Carboniferous to P e r m i a n of N o r t h and South America, Europe, Arabia, Asia and Australia.

MGL69438 MGL63176 OL12-1 OL12-2 OL12-3 OL12-8 OL12-30 OL12-68 Ol13-18 OL13-17 0L13-21 OL13-22 OL13-24 OL22-1 OL29-4 OL38-1 OL12-92 OL12-96 OL12-105 OL12-108 OL12-113 OL12-119 0L12-121 0L12-131

Linoproductus sp. aff. L. kaseti GRANT,1976 Fig. 15.1-14; Table 9 1959 Linoproductus "eora" - Hudson & Sudbury, p. 37-38, pl. 2, figs 7-9. O c c u r r e n c e a n d a g e - Section HUQF 1:1281 (1 v.v.), 1284 (1 art.); section 1:OL8 (1 v.v.), OL20 (1 v.v.), OL22 (1 v.v.); section 5:OL12 (90 v.v., 59 d.v.), OL13 (15 v.v.); section 7:OL29 (1 art., 5 v.v.), OL33 (1 d.v.), OL37 (2 v.v.), OL38 (1 v.v.), OL42 (1 v.v.), OL43 (1 v.v.), OL47 (1 v.v.); section 7his: OL51 (2 d.v.), OL53 (1 d.v.), OL54 (1 v.v.), OL60 (1 d.v.); section 9:OL57 (2 v.v.); section HS2526: JPP526B (3 v.v.). Khuff Fm. Wordian.

Concavo-convex, medium sized shell with suboval outline. Maximum width near the anterior margin. Hinge line wide. Ears flat, triangular, rugose. Ventral valve convex with a blunt umbo, slightly projecting beyond the hinge. Venter flattened, rarely slightly sulcate. Dorsal valve thin, concave, geniculated, coarsely rugose near the geniculation. Ornamentation of fine costellae, increasing in number by intercalation up to 14-18 per 1 cm at mid-lenght. Few rugae m a y occur on the ears or on the venter. Coarse and long spines, widely spaced, are present on the venter, where they are arranged in two symmetrical divergent rows, with one or two anteriorly placed medianly. The spine holes are two costellae-wide and the further pair of costellae curve around the spine bases. The spine bases are up to 1.9 mm in diameter. Thin attachment spines occur on the median part of the hinge, whereas few stout cardinal spines are present in two rows on its lateral part. Interior of dorsal valve with a strongly sessile, bilobed, trifid cardinal process; median lobe strongly sculptured by myophore; cardinal process pit filled by an elongated callus in the adults; lateral ridges short, enclosing the posterior edges of the dendritic adductor scars; blade-like breviseptum, extending to 3/4 the lenght of visceral disc. Description

Dimensions

(in ram) - see Table 9.

Discussion - Diagnostic characters of Linoproductus kaseti GRANT, 1976 are its rather small size

for the genus, its coarse spines arranged in two symmetrical diverging rows on the trail and the absence of a median sulcus. The specimens from southeastern Oman are very similar to Linoproductus kaseti differing only by a more elongated outline and finer costellae: the adults ofL. kaseti have 4 costellae per 5 mm at the anterior margin, whereas those from southeastern Oman have 6-8 costellae per 5 mm. Grant (1976) suggested that some specimen of an undescribed species of the Arab Fm. of Salt Range

Width

Length

34.2 42.4 31.7 29.9 31.7 37.9 28.2 34.4 33.2 29.1 25.4 27.5 28.3 30.1 40.4 36.4 20 30.1 25 30.2 28.1 23.5 23.8

32.7

18.1

32.3 34.3 35 40 34.7 35.4 38.6 30.7 28..8 31.6 29 31 41..9 378 20.5 29 28.6 29.2 27 22.7 20.6 16.7

TABLE 9 - Linoproductus sp. aff. L. kaseti.

(USNM collection) are comparable to L. kaseti. According to Grant (1976) also the Cambodian (Phnom Ta Kreem) Linoproductus described by Mansuy (1914) is very similar to L. kaseti. In the Roadian of Karakorum, I have recently found few specimens of Linoproductus very similar to those from southeastern Oman. O t h e r o c c u r r e n c e s - Linoproductus kaseti occurs in the Rat Buri Limestone of southern T h a i l a n d ( G r a n t 1976) and probably in the Arab Fm. of Salt Range and in Cambodia ( P h n e m Ta Kreem) (Grant 1976).

Subfamily GRANDAURISPININAELazarev, 1986 Genus

Grandaurispina

MUIR-WOOD ~; COOPER,

1960 T y p e s p e c i e s - Grandaurispina kingorum Mum-WooD & COOPER, 1960. R e m a r k s - The genus Grandaurispina was throughly discussed and investigated by Cooper & G r a n t (1975). Diagnostic characters of Grandaurispina are the quincuncially a r r a n g e d spine bases, the i n t e r r u p t i n g costellae, the strong dimples, the large halteroid spines on the ears and on the flanks, the occurrence of spines without expanded bases on the dorsal valve and the oblique lateral ridges supporting the cardinal process. Grandaurispina ranges from the K u n g u r i a n (upper part of Early Permian) to the Wordian (Guadalupian) of w e s t e r n Texas.

Grandaurispina ghabaensis nov. sp. Fig. 14.24-29; Table 10 E t y m o l o g y - Species n a m e d for Ghaba, the n e a r e s t locality on the road Muscat-Salalah. H o l o t y p e - MPUM 8462 (OL51-17), complete specimen. T y p e l o c a l i t y a n d a g e - S o u t h e r n Oman, K_huffFm., section 7bis, bed OL51. Wordian.

688 O c c u r r e n c e a n d a g e - Section 7:OL46 (1 v.v.); section 7bis: OL51 (4 art., 26 v.v., 11 d.v.); section 9:OL59 (1 v.v.); section TQB2392: JPP392A (1 art.). Khuff Fro. Wordian.

- Small size, concavo-convex, globose shell, with transversely subrectangular outline. Corpus cavity deep. Maximum width anterior to the hinge. Ventral valve strongly convex with flat ears. No sulcus. Dorsal valve slightly concave with short, geniculated trail. Ornamentation of ventral valve of costellae (2-3 per mm) interrupted by elongated spines bases, irregular and impersistent rugae, low dimples and spines. Spines are of three kinds: i) fine, with elongated bases and arranged in quincunx on the venter; ii) small to large, slightly curved spines along the hinge; iii) large, laterally to ventrally directed halteroid spines arranged in tufts on the ears and on the flanks. Ornamentation of dorsal valve of costellae interrupted by dimples; large and rounded dimples on the ears (corresponding to the large hateroid spines of the ventral valve) and oval dimples on the visceral disc; irregular rugae more prominent than on the other valve; hair-like spines without expanded bases. Interior of dorsal valve with triangular, sessile, trifid cardinal process. The lateral lobes form a triangular chamber occupied by the median lobe which is incised and rugose posteriorly. The cardinal process is supported by oblique and short lateral ridges. A low breviseptum occurs anteriorly. Description

D i m e n s i o n s (in ram) - see Tabl. 10. - Diagnostic characters of Grandaurispina ghabaensis nov. sp. are its small size, its Discussion

transverse outline, the regular, delicate but clear ornamentation, the elongate dimples of the dorsal valve, the low impersistent rugae.

OL51-17 OL51-18 OL51-19 OL51-20 OL51-21 OL51-38 OL51-56 OL51-53

Width

Length

16 17.2 13.2 8.9 16.7 13.7 13.8 12.1

11.9 12.8 12.3 8.2 13.4 12.3 10.6 10.3

TABLE 10 - Grandaurispina ghabaensis nov. sp.

Thickness 5.4 6.3 6.9

Among the western Texas species Grandaurispina ghabaensis nov. sp. resembles G. bella COOPER & GRANT, 1975, but it differs in its more transverse outline and more prominent costellae. Family MONTICULIFERIDAEMuir Wood & Cooper, 1960 Subfamily AURICULISPINAEWaterhouse, 1986 Genus Magniplicatina WATERHOUSE,1983 T y p e s p e c i e s - Cancrinella magniplica CAMPBELL,1953. R e m a r k s - Magniplicatina differs from Cancrinella TSCHERNYSCHEW~1902 by means of the absence of dorsal spines, shorter trail, coarser and more prominent ventral rugae, wider and longer ventral spines ridges. Magniplicatina differs from Costatumulus WATERHOUSE,1983 by its coarser rugae and from Coolkilella ARCHBOLD, 1986 by its less enrolled ventral valve and the lack of a striking geniculation on the dorsal valve.

Magniplicatina sp. Fig. 13.27-28

O c c u r r e n c e a n d a g e - Section HUQF 1:1281 (4 v.v., 3 d.v.), 1284 (1 v.v.). Khuff Fro. Wordian. - Shallow, concavo-convex shell. Maximum width anterior to mid-lenght. Ventral valve convex, with recurved umbo. Dorsal valve concave with long trail. O r n a m e n t a t i o n of costellae, rugae, p r o s t r a t e spines on the ventral valve and dimples on the dorsal valve. The costellae numbers about 8-9 per 5 mm at a distance of 10 mm from the umbo. The rugae are coarse and prominent, and become larger anteriorly, up to 2 mm wide. The spines occurs only on the ventral valve, where they are very long, thin and arise from elongate ridges. Spines are also present on the ears where they are moderately dense. Elongate dimples occur on the dorsal valve. Interior of the dorsal valve with bilobate linoproductid cardinal process supported by a low septum. Description

- This species resembles Magniplicatina johannis ANGIOLINI,1994 from the Roadian of

Discussion

Karakorum, but differs from it by having longer and finer spine ridges, coarser costellae and a more strongly recurved ventral valve. The available specimens differ from the Australian species of Magniplicatina (Waterhouse 1986; Archbold 1993) by their codrser radial ornamentation. Magniplicatina sp. is rather similar to Coolkilella bella (ETHERIDGE, 1918) from the Late

FIGURE 15 - 1-14. Linoproductus aff. L. kaseti GRANT. 1-6, ventral valves, MPUM 8465 (OL38-1) (1), MPUM 8466 (OL12-8) (2), MPUM 8467 (OL12-2) (3), MPUM 8468 (OL12-3) (4), MPUM 8469 (OL12-4) (5), MPUM 8470 (OL12-1) (6). 7-12, dorsal valves, MPUM 8471 (OL12-113) (7), MPUM 8472 (OL12-97) (8), MPUM 8473 (OL12-129) (9), MPUM 8474 (OL12-130) (10), MPUM 8475 (OL12-131) (11), MPUM 8476 (OL12-132) (12). 13-14, interior of dorsal valve, MPUM 8477 (OL33-1) (13), MPUM 8478 (OL51-B) (14). 15-20. Acritosia sp. 15-16, ventral (15) and dorsal (16) view of an articulated shell, MPUM 8479 (OLD). 17, ventral valve, MPUM 8480 (OL23-2). 18, posterior view of a ventral valve, MPUM 8481 (OL23-1). 19-20, ventral (19) and dorsal (20) view of an articulated shell, MPUM 8482 (OL33-3). 21-22. Cyclacantharia sp. 21, lateral view of a ventral valve, MPUM 8483 (OL46-4). 22, posterior view of a ventral valve, MPUM 8484 (OL12-175). 23-26. Cleiothyridina sp. cf. C. seriata GRANT. 23-24, ventral (23) x 1, 5 and dorsal (24) view of an articulated shell, MPUM 8485 (392A-27). 25-26, ventral (25) and dorsal (26) view of an articulated shell, MPUM 8486 (392A-28). All figures natural size, unless otherwise indicated.

6~9

? O

13

21

15

~2

14

16 18

19

24

20

'5

690 Artinskian of western Australia, differing from it by having coarser and more prominent rugae and a less enroled ventral valve. The Thai specimens described by Grant (1976, p. 156, P1. 33, figs. 17-18; P1. 44, Fig. 36) as Cancrinella sp. ind. are very similar to the available material and m a y belong to the genus Magnipli-

catina. Suborder STROPHALOSIIDINAWaagen, 1883 Superfamily RICHTHOFENIOIDEAWaagen, 1885 Family CYCLACANTHARIIDAECooper & Grant, 1975 Subfamily CYCLACANTHARIINAECooper & Grant, 1975 Genus Cyclacantharia COOPER • GRANT,1969 T y p e s p e c i e s - Cyclacantharia kingorum COOPER & GRANT, 1969. R e m a r k s - The genus Cyclacantharia has been discussed in great details by Cooper & Grant (1975). Cyclacantharia is a genus which lived cemented to the substrate by the beak and by long rhizoid spines. Cyclacantharia occurs in the Guadalupian of w e s t e r n Texas.

Cyclacantharia sp.

with sulcate trail. The sulcus is shallow and narrow, producing a small emargination at the anterior margin. Beak hidden by a large and rounded secretion of smooth shelly tissue cementing the shell to the substrate (such as bryozoans). The shelly tissue is surrounded by a circle of attachment spines, which are partially united by the tissue. The trail is densely pustolose and weakly ribbed; it is ornamented by prostrate spines which seem to bend inwardly at the anterior margin, acting for protection. The space between the spines is filled by shelly tissue, giving a costate appearence to the valve. Growth lines are also present. Dorsal valve concave resting inside the ventral valve, ornamented by spines at the anterior margin. Interior of the ventral valve costate. D i m e n s i o n s (in mm) - see Tabl. 11.

- A c r i t o s i a sp. from southeastern Oman is more similar to the Thai specimens of Acritosia (GRANT, 1976) than to the species from western Texas (Cooper & Grant 1975). However, the Oman specimens are distinguished by the lack of concentric rugae. Discussion

Fig. 15.21-22 O c c u r r e n c e a n d a g e - Section 5 : O L 1 2 (1 v.v.); section 7: OL46 (1 v.v.). Khuff Fro. Wordian.

Ventral valve conical with wide aperture. Ornamentation of irregular concentric wrinkles and long rhizoid spines. Description

-

These specimens have been placed in the genus Cyclacantharia because of their conical shape, ornamentation and absence of myocoelidium. The state of preservation prevents a specific determination. Discussion

-

Subfamily TEGULIFERININAEMuir-Wood & Cooper, 1960 Genus Acritosia COOPER & GRANT,1969 T y p e s p e c i e s - Acritosia magna COOPER & GRANT, 1969. R e m a r k s - Acritosia is a genus which lived cemented to the substrate by the beak and by tubular anchor spines. Acritosia differs from Cyclacantharia by its spheRoid shape, the absence of protective spines in a circle around the cup and its larger teguliferoid cardinal process; from Teguliferina SCHUCHERT& LEVENE,1929 by its larger size and tubular attachment spines. Acritosia occurs in the Late Carboniferous-Permian of western Texas and in the Rat Buri Lmst. of southern Thailand.

Acritosia sp. Fig. 15.15-20; Table 11 O c c u r r e n c e a n d a g e - Section 1:OL6 (1 v.v.), OL23 (2 v.v.), OL25 (1 v.v.); section 7:OL33 (1 art.), OL28 (1 v.v.), OL45 (1 v.v.); scree: OLD (1 art.). K h u f f F m . Wordian. - Concavo-convex shell with rectimarginate and lobate anterior commissure. Shell substance pseudopunctate. Ventral valve spheRoid,

Description

Width OL6-1 OL23-1 OL23-2 OLD OL33-3

12.3 16.6 23.2 21.4 18.7

Lenght 7 11.7 14 19 16.8

D.c. 11.8 12

TABLE 11 - Acritosia sp. D.c.: Diameter of the cicatrix of attachineRt.

Class RHYNCHONELLATA Williams, Carlson, Brunton, Holmer & Popov, 1996 Order ORTHIDA Woodward, 1852 Suborder ORTHIDINA Woodward, 1852 Superfamily ENTELETOIDEA Waagen, 1884 Family SCHIZOPHORIIDAE Schuchert & Le Vene, 1929 Subfamily SCHIZOPHORIINAE Schuchert & Le Vene, 1929 Genus Orthotichia HALL & CLARKE,1892 T y p e s p e c i e s - Orthis ? morganiana DERBY, 1874. R e m a r k s - The genus Orthotichia has been discussed in detail by Grant (1976) and Cooper & Grant (1976). It differs from Schizophoria KING,by the presence of long dental plates; from Acosarina COOPER & GRANT, 1969 in having a non sulcate dorsal valve, longer dental plates and a lower but longer ventral septum.

Orthotichia sp. cf. O. bistriata REED,1944 Fig. 17.1-9; Table 12 ? 1994 Acosarina aff. indica (WAAGEN)-Yanagida & Pillevuit, p. 76, pl. 4, figs 13-15. O c c u r r e n c e a n d age - Section 1:OL21 (3 art.), OL3 (8 art.); section TBQ2392: JPP392A (4 art.). Khuff Fm. Wordian.

691 Description - Large for the genus, biconvex shell with rounded to transversally elliptical outline. Hinge line narrower than maximum width which is at mid-lenght. Cardinal extremities sharp and obtuse. Anterior commissure rectimarginate or slightly sulcate. Shell substance endopunctate. Ventral valve less convex than the dorsal one. Ventral umbo not very high, recurved. Interarea concave with delthyrium closed under umbo. Dorsal valve very convex with a median flattening near the anterior margin. A small interarea is also present. Ornamentation of rows of swollen, interrupted costellae terminating in small pits. The costellae reach about 15 mm of length. In the anterior part of the valve the costellae are separated by fiat interspaces about 3-4 times wider t h a n the costellae, but housing finer costellae. Widely spaced growth lamellae occur throughout the valve, but are denser near the anterior margin. Interior of ventral valve with long dental plates extending to mid-length; a low median septum is also present, extending to nearly mid-length (Fig. 16). Interior of dorsal valve with strong socket plates and blade-like cardinal process; crura strong and curved. Dimensions

(in ram) - see Tabl. 12.

Discussion - This species is characterized by its very large size and ornamentation of impersistent unequal costellae. It fits quite well with the original description of Orthotichia bistriata REED, 1944 (p. 10, pl. 1, Fig. 5). In fact the ornamentation of costellae separated by flat interspaces with finer striae occurs also in the specimens from Oman. O. cf. bistriata differs from O. waterhousei GRANT, 1976 from the Rat Buri Limestone of southern Thailand by means of its larger size and comparatively finer ornamentation. The specimens from North Oman described as Acosarina cf. indica (W~GEN, 1884) by Yanagida & Pillevuit (1994) are very similar to O. cf. bistriata for the overall shape, ornamentation and the long dental plates. Furthermore they do not possess the deep ventral sulcus of ? Orthotichia indica (see discussion in Grant 1976, p. 36).

Other occurrences - O. bistriata occurs in the Arab Formation of Salt Range (Reed 1944) and probably in the Jebel Qamar South faunule of North Oman. Width Length Thickness OL3-1 OL3-2 OL3-3 OL21-1 OL21-2 OL21-3 392A-23 392A-26

22.8 23.1 21.7 11.3 14.2 13.5 16.9 13.6

20.5 18.7 19.3 i0.I 13.3 12.6 15.1 11.9

TABLE12 - Orthotichia sp. cf. O. bistriata

15.5 13.9 6.8 8.1 9.3 11.7 8.5

Order ATHYRIDIDABoucot, Johnson & Staton, 1964 Suborder ATHYRIDIDINABoucot, Johnson & Staton, 1964 Superfamily ATHYRIDOIDEAM'Coy, 1844 Family ATHYRIDIDAEMcCoy, 1844 Genus C l e i o t h y r i d i n a BUCKM~, 1906 Type species -Atrypa pectinifera SOWERBY,1840. Remarks - The genus Cleiothyridina has been revised and discussed in details by Brunton (1972).

Cleiothyridina sp. cf. C. seriata GR~NT, 1976 Fig. 15.23-26 Occurrence and age - SectionTBQ2392:JPP392A(2 art.). - Equibiconvex shell with transverse outline. Maximum width (20.1-20.3 ram) at about mid-length; corresponding length: 17.7-18 ram. Anterior commissure uniplicate. Ventral valve as convex as the dorsal valve with short, recurved umbo; a shallow median sulcus occurs anteriorly, starting at mid-length. Dorsal valve swollen posteriorly with a low median fold anteriorly. Anterior margin slightly emarginate. Ornamentation of closely spaced, narrow concentric lamellae, numbering about 12 per 5 mm and bearing long flat fringe spines. Description

- According to Grant (1976) C. seriata differs from the Salt Range species, in particular from those of the Amb Fm., by having less convex valves, narrower and more closely spaced lamellae and a less strongly folded commissure. However, among the Salt Range species illustrated by Reed (1944), there is one specimen (K29-14, pl. 39, figs. 4-4b) described as Cleiothyridina interposita REED, 1944, from the Amb Fm., which is more similar to the Thai C. seriata t h a n to the other specimens of C. interposita from the Chhidru Fm. (Reed 1944, p. 261, P1. 37, figs. 3-3b; P1. 38, figs. 4-4a; P1. 39, figs. 3, 5-5b). Discussion

Other occurrences - C. seriata occurs in the Rat Buri Lmst. of southwestern Thailand. Order SPIRIFERINIDAIvanova, 1972 Suborder SPIRIFERINIDINAIvanova, 1972 Superfamily PENNOSPIRIFERINOIDEADagys, 1972 Family, genus and species u n d e t e r m i n e d Occurrence and age - Section 7:OL51 (1 d.v.); section 7bis: OL57 (1 v.v., 1 d.v.). Description - Biconvex shell with transverse outline. Maximum width at the hinge. Shell substance coarsely endopunctate. Ventral interarea with perideltidial areas and closed delthyrium. Ventral valve with 4 sharp, fiat topped costae at each side of the sulcus. Dorsal valve with 4 costae at each side of the median fold. Micrornamentation of closely spaced growth lamellae.

692

2

3

4

7

8 0 I

9

0,5 cm t

10

11

FIGURE 16 - Serial sections of Orthotichia sp. cf. O. bistriata, specimen MPUM 8507 (OL3-5), respectively at 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 ram, 2.2 mm, 2.5 mm, 2.7 ram, 2.9 mm, 3.5 m m and 3.9 m m from the umbo. Sections sdriges de Orthotichia sp. cf. 0. bistriata, spgcimen ( M P U M 8507) (0L3-5), respectivement ~ 1 ram, 1.2 ram, 1.5 ram, 1.8 ram, 2 ram, 2.2 ram, 2.5 ram, 2.7 ram, 2.9 ram, 3.5 m m et 3.9 m m de F umbo.

- The wide hinge and the general shape of the available specimens suggest assignment to the families Punctospiriferidae or

D i e l a s m a sp. A

Discussion

Crenispiriferidae.

However

17.20-31;Table 13 1959 Dielasma hochstetteripersonata REED-HUDSON• SUDBU Fig.

the micrornamentation

EY, p. 50, pl. 6, figs 7, 8, 9, 12, 13.

is not well preserved, except for imbricating lamellae, preventing

a correct determination.

O r d e r TEREBRATULIDA W a a g e n , 1 8 8 3 S u b o r d e r TEREBRATULIDINA W a a g e n , 1 8 8 3 Superfamily DIELASMATOIDEA Schuchert, 1913 Family DIELASMATIDAE Schuchert, 1913

Genus Dielasma KINO, 1859 T y p e species- Terebratulites elongatus YONSCHLOTHEIM,1816.

O c c u r r e n c e a n d a g e - Section HS2526: JPP526B (2 v.v.), JPP526E (1 d.v.); section 5:O13 (2 art., 1 v.v.); section 7:OL28 (3 art.), OL35 (!9 art., 17 v.v., 6 d.v.), OL43 (8 art., i v.v.), OL46 (1 art., 3 v.v.), OL50 (6 v.v., 6 art.); section 7bis: OL51 (2 art., 3 v.v., 2 d.v.); section TBQ2392: J P P 3 9 2 A (5 art.); section AJZ2347: JPP347B (4 art., 1 v.v.). Khuff Fm. Wordian.

Description form

shape,

- Equibiconvex shell with spatuliflattened

near

the

anterior

margin.

FIGURE 17 - 1-9. Orthotichia sp. cf. O. bistriata REED. 1-2, ventral (1) and dorsal (2) view of a n articulated shell, MPUM 8487 (OL211) x 1,5.3-4, v e n t r a l (3) and dorsal (4) view of an articulated shell, MPUM 8488 (392A-26) x 1,5.5-6, v e n t r a l (5) and dorsal (6) view of a n articulated shell, MPUM 8489 (OL3-1). 7, posterior view of a n articulated shell, MPUM 8490 (OL3-3). 8-9, v e n t r a l (5) and dorsal (6)view of a n articulated shell, MPUM 8491 (OL3-2). 10-13. D i e l a s m a sp. C. 10-11, v e n t r a l (10) and dorsal (11)view of a n articulated shell, MPUM 8492 (392A-17). 12-13, ventral (12) and dorsal (13) view of an articulated shell, MPUM 8493 (392A-18). 14-17. D i e l a s m a sp. B. 14-15, v e n t r a l (14) and dorsal (15) view of an articulated shell, MPUM 8494 ( 3 9 2 A q l ) . 16-17, v e n t r a l (16) and dorsal (17)view of an articulated shell, MPUM 8495 (OL28-1). 18-19. D i e l a s m a aff. m i n o r WAAGEN. 18-19, v e n t r a l (18) and dorsal (19) view of a n articulated shell, MPUM 8496 (OL26-26), x 1,5.20-31. D i e l a s m a sp. A. 20-21, v e n t r a l (20) and dorsal (21) view of an articulated shell, MPUM 8497 (OL28-6). 22-23, v e n t r a l (22) and dorsal (23) view of a n articulated shell, MPUM 8498 (392A13). 24-25, v e n t r a l (24) and dorsal (25) view of a n articulated shell, MPUM 8499 (392A-10). 26-27,30, dorsal view of articulated shells, MPUM 8500 (OL35-21) (26), MPUM 8501 (OL35-20) (27), MPUM 8504 (OL35-24) (30). 28-29, v e n t r a l view of articulated shells, MPUM 8502 (OL35-28) (28), MPUM 8503 (OL35-33) (29). 31, interior of a dorsal valve, MPUM 8505 (OL35-23). 32. H e m i p t y c h i n a sp. Dorsal valve, MPUM 8506 (OL51-A). All figures n a t u r a l size, unless otherwise indicated.

693

20

1

11

10

7 Y

12 b

9

8

m4

21

20

22

4

32

J5

694 Greatest width anterior to midlength. Anterior commissure rectimarginate or slighty and widely uniplicate. Lateral commissure slightly concave. Shell substance densely endopunctate. Ventral valve as convex as the dorsal one, more convex in the umbonal region and flatter anteriorly. Umbo short, recurved, with permesothyrid to epithyridid, subtriangular, labiate foramen. Delthyrium closed by a symphytium partially hidden by the lip of the foramen. Umbonal slopes extending to about 1/3 the length of the valve, rather sharply marked off from the rest of the valve. Dorsal valve convex posteriorly, flatter towards the anterior margin. Growth lines weak and widely spaced, passing to growth lamellae anteriorly. Interior of ventral valve with pedicle collar and short dental plates supporting elongated teeth (Fig. 18). Interior of dorsal valve with socket ridges connected to the lateral walls by fulcral plates; hinge plate divided, with the paired inner hinge plates extending forward on the floor of the valve. Dimensions

(in m m ) - s e e Tabl. 13.

I n t r a s p e c i f i c v a r i a b i l i t y - T h i s is a quite variable species. T h e m o r e v a r i a b l e c h a r a c t e r s are t h e outline, from s p a t u l a t e to suboval, t h e l e n g t h a n d s h a r p n e s s of t h e u m b o n a l slopes a n d t h e a n t e r i o r c o m m i s s u r e from r e c t i m a r g i n a t e to slightly uniplicate. - The specimens from southeastern Oman are very similar to those described as Dielasma itaitubense (DERBY,1874) by Waagen (1882 p. 348, pl. 26, Fig. 5.) for the top of the Amb Fm. (Salt Range). Furthermore some of the Thai specimens described by Grant (1976) as Dielasma species (i.e. USNM213226, pl. 68, Fig. 23-27; USNM213225, pl. 68, Fig. 6-10) are very similar to the southeastern Oman material. In fact Grant (1976) suggested a strong similarity between his specimen USNM213226 and Dielasma itaitubense Discussion

1

OL13-9 0L28-4 0L28-5 OL28-6 0L35-3 0L35-7 OL35-20 0L35-29 OL35-33 0L35-54 OL43-2 OL43-7 OL50-6 0L50-16 0L50-4 OL50-11 392A-I0 392A-12 392A-13 392A-14

Width

Lenght

Thickness

17.3 19.9 18.5 14.6 18.5 17.2 16 18.3 23 11.6 20.3 18.7 18.4 14.3 15.7 15 21.2 19.5 20 20.3

22.6 26.1 25.3 20 26.6 26.8 24.1 26.4 29 17.7 27.2 24.2 22.2 18.6 20.9 20.3 31.3 30.5 29.6 32.2

i0.I i0.I 9.2 7.7 9.5

10.8 9.8

12.5 12.5 13.9 13.1

TABLE 13 - D i e l a s m a sp. A.

(in the sense of Waagen, not Derby). The real Dielasma itaitubense from Brasil differs in its general shape and its carinate ventral umbo. Finally Dielasma trimuense REED, 1944 and D. truncatum WAAGEN,1882 are more strongly biconvex shells and do not have the spatuliform shape, whereas Dielasma hochstetteri var. personata REED, 1944 shows two furrows in the anterior region of the ventral valve. O t h e r o c c u r r e n c e s - D i e l a s m a sp. A occurs in t h e R a t B u r i L i m e s t o n e of s o u t h e r n T h a i l a n d ( G r a n t 1976) a n d in t h e Arab Fro. of Salt R a n g e .

Dielasma sp. aff. D. minor WAAGEN, 1882 Fig. 17.18-19 Occurrence Wordian.

a n d a g e - Section 7 : O L 2 6 (1 art.). K h u f f Fro.

2 0 1

5

0,5 cm I

FIGURE 18 - Serial sections of D i e l a s m a sp. A, s p e c i m e n M P U M 8508 (OL13-9), r e s p e c t i v e l y at 1 m m , 1.8 ram, 2.2 m m , 2.5 ram, 3 m m from t h e u m b o . Sections sdri~es de D i e l a s m a sp. A, spgcimen ( M P U M 8508) 0 L 1 3 - 9 , r e s p e c t i v e m e n t ~t 1 ram, 1.8 ram, 2.2 m m , 2.5 m m , 3 m m de l'umbo.

695 - Small sized, biconvex shell with subovate outline. Maximum width of 7.3 mm at mid-length; corresponding length and thickness respectively: 9.3 mm and 3.7 mm. Anterior commissure rectimarginate. Shell substance densely endopunctate. Ventral valve with suberect umbo.

occurrence of two plicae and a median sulcus on the dorsal valve and its labiate foramen opening more dorsally.

- This specimen differs from Dielasma sp. A by its very small size.

T y p e s p e c i e s - Terebratula himalayensis DAVIDSON, 1862.

Description

Discussion

Subfamily HEMIPTYCHININAECampbell, 1965 Genus H e m i p t y c h i n a WAAGEN,1882

Hemiptychina sp. Fig. 17.32

Dielasma sp. B Fig. 17.14-17; Table 14

Width

O c c u r r e n c e a n d a g e - Section HS2526: J P P 5 2 6 B (1 art.); s e c t i o n 7 : O L 2 8 (1 art.); s e c t i o n TBQ2392: J P P 3 9 2 A (1 art.). K h u f f Fro. W o r d i a n .

Biconvex shell, with elongated oval outline. Maximum width at about mid-lenght. Anterior commissure slightly uniplicate. Shell substance densely endopunctate. Ventral valve more convex than the dorsal valve. Ventral umbo short, slighty recurved with permesothyrid foramen. Ornamentation of growth lamellae. Description

0L4-4 OL4-5 392A-17 392A-18 392A-19

-

D i m e n s i o n s (in m m ) - s e e Table 14. Discussion - These specimens differ from Dielasma sp. A by their uniplicate anterior commissure, elongated outline, anterior outline more rounded and narrower and more swollen ventral valve. They are similar to Dielasma purdoni REED, 1944 from the Arab Fro. of Salt Range.

- Strongly biconvex shell with oval outline. Maximum width at mid-length. Anterior commissure emarginate, varying from sulcate to sulciplicate. Shell substance densely endopunctate. Ventral valve more convex posteriorly. Beak short, recurved with foramen epithyridid, labiate and thickened, opening dorsally. A very low median depression may be present near the anterior margin. Dorsal valve less convex than the ventral valve. Two rounded plicae separated by a median sulcus occur anteriorly from mid-length. Ornamentation of growth lines and lamellae. Interior of ventral valve with dental plates. Interior of dorsal valve with divided hinge plate, with the paired inner hinge plates extending forward along the floor of the valve. D i m e n s i o n s (in ram) - s e e Tabl. 15 in A p p e n d i x 2. - These specimens are similar to D. breviplicatum W~GEN, 1884 from the Amb Fro. of the Salt Range. Dielasma sp. C differs from Dielasma sp. A and Dielasma sp. B by its general shape, its emarginate anterior commissure, the Discussion

13.3 10.2 12.4

O c c u r r e n c e a n d a g e - Section 7bis: OL51 (1 d.v.). I~huff F m . Wordian - Convex valve, with elongate oval outline and truncated anterior margin. Maximum width of 13.3 mm at mid-length; corresponding length of 16.1 ram. Shell substance finely punctate. Costae low, beginning at about 2/3 the length of the valve, numbering about 10 at the anterior margin. Growth lines and lamellae are very dense. Description

Discussion

-

This specimen is similar to H. hima-

Dielasma sp. C

Description

20 17.6 19.7 17.2 20

Thickness

TABLE 15 - Dielasma sp. C.

Fig. 17.10-13; Table 15

O c c u r r e n c e a n d a g e - Section 1 : e L 4 (2 art.); s e c t i o n TBQ2392: J P P 3 9 2 A (4 art.). K h u f f F m . W o r d i a n .

14.2 10.9 12.8 12 14.8

Length

Width

Length

Thickness

13.4 16.8

25.8 27.9

11.3 11.4

OL28-1 392A-11 TABLE 14 - Dielasma sp. B.

layensis (Davidson, 1862) from the Arab and Wargal Fms. of Salt Range (Waagen 1882), having a similar number of costae, great convexity and a truncated anterior margin. CONCLUSIONS

This paper gives an overview of the Guadalupian brachiopod fauna of the Khuff Fro. in southeastern Oman. Twenty-one genera and five new species are recorded and described, contributing to the general knowledge about the mid-Permian Tethyan brachiopod faunas and the productids in particular. The palaeoecological analyses of the brachiopod fauna supports the depositional model of the Khuff Fro. in southeastern Oman (Angiolini et al. 1998) and records a trasgressive-regressive cycle with the chonetids of the first member documenring the beginning of the marine transgression, the quasi-infaunal productids of the second and third members suggesting outer shelf muddy bet-

696 toms, and the increase of disarticulated attached forms in the fourth member indicating shallow water conditions. The biochronological analysis of the Khuff brachiopods leads to the establishment of a local biochronological sequence of eight faunal associations. It is worh of note that D. rugosa and B. yanagidai are not strictly facies-controlled, their FADs being linked to the installation of the deepest facies but their range extending up into the shoreface deposits ending the regressive tract. The same holds true for C. manaroUai nov. sp., which only occurs in the most contrasted facies of first and second members. O. sp. cf. O. bistriata and N. (S.) arabicus are restricted to the shoreface deposits of the first member, but do not reappear in the shoreface deposits of the fourth member: their last appearence may thus be a potential biochronological marker. The brachiopod fauna of the Khuff Fm. of southeastern Oman is of particular importance in establishing mid-Permian correlation. In fact, the accompanying conodonts, molluscs and foraminifers constrain to the Wordian the age of the brachiopod assemblage, which shows strong affinities with the faunas of the Amb Fro. of Salt Range (Pakistan) and the Rat Buri Lmst. of southern Thailand. A c k n o w l e d g e m e n t s - The manuscript has greatly benefited of the revisions by P. Racheboeuf, C.H.C. Brunton, M. Gaetani and J.M. Dickins. Field work in Oman was supported by the Peri-T~thys Project with the assistence of J. Roger and J-P. Platel. A. Nicora, A. Baud, J. Broutin, J. Marcoux, A. Pillevuit, H, A1 Hashmi and the Oman Ministry of Petroleum and Minerals are warmly thanked.

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Paleontology of Southeast Asia. Contributions to Geology and Palaeontology of SE Asia LXXXI, 8: 69-96. YANAGIDAJ. • PILLEVUITA. 1994 - Permian Brachiopods i~om Oman. Memoirs Faculty of Sciences, Kyushu University, Set. D., Earth Planetary Sciences, 28, 2: 61-99. L. A N G I O L I N I Dip. Scienze della Terra Universit~ di Milano Via Mangiagalli 34 1-20133 Milano ([email protected]) H. B U C H E R Centre des Sciences de la Terre, ERS 2042 Universitg Claude-Bernard, Lyon I 27-43 Bd. du 11 novembre F-69622 Villeurbanne

(bucherC~miv-lyonl.fr)

698 A P P E N D I X 1 - Distribution of the taxa in the composite section and in the 7 partial sections. codes of taxa

CODES 01obi 02pra 03ddi 04nar 05cma 06hay 07dru 08kte

09cal 10jom llbya 121ka 13ggh 14mag 15cyc 16acr 18dia 19dim 20dib 21dic 22hem

TAXA O. cf. bistriata P. raffaellae D. cf. diversa

N. (S.) arabicus C. manarolla~ Haydenella sp. D. rugosa K. tescorum

Sections

Calliprotonia sp J. omanensis B. yanagidai L. aff. kaseti G. ghabaensis Magniplicatina sp. Cyclacantharia sp. Acritosia sp. Dielasma sp. A Dielasma aff. minor Dielasma sp. B Dielasma sp. C Hemiptychina sp.

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