Chapter D4d Scaphitid ammonites of the Campanian-Maastrichtian at Tercis les Bains (Landes, France)

The Campanian-Maastrichtian Boundary G. S. Odin (editor) 2001 Elsevier Science B.V.

CHAPTER D4d

Scaphitid ammonites of the Campanian-Maastrichtian at Tercis les Bains (Landes, France) M. Machalski & G. S. Odin

Sommaire Le site geologique de Tercis les Bains (Landes, France) a livre des ammonites scaphitidees dans les niveaux du Campanien superieur et du Maastrichtien. L'essentiel des specimens a ete trouve autour de la limite entre les Etages Campanien et Maastrichtien entre les cotes 94 et 127; vingt specimens proviennent de 1'Unite Les Vignes, entre les cotes 160 et 172; une seule trace a ete observee dans r Unite Bedat du Maastrichtien superieur. Parmi les 124 specimens etudies, 82 representent Hoploscaphites pumilus (Stephenson, 1941), 3 sont identifies comme Hoploscaphites sp. cf. constrictus (J. Sowerby, 1817) et le reste est rapporte a Hoploscaphites sp. (probablement diverses especes). Une abondante collection de I'espece americaine H. pumilus est ainsi decouverte en Europe pour la premiere fois et 19 specimens sont illustres. Le specimen le plus ancien trouve en place provient de la cote III 94,2 (specimen 90); des exemplaires d'assez bonne qualite sont presents jusqu'au niveau 126 et quelques autres sont presents jusqu'au niveau V 170 (specimen 289). Le taxon est done caracteristique du Campanien terminal et du Maastrichtien inferieur tel que defini dans le site. Hoploscaphites constrictus anterior Blaszkiewicz, 1980 de la partie superieure du Maastrichtien inferieur de Pologne qui serait mieux nomme H. anterior (Blaszkiewicz, 1980) selon nous, semble etre morphologiquement intermediaire entre H. pumilus et H. constrictus. II a aussi ete identifie dans la partie inferieure du Maastrichtien inferieur

de Nagoriany (Ukraine). D'apres notre etude, des formes indubitables de H. constrictus ne sont pas evidentes a Tercis; les quelques specimens rapportes a Hoploscaphites sp. cf. constrictus sont tous du Maastrichtien inferieur. On notera enfin que les formes non determinees specifiquement {Hoploscaphites sp.), dont certaines possedent des caracteres qui pourraient les rapprocher de H. constrictus, sont aussi preferentiellement localisees dans le Maastrichtien des sa base. 1. Introduction The field work carried out by one of us in the Tercis les Bains geological site between 1992 and 1997 has resulted in a fairly rich collection of late Campanian and early Maastrichtian scaphitid ammonites. The present study discusses the taxonomy and distribution pattern of these ammonites. The study is based on 124 specimens examined by M. Machalski during his stay in Paris in May 1997; more specimens were found later. The specimens from Tercis described in this paper are registered with a number corresponding to their finding order among other ammonites from the site. They are stored at the Universite Pierre et Marie Curie in Paris. They may be quoted elsewhere as "GSO AMMO n"; in this volume, they are simply quoted by their number. Each specimen has been referred to its finding place, which can either be the main outcrop on platforms I to V or the E outcrop, and to its level indicated as it is marked in the field (for example "II 97.5" means "specimen found on platform II of the main outcrop at level 97.5"). When a specimen has been collected loose.

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the nearest level is indicated in brackets. A few specimens were collected from the northern wall of the quarry (their precise level is uncertain); several specimens were collected from fallen rocks following dynamitizing of the northern wall: their provenance is the mid portion of the pale-flintbearing subunit (above the stage boundary). A single specimen comes from the upper Maastrichtian B outcrop. The studied material will be stored in the planned Museum at Tercis. Plaster casts of some specimens are available on request (specimens: 52, 187, 214, 273). The preservation is generally poor; frequently, only one side of the composite mould (never the shell) is available. The shaft body chamber is more commonly preserved than the spire. This spiral portion of the fossil is often crushed and consists of a thin layer of sediment (see views 31 & 36). Of the 124 specimens studied here, half a dozen show more than one well-preserved side (specimens 52, 187, 214, 253, 273, 284); also reasonably preserved are specimens 56, 123, 159, 254, and 270. In short, scaphitids are not rare but good specimens are; in addition, their removal from the rock requires caution; for these reasons, sampling of this material is not allowed without a written permission from the people responsible for the geological site. The comparative material illustrated in this paper comprises specimens from the following sources: collection of A. Blaszkiewicz housed in the Museum of Polish Geological Institute, Warsaw, Poland (abbreviated IG), collection of M. Machalski. Institute of Paleobiology, Polish Academy of Sciences, Warsaw, Poland (abbreviated ZPAL) and collection of R. Marcinowski, Institute of Geology, Geology Department, Warsaw University, Warsaw, Poland (abbreviated IGP/RM). 2. Previous work To our knowledge, the first report on a scaphitid ammonite in Tercis is that of Delbos (1854), who quoted "Scaphites compressus d'Orbigny, 1848" from the quarry. Jacquot & Raulin (1888, p. 287) quote the same taxon from levels below the Mur de Bedat. De Grossouvre (1901, p. 398) mentioned "Scaphites constrictus J. Sowerby, 1817" from the flint-free limestone of the main quarry. However,

the present study shows that specimens corresponding to H. constrictus are known exclusively from the flint-bearing limestone of the Les Vignes Unit. So, De Grossouvre probably found what is called H. pumilus in the present paper since the latter species occurs in the uppermost part of the flintfree d'Avezac Unit. Hancock & Kennedy (1993) reported and illustrated H. constrictus from Tercis; they wrote (p. 166): "there are a number of unregistered specimens in the SP (Sorbonne, Paris) and UPST (University P. Sabatier, Toulouse) Collections", but one of us (G.S.O.) failed to locahse any scaphitid from Tercis in these collections. M. Bilotte (the curator) just indicated that, in Toulouse, there are only specimens from the Pyrenees (Kennedy, Bilotte et al. 1986). Up to 1995, only a single scaphitid species, H. constrictus, was thought to occur in Tercis. In 1995, W. J. Kennedy (Oxford) and W. A. Cobban (Denver) independently found that, besides H. constrictus, H, pumilus was also present in a selection of Tercis specimens sent to them. Both species have been subsequently reported, but not illustrated, by Ward & Orr (1997). 3. Systematic palaeontology 3.1. Methodologic remarks The taxonomic part of this study is based on two important principles: 1) The dimorphism in scaphitid ammonites is accepted here, macroconchs (M) differing from microconchs (m) in having usually larger-sized shells, a higher whorl of the body chamber and a distinct umbilical bulge on the body chamber (Makowski, 1962; Cobban, 1969; Kennedy, 1989; Machalski, 1996a). Some authors regarded macroconchs (M) as females and microconchs (m) as males (Makowski, 1962; Cobban, 1969), but this interpretation may be questioned due to the lack or almost total absence of one "sex" in some sections and/or areas. For example, Birkelund (1982) recorded about 260 macroconchs of Hoploscaphites constrictus (J. Sowerby, 1817) accompanied by only one questionable microconch from the ca. 140 m thick section of the Maastrichtian deposits in Hemmoor, Germany (see Matyja, 1986, for Jurassic examples of this kind).

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2) The population concept of the species is used instead of the morphologic one (see Callomon, 1985; Callomon et al., 1992; Dzik, 1990). The holotype is thus treated as an indicator of the temporal and spatial position of the type population rather than the morphological standard for identification of the species. The proper reference standard for the species identification is its type population, coming from the same locality and the same level as the holotype. This standard rarely fulfils the criteria of the true neontologic population. It is, however, pragmatic to treat all topotypic material of the species as its "type population" as long as it has not been proved that it is heterogeneous with respect to geologic time (Dzik, 1990). Identification of the species in a section thus results in the comparison between the investigated material and the "type population". 3.2. Systematic palaeontology Order Ammonitina Zittel, 1884; Suborder Ancyloceratina Wiedmann, 1966 Superfamily Scaphitaceae Gill, 1871; Family Scaphitidae Gill, 1871 Subfamily Scaphitinae Gill, 1871; Genus Hoploscaphites Nowak, 1911 Hoploscaphites pumilus (Stephenson, 1941) 71852 Scaphites constrictus d'Orbigny. var. Kner: p. 300; PL 15;fig.13 1941 Scaphites pumilus - Stephenson: p. 426; PL 90: fig. 10-12 71969 Scaphites {Hoploscaphites) elatensis - Lewy: p. 129; PL IV:fig.2a-c 1974 Hoploscaphites pumilus (Stephenson) - Cobban: p. 16; PL 11:fig.9-12 1986 Hoploscaphites pumilis [sic] Stephenson [sic]Kennedy et al: p. 1018; PL 5: fig. 18-20 71987 Hoploscaphites constrictus (J. Sowerby, 1817) Kennedy & Summesberger: p. 34; PL 6: fig. 10-12 1993 Hoploscaphites pumilis (Stephenson, 1941) Kennedy & Cobban: p. 426; fig. 9.3, 9.6, 12.5, 16.1-16.26, 17.1-17.21. 1993 Hoploscaphites constrictus (J. Sowerby, 1817) Hancock & Kennedy: p. 166; PL 20: fig. 1-4. 2001 Hoploscaphites pumilus (Stephenson, 1941) Ktichler et al. this volume, chap. E3: PL III: 4, 5.

Material: 82 specimens preserved as moulds and imprints, most of them more or less incomplete and affected by post-mortem distortion. Discussion: The species was based on a single microconch from the Nacatoch Sand of Navarro County, Texas, U.S (Stephenson 1941), which is probably of early Maastrichtian age (Kennedy et al., 1986). Cobban (1974) subsequently described an additional specimen from the Nacatoch Sand and three specimens from the base of Navesink Formation, New Jersey ("?upper Campanian" according to Kennedy et al., 1986). Kennedy & Cobban (1993) described several specimens from the Saratoga Chalk (upper Campanian Nostoceras hyatti Zone). The first identification of the species in Europe by Kennedy et al. (1986) was based on a single specimen from "the Marnes de Plagne of Paillon, Haute Garonne, France" thought to be upper Campanian. According to M. Bilotte, (personal communication to G. S. Odin, IX-1997), there are at present 2 specimens of H. pumilus (identified as such by W. J. Kennedy) known from the Petites Pyrenees. The first one is in the collection of the Laboratoire de Geologic (Toulouse) and is labelled "Le Picon de Roquefort". At Le Picon de Roquefort, it must come from the Marnes de Saint-Martory facies which outcropped over more than 100 m in the past. The Marnes de la Plagne initially quoted by Kennedy et al. (1986) are strictly Campanian in age. But the Marnes de SaintMartory, (partly a lateral equivalent and partly a late deposit of the Marnes de La Plagne) deposited during an interval of time from the Campanian (late?) to the Maastrichtian (early?) since they locally overlie the Marnes de La Plagne (Bilotte, personal communication, IX-97). The second specimen, a portion of a body chamber, was collected nearby the Larin farm (locality Le Paillon) from the grey marls of the same facies. At Le Paillon, the level it comes from could be located within the Gansserina gansseri foraminiferal zone (latest Campanian?/early Maastrichtian). The species was subsequently identified in the Tercis section by W. J. Kennedy, W. A. Cobban (personal communications, 1995), and Ward & Orr (1997). The "type population" of the species from the Nacatoch Sand consists of two specimens, only the

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holotype being illustrated (Stephenson, 1941, PL 90, fig. 10-12; Kennedy & Cobban, 1993, fig. 17.12). However, it seems that the material coming from other levels and described by Cobban (1974) or Kennedy & Cobban (1993) does not significantly differ from the topotypic one. Both papers show the species as variable and dimorphic, characterised by a robust "hump-backed" shell with: 1) flat flanks of the shaft, 2) a flank groove at the hook resulting in its concave profile, 3) sharply defined ventro-lateral and umbilical shoulders and a trapezoidal cross-section of the shaft (especially in microconchs), 4) a venter more inflated on the hook than on the shaft, giving an impression that the ventro-lateral tubercles migrate into the outer flank, 5) marked expansion of the whorls, 6) presence of inner ventro-lateral tubercles on the phragmocone in some specimens; these tubercles are offset the outer ventro-lateral tuberculation which starts at the end of the spire, 7) a relatively long shaft and a big gap between the hook and the phragmocone in most specimens (especially in microconchs; macroconchs are less long-shafted and their hook is closer to the phragmocone), 8) an apertural angle about 100° in macroconchs and 90° in microconchs, 9) indistinct, broad ribs on the shaft. The venter ofH. pumilus was said by Kennedy & Cobban (1993) to be variable, often undulating, with closely spaced even ribs in some specimens, or devoid of ribs in others, or else with rare distant ribs in others. This variation, however, seems to be caused by preservation. Some of the American specimens show every third ventral rib more accentuated (Kennedy & Cobban 1993, fig. 16.22). The specimens with no ventral ribs or with only a few distant ribs in Kennedy & Cobban (1993) seem to be more worn than the rest of the material. They possibly represent cases of mould-reworking which led to the total elimination of the ventral ribbing or only left the strongest ribs. The ribbing of the North American H. pumilus seems to be actually com-

posed of evenly spaced ribs distributed on the whole section of the body chamber. Macroconchs and microconchs are said by Kennedy & Cobban (1993) to be equal in numbers in the North American material, but among their specimens only those in fig. 16. 7-8, 12-13, and 22-26 fit the macroconch criteria. The largest specimen illustrated by Kennedy & Cobban (1993, fig. 17. 16-19) is certainly a microconch, not a macroconch as suggested in the text. This is a rather curious reversal of the common situation with large sized specimens being macroconchs. The material from Tercis generally shows many common points with the above characteristics of H. pumilus (plate I) although usually deformed and fragmented during collection. Both macroconchs (the best preserved is specimen 214; views 25-26; reconstructed in figure lA) and microconchs (e. g. specimen 263, views 15-16) can be distinguished. Many poorly preserved specimens cannot be attributed to either of these categories. Undoubted microconchs range from 24 to 35 mm and the macroconchs from 26 to 47 mm in diameter (the exact figures cannot be given due to the postmortem distortion of the specimens). The largest macroconchs thus exceed the length of the largest microconchs and there is a significant overlap in size between the two dimorphs. Specimen 56, views 27-29 (diameter 43 mm) may be a giant microconch, like the one figured in Kennedy & Cobban (1993, fig. 17. 16-19). However, its umbilical shoulder is destroyed which makes its assignment to either of these categories problematic. The features of H. pumilus in the present material are: i - flat or concave flank profile and a sharply defined ventro-lateral shoulder (e. g. views 3-4, 9-10, 23-24, 25-26), ii - the trapezoidal cross-section (especially view 4), iii - the hook well separated from the phragmocone in microconchs (views 15, 17, 27), iv - the apertural angle close to normal (e. g. view 27), v - apparent

Plate I. Hoploscaphites pumilus (Stephenson, 1941) from the upper Campanian and lower Maastrichtian of Tercis, France. M: macroconchs, m: microconchs; all xl. 1-2: 208, IV 97.3; 3-4: 314, V 115.3; 5-6: 52 (?m), II (93.5); 7-8: 268 (m), V 115,6; 9-10: 313, IV 97,5; 11-12: 284 (m), V 125.8; 13: 312, level E 52.5; 14: 232 (m), II 97.3; 15-16: 263 (m), V 115.3; 17-18: 273 (m), V 116,6; 19-20: 150 (m). III 110.8; 21-22: 123 (M), (-120-125); 23-24: 119 (m), IV 120.5; 25-26: 214 (M), III 114.7; 27-29: 56 (?m), III 117.7; 30-31: 270 (M), V 115.9; 32: 187 (M), E 48.8; 33-35: 254 (M), E 3.4; 36: 159 (M), (-115-125). N.B.: reduced 90%.

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migration of the ventro-lateral tubercles onto the flank toward the aperture (e. g. views 25-26, 36), and vi - presence of evenly spaced ventral ribs over the whole diameter of the body chamber contrasted with indistinct flank ribbing in the shaft (e. g. views 34-35). There are also differences between the Tercis and the North American specimens. The Tercis specimens are in average more compressed than those from the Nacatoch and Saratoga (but see views 3-4, 32 for notable exceptions). This is almost certainly an effect of post-mortem distortion (the Tercis material is deformed to various degrees whereas that from North America is represented by essentially undeformed internal moulds). Another effect of compaction is the accentuation of the ventro-lateral shoulders by oblique deformation (views 9-10, 23-24), whereas the heavy lateral one almost totally obliterates them (e. g. views 11-12). Similarly, the open apertural angle in specimen 150 (view 19) which is otherwise apparently linked with other specimens by its ornamentation, seems to be caused by post-mortem deformation. Some differences between the Tercis and the North American collections cannot simply be explained by post-mortem distortion. Some of the American specimens are significantly larger than the largest specimens of Tercis. The gap between hook and spire is usually smaller in microconchs from Tercis than in some of their North American counterparts. This is well visible when comparing e. g. the specimen illustrated in view 17 herein and that in figure 17.13 in Kennedy & Cobban (1993). However, when restored, the specimen in views 27-29 seems to show a gap between hook and spire of the same magnitude as in the extreme North American specimens. Only a few specimens from Tercis (specimens 263, 273, 159: views 15-18; 36) show a faint inner ventro-lateral tuberculation of the phragmocone (this may be partly due to postmorten crushing). Some specimens from Tercis find no match in the American material, being more slender and finely ribbed (e. g. specimen 208, views 1-2), but they seem to be linked with others by intermediate forms. As concerns the shell outline, it seems that the microconchs of the Tercis site fit the American material better than the macroconchs. Some of the

macroconchs from Tercis are more rounded in outline than their distinctly "hump-backed" American counterparts, and are closer in this respect to Hoploscaphites anterior (figure 1 A, B and next section). However, as H. pumilus was defined on microconch, and taking into account the differences in preservation, it seems that the Tercis material does not deserve separation even at the sub specific level. H. pumilus seems to have been occasionally confused with Hoploscaphites constrictus (J. Sowerby, 1817). The latter, as defined by its "type population" from the upper Maastrichtian of Cotentin (Kennedy, 1986b: see views 49 to 53), is a very variable species ranging from robust specimens with coarse ribbing to slender and finely ribbed ones. The species is characterised by the final hook rather tightly attached to the phragmocone (both in macroconchs and microconchs), the apertural angle generally about 120° - 130°, and the venter mostly devoid of ribs in the main part of the shaft (often

Fig. 1. Reconstructed macroconchs of some Campanian and Maastrichtian scaphitids: A: Hoploscaphites pumilus (Stephenson, 1941), based on specimen n°214, level HI 114.7, uppermost Campanian, Tercis; B: Hoploscaphites anterior (Blaszkiewicz, 1980), based on specimen IG 1,310.11.283, Sladow, Miechow region, upper lower Maastrichtian, Poland. C & D: Hoploscaphites constrictus (J. Sowerby, 1817) from Kazimierz Opoka unit, upper upper Maastrichtian, Poland, based on specimens ZPAL Am. XII/62 and IGP/RM Na 1, respectively, both from the Nasilow quarry (taken from Machalski, 1996).

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with an incipient siphonal row of tubercles as seen in a typical specimen from the upper upper Maastrichtian of Poland: views 59, 60). The ventrolateral shoulder is rounded in macroconchs. It is angular and sharply defined in some microconchs, but in such cases the body chamber cross-section is rectangular rather than trapezoidal as in H. pumilus. Moreover, H. constrictus never develops a second row of ventro-lateral tubercles, which may be present in H. pumilus (Kennedy & Cobban, 1993). Hancock & Kennedy (1993) illustrated two scaphitid ammonites from Tercis which they referred to as Hoploscaphites constrictus (J. Sowerby, 1817). Both are incomplete macroconchs, but the relatively low whorl of the shaft, flat flanks, distinct ventro-lateral shoulder and the presence of regular ventral ribbing in the shaft, all indicate that they are better assigned to H. pumilus. Hoploscaphites constrictus anterior Blaszkiewicz, 1980 is a subspecies which was separated from the nominate one "in a smaller apertural angle, not so close contact of body chamber and phragmocone, and a smaller degree of flattening of the ventral side of shaft" (Blaszkiewicz, 1980). However, it differs so much from the type material of H. constrictus, that its separation at specific level, as H. anterior (Blaszkiewicz, 1980) is proposed here. The species comes from the upper lower Maastrichtian (Belemnella occidentalis Zone) of Poland and is intermediate in morphology between H. pumilus and H. constrictus. Only macroconchs were illustrated by Blaszkiewicz (1980). Two of his specimens, including the holotype, are re-illustrated here (views 50-52, 54-56; figure IB). The smaller apertural angle (95° according to Blaszkiewicz) and the shell outline locate the macroconchs of H. anterior close to those of H. pumilus which is probably its ancestor. The well rounded ventro-lateral shoulder, the lack of ventral ribs near the base of the shaft, and the lack of inner ventro-lateral tubercles on the spire place H. anterior close to H. constrictus. An unpubUshed microconch ofH. anterior seen by one of us (M.M.) in the collections of the Pohsh Geological Institute (upper lower Maastrichtian, locality Tur Gorny, Miechow Trough, Poland, MUZPIG 1410.II.4.), shows the apertural angle and gap between the phragmocone and the hook very

similar to those of the published macroconchs of the species. Some other records of H. constrictus from the European lower Maastrichtian seem to actually represent H. anterior or forms intermediate between the latter species and H. pumilus. This concerns the specimens from Nagoriany (Nagorzany in old Polish literature) near Lvov (Ukraine) described by Kner (1852), Favre (1869) and Kennedy & Summesberger (1987). According to Kennedy & Summesberger (1987) and Christensen (1987) the age of the Nagoriany sandy chalk, called the Nagorzany Opoka, is early early Maastrichtian (note: another important Maastrichtian ammonite Hoploscaphites tenuistriatus (Kner, 1852) does not occur in Nagoriany as stated by Kennedy & Summesberger 1987 and Kennedy 1993, but in the Lemberg Opoka of Lvov, which overlies the Nagoriany Opoka and is of B. junior age). The only published indisputable macroconch from Nagoriany (Favre, 1869, PI. 5, fig. 2; Kennedy & Summesberger, 1987, PI. 6, fig. 13-15), with an apertural angle at about 100°, fits very well the macroconchs of H. anterior as illustrated by Blaszkiewicz (1980). Microconchs from Nagoriany are generally robust and have a distinct gap between the hook and the phragmocone, an apertural angle at about 90°-100°. They fit very well the unpublished microconch of H. anterior in the collections of the Polish Geological Institute. However, the specimen of Kennedy & Summesberger (1987, PL 6, fig. 10-12) shows a trapezoidal cross-section and concave flanks of the body chamber, like in H. pumilus. The specimen of Kner (1852, PI. 15, fig. 13) even seems to show inner ventro-lateral tubercles on the phragmocone, but it is badly crushed. On the other hand, some more slender and finely ribbed microconchs from Nagoriany with a relatively small gap between the hook and the spire (Kennedy & Summesberger, 1987, PI. 6, fig. 6-9) do not resemble H. pumilus at afl. Thus, most of the material from Nagoriany illustrated yet is better to be provisionally assigned to H. anterior (the investigation of a new material from the site by one of us, M.M., should clarify its taxonomic composition). Atabekian (1979) grouped the material from Nagoriany illustrated by Favre and Kner with some

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specimens of H, constrictus from Cotentin. The latter are stout, coarsely ribbed specimens with a relatively long shaft and a smaller apertural angle than the rest of the "type population" (Kennedy, 1986b, PL 15, fig. 29-31). Atabekian (1979) grouped them into the new genus and species, Mesoscaphites grossouvrei (nomen nudum according to Kennedy, 1986b). The "aberrant" specimens from Cotentin seem to represent extreme variants of their own population rather than a separate form (cf. Kennedy, 1986b). Similarly robust and coarsely ribbed specimens, although with a greater apertural angle, occur in the upper upper Maastrichtian of Poland (Machalski, 1996a) (figure ID; views 57, 58), Denmark (Birkelund, 1993) and the Netherlands. The resemblance of such forms to the early early Maastrichtian specimens from Nagoriany is superficial. They are distinctive enough by their large diameter, coarse ornament, inflated flanks and age. It should also be noted that such specimens sometimes differ from the rest of "typical" H. constrictus in having pronounced ventral ribbing, but it only occurs when the distinct flank ribbing in the shaft is present and of the same strength (view 57; figure ID). Hoploscaphites elatensis (Lewy, 1969) from the uppermost part of the Mishash Formation, Israel, is late Campanian in age and seems to be very close to, if not conspecific with, H. pumilus. It is characterised by the marked expansion of the phragmocone, the venter fully ornamented with distinct ribs, and the trapezoidal cross-section of the body chamber (Lewy, 1969). Inner ventrolateral tubercles on the spire seem to be present in the only specimen illustrated by Lewy (1969). A relatively small gap of 2-3 mm between the phragmocone and the hook is present in H. elatensis (Lewy, 1969). This feature locates it near the material from Tercis rather than near that from

North America. H. pumilus is present in the lower Lower Maastrichtian of Navarra Province, northern Spain. Two specimens of the species, kindly send for examination to M. Machalski by T. Kiichler, reveal the typical morphology of the species. One of them, a macroconch Jul 66/1 (see plate III, figure 4-5 in Kiichler et al., this volume, chap E3) was found in the deposits of the Pachydiscus neubergicus/Pachydiscus epiplectus Zone sensu Kiichler (1998) in Juandechaco near Imiscoz. Another one, a presumable microconch (level A-3 unregistered) comes from the same zone from Imiscoz. The species seems to be missing from the upper Campanian of the European areas East of France, e. g. in the well sampled outcrop of the Nostoceras hyatti (= Nostoceras pozaryskii) Zone in Piotrawin, Poland (see Blaszkiewicz, 1980; Kennedy, 1993a; Machalski, 1996b for faunal lists). It is thus reasonable to conclude that the European record of H. pumilus might reflect its slow migration eastwards, the areas of the present-day middle and eastern Europe being reached by the species during the early Maastrichtian provided that the Nagoriany records represent true H.pumilus. Occurrence: upper upper Campanian and lower lower Maastrichtian of the United States, France, Spain, Tunisia (personal communication F. Robaszynski, VII-2000), ?Israel, ?Ukraine. Hoploscaphites sp. cf. constrictus (J. Sowerby, 1817); views 37-40 Compare: 1986b Hoploscaphites constrictus (J. Sowerby, 1817) Kennedy: p. 64; PI. 13: fig. 1-13, 16-24; PI. 14: fig. 1-38; PL 15; text-fig. 9, llA-H.

Material: Three incomplete moulds. Discussion: Specimen 134 (views 37-38) is a fragment of body chamber with the final hook. It is

Plate II. 37-40: Hoploscaphites sp. cf. constrictus, Tercis, France. 37-38: 134 (m), E 54.9; 39: 186 (m), E 48.7; 40: 43 (m), MN 123?: 41-46: Hoploscaphites sp., Tercis, France. 41: 66 (m), 117.0; 42: 253 (m), E 3.3; 43: 139 (?m), E 49.5; 44: 290 (?m), V 170; 45-46; 138 (m), E 49.5; 47-49, 53, 57-60: Hoploscaphites constrictus. 47, 48, 57-60: upper upper Maastrichtian, Nasilow quarry, Poland: 47: ZPAL Am. XII/16 (m); 48: ZPAL Am. XII/10 (m); 49, 53: upper? upper Maastrichtian, Cotentin, France. 49: Specimen 6411 labelled Orglandes coll. Universite P. & M. Curie, Paris (m) (plaster cast); 53: Plaster cast of lectotype of the species (M) (original is BMNH C36733), courtesy to Dr. A. Blaszkiewicz. 57-58: IGP/RM Na 1 (M); 59-60: ZPAL Am. XII/62 (M); 50-52, 54-56: Hoploscaphites anterior, upper lower Maastrichtian, Miechow region, Poland. 50-52: IG 1,310.11.283 (M), Sladow; 54-56: holotype IG 1, 310.11. 14 (M), Polichno. N.B.: original plate reduced 93%.

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a microconch and seems to be undistorted. It shows inflated flanks and details of ribbing matching wefl some coarsely ribbed microconchs of H. constrictus from Cotentin (Kennedy, 1986b, PL 15, fig. 4-9; also PL 2, view 49 herein). The specimen was found at level E 54.9 ( - P 169). Specimen 186 (view 39), also a microconch, is deformed and incomplete. It shows the same coarse ribbing as the specimen above. Moreover, its apertural angle is comparable to those in microconchs of H. constrictus from Cotentin. The specimen comes from level E 48.7 ( ~ P 163). The last microconch, specimen 43 (view 40), from the northern wall, level MN 123 ( ~ P 123?), resembles some more finely ribbed microconchs of H. constrictus from Cotentin. The poor preservation of the discussed specimens precludes unambiguous specific assignment. Another obstacle to identify H. constrictus at Tercis is that the species has been originally defined based on a macroconch and the unquestionable macroconchs comparable to the type material are absent in the section. In our opinion (M.M.), none of the specimens under study in the Tercis material can be firmly assigned to H. constrictus. This contrasts with the opinion of Ward & Orr (1997), W. J. Kennedy, and W. A. Cobban (chap. D4b and D4c), who identified this species in Tercis with confidence. Hoploscaphites sp. (probably several species); views 41-46 Material: 39 specimens preserved as internal and external moulds. Discussion: The specimens assigned here are either phragmocones which are indeterminable at the species level, or poorly preserved adults (views 41-46). Among the latter there are incomplete specimens which are either H. pumilus or H. constrictus (views 41, 43, 44). Specimens 253 and 138 (views 42, 45, 46) are better preserved and resemble finely ribbed microconchs of H. constrictus from Cotentin and other regions (Kennedy, 1986b; views 47, 48), but there are some features which exclude the assignment to this species. Specimen 138 reveals the inner ventrolateral tubercles typical of H. pumilus. Specimen

253, in turn, shows the lateral groove on the hook and the ventral ribbing over the whole diameter of the shell. Moreover, its evident deformation does not allow to evaluate the original apertural angle. Both specimens may merely be finely ribbed and slender variants of H. pumilus. 4. Vertical distribution of scaphitid ammonites in Tercis The distribution of the 124 studied specimens of the genus is shown in figure 2 along the two sections investigated, i.e. the main outcrop (section P) and the E outcrop about 400 metres apart. The lithologic correlation between these two outcrops is explained elsewhere (chap. A5) with level E 0. 0 contemporaneous with level P 114.1. All specimens found in every one metre interval are summed together. The distribution shown in figure 2 correlates from one (P) to the other (E) outcrop well. It also indicates that the genus is rather discontinuously represented in the investigated sections. Three Hoploscaphites peaks can be seen: 1) between levels 94-99, 2) between levels 114 and 123 and 3) above level 160. The abundance of the specimens around the Campanian-Maastrichtian boundary is probably overemphasised due to the special attention paid to this interval but the scaphitid ammonites are not rare across the stage boundary (figure 2). The only scaphitid species identified with certainty in the present study is H. pumilus. Its first occurrence in Tercis is recorded here at level II 94.2 (specimen 90). Specimen 52 (view 5-6, level II 93.5) was not collected in situ. The last common occurrence of the taxon is at level 126.6; above this level, few well preserved specimens are referred to H. pumilus; the youngest seems to be specimen 289 collected from V 170; another specimen: 312 (view 13) is of approximately similar age. The range of H. pumilus thus includes Campanian and Maastrichtian levels in contrast to that stated for the species by Ward & Orr (1997), who reported it from the interval between levels 98 to 103 (see Ward & Orr 1997, figure 3). Three specimens provisionally referred to H. sp. cf. constrictus in our study were found from levels MN 123 (specimen 43), E 48.7 (specimen 186),

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and E 54.9 (specimen 134). Additional specimens here referred to H. sp. also show some characters which could be compared to those of H. constrictus including specimen 66 (level 117.0, view 41), or specimen 253 (level E 3.3, view 42). According to Ward & Orr (1997) H. constrictus occurs in the Tercis quarry from level 120 to 150. There is a significant gap in the vertical distribution of scaphitids in the Tercis quarry, corresponding to the interval P 127-P 159. This interval would represent a duration of about 1 Ma if one takes into account the interpretation of the rhythmic flint formation preferred in this volume (chap. Blc). Explaining this gap is difficult; there

are two contemporaneous factors: the total distribution of macrofossils, and the clay content of the rock. Concerning the total distribution of ammonites (chap. D4a) few fossils of ammonites were found in this interval in spite of the time spent looking for them. The reason may be a real absence of fossils in the basin or inappropriate conditions of preservation. Among the macrofossils, only brachiopods show a similar distribution (chap. Bid) with common specimens up to level 125, absence higher up to level 155, and presence above. We do not know which environmental reason might explain this observation.

Fig. 2. Distribution chart of H. pumilus, H. sp. cf. constrictus and H. sp. in the Tercis succession. The total distribution is shown to the left; data from the main outcrop (P) and E section are given independently; three more specimens were found in the P section after the study was achieved resulting in a total of 127 collected specimens. The results of the taxonomic determination (M.M.) are shown to the right; the stars point to the three morphotypes here called H. sp. cf. constrictus. Note the significant increase in the abundance of H. sp. above the stage boundary.

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Concerning the clay content, scaphitid ammonites in the Tercis section seem to be most common in beds with higher clay content than the surrounding ones. For example, the lowest abundance peak of scaphitid in the Tercis section (figure 2) precisely corresponds to a softer series of beds, especially between levels 98 and 99 where the thickest marl bed in the d'Avezac Unit is located; beds between levels 115 and 118 are also slightly clayish and the genus Hoploscaphites is common there. Finally, most specimens collected from section E come from around level E 48 which is a softer bed. This suggests that a moderate clay input (or an event related to it) was beneficial either to preservation or to ecology of these ammonites. A similar observation could be done for other scaphitids (Trachyscaphites) only found in between levels 6 and 37 at the (locally more clayish) base of the succession. 5. Conclusions During this study, we investigated a collection of 124 specimens of scaphitid ammonites amongst which about six are well preserved and six more are reasonably preserved. They are illustrated together with other specimens from Tercis, Poland, and Cotentin. Two taxa have been distinguished: Hoploscaphites pumilus and H. sp. cf. constrictus. Specimens which show features of both taxa or are too poorly preserved to be undisputably identified have been called: Hoploscaphites sp. According to our investigations and keeping in mind that crushing may have modified the original form of the shells, six features should be considered for identification of H. pumilus in Tercis versus H. constrictus. i) apertural angle close to normal in H. pumilus versus 120° for H. constrictus; ii) flat or concave flank profile and sharply defined ventrolateral shoulder, versus rounded profile, never concave; iii) hook well separated from the phragmocone (spire) in microconchs versus continuous tightly coiled shell for H constrictus; iv) presence of evenly spaced ventral ribs over the whole diameter of the body chamber contrasted with indistinct ribbing in the shaft versus continuous presence or absence of ribbing for H. constrictus; v) ventral profile of the hook quickly increasing

versus more regular profile for H. constrictus; vi) apparent migration of the ventro-lateral tubercles into the flank toward aperture versus constant position. For the first time in literature, this chapter quotes a large amount of specimens of the American species H pumilus from Europe. Also for the first time, its stratigraphic distribution is established in this volume with regard to a number of other biostratigraphical criteria. The result is that the taxon appears to be common, at Tercis, from about 20 metres (corresponding to less than 1 Ma) below the top of the Campanian up to 10 metres (corresponding to less than 0.5 Ma) above the base of the Maastrichtian. In the present study, some specimens are also referred to the taxon H. pumilus up to 50 metres (corresponding to a 2 Ma long interval of time) above the base of the Maastrichtian. From near the base of the Maastrichtian upward, a few specimens here referred as H. sp. cf. constrictus show common features with H. constrictus but it is generally difficult to unambiguously identify the collected forms. The absence of typical macroconch does not allow to identify forms similar to the ones from Cotentin where H. constrictus has been defined based on late Maastrichtian macroconch specimens. More generally, it seems that forms previously identified in the literature as H. constrictus and coming from lower lower Maastrichtian deposits would need to be revised in the light of the now well documented presence of H. pumilus in Europe. Acknowledgements Photos of the specimens were prepared by Grazyna Dziewinska (Institute of Paleobiology of the Polish Academy of Sciences) and the reconstructions of the specimens by Boguslaw Waksmundzki (Geology Department of Warsaw University). Authors offer warm thanks to both people. Thomas Kiichler (Bielefeld), Andrzej Blaszkiewicz (Polish Geological Institute, Warszawa) and Ryszard Marcinowski (Geology Department of Warsaw University) are acknowledged for the loan of specimens from their collections to M. Machalski. M.M. also aknowledges the help of W. A. Cobban who provided him with plaster casts of four

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specimens of H. pumilus from the United States. Michel Bilotte (Geologic, Universite de Toulouse) is thanked for his useful discussion on the scaphitids from the Pyrenees. We are indebted to M. A. Lamaurelle for her careful improvement of the form of this manuscript and to W. J. M. Jagt for comment on the content. The stay of M.M. in Paris was sponsored by the Institute of Paleobiology of the Polish Academy of Sciences. (Prepared: May 1998; revised: July 2000) Note added in proofs More information on Hoploscaphites by M. Machalski A photograph of the often quoted supposedly oldest record of Hoploscaphites constrictus, has been kindly sent to me by B. Niebuhr (Wuerzburg, Germany). The specimen is at the University of Kiel (Germany) and comes from about 4 m above the base of the lowermost Maastrichtian Belem-

nella lanceolata Zone in Kronsmoor (B. Niebuhr, e-mail communication, November 2000). The specimen will be described by Niebuhr B., Neumann Ch. & Esser, K. (Upper Campanian to Lower Maastrichtian ammonites from white chalk of Kronsmoor, North Germany, in prep.) I recently examined some unpublished macroconchs of Hoploscaphites from Nagoriany in slightly younger, upper B. lanceolata to B. pseudobtusa Zones at Nagoriany, Ukraine. These specimens show tight attachment of the hook to the spire, and their apertural angle is 120-135°. They probably represent true Hoploscaphites constrictus (Machalski, in prep.), although they are small when compared to macroconchs from Cotentin. In addition, the recently investigated specimens from Nagoriany differ from most of the hitherto illustrated Hoploscaphites material from that locality (provisionally assigned to H. anterior in chapter D4d, this volume).