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Upper Moscovian-middle Kasimovian conodonts (Pennsylvanian, Carboniferous) from the Las LLacerias Section (Cantabrian Zone, north Spain)
Geobios 39 (2006) 245–254 http://france.elsevier.com/direct/GEOBIO/
Upper Moscovian-middle Kasimovian conodonts (Pennsylvanian, Carboniferous) from the Las LLacerias Section (Cantabrian Zone, north Spain) Conodontes du Moscovien supérieur-Kasimovien moyen (Pennsylvanien, Carbonifère) de la coupe de Las LLacerias (Zone Cantabrique, nord de l’Espagne) Carlos A. Méndez Departamento de Geología, Universidad de Oviedo, Campus de LLamaquique, 33005 Oviedo, Asturias, Spain Received 10 June 2004; accepted 15 November 2004 Available online 15 February 2006
Abstract Las LLacerias Section in the western part of the Picos de Europa Unit (Cantabrian Zone) in northern Spain offers the best (essentially continuous) Upper Moscovian-Kasimovian succession in the Pennsylvanian of the Cantabrian Zone. The section consists almost entirely of limestones, and conodonts are scarce in general, but some Myachkovian levels are significantly more productive. Most specimens recovered are Pa pectiniform elements, and are generally well preserved. Idiognathodus, Streptognathodus, Gondolella, and Neognathodus are the most significant genera and Ubinates and Hindeodus are present. Idiognathodus is the dominant genus. Most of the idiognathodids differ morphologically from those elsewhere, and one, Idiognathodus covadongae, is formally recognized a new species. The presence of Idiognathodus eccentricus in the upper part of the Kreviakinian levels suggests a correlation with the lower Missourian of the United States. Neognathodus disappears in the upper part of the Myachkovian beds. Gondolella pohli was recovered from a short interval in the upper portion of the Myachkovian beds. Paleoecological conditions representing shallow, open, normal marine offshore deposits of the Idiognathodus-biofacies are interpreted for the lower portion of the Myachkovian interval. © 2006 Elsevier SAS. All rights reserved. Résumé La coupe stratigraphique de Las LLacerias est située dans l’ouest de l’Unité de Picos de Europa (Zone Cantabrique) dans le nord de l’Espagne. La coupe est composée en grande partie de calcaires, en présentant la meilleure succession (essentiellement continue) du Moscovien supérieur–Kasimovien du Pennsylvanien de la Zone Cantabrique. Les conodontes y sont rares en général mais quelques niveaux myachkoviens en sont significativement plus productifs. La plupart des spécimens récoltés sont des éléments pectiniformes Pa, généralement bien conservés. Idiognathodus, Streptognathodus, Gondolella et Neognathodus sont les genres les plus remarquables. Ubinates et Hindeodus sont aussi présents. Idiognathodus serait le genre dominant. La plupart des idiognathodidés différent morphologiquement des idiognathodidés d’autres régions du monde. Une des espèces, en particulier, Idiognathodus covadongae nov. sp., est ici formellement proposée comme une nouvelle espèce. La présence d’Idiognathodus eccentricus dans la partie supérieure des niveaux kreviakiniens suggérerait une corrélation avec le Missourien inférieur des États Unis. Neognathodus disparaît dans la partie supérieure des couches myachkoviennes. Gondolella pohli fut récoltée dans un intervalle peu étendu dans la partie supérieure du Myachkovien. Les conditions paléoécologiques dans la partie inférieure des niveaux myachkoviens représenterait une sédimentation marine normale, sommaire, ouverte du biofaciès d’Idiognathodus. © 2006 Elsevier SAS. All rights reserved.
E-mail address: [email protected] (C.A. Méndez). 0016-6995/$ - see front matter © 2006 Elsevier SAS. All rights reserved. doi:10.1016/j.geobios.2004.11.002
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Keywords: Conodonts; Carboniferous; Pennsylvanian; Cantabrian Zone; North Spain Mots clés : Conodontes ; Carbonifère ; Pennsylvanien ; Zone Cantabrique ; Nord de l’Espagne
1. Introduction Carboniferous conodonts from the Cantabrian Zone of northern Spain (Fig. 1) have been investigated since 1958. The Mississippian Alba Formation (Late Tournaisian-Namurian) provides the richest and, in general, best preserved conodont fauna in the region. In contrast, Pennsylvanian conodonts are scarce but well preserved, although some levels can be significantly more productive. Moscovian to Gzhelian (Pennsylvanian) conodonts have not been as extensively studied throughout the world as those of the lower part of Mississippian and their utility for biostratigraphy may be significant, once their systematic instability is resolved. For several years the conodont research of the author has concentrated on the Upper Moscovian-Gzhelian levels of the Picos de Europa Unit of the Cantabrian Zone (northern Spain)
(Fig. 2), although other units are under study. The Picos de Europa Unit is well differentiated with good exposure of the Carboniferous succession comprising mainly marine limestones that have proved to be favourable for conodont recovery (chiefly in the Moscovian levels) (Méndez, 1990, 2002; Méndez in Villa et al., 1993 and in Villa et al., 1997). 2. Stratigraphy The Las LLacerias Section is in the western part of the Picos de Europa Unit (Fig. 2) in the locality of Las LLacerias near the village of Covadonga, within the Picos de Europa National Park. The series is shown on sheet 55 (Beleño) of the Geological Map of Spain (1:50 000) (Julivert and Navarro, 1984). The section is exposed along a footpath, which leads from the Covadonga Lakes local road to the cattle sheds of Las LLacerias (Fig. 3). The studied interval constitutes the best, and essentially continuous Upper Moscovian-Kasimovian succession in the Pennsylvanian of the Cantabrian Zone. Outcrops are discontinuous and covered by vegetation in many places. Where present, the limestone outcrops lie on both sides of the path and cross it. Lithostratigraphic units of the interval studied (Figs. 3 and 4) include the massive member (uppermost part) of the Picos de Europa Formation (Maas, 1974) followed by the Las LLacerias Formation (Villa and van Ginkel, 2000). The interval starts with a red crinoidal limestone, which is about 480 m above the base of the Picos de Europa Formation and can be traced easily in the field. Above it lie grey, sometimes red limestone beds, which are massive in places. The Las LLacerias Formation consists of grey, thin-bedded limestones with some marly limestone intervals and a few levels of sandy limestone near the top. The age of the succession is middle Myachkovian-Khamonivkian based on fusulinoideans (Villa et al., 1997; Villa and van Ginkel, 2000). The Moscovian-Kasimovian boundary lies within the sequence at the lower part of Interval 5 (Fig. 4), along which a succession of Protriticites (fusulinoideans) faunas from primitive to typical forms occur. 3. The conodont fauna and comments about correlation
Fig. 1. Geological map of the Iberian Variscan Belt. The Cantabrian Zone is situated in the north (horizontal line drawing) (after Julivert et al., 1972). Fig. 1. Carte géologique de la Bande Varisque Ibérique. La Zone Cantabrique (représentée par des lignes horizontales) est située dans le Nord (d’après Julivert et al., 1972).
Conodonts are scarce in general in the Las LLacerias Section, but some Myachkovian levels in the Upper Moscovian are significantly more productive. A major reduction in the number of conodont elements occurs in the Kasimovian (Kreviakinian and Khamonivkian) beds (Fig. 4). Specimens recovered are mainly Pa pectiniform elements and are generally well preserved. Other elements of the conodont apparatus are not very well preserved nor are they common.
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Fig. 2. Geological sketch map of the Cantabrian Zone showing the position of the Las LLacerias Section (after Julivert, 1971 and Pérez Estaún et al., 1988). Fig. 2. Carte géologique schématique de la Zone Cantabrique montrant la situation de la coupe stratigraphique de Las LLacerias (d’après Julivert, 1971 et Pérez Estaún et al., 1988).
Idiognathodus, Streptognathodus, Gondolella, and Neognathodus are the most significant genera present for biostratigraphy. Ubinates and Hindeodus are also present. Idiognathodus is the dominant genus and extends from the middle Myachkovian into the Khamonivkian, but is much more abundant in Myachkovian beds. The idiognathodids are morphologically different from those elsewhere, except I. eccentricus. At least one of the different forms is a new species, Idiognathodus covadongae, nov. sp. However, half show affinities with species from the Moscow Basin and the Donets Basin. These forms are Idiognathodus aff. I. podolskensis Goreva, I. aff. I. trigonolobatus Barskov and Alekseev, and I. aff. I. sagittalis Kozitskaya. We found I. eccentricus (sample LL-9030, Fig. 4) in the upper part of the Kreviakinian levels 16 m below the entry of the fusulinoidean species Montiparus, that is, the base of Khamonivkian. In their provisional conodont zonation for the Late Pennsylvanian in North American Midcontinent Region, Barrick and Heckel (2000) propose the Idiognathodus eccentricus Zone (lowest Missourian) to extend from the first appearance of the nominate species up to the first appearance of Streptognathodus cancellosus. In North America, I. eccentricus ranges into the Streptognathodus cancellosus Zone. These data suggest the correlation of a level within the upper part of the Kreviakinian beds in Las LLacerias Section with the lower Missourian. Idiognathodus covadongae, nov. sp. is a form with a biostratigraphic range potentially restricted to the Myachkovian, below the extinction of the genus Neognathodus.
The rest of idiognathodids are placed in open nomenclature as Idiognathodus sp. The morphology of these specimens is distinctive, and at the same time, highly variable, so it is not possible at the moment to assign the material to a species level taxon with certainty. Streptognathodus, which is relatively scarce, appears in the upper Myachkovian a few metres above the extinction of Neognathodus and it ranges to the Khamonivkian near the top of the studied interval. In this part of the series Idiognathodus and Streptognathodus are the only conodonts recovered, although idiognathodids are more diversified and a little more abundant than streptognathodids. With the exception of Streptognathodus aff. S. subexcelsus, whose position in the upper Myachkovian in LLacerias Section is near to that of the entry of Streptognathodus subexcelsus in the Donets Basin, the material recovered is assigned to the genus without specific determination; the low number of specimens prevents any definitive consideration beyond the generic level. Gondolella is recorded from the middle to upper Myachkovian, and is represented by Gondolella laevis, Gondolella pohli, and specimens of Gondolella sp. We have recently recovered G. pohli from a short interval in the upper portion of the Myachkovian levels. This species was reported in North America from the middle to ? upper Desmoinesian (von Bitter and Merrill, 1998) in northwestern Illinois, western Indiana and south-central Iowa, and from the middle Desmoinesian (Barrick et al., 2002) in the Midcontinent. Therefore, the base of the Missourian could be correlative, not with the base of
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Genus Gondolella Stauffer and Plummer, 1932. Type species: Gondolella elegantula Stauffer and Plummer, 1932.
Fig. 3. Geological sketch map of the zone around Las LLacerias Section (after Marquínez et al., 1982). Fig. 3. Géologie détaillée près de la localité de Las LLacerias (d’après Marquínez et al., 1982).
Kasimovian, but higher as suggested by some authors (for example: Villa and van Ginkel, 2000). Neognathodus ranges through most of the Myachkovian levels, until the genus disappears in the upper part of Interval 4 with the loss of Neognathodus aff. N. inaequalis (Fig. 4). This taxon was reported from the Myachkovian of the Donets Basin, and from the Podolskian to Myachkovian of the Moscow Basin. Neognathodus is not recorded in levels higher than Moscovian in the Moscow Basin or Donets Basin. The same holds in the Las Llacerias Section, where Neognathodus is not recovered in beds dated as Kasimovian. Several specimens are assigned to Hindeodus sp. due to low numbers and poor preservation. About one half of the conodont taxa identified at species level show affinities with those of the Moscow Basin and Donets Basin, except Idiognathodus trigonolobatus Barskov and Alekseev, reported from the Moscow Basin only. 4. Systematic paleontology The material illustrated and/or described is deposited in the Department of Geology (Paleontology) of the University of Oviedo (DPO).
Gondolella laevis Kossenko and Kozitskaya in Kossenko, 1975. (Pa element). Fig. 5(3A, 3B) (A synonymy was provided by Méndez et al., 1998 for this species). Material: Two well-preserved specimens: DPO 126. 338 and 126. 339 (sample S-230, Picos de Europa Formation). Description: In upper view, elongate specimens with a slight bend; anterior end pointed; platform smooth, narrow, slightly concave, and more wide in the posterior half; carina with several denticles situated in the centre of the platform; cusp inclined in posterior direction very close to the posterior end of the unit. In lower view, basal cavity very broad, deep, and situated in a posterior position; this structure is bordered by a loop, back closed, and continues to the anterior end of the unit like a grooved keel. No microsculpture has been observed. Remarks: The characteristics of the Gondolella laevis material from this locality and those of the Río Nevandi Section were dealt with in Méndez et al. (1998). The general features of the Pa element of this species are like those of G. laevis Kossenko and Kozitskaya, in Kossenko, 1975 from the Myachkovian of the Donets Basin. Distribution: middle Myachkovian. Gondolella pohli von Bitter and Merrill, 1998. (Pa element). Fig. 5(2A, 2B). 1975. Gondolella bella? Stauffer and Plummer—Merrill, 1975 pp. 58, Fig. 17: 3 (only). 1985. Gondolella sp. 1—Swade, Pl. 4, Fig. 18: 44, 45. *1998. Gondolella pohli n. sp.—von Bitter and Merrill, p. 128, Figs. 3–8. V.1998. Gondolella nov. sp. 1—Méndez et al., p. 344, Fig. 6: 8, 9. 2001. Gondolella pohli von Bitter and Merrill—Rexroad et al., p. 2, Fig. 5: 13–18. Material: Two specimens, one of them damaged: DPO 38518 and DPO 126.341 (samples S-370 and S-232, respectively, Picos de Europa Formation). Remarks: This species is quite similar to Gondolella laevis, from which it is distinguished by a “significantly wider Pa element platform” (von Bitter and Merrill, 1998). The platform in our material is very well developed, like that of Gondolella pohli von Bitter and Merrill, 1998 from the Desmoinesian of northwestern Illinois (USA). The outline of the posterior half of the platform in one of our specimens (Fig. 5B) resembles a specimen figured and described by Swade (1985) as Gondolella sp. 1 (Fig. 18: 45)
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Fig. 4. Location of samples and conodont distribution along the uppermost part of the Picos de Europa Formation and the Las LLacerias Formation within the Las LLacerias Section. 1–10 = sedimentological intervals distinguished in Villa et al. (1993) (after Méndez, 2002, modified). Fig. 4. Situation des échantillons et distribution des conodontes tout au long de la partie la plus supérieure de la Formation Picos de Europa et de la Formation Las LLacerias dans la coupe stratigraphique de Las LLacerias. 1–10 = intervalles sédimentologiques distingués par Villa et al. (1993) (d’après Méndez, 2002, modifié).
from the Verdigris Formation (Demoinesian) in the Midcontinent of the United States. Distribution: middle to Upper Myachkovian. Genus Idiognathodus Gunnell, 1931. Type species: Idiognathodus claviformis Gunnell, 1931. Idiognathodus eccentricus (Ellison, 1941). (Pa element). Fig. 5(14). Material: One specimen: DPO 38532 (sample LL-9030, Las LLaceriasFormation). Description: Pectiniform element. In upper view unit lanceolate, most of the outer margin of platform convex, inner margin relatively straight, both margins join posteriorly to pro-
duce a moderately pointed form; a couple of short, nodose adcarinal ridges are present anteriorly; poorly defined eccentric trough in the posterior part of the platform cuts several welldeveloped transverse ridges; carina of moderate length, a few irregular nodes are situated below it; lobes poorly developed: outer lobe with two nodes and inner lobe with one node. Remarks: The trough on the inner side of the platform, the lobes on both sides of this structure, together with the relatively long carina permit us to assign this specimen to Idiognathodus eccentricus (Ellison). We agree with the concept of Barrick and Walsh (1999) for this species, as the holotype figured by Ellison (1941) is early Missourian in age, and distinct from the late Missourian to early Virgilian eccentric Pa elements. On the other hand, our specimen shows some similarity to one figured by Barrick and Boardman (1989: Pl. 1, Fig. 8)
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Fig. 5. 1, 6. Idiognathodus covadongae nov. sp., 1, upper view, × 52, holotype. Picos de Europa Formation, sample S-230 (DPO 38517); 6, upper view, × 62, paratype. Picos de Europa Formation, sample S-231 (DPO 38536). 2a, 2b. Gondolella pohli Von Bitter and Merrill, 1998. 2a, upper view, × 43, 2b, lower view, × 38. Picos de Europa Formation, sample S-370 (DPO 38518). 3a, 3b. Gondolella laevis Kossenko and Kozitskaya, 1975. 3a, upper view, × 48, 3b, lower view, × 50. Picos de Europa Formation, sample S-230 (DPO 38519). 4. Streptognathodus aff. S. subexcelsus Alekseev and Goreva, 2001, upper view, × 54. Picos de Europa Formation, sample S-232 (DPO 38520). 5. Idiognathodus sp., upper view, × 29. Las LLacerias Formation, sample LL-9030 DPO (38521). 7. Neognathodus aff. N. inaequalis Kozitskaya and Kossenko, 1978, upper view, × 68, Picos de Europa Formation, sample S-232b (DPO 38529). 8, 9. Streptognathodus sp. 8, upper view, × 46. Picos de Europa Formation, sample LL-9022 (DPO 38523), 9, upper view, × 34. Picos de Europa Formation, sample LL-9022 (DPO 38524). 10. Ubinates sp., inner lateral view, × 30. Picos de Europa Formation, sample S-230 (DPO 38528). 11. Idiognathodus aff. I. trigonolobatus Barskov and Alekseev, 1976, upper view, × 33. Picos de Europa Formation, sample LL-9026 (DPO 38526). 12. Idiognathodus sp. B, upper view, × 46. Picos de Europa Formation, sample S-230 (DPO 38527). 13. Idiognathodus aff. I. podolskensis Goreva, 1984, upper view, × 31. Picos de Europa Formation, sample S-371 (DPO 38530). 14. Idiognathodus eccentricus (Ellison, 1941), upper view, × 52. Las LLacerias Formation, sample, LL-9030 (DPO 38532). 15, 16. Idiognathodus aff. I. sagittalis Kozitskaya, 1978. 15, upper view, × 38. Las LLacerias Formation, sample S-236-K (DPO 38540), 16, upper view, × 38. Las LLacerias Formation, sample S-236-K (DPO 38531). All illustrated specimens are Pa elements except that of Fig. 10 (X element). DPO is the repository number in the Department of Geology (Paleontology). University of Oviedo. Fig. 5. 1, 6. Idiognathodus covadongae nov. sp., 1, vue supérieure, × 52, holotype. Formation Picos de Europa, échantillon S-230 (DPO 38517) ; 6, vue supérieure, × 62, paratype. Formation Picos de Europa, échantillon S-231 (DPO 38536). 2a, 2b. Gondolella pohli von Bitter et Merrill, 1998. 2a, vue
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from upper Salesville core shale (lower Missourian) of northcentral Texas, USA. Distribution: Kreviakinian. Idiognathodus covadongae nov. sp. (Pa element) Fig. 5(1, 6) Material: Seven well-preserved specimens, one of them the holotype: DPO 38517 (sample S-230, Picos de Europa Formation); the rest are paratypes from the same formation: DPO 38533 (sample S-370); DPO 38534-38538 (sample S-231). Locus typicus: Near Covadonga Village. Left side of the footpath that leads from the Covadonga Lakes local road to the cattle sheds of Las LLacerias, down to the road, in the middle of the meadow (Fig. 3). Stratum typicum: Level of red crinoidal limestone. At the base of the studied interval (Fig. 4). Derivatio nominis: After the name of my wife Covadonga. Diagnosis: A species of the genus Idiognathodus whose Pa element has a well-developed lanceolate platform with a field of numerous transverse ridges; field of transverse ridges subrhombic in outline and slightly depressed, greatest width near anterior one third. Description: In upper view platform lanceolate, outline subtriangular, inner margin slightly bent, outer margin rounded; unit posteriorly pointed; adcarinal ridges converge towards carina anteriorly in the platform then diverge, develop and go away tending to fuse with the free blade; inner adcarinal ridge more developed in some specimens showing short ridges; field with numerous transverse ridges on platform, sub-rhombic in outline and slightly depressed, greatest width near anterior one third; carina short; lobes not equally developed, situated towards the anterior termination of platform, the inner more developed with several relatively abundant organised nodes semicircular in outline, the outer with a row of a few nodes. Remarks: Idiognathodus covadongae shows some similarity with Idiognathodus podolskensis Goreva, 1984, recorded from the Podolskian of the Moscow Basin and the Myachkovian of the Donets Basin. However, our species has a more elongate platform and the field of transverse ridges is subrhombic, not subtriangular like that of Russian species. Another species that shows some similarity with ours is Idiognathodus obliquus Kossenko and Kozitskaya, 1978, re-
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corded from Podolskian to Myachkovian from the Donets Basin and from Kashirian to Myachkovian from the Moscow Basin. Nevertheless the Spanish species has a more bent inner margin, a more elongate platform, a more depressed ridged field of the platform, and less developed lobes than in the Russian species. Distribution: middle to upper Myachkovian. Idiognathodus aff. I. podolskensis Goreva, 1984. (Pa element). Fig. 5 (13). Material: Two specimens: DPO 38530 and DPO 38539 (sample S-371, Picos de Europa Formation). Description: In upper view, platform very long, subtriangular, outer margin convex, inner margin straight or relatively straight, both margins join posteriorly giving way to an acute termination; platform with a slightly concave subtriangular field of numerous transverse ridges, greatest width in the anterior one-half; adcarinal ridges approach to carina near the anterior termination of platform then diverge, the inner giving way to a parapet-like structure (with short ridges in the adult figured specimen); carina very short; lobes not equally developed, situated near the anterior termination of platform, outer lobe poorly developed with several nodes, inner lobe semi-circular with several irregular coarse nodes. Remarks: Our material resembles Idiognathodus podolskensis Goreva, 1984, from the Podolskian of the Moscow Basin and the Myachkovian of the Donets Basin, but differs by its more elongate platform. Distribution: middle to upper Myachkovian. Idiognathodus aff. I. sagittalis Kozitskaya in Kozitskaya et al., 1978. (Pa element). Fig. 5 (15, 16). Material: Five specimens with acceptable preservation: DPO 38531, DPO 38540, DPO 38541 and DPO 38542 (sample S-236-K, Las LLacerias Formation); DPO 38543 (sample S-238, Las LLacerias Formation). Description: In upper view, platform resembles an arrowhead, inner margin slightly convex, outer margin more convex; unit posteriorly pointed; adcarinal ridges (when present) converge near anterior termination of platform, then diverge and
supérieure, × 43, 2b, vue inférieure, × 38. Formation Picos de Europa, échantillon S-370 (DPO 38518). 3a, 3b. Gondolella laevis Kossenko et Kozitskaya, 1975. 3a, vue supérieure, × 48, 3b, vue inférieure, × 50. Formation Picos de Europa, échantillon S-230 (DPO 38519). 4. Streptognathodus aff. S. subexcelsus Alekseev et Goreva, 2001, vue supérieure, × 54. Formation Picos de Europa, échantillon S-232 (DPO 38520). 5. Idiognathodus sp., vue supérieure, × 29. Formation Las LLacerias, échantillon LL-9030 (DPO 38521). 7. Neognathodus aff. N. inaequalis Kozitskaya et Kossenko, 1978, vue supérieure, × 68. Formation Picos de Europa, échantillon S-232b (DPO 38529). 8, 9. Streptognathodus sp. 8, vue supérieure, × 46. Formation Picos de Europa, échantillon LL-9022 (DPO 38523), 9, vue supérieure, × 34. Formation Picos de Europa, échantillon LL-9022 (DPO 38524). 10. Ubinates sp., vue latérale interne, × 30. Formation Picos de Europa, échantillon S-230 (DPO 38528). 11. Idiognathodus aff. I. trigonolobatus Barskov et Alekseev, 1976, vue supérieure, × 33. Formation Picos de Europa, échantillon LL-9026 (DPO 38526). 12. Idiognathodus sp. B, vue supérieure, × 46. Formation Picos de Europa, échantillon S-230 (DPO 38527). 13. Idiognathodus aff. I. podolskensis Goreva, 1984, vue supérieure, × 31. Formation Picos de Europa, échantillon S-371 (DPO 38530). 14. Idiognathodus eccentricus (Elison, 1941), vue supérieure, × 52. Formation Las LLacerias, échantillon LL-9030 (DPO 38532). 15, 16. Idiognathodus aff. I. sagittalis Kozitskaya, 1978. 15, vue supérieure, × 38. Formation Las LLacerias, échantillon S-236-K (DPO 38540), 16, vue supérieure, × 38. Formation Las LLacerias, échantillon S-236-K (DPO 38531). Tous les spécimens figurés sont des éléments Pa à l’exception du 10 (élément X) et ont été déposés au Département de Géologie (Paléontologie) de l’Université d’Oviedo (DPO).
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go away for some distance before fusing with free blade, inner adcarinal ridge more developed with very short ridges from the anterior termination of platform until their fusion with free blade; field of transverse ridges on platform mostly triangular, with a variable number (but never much) of poorly developed ridges in a couple of specimens (Fig. 5: 15, 16), the posterior most are interrupted, greatest width in anterior one-half; carina short in general; lobes well developed in more adult specimens, the inner usually with several nodes situated on a flaring structure, the outer with fewer nodes in a variable arrangement. Remarks: Our material resembles Idiognathodus sagittalis Kozitskaya in Kozitskaya et al., 1978, recorded from Kasimovian of the Russian Platform and the Donets Basin. The differences are in the more narrow outline of platform and more elongate field of transverse ridges in our material. Distribution: Kreviakinian-Khamonivkian. Idiognathodus aff. I. trigonolobatus Barskov and Alekseev, 1976. (Pa element). Fig. 5(11). Material: One well-preserved specimen: DPO 38526 (sample LL-9026, Picos de Europa Formation). Description: In upper view, platform with irregular outline, inner margin strongly convex in anterior half and moderate in posterior half, outer margin mostly straight with a strong curvature near the anterior termination of platform; unit posteriorly pointed; inner adcarinal ridge moderately developed, short, continues anteriorly like a ridged parapet from the termination of platform until its fusion with free blade; field of transverse ridges on the platform sub-rhombic with a moderate number of ridges, some of them poorly defined and broken into nodes, greatest width in anterior one half; lobes not equally developed, occupy much of the platform, inner lobe not rounded, very developed, showing a flaring structure with two different node sizes arranged in rows, outer lobe rounded, very poorly defined, fused to the platform with a few coarse nodes. Remarks: Our specimen resembles Idiognathodus trigonolobatus Barskov and Alekseev, 1976, recorded from Myachkovian to Kreviakinian in the Moscow Basin. However, the Russian species has a convex outer platform margin, triangular field of transverse ridges on the platform, rostral ridges that are not as wide, and an inner lobe that is more rounded. Distribution: Kreviakinian. Idiognathodus sp. B. (Pa element). Fig. 5(12). Material: Six mostly well-preserved specimens: DPO 38527, DPO 38545 to 38549 (sample S-230, Picos de Europa Formation). Description: In upper view, moderately curved, long, subtriangular platform, posteriorly pointed; inner margin mostly straight, can be concave about the middle or irregular, outer margin convex, more strongly near the anterior termination;
short adcarinal ridges initiate near the anterior termination of the platform and extend anteriorly like nodose or ridged parapets, although fusion with the free blade does not take place in all specimens (when visible), standing as free edges, inner adcarinal ridge more developed; field of numerous transverse ridges on the platform mostly sub-rhombic, greatest width in anterior one-half; short strong carina; lobes in general integrated into the platform, mostly well developed, sub-rounded inner lobe with abundant nodes that tend to be arranged in rows, sometimes fused, outer lobe, slightly droping, shoulderlike, extending posteriorly, giving a robustness to the platform, nodes on outer lobe sometimes abundant. Remarks: The long platform, short, strong, carina, well-developed adcarinal ridges, and shape of outer lobe are the main characteristics of this form, which probably represents a new species, although the modest number of specimens and absence in other samples prevent a formal definition. The subtriangular shape of the platform, development of the outer lobe, and non-depressed field of transverse ridges on the platform are major differences with Idiognathodus covadongae nov. sp. described in this paper. The non-depressed field of transverse ridges on the platform, development of the lobes, shape of the outer lobe, and more abundant nodes in relation to the adult specimen of Idiognathodus aff. podolskensis are the main differences with the latter. Distribution: middle Myachkovian. Genus Neognathodus Dunn, 1970. Type species: Polygnathus bassleri Harris and Hollingsworth, 1933. Neognathodus aff. N. inaequalis Kozitskaya and Kossenko in Kozitskaya et al., 1978. (Pa element). Fig. 5(7). Material: Four specimens with acceptable preservation (one adult and three juveniles): DPO 38529 (sample S-232b, Picos de Europa Formation). Description: In upper view, platform slightly bowed, sublanceolate, posteriorly pointed, directed downwards in the adult specimen, greatest width in anterior one-third; blade continues posteriorly on platform as a strong, high carina that terminates near to the posterior end of the unit, ends as a few nodes except in juveniles where this structure is unbroken, carina higher than platform in adult and in one larger juvenile specimen; outer side of platform is a slightly steep parapet with short ridges, not very wide and reduced near its posterior termination to the end of the unit, essentially parallel to carina, separated from it by a slight sulcus crossed by a few ridges near the posterior end of the unit; in most juvenile specimens outer parapet reduced or absent; inner side of platform developed like the outer in a very much wider structure, steeper with developed radiating ridges, moderate sulcus separates the carina from inner side of platform; both parapets converge at the posterior end of the unit.
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Remarks: The morphology displayed by our specimens resembles that of Neognathodus inaequalis Kozitskaya and Kossenko in Kozitskaya et al., 1978, recorded from the Myachkovian of the Donets Basin and from Podolskian to Myachkovian of the Moscow Basin, but have a wider and less triangular platform. Distribution: upper Myachkovian. Genus Streptognathodus Stauffer and Plummer, 1932. Type species: Streptognathodus excelsus Stauffer and Plummer, 1932. Streptognathodus aff. S. subexcelsus Alekseev and Goreva in Makhlina et al., 2001. (Pa element). Fig. 5(4). Material: Two specimens: DPO 38520 and DPO 38545 (sample S-232, Picos de Europa Formation). Description: In upper view, unit lanceolate; outer and inner margins convex, more so for the outer; platform, wide, tonguelike, slightly depressed towards the middle in the surface posterior to the end of carina, where several transverse ridges exist, surface of platform mostly directed downwards; carina, short, ending near the anterior termination of the platform; adcarinal ridges, not very long, fused with the free blade, developed towards its anterior part in wide, steep, structures ornamented with short ridges; lobes situated near the anterior termination of the platform in the more adult specimen, outer lobe poorly developed, with one or few nodes, inner lobe, well developed, showing a variable number of coarse nodes. Remarks: The material described resembles Streptognathodus subexcelsus Alekseev and Goreva in Makhlima et al., 2001, from the Kreviakinian of the Moscow Basin and Myachkovian to Kreviakinian of the Donets Basin. Differences exist, however, such as the wider, not subtriangular, depressed area of the platform, and the less well-developed outer lobe in the Spanish form. Distribution: upper Myachkovian. Streptognathodus spp. (Pa Elements). Fig. 5(8, 9). Material: Nineteen specimens: DPO 38546 to 38551 (sample S-232, Picos de Europa Formation); DPO 38552 and DPO 38553 (sample S-234, Picos de Europa Formation); DPO 38523 to 38525 (sample LL 9022, Picos de Europa Formation); DPO 38554 (sample LL-9026, Picos de Europa Formation); DPO 38555 to 38557 (sample S-239, Las LLacerias Formation); DPO 38558 to 38560 (sample S-240, Las LLacerias Formation). Remarks: The specimens assigned to this genus (some of them juveniles) that were recovered in the studied interval show several types of morphologies, including forms with long carinae, present or absent inner lobe, and a variable number of transverse ridges below the carina. An additional another different morphology also exists. It’s possible that all of these
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belong to a few species, but the paucity of material precludes any specific assignment now. Distribution: middle Myachkovian-Khamonivkian. Genus Ubinates (Baesemann, 1973). Type species: Ubinates advena (Baesemann, 1973). (X element). Fig. 5(10) Material: One relatively well-preserved specimen: DPO 38528 (sample S-230, Picos de Europa Formation). Description: In lateral view, anterior process laterally compressed, deflected downward, denticles on the process, the second from the cusp is the largest; posterior process sinuously deflected, one discrete denticle preserved only; pit expanded inward. Remarks: The unique element we recovered, although not very well preserved, shows in general the same features described for the Aethotaxis, X element by Baesemann (1973), the author who erected the genus. That name was later changed to Ubinates, nomen novum by Baesemann and Purnell (2000), because Aethotaxis was preoccupied. Distribution: middle Myachkovian. 5. Some remarks on paleoecological conditions A thick limestone succession representing rapid sedimentation characterizes the lower part of the studied interval. Paleoecological conditions derived from the conodonts are best limited to the lower part, where the number of specimens is higher. The absence of Adethognathus shows us that nearshore biofacies must be excluded. Idiognathodus is the dominant genus throughout the interval studied. An Idiognathodus-biofacies is present from the level S-230 to the level S-231, in the lower part of the Myachkovian beds (Fig. 4), where the number of the specimens of that genus is higher. According to Merrill and von Bitter (1976), the Idiognathodus-biofacies is one that dominates most Pennsylvanian sedimentary rocks, and represents shallow, open, normal marine offshore deposits. Sedimentological data from Leyva (in Villa et al., 1993) indicate a platform-lagoon in the levels with abundant Idiognathodus (sedimentological intervals 1–3, Fig. 4). A more recent sedimentological study from Bahamonde et al. (2000) indicates a shallow, flat-topped platform environment with a poorly rhythmic character for the same intervals. Acknowledgements This work has been supported by Spanish government funding through Project BTE 2003-01012. The paper benefited from referees’ comments by Dr. James E. Barrick, Texas Tech University and Dr. Hans P. Schönlaub, Geologische Bundesansalt, Viena. Thanks are also due to Dr. Lance L. Lambert, University of Texas at San Antonio, for his revision of the English
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language and useful suggestions, Dr. J.L. García-Alcalde, Universidad de Oviedo, for his revision of the French language of the abstract and Dr. C. Brime, from the same university, for her help with the figures format. The author wants to thank Mr. Severino Méndez for his valuable help in the field work. References Baesemann, J., 1973. Missourian (Upper Pennsylvanian) conodonts of northeastern Kansas. Journal of Paleontology 47, 689–710. Baesemann, J., Purnell, M., 2000. Ubinates, a new name for the genus Aethotaxis Baesemann, 1973 (Vertebrata, Conodonta) preoccupied by Aethotaxis De Witt, 1962 (Vertebrata, Osteichtyes). Journal of Paleontology 74, 544. Bahamonde, J.R., Vera, C., Colmenero, J.R., 2000. A steep-fronted Carboniferous carbonate platform: clinoformal geometry and lithofacies (Picos de Europa, NW Spain). Sedimentology 47, 645–664. Barrick, J.E., Boardman II, D.R., 1989. Stratigraphic distribution of morphotypes of Idiognathodus and Streptognathodus in Missourian-lower Virgilian strata, north central Texas. In: Boardman II, D.R., Barrick, J.E., Cocke, J., Nestell, M.K. (Eds.), Middle and Late Pennsylvanian chronostratigraphic boundaries in north-central Texas: glacial-eustatic events, biostratigraphy and paleoecology: a guidebook.-Part II: contributed papers. Texas Tech University. Studies in Geology 2. pp. 167–188. Barrick, J.E., Walsh, T.R., 1999. Some older north American types of Idiognathodus and Streptognathodus. In: Heckel, P.H. (Ed.), Middle and Upper Pennsylvanian (Upper Carboniferous) Cyclothem Succession in Midcontinent Basin, USA. XIV International Congress on the Carboniferous-Permian, Field Trip #8 Guidebook. Kansas Geological Survey, Open-file Report 99/27, pp. 147–161. Barrick, J.E., Heckel, P.H., 2000. A provisional conodont zonation for Late Pennsylvanian (late Late Carboniferous) strata in Midcontinent Region of North America. Newsletter on Carboniferous Stratigraphy 18, 15–21. Barrick, J.E., Lambert, L.L., Heckel, P.H., 2002. Pennsylvanian conodont zonation for Midcontinent North America. Eighth International Conodont Symposium in Europe, ECOS VIII, abstracts, Strata (1) 12, p. 74. Barskov, I.S., Alekseev, A.S., 1976. New species of the genus Idiognathodus (Conodonta) from the Middle Upper Carboniferous of the Moscow Region. Paleontologicheskiy Zhurnal 4, 119–121 (in Russian). Dunn, D.L., 1970. Middle Carboniferous conodonts from western United States and phylogeny of the platform group. Journal of Paleontology 44, 312–342. Ellison, S., 1941. Revision of the Pennsylvanian conodonts. Journal of Paleontology 15, 107–143. Goreva, N.V., 1984. Moscovian conodonts of the Moscow Syneclise. In: Menner, V.V. (Ed.), Paleontologichyeskaya jarakteristika stratotipicheskij i opornîj razrezov karbona moskovskoy sineklizî. Moscow University Press, Moscow, pp. 44–123 (in Russian). Gunnell, F.H., 1931. Conodonts from the Ford Scott Limestone of Missouri. Journal of Paleontology 5, 244–252. Harris, R.W., Hollingsworth, R.V., 1933. New Pennsylvanian conodonts from Oklahoma. American Journal of Science 25, 193–204. Julivert, M., 1971. Décollement tectonics in the Hercynian Cordillera of northwest Spain. American Journal of Science 270, 1–29. Julivert, M., Fontboté, J.M., Ribeiro, A., Conde, L., 1972. Mapa Tectónico de la Península Ibérica y Baleares. E1: 1000000. Instituto Geológico y Minero de España, Madrid 1–119. Julivert, M., Navarro, D., 1984. Mapa Geológico de España. E1: 50 000. Hoja no. 55 (15-5), Beleño. Instituto Geológico y Minero de España, Madrid 1– 47. Kozitskaya, R.I., Kossenko, Z.A., Lipnyagov, O.M., Nemirovskaya, T.I., 1978. Konodontî karbona donetskogo basseyna. Izd-vo Nauka Dumka, Kiev, 1–136 (in Russian). Kossenko, Z.A., 1975. New species of conodonts from the deposits of the Moscovian stage in the southwestern part of the Donets Basin. Academy Nauk USSR. Geologicheskiy Zhurnal 35, 126–133 (in Russian, with English abstract).
Makhlina, M.Kh., Alekseev, A.S., Goreva, N.V., Gorjunova, R.V., Isakova, T.N., Kossovaya, O.L., Lazarev, S.S., Lebedev, O.A., Shkolin, A.A., (Alekseev, A.S. and Shik, S.M., Eds.), 2001. Sredniy karbon Moskovskoy sineklizî (yuzhnaya chast’). Tom 2. Paleontologicheskaya jarakteristika. (Paleontological Institute). Moscow: Scientific World (in Russian, with English abstract). Maas, K., 1974. The geology of Liebana, Cantabrian Mountains, Spain; deposition and deformation in a flysch area. Leidse Geologische Mededelingen 49, 379–465. Marquínez, J., Méndez, C.A., Menéndez-Alvarez, J.R., Sánchez de Posada, L. C., Villa, E., 1982. Datos bioestratigráficos de la sucesión carbonífera (Turnesiense-Kasimoviense) de Las LLacerias, Picos de Europa, Norte de España. Trabajos de Geología de la Universidad de Oviedo 12, 187–193. Méndez, C.A., 1990. Conodontos del Carbonífero Superior de la Cordillera Cantábrica. Ph.D. Dis. (unpublished), Universidad de Oviedo 1–213. Méndez, C.A., 2002. Carboniferous conodonts of the Ponga and Picos de Europa units (Cantabrian Zone, North Spain). In: García-López, S., Bastida, F. (Eds.), Palaeozoic conodonts from northern Spain. Instituto Geológico y Minero de España, serie Cuadernos del Museo Geominero 1. pp. 207–227. Méndez, C.A., García López, S., Sánchez de Posada, L.C., 1998. Gondolellidae (Conodonta), del Carbonífero Superior de la Zona Cantábrica (N. de España). Sistemática e implicaciones paleotérmicas. Geobios 31, 337–348. Merrill, G.K., 1975. Pennsylvanian conodont biostratigraphy and paleoecology of northwestern Illinois. The Geological Society of America, Inc. Microform Publication 3, 1–128. Merrill, G.K., von Bitter, P.H., 1976. Revision of conodont biofacies nomenclature and interpretations of environmental controls in Pennsylvanian rocks of eastern and central North America. Life Sciences Contributions Royal Ontario Museum 108, 1–46. Pérez Estaún, A., Bastida, F., Alonso, J.L., Marquínez, J., Aller, J., Alvarez Marrón, J., Marcos, A., Pulgar, J.A., 1988. A thin-skinned tectonics model for an arcuate fold and thrust belt: the Cantabrian Zone. Tectonics 7, 517– 537. Rexroad, C.B., Wade, J.A., Merrill, G.K., Brown, L.M., Padgett, P., 2001. Conodont biostratigraphy and depositional environments of the Mecca Quarry Shale Member and the Velpen Limestone Member of the Linton Formation (Pennsylvanian, Desmoinesian) in the eastern part of the Illinois Basin, USA. Indiana Geological Survey Special Report 63, 1–17. Stauffer, C.R., Plummer, H.J., 1932. Texas Pennsylvanian conodonts and their stratigraphic relations. The University of Texas Bulletin 3201, 13–50. Swade, J.W., 1985. Conodont distribution, paleoecology, and preliminary biostratigraphy of the Upper Cherokee and Marmaton Groups (Upper Desmoinesian, Middle Pennsylvanian) from two cores in south-central Iowa. Iowa Geological Survey Technical Information Series 14, 1–71. Villa, E., van Ginkel, A.C., Leyva, F., Martínez-Chacón, M., Méndez, C., Rodríguez-González, R.M., Rodríguez, S., Sánchez de Posada, L.C., 1993. Fossil content of the Moscovian-Kasimovian boundary in a section of the Picos de Europa area (Carboniferous, NW Spain). Comptes Rendus XII ICC-P 2, 385–406. Villa, E., Alekseev, A.S., Barskov, A.S., Coquel, R., Davydov, V.I., van Ginkel, A.C., Goreva, N.V., Isakova, T.N., Kabanov, P.V., Kononova, L.I., Lazarev, S.S., Lebedev, O.A., Makhlina, M.K., Mamet, B., Martínez-Chacón, M.L., Méndez, C., Rodríguez, R.M., Rodríguez, S., Sánchez de Posada, L.C., Shkolin, A.V., 1997. Paleontological analysis and comparison of the Moscovian/Kasimovian boundary beds in the Moscow Basin (Russia) and in the Cantabrian Mountains (Spain). Prace Panstwowego Instytutu Geologicznego CLVII. Proceedings of the XIII ICC-P, Part 1, 173–185. Villa, E., van Ginkel, A.C., 2000. Some Late Moscovian and Kasimovian fusulinaceans from the Las LLacerias Section (Cantabrian Mountains, Spain). Journal of Foraminiferal Research 30, 219–243. von Bitter, P.H., Merrill, G.K., 1998. Apparatus composition and structure of the Pennsylvanian conodont genus Gondolella based on assemblages from the Desmoinesian of northwestern Illinois USA. Journal of Paleontology 72, 112–132.
Upper Moscovian-middle Kasimovian conodonts (Pennsylvanian, Carboniferous) from the Las LLacerias Section (Cantabrian Zone, north Spain) Conodontes du Moscovien supérieur-Kasimovien moyen (Pennsylvanien, Carbonifère) de la coupe de Las LLacerias (Zone Cantabrique, nord de l’Espagne) Carlos A. Méndez Departamento de Geología, Universidad de Oviedo, Campus de LLamaquique, 33005 Oviedo, Asturias, Spain Received 10 June 2004; accepted 15 November 2004 Available online 15 February 2006
Abstract Las LLacerias Section in the western part of the Picos de Europa Unit (Cantabrian Zone) in northern Spain offers the best (essentially continuous) Upper Moscovian-Kasimovian succession in the Pennsylvanian of the Cantabrian Zone. The section consists almost entirely of limestones, and conodonts are scarce in general, but some Myachkovian levels are significantly more productive. Most specimens recovered are Pa pectiniform elements, and are generally well preserved. Idiognathodus, Streptognathodus, Gondolella, and Neognathodus are the most significant genera and Ubinates and Hindeodus are present. Idiognathodus is the dominant genus. Most of the idiognathodids differ morphologically from those elsewhere, and one, Idiognathodus covadongae, is formally recognized a new species. The presence of Idiognathodus eccentricus in the upper part of the Kreviakinian levels suggests a correlation with the lower Missourian of the United States. Neognathodus disappears in the upper part of the Myachkovian beds. Gondolella pohli was recovered from a short interval in the upper portion of the Myachkovian beds. Paleoecological conditions representing shallow, open, normal marine offshore deposits of the Idiognathodus-biofacies are interpreted for the lower portion of the Myachkovian interval. © 2006 Elsevier SAS. All rights reserved. Résumé La coupe stratigraphique de Las LLacerias est située dans l’ouest de l’Unité de Picos de Europa (Zone Cantabrique) dans le nord de l’Espagne. La coupe est composée en grande partie de calcaires, en présentant la meilleure succession (essentiellement continue) du Moscovien supérieur–Kasimovien du Pennsylvanien de la Zone Cantabrique. Les conodontes y sont rares en général mais quelques niveaux myachkoviens en sont significativement plus productifs. La plupart des spécimens récoltés sont des éléments pectiniformes Pa, généralement bien conservés. Idiognathodus, Streptognathodus, Gondolella et Neognathodus sont les genres les plus remarquables. Ubinates et Hindeodus sont aussi présents. Idiognathodus serait le genre dominant. La plupart des idiognathodidés différent morphologiquement des idiognathodidés d’autres régions du monde. Une des espèces, en particulier, Idiognathodus covadongae nov. sp., est ici formellement proposée comme une nouvelle espèce. La présence d’Idiognathodus eccentricus dans la partie supérieure des niveaux kreviakiniens suggérerait une corrélation avec le Missourien inférieur des États Unis. Neognathodus disparaît dans la partie supérieure des couches myachkoviennes. Gondolella pohli fut récoltée dans un intervalle peu étendu dans la partie supérieure du Myachkovien. Les conditions paléoécologiques dans la partie inférieure des niveaux myachkoviens représenterait une sédimentation marine normale, sommaire, ouverte du biofaciès d’Idiognathodus. © 2006 Elsevier SAS. All rights reserved.
E-mail address: [email protected] (C.A. Méndez). 0016-6995/$ - see front matter © 2006 Elsevier SAS. All rights reserved. doi:10.1016/j.geobios.2004.11.002
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Keywords: Conodonts; Carboniferous; Pennsylvanian; Cantabrian Zone; North Spain Mots clés : Conodontes ; Carbonifère ; Pennsylvanien ; Zone Cantabrique ; Nord de l’Espagne
1. Introduction Carboniferous conodonts from the Cantabrian Zone of northern Spain (Fig. 1) have been investigated since 1958. The Mississippian Alba Formation (Late Tournaisian-Namurian) provides the richest and, in general, best preserved conodont fauna in the region. In contrast, Pennsylvanian conodonts are scarce but well preserved, although some levels can be significantly more productive. Moscovian to Gzhelian (Pennsylvanian) conodonts have not been as extensively studied throughout the world as those of the lower part of Mississippian and their utility for biostratigraphy may be significant, once their systematic instability is resolved. For several years the conodont research of the author has concentrated on the Upper Moscovian-Gzhelian levels of the Picos de Europa Unit of the Cantabrian Zone (northern Spain)
(Fig. 2), although other units are under study. The Picos de Europa Unit is well differentiated with good exposure of the Carboniferous succession comprising mainly marine limestones that have proved to be favourable for conodont recovery (chiefly in the Moscovian levels) (Méndez, 1990, 2002; Méndez in Villa et al., 1993 and in Villa et al., 1997). 2. Stratigraphy The Las LLacerias Section is in the western part of the Picos de Europa Unit (Fig. 2) in the locality of Las LLacerias near the village of Covadonga, within the Picos de Europa National Park. The series is shown on sheet 55 (Beleño) of the Geological Map of Spain (1:50 000) (Julivert and Navarro, 1984). The section is exposed along a footpath, which leads from the Covadonga Lakes local road to the cattle sheds of Las LLacerias (Fig. 3). The studied interval constitutes the best, and essentially continuous Upper Moscovian-Kasimovian succession in the Pennsylvanian of the Cantabrian Zone. Outcrops are discontinuous and covered by vegetation in many places. Where present, the limestone outcrops lie on both sides of the path and cross it. Lithostratigraphic units of the interval studied (Figs. 3 and 4) include the massive member (uppermost part) of the Picos de Europa Formation (Maas, 1974) followed by the Las LLacerias Formation (Villa and van Ginkel, 2000). The interval starts with a red crinoidal limestone, which is about 480 m above the base of the Picos de Europa Formation and can be traced easily in the field. Above it lie grey, sometimes red limestone beds, which are massive in places. The Las LLacerias Formation consists of grey, thin-bedded limestones with some marly limestone intervals and a few levels of sandy limestone near the top. The age of the succession is middle Myachkovian-Khamonivkian based on fusulinoideans (Villa et al., 1997; Villa and van Ginkel, 2000). The Moscovian-Kasimovian boundary lies within the sequence at the lower part of Interval 5 (Fig. 4), along which a succession of Protriticites (fusulinoideans) faunas from primitive to typical forms occur. 3. The conodont fauna and comments about correlation
Fig. 1. Geological map of the Iberian Variscan Belt. The Cantabrian Zone is situated in the north (horizontal line drawing) (after Julivert et al., 1972). Fig. 1. Carte géologique de la Bande Varisque Ibérique. La Zone Cantabrique (représentée par des lignes horizontales) est située dans le Nord (d’après Julivert et al., 1972).
Conodonts are scarce in general in the Las LLacerias Section, but some Myachkovian levels in the Upper Moscovian are significantly more productive. A major reduction in the number of conodont elements occurs in the Kasimovian (Kreviakinian and Khamonivkian) beds (Fig. 4). Specimens recovered are mainly Pa pectiniform elements and are generally well preserved. Other elements of the conodont apparatus are not very well preserved nor are they common.
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Fig. 2. Geological sketch map of the Cantabrian Zone showing the position of the Las LLacerias Section (after Julivert, 1971 and Pérez Estaún et al., 1988). Fig. 2. Carte géologique schématique de la Zone Cantabrique montrant la situation de la coupe stratigraphique de Las LLacerias (d’après Julivert, 1971 et Pérez Estaún et al., 1988).
Idiognathodus, Streptognathodus, Gondolella, and Neognathodus are the most significant genera present for biostratigraphy. Ubinates and Hindeodus are also present. Idiognathodus is the dominant genus and extends from the middle Myachkovian into the Khamonivkian, but is much more abundant in Myachkovian beds. The idiognathodids are morphologically different from those elsewhere, except I. eccentricus. At least one of the different forms is a new species, Idiognathodus covadongae, nov. sp. However, half show affinities with species from the Moscow Basin and the Donets Basin. These forms are Idiognathodus aff. I. podolskensis Goreva, I. aff. I. trigonolobatus Barskov and Alekseev, and I. aff. I. sagittalis Kozitskaya. We found I. eccentricus (sample LL-9030, Fig. 4) in the upper part of the Kreviakinian levels 16 m below the entry of the fusulinoidean species Montiparus, that is, the base of Khamonivkian. In their provisional conodont zonation for the Late Pennsylvanian in North American Midcontinent Region, Barrick and Heckel (2000) propose the Idiognathodus eccentricus Zone (lowest Missourian) to extend from the first appearance of the nominate species up to the first appearance of Streptognathodus cancellosus. In North America, I. eccentricus ranges into the Streptognathodus cancellosus Zone. These data suggest the correlation of a level within the upper part of the Kreviakinian beds in Las LLacerias Section with the lower Missourian. Idiognathodus covadongae, nov. sp. is a form with a biostratigraphic range potentially restricted to the Myachkovian, below the extinction of the genus Neognathodus.
The rest of idiognathodids are placed in open nomenclature as Idiognathodus sp. The morphology of these specimens is distinctive, and at the same time, highly variable, so it is not possible at the moment to assign the material to a species level taxon with certainty. Streptognathodus, which is relatively scarce, appears in the upper Myachkovian a few metres above the extinction of Neognathodus and it ranges to the Khamonivkian near the top of the studied interval. In this part of the series Idiognathodus and Streptognathodus are the only conodonts recovered, although idiognathodids are more diversified and a little more abundant than streptognathodids. With the exception of Streptognathodus aff. S. subexcelsus, whose position in the upper Myachkovian in LLacerias Section is near to that of the entry of Streptognathodus subexcelsus in the Donets Basin, the material recovered is assigned to the genus without specific determination; the low number of specimens prevents any definitive consideration beyond the generic level. Gondolella is recorded from the middle to upper Myachkovian, and is represented by Gondolella laevis, Gondolella pohli, and specimens of Gondolella sp. We have recently recovered G. pohli from a short interval in the upper portion of the Myachkovian levels. This species was reported in North America from the middle to ? upper Desmoinesian (von Bitter and Merrill, 1998) in northwestern Illinois, western Indiana and south-central Iowa, and from the middle Desmoinesian (Barrick et al., 2002) in the Midcontinent. Therefore, the base of the Missourian could be correlative, not with the base of
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Genus Gondolella Stauffer and Plummer, 1932. Type species: Gondolella elegantula Stauffer and Plummer, 1932.
Fig. 3. Geological sketch map of the zone around Las LLacerias Section (after Marquínez et al., 1982). Fig. 3. Géologie détaillée près de la localité de Las LLacerias (d’après Marquínez et al., 1982).
Kasimovian, but higher as suggested by some authors (for example: Villa and van Ginkel, 2000). Neognathodus ranges through most of the Myachkovian levels, until the genus disappears in the upper part of Interval 4 with the loss of Neognathodus aff. N. inaequalis (Fig. 4). This taxon was reported from the Myachkovian of the Donets Basin, and from the Podolskian to Myachkovian of the Moscow Basin. Neognathodus is not recorded in levels higher than Moscovian in the Moscow Basin or Donets Basin. The same holds in the Las Llacerias Section, where Neognathodus is not recovered in beds dated as Kasimovian. Several specimens are assigned to Hindeodus sp. due to low numbers and poor preservation. About one half of the conodont taxa identified at species level show affinities with those of the Moscow Basin and Donets Basin, except Idiognathodus trigonolobatus Barskov and Alekseev, reported from the Moscow Basin only. 4. Systematic paleontology The material illustrated and/or described is deposited in the Department of Geology (Paleontology) of the University of Oviedo (DPO).
Gondolella laevis Kossenko and Kozitskaya in Kossenko, 1975. (Pa element). Fig. 5(3A, 3B) (A synonymy was provided by Méndez et al., 1998 for this species). Material: Two well-preserved specimens: DPO 126. 338 and 126. 339 (sample S-230, Picos de Europa Formation). Description: In upper view, elongate specimens with a slight bend; anterior end pointed; platform smooth, narrow, slightly concave, and more wide in the posterior half; carina with several denticles situated in the centre of the platform; cusp inclined in posterior direction very close to the posterior end of the unit. In lower view, basal cavity very broad, deep, and situated in a posterior position; this structure is bordered by a loop, back closed, and continues to the anterior end of the unit like a grooved keel. No microsculpture has been observed. Remarks: The characteristics of the Gondolella laevis material from this locality and those of the Río Nevandi Section were dealt with in Méndez et al. (1998). The general features of the Pa element of this species are like those of G. laevis Kossenko and Kozitskaya, in Kossenko, 1975 from the Myachkovian of the Donets Basin. Distribution: middle Myachkovian. Gondolella pohli von Bitter and Merrill, 1998. (Pa element). Fig. 5(2A, 2B). 1975. Gondolella bella? Stauffer and Plummer—Merrill, 1975 pp. 58, Fig. 17: 3 (only). 1985. Gondolella sp. 1—Swade, Pl. 4, Fig. 18: 44, 45. *1998. Gondolella pohli n. sp.—von Bitter and Merrill, p. 128, Figs. 3–8. V.1998. Gondolella nov. sp. 1—Méndez et al., p. 344, Fig. 6: 8, 9. 2001. Gondolella pohli von Bitter and Merrill—Rexroad et al., p. 2, Fig. 5: 13–18. Material: Two specimens, one of them damaged: DPO 38518 and DPO 126.341 (samples S-370 and S-232, respectively, Picos de Europa Formation). Remarks: This species is quite similar to Gondolella laevis, from which it is distinguished by a “significantly wider Pa element platform” (von Bitter and Merrill, 1998). The platform in our material is very well developed, like that of Gondolella pohli von Bitter and Merrill, 1998 from the Desmoinesian of northwestern Illinois (USA). The outline of the posterior half of the platform in one of our specimens (Fig. 5B) resembles a specimen figured and described by Swade (1985) as Gondolella sp. 1 (Fig. 18: 45)
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Fig. 4. Location of samples and conodont distribution along the uppermost part of the Picos de Europa Formation and the Las LLacerias Formation within the Las LLacerias Section. 1–10 = sedimentological intervals distinguished in Villa et al. (1993) (after Méndez, 2002, modified). Fig. 4. Situation des échantillons et distribution des conodontes tout au long de la partie la plus supérieure de la Formation Picos de Europa et de la Formation Las LLacerias dans la coupe stratigraphique de Las LLacerias. 1–10 = intervalles sédimentologiques distingués par Villa et al. (1993) (d’après Méndez, 2002, modifié).
from the Verdigris Formation (Demoinesian) in the Midcontinent of the United States. Distribution: middle to Upper Myachkovian. Genus Idiognathodus Gunnell, 1931. Type species: Idiognathodus claviformis Gunnell, 1931. Idiognathodus eccentricus (Ellison, 1941). (Pa element). Fig. 5(14). Material: One specimen: DPO 38532 (sample LL-9030, Las LLaceriasFormation). Description: Pectiniform element. In upper view unit lanceolate, most of the outer margin of platform convex, inner margin relatively straight, both margins join posteriorly to pro-
duce a moderately pointed form; a couple of short, nodose adcarinal ridges are present anteriorly; poorly defined eccentric trough in the posterior part of the platform cuts several welldeveloped transverse ridges; carina of moderate length, a few irregular nodes are situated below it; lobes poorly developed: outer lobe with two nodes and inner lobe with one node. Remarks: The trough on the inner side of the platform, the lobes on both sides of this structure, together with the relatively long carina permit us to assign this specimen to Idiognathodus eccentricus (Ellison). We agree with the concept of Barrick and Walsh (1999) for this species, as the holotype figured by Ellison (1941) is early Missourian in age, and distinct from the late Missourian to early Virgilian eccentric Pa elements. On the other hand, our specimen shows some similarity to one figured by Barrick and Boardman (1989: Pl. 1, Fig. 8)
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Fig. 5. 1, 6. Idiognathodus covadongae nov. sp., 1, upper view, × 52, holotype. Picos de Europa Formation, sample S-230 (DPO 38517); 6, upper view, × 62, paratype. Picos de Europa Formation, sample S-231 (DPO 38536). 2a, 2b. Gondolella pohli Von Bitter and Merrill, 1998. 2a, upper view, × 43, 2b, lower view, × 38. Picos de Europa Formation, sample S-370 (DPO 38518). 3a, 3b. Gondolella laevis Kossenko and Kozitskaya, 1975. 3a, upper view, × 48, 3b, lower view, × 50. Picos de Europa Formation, sample S-230 (DPO 38519). 4. Streptognathodus aff. S. subexcelsus Alekseev and Goreva, 2001, upper view, × 54. Picos de Europa Formation, sample S-232 (DPO 38520). 5. Idiognathodus sp., upper view, × 29. Las LLacerias Formation, sample LL-9030 DPO (38521). 7. Neognathodus aff. N. inaequalis Kozitskaya and Kossenko, 1978, upper view, × 68, Picos de Europa Formation, sample S-232b (DPO 38529). 8, 9. Streptognathodus sp. 8, upper view, × 46. Picos de Europa Formation, sample LL-9022 (DPO 38523), 9, upper view, × 34. Picos de Europa Formation, sample LL-9022 (DPO 38524). 10. Ubinates sp., inner lateral view, × 30. Picos de Europa Formation, sample S-230 (DPO 38528). 11. Idiognathodus aff. I. trigonolobatus Barskov and Alekseev, 1976, upper view, × 33. Picos de Europa Formation, sample LL-9026 (DPO 38526). 12. Idiognathodus sp. B, upper view, × 46. Picos de Europa Formation, sample S-230 (DPO 38527). 13. Idiognathodus aff. I. podolskensis Goreva, 1984, upper view, × 31. Picos de Europa Formation, sample S-371 (DPO 38530). 14. Idiognathodus eccentricus (Ellison, 1941), upper view, × 52. Las LLacerias Formation, sample, LL-9030 (DPO 38532). 15, 16. Idiognathodus aff. I. sagittalis Kozitskaya, 1978. 15, upper view, × 38. Las LLacerias Formation, sample S-236-K (DPO 38540), 16, upper view, × 38. Las LLacerias Formation, sample S-236-K (DPO 38531). All illustrated specimens are Pa elements except that of Fig. 10 (X element). DPO is the repository number in the Department of Geology (Paleontology). University of Oviedo. Fig. 5. 1, 6. Idiognathodus covadongae nov. sp., 1, vue supérieure, × 52, holotype. Formation Picos de Europa, échantillon S-230 (DPO 38517) ; 6, vue supérieure, × 62, paratype. Formation Picos de Europa, échantillon S-231 (DPO 38536). 2a, 2b. Gondolella pohli von Bitter et Merrill, 1998. 2a, vue
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from upper Salesville core shale (lower Missourian) of northcentral Texas, USA. Distribution: Kreviakinian. Idiognathodus covadongae nov. sp. (Pa element) Fig. 5(1, 6) Material: Seven well-preserved specimens, one of them the holotype: DPO 38517 (sample S-230, Picos de Europa Formation); the rest are paratypes from the same formation: DPO 38533 (sample S-370); DPO 38534-38538 (sample S-231). Locus typicus: Near Covadonga Village. Left side of the footpath that leads from the Covadonga Lakes local road to the cattle sheds of Las LLacerias, down to the road, in the middle of the meadow (Fig. 3). Stratum typicum: Level of red crinoidal limestone. At the base of the studied interval (Fig. 4). Derivatio nominis: After the name of my wife Covadonga. Diagnosis: A species of the genus Idiognathodus whose Pa element has a well-developed lanceolate platform with a field of numerous transverse ridges; field of transverse ridges subrhombic in outline and slightly depressed, greatest width near anterior one third. Description: In upper view platform lanceolate, outline subtriangular, inner margin slightly bent, outer margin rounded; unit posteriorly pointed; adcarinal ridges converge towards carina anteriorly in the platform then diverge, develop and go away tending to fuse with the free blade; inner adcarinal ridge more developed in some specimens showing short ridges; field with numerous transverse ridges on platform, sub-rhombic in outline and slightly depressed, greatest width near anterior one third; carina short; lobes not equally developed, situated towards the anterior termination of platform, the inner more developed with several relatively abundant organised nodes semicircular in outline, the outer with a row of a few nodes. Remarks: Idiognathodus covadongae shows some similarity with Idiognathodus podolskensis Goreva, 1984, recorded from the Podolskian of the Moscow Basin and the Myachkovian of the Donets Basin. However, our species has a more elongate platform and the field of transverse ridges is subrhombic, not subtriangular like that of Russian species. Another species that shows some similarity with ours is Idiognathodus obliquus Kossenko and Kozitskaya, 1978, re-
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corded from Podolskian to Myachkovian from the Donets Basin and from Kashirian to Myachkovian from the Moscow Basin. Nevertheless the Spanish species has a more bent inner margin, a more elongate platform, a more depressed ridged field of the platform, and less developed lobes than in the Russian species. Distribution: middle to upper Myachkovian. Idiognathodus aff. I. podolskensis Goreva, 1984. (Pa element). Fig. 5 (13). Material: Two specimens: DPO 38530 and DPO 38539 (sample S-371, Picos de Europa Formation). Description: In upper view, platform very long, subtriangular, outer margin convex, inner margin straight or relatively straight, both margins join posteriorly giving way to an acute termination; platform with a slightly concave subtriangular field of numerous transverse ridges, greatest width in the anterior one-half; adcarinal ridges approach to carina near the anterior termination of platform then diverge, the inner giving way to a parapet-like structure (with short ridges in the adult figured specimen); carina very short; lobes not equally developed, situated near the anterior termination of platform, outer lobe poorly developed with several nodes, inner lobe semi-circular with several irregular coarse nodes. Remarks: Our material resembles Idiognathodus podolskensis Goreva, 1984, from the Podolskian of the Moscow Basin and the Myachkovian of the Donets Basin, but differs by its more elongate platform. Distribution: middle to upper Myachkovian. Idiognathodus aff. I. sagittalis Kozitskaya in Kozitskaya et al., 1978. (Pa element). Fig. 5 (15, 16). Material: Five specimens with acceptable preservation: DPO 38531, DPO 38540, DPO 38541 and DPO 38542 (sample S-236-K, Las LLacerias Formation); DPO 38543 (sample S-238, Las LLacerias Formation). Description: In upper view, platform resembles an arrowhead, inner margin slightly convex, outer margin more convex; unit posteriorly pointed; adcarinal ridges (when present) converge near anterior termination of platform, then diverge and
supérieure, × 43, 2b, vue inférieure, × 38. Formation Picos de Europa, échantillon S-370 (DPO 38518). 3a, 3b. Gondolella laevis Kossenko et Kozitskaya, 1975. 3a, vue supérieure, × 48, 3b, vue inférieure, × 50. Formation Picos de Europa, échantillon S-230 (DPO 38519). 4. Streptognathodus aff. S. subexcelsus Alekseev et Goreva, 2001, vue supérieure, × 54. Formation Picos de Europa, échantillon S-232 (DPO 38520). 5. Idiognathodus sp., vue supérieure, × 29. Formation Las LLacerias, échantillon LL-9030 (DPO 38521). 7. Neognathodus aff. N. inaequalis Kozitskaya et Kossenko, 1978, vue supérieure, × 68. Formation Picos de Europa, échantillon S-232b (DPO 38529). 8, 9. Streptognathodus sp. 8, vue supérieure, × 46. Formation Picos de Europa, échantillon LL-9022 (DPO 38523), 9, vue supérieure, × 34. Formation Picos de Europa, échantillon LL-9022 (DPO 38524). 10. Ubinates sp., vue latérale interne, × 30. Formation Picos de Europa, échantillon S-230 (DPO 38528). 11. Idiognathodus aff. I. trigonolobatus Barskov et Alekseev, 1976, vue supérieure, × 33. Formation Picos de Europa, échantillon LL-9026 (DPO 38526). 12. Idiognathodus sp. B, vue supérieure, × 46. Formation Picos de Europa, échantillon S-230 (DPO 38527). 13. Idiognathodus aff. I. podolskensis Goreva, 1984, vue supérieure, × 31. Formation Picos de Europa, échantillon S-371 (DPO 38530). 14. Idiognathodus eccentricus (Elison, 1941), vue supérieure, × 52. Formation Las LLacerias, échantillon LL-9030 (DPO 38532). 15, 16. Idiognathodus aff. I. sagittalis Kozitskaya, 1978. 15, vue supérieure, × 38. Formation Las LLacerias, échantillon S-236-K (DPO 38540), 16, vue supérieure, × 38. Formation Las LLacerias, échantillon S-236-K (DPO 38531). Tous les spécimens figurés sont des éléments Pa à l’exception du 10 (élément X) et ont été déposés au Département de Géologie (Paléontologie) de l’Université d’Oviedo (DPO).
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go away for some distance before fusing with free blade, inner adcarinal ridge more developed with very short ridges from the anterior termination of platform until their fusion with free blade; field of transverse ridges on platform mostly triangular, with a variable number (but never much) of poorly developed ridges in a couple of specimens (Fig. 5: 15, 16), the posterior most are interrupted, greatest width in anterior one-half; carina short in general; lobes well developed in more adult specimens, the inner usually with several nodes situated on a flaring structure, the outer with fewer nodes in a variable arrangement. Remarks: Our material resembles Idiognathodus sagittalis Kozitskaya in Kozitskaya et al., 1978, recorded from Kasimovian of the Russian Platform and the Donets Basin. The differences are in the more narrow outline of platform and more elongate field of transverse ridges in our material. Distribution: Kreviakinian-Khamonivkian. Idiognathodus aff. I. trigonolobatus Barskov and Alekseev, 1976. (Pa element). Fig. 5(11). Material: One well-preserved specimen: DPO 38526 (sample LL-9026, Picos de Europa Formation). Description: In upper view, platform with irregular outline, inner margin strongly convex in anterior half and moderate in posterior half, outer margin mostly straight with a strong curvature near the anterior termination of platform; unit posteriorly pointed; inner adcarinal ridge moderately developed, short, continues anteriorly like a ridged parapet from the termination of platform until its fusion with free blade; field of transverse ridges on the platform sub-rhombic with a moderate number of ridges, some of them poorly defined and broken into nodes, greatest width in anterior one half; lobes not equally developed, occupy much of the platform, inner lobe not rounded, very developed, showing a flaring structure with two different node sizes arranged in rows, outer lobe rounded, very poorly defined, fused to the platform with a few coarse nodes. Remarks: Our specimen resembles Idiognathodus trigonolobatus Barskov and Alekseev, 1976, recorded from Myachkovian to Kreviakinian in the Moscow Basin. However, the Russian species has a convex outer platform margin, triangular field of transverse ridges on the platform, rostral ridges that are not as wide, and an inner lobe that is more rounded. Distribution: Kreviakinian. Idiognathodus sp. B. (Pa element). Fig. 5(12). Material: Six mostly well-preserved specimens: DPO 38527, DPO 38545 to 38549 (sample S-230, Picos de Europa Formation). Description: In upper view, moderately curved, long, subtriangular platform, posteriorly pointed; inner margin mostly straight, can be concave about the middle or irregular, outer margin convex, more strongly near the anterior termination;
short adcarinal ridges initiate near the anterior termination of the platform and extend anteriorly like nodose or ridged parapets, although fusion with the free blade does not take place in all specimens (when visible), standing as free edges, inner adcarinal ridge more developed; field of numerous transverse ridges on the platform mostly sub-rhombic, greatest width in anterior one-half; short strong carina; lobes in general integrated into the platform, mostly well developed, sub-rounded inner lobe with abundant nodes that tend to be arranged in rows, sometimes fused, outer lobe, slightly droping, shoulderlike, extending posteriorly, giving a robustness to the platform, nodes on outer lobe sometimes abundant. Remarks: The long platform, short, strong, carina, well-developed adcarinal ridges, and shape of outer lobe are the main characteristics of this form, which probably represents a new species, although the modest number of specimens and absence in other samples prevent a formal definition. The subtriangular shape of the platform, development of the outer lobe, and non-depressed field of transverse ridges on the platform are major differences with Idiognathodus covadongae nov. sp. described in this paper. The non-depressed field of transverse ridges on the platform, development of the lobes, shape of the outer lobe, and more abundant nodes in relation to the adult specimen of Idiognathodus aff. podolskensis are the main differences with the latter. Distribution: middle Myachkovian. Genus Neognathodus Dunn, 1970. Type species: Polygnathus bassleri Harris and Hollingsworth, 1933. Neognathodus aff. N. inaequalis Kozitskaya and Kossenko in Kozitskaya et al., 1978. (Pa element). Fig. 5(7). Material: Four specimens with acceptable preservation (one adult and three juveniles): DPO 38529 (sample S-232b, Picos de Europa Formation). Description: In upper view, platform slightly bowed, sublanceolate, posteriorly pointed, directed downwards in the adult specimen, greatest width in anterior one-third; blade continues posteriorly on platform as a strong, high carina that terminates near to the posterior end of the unit, ends as a few nodes except in juveniles where this structure is unbroken, carina higher than platform in adult and in one larger juvenile specimen; outer side of platform is a slightly steep parapet with short ridges, not very wide and reduced near its posterior termination to the end of the unit, essentially parallel to carina, separated from it by a slight sulcus crossed by a few ridges near the posterior end of the unit; in most juvenile specimens outer parapet reduced or absent; inner side of platform developed like the outer in a very much wider structure, steeper with developed radiating ridges, moderate sulcus separates the carina from inner side of platform; both parapets converge at the posterior end of the unit.
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Remarks: The morphology displayed by our specimens resembles that of Neognathodus inaequalis Kozitskaya and Kossenko in Kozitskaya et al., 1978, recorded from the Myachkovian of the Donets Basin and from Podolskian to Myachkovian of the Moscow Basin, but have a wider and less triangular platform. Distribution: upper Myachkovian. Genus Streptognathodus Stauffer and Plummer, 1932. Type species: Streptognathodus excelsus Stauffer and Plummer, 1932. Streptognathodus aff. S. subexcelsus Alekseev and Goreva in Makhlina et al., 2001. (Pa element). Fig. 5(4). Material: Two specimens: DPO 38520 and DPO 38545 (sample S-232, Picos de Europa Formation). Description: In upper view, unit lanceolate; outer and inner margins convex, more so for the outer; platform, wide, tonguelike, slightly depressed towards the middle in the surface posterior to the end of carina, where several transverse ridges exist, surface of platform mostly directed downwards; carina, short, ending near the anterior termination of the platform; adcarinal ridges, not very long, fused with the free blade, developed towards its anterior part in wide, steep, structures ornamented with short ridges; lobes situated near the anterior termination of the platform in the more adult specimen, outer lobe poorly developed, with one or few nodes, inner lobe, well developed, showing a variable number of coarse nodes. Remarks: The material described resembles Streptognathodus subexcelsus Alekseev and Goreva in Makhlima et al., 2001, from the Kreviakinian of the Moscow Basin and Myachkovian to Kreviakinian of the Donets Basin. Differences exist, however, such as the wider, not subtriangular, depressed area of the platform, and the less well-developed outer lobe in the Spanish form. Distribution: upper Myachkovian. Streptognathodus spp. (Pa Elements). Fig. 5(8, 9). Material: Nineteen specimens: DPO 38546 to 38551 (sample S-232, Picos de Europa Formation); DPO 38552 and DPO 38553 (sample S-234, Picos de Europa Formation); DPO 38523 to 38525 (sample LL 9022, Picos de Europa Formation); DPO 38554 (sample LL-9026, Picos de Europa Formation); DPO 38555 to 38557 (sample S-239, Las LLacerias Formation); DPO 38558 to 38560 (sample S-240, Las LLacerias Formation). Remarks: The specimens assigned to this genus (some of them juveniles) that were recovered in the studied interval show several types of morphologies, including forms with long carinae, present or absent inner lobe, and a variable number of transverse ridges below the carina. An additional another different morphology also exists. It’s possible that all of these
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belong to a few species, but the paucity of material precludes any specific assignment now. Distribution: middle Myachkovian-Khamonivkian. Genus Ubinates (Baesemann, 1973). Type species: Ubinates advena (Baesemann, 1973). (X element). Fig. 5(10) Material: One relatively well-preserved specimen: DPO 38528 (sample S-230, Picos de Europa Formation). Description: In lateral view, anterior process laterally compressed, deflected downward, denticles on the process, the second from the cusp is the largest; posterior process sinuously deflected, one discrete denticle preserved only; pit expanded inward. Remarks: The unique element we recovered, although not very well preserved, shows in general the same features described for the Aethotaxis, X element by Baesemann (1973), the author who erected the genus. That name was later changed to Ubinates, nomen novum by Baesemann and Purnell (2000), because Aethotaxis was preoccupied. Distribution: middle Myachkovian. 5. Some remarks on paleoecological conditions A thick limestone succession representing rapid sedimentation characterizes the lower part of the studied interval. Paleoecological conditions derived from the conodonts are best limited to the lower part, where the number of specimens is higher. The absence of Adethognathus shows us that nearshore biofacies must be excluded. Idiognathodus is the dominant genus throughout the interval studied. An Idiognathodus-biofacies is present from the level S-230 to the level S-231, in the lower part of the Myachkovian beds (Fig. 4), where the number of the specimens of that genus is higher. According to Merrill and von Bitter (1976), the Idiognathodus-biofacies is one that dominates most Pennsylvanian sedimentary rocks, and represents shallow, open, normal marine offshore deposits. Sedimentological data from Leyva (in Villa et al., 1993) indicate a platform-lagoon in the levels with abundant Idiognathodus (sedimentological intervals 1–3, Fig. 4). A more recent sedimentological study from Bahamonde et al. (2000) indicates a shallow, flat-topped platform environment with a poorly rhythmic character for the same intervals. Acknowledgements This work has been supported by Spanish government funding through Project BTE 2003-01012. The paper benefited from referees’ comments by Dr. James E. Barrick, Texas Tech University and Dr. Hans P. Schönlaub, Geologische Bundesansalt, Viena. Thanks are also due to Dr. Lance L. Lambert, University of Texas at San Antonio, for his revision of the English
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language and useful suggestions, Dr. J.L. García-Alcalde, Universidad de Oviedo, for his revision of the French language of the abstract and Dr. C. Brime, from the same university, for her help with the figures format. The author wants to thank Mr. Severino Méndez for his valuable help in the field work. References Baesemann, J., 1973. Missourian (Upper Pennsylvanian) conodonts of northeastern Kansas. Journal of Paleontology 47, 689–710. Baesemann, J., Purnell, M., 2000. Ubinates, a new name for the genus Aethotaxis Baesemann, 1973 (Vertebrata, Conodonta) preoccupied by Aethotaxis De Witt, 1962 (Vertebrata, Osteichtyes). Journal of Paleontology 74, 544. Bahamonde, J.R., Vera, C., Colmenero, J.R., 2000. A steep-fronted Carboniferous carbonate platform: clinoformal geometry and lithofacies (Picos de Europa, NW Spain). Sedimentology 47, 645–664. Barrick, J.E., Boardman II, D.R., 1989. Stratigraphic distribution of morphotypes of Idiognathodus and Streptognathodus in Missourian-lower Virgilian strata, north central Texas. In: Boardman II, D.R., Barrick, J.E., Cocke, J., Nestell, M.K. (Eds.), Middle and Late Pennsylvanian chronostratigraphic boundaries in north-central Texas: glacial-eustatic events, biostratigraphy and paleoecology: a guidebook.-Part II: contributed papers. Texas Tech University. Studies in Geology 2. pp. 167–188. Barrick, J.E., Walsh, T.R., 1999. Some older north American types of Idiognathodus and Streptognathodus. In: Heckel, P.H. (Ed.), Middle and Upper Pennsylvanian (Upper Carboniferous) Cyclothem Succession in Midcontinent Basin, USA. XIV International Congress on the Carboniferous-Permian, Field Trip #8 Guidebook. Kansas Geological Survey, Open-file Report 99/27, pp. 147–161. Barrick, J.E., Heckel, P.H., 2000. A provisional conodont zonation for Late Pennsylvanian (late Late Carboniferous) strata in Midcontinent Region of North America. Newsletter on Carboniferous Stratigraphy 18, 15–21. Barrick, J.E., Lambert, L.L., Heckel, P.H., 2002. Pennsylvanian conodont zonation for Midcontinent North America. Eighth International Conodont Symposium in Europe, ECOS VIII, abstracts, Strata (1) 12, p. 74. Barskov, I.S., Alekseev, A.S., 1976. New species of the genus Idiognathodus (Conodonta) from the Middle Upper Carboniferous of the Moscow Region. Paleontologicheskiy Zhurnal 4, 119–121 (in Russian). Dunn, D.L., 1970. Middle Carboniferous conodonts from western United States and phylogeny of the platform group. Journal of Paleontology 44, 312–342. Ellison, S., 1941. Revision of the Pennsylvanian conodonts. Journal of Paleontology 15, 107–143. Goreva, N.V., 1984. Moscovian conodonts of the Moscow Syneclise. In: Menner, V.V. (Ed.), Paleontologichyeskaya jarakteristika stratotipicheskij i opornîj razrezov karbona moskovskoy sineklizî. Moscow University Press, Moscow, pp. 44–123 (in Russian). Gunnell, F.H., 1931. Conodonts from the Ford Scott Limestone of Missouri. Journal of Paleontology 5, 244–252. Harris, R.W., Hollingsworth, R.V., 1933. New Pennsylvanian conodonts from Oklahoma. American Journal of Science 25, 193–204. Julivert, M., 1971. Décollement tectonics in the Hercynian Cordillera of northwest Spain. American Journal of Science 270, 1–29. Julivert, M., Fontboté, J.M., Ribeiro, A., Conde, L., 1972. Mapa Tectónico de la Península Ibérica y Baleares. E1: 1000000. Instituto Geológico y Minero de España, Madrid 1–119. Julivert, M., Navarro, D., 1984. Mapa Geológico de España. E1: 50 000. Hoja no. 55 (15-5), Beleño. Instituto Geológico y Minero de España, Madrid 1– 47. Kozitskaya, R.I., Kossenko, Z.A., Lipnyagov, O.M., Nemirovskaya, T.I., 1978. Konodontî karbona donetskogo basseyna. Izd-vo Nauka Dumka, Kiev, 1–136 (in Russian). Kossenko, Z.A., 1975. New species of conodonts from the deposits of the Moscovian stage in the southwestern part of the Donets Basin. Academy Nauk USSR. Geologicheskiy Zhurnal 35, 126–133 (in Russian, with English abstract).
Makhlina, M.Kh., Alekseev, A.S., Goreva, N.V., Gorjunova, R.V., Isakova, T.N., Kossovaya, O.L., Lazarev, S.S., Lebedev, O.A., Shkolin, A.A., (Alekseev, A.S. and Shik, S.M., Eds.), 2001. Sredniy karbon Moskovskoy sineklizî (yuzhnaya chast’). Tom 2. Paleontologicheskaya jarakteristika. (Paleontological Institute). Moscow: Scientific World (in Russian, with English abstract). Maas, K., 1974. The geology of Liebana, Cantabrian Mountains, Spain; deposition and deformation in a flysch area. Leidse Geologische Mededelingen 49, 379–465. Marquínez, J., Méndez, C.A., Menéndez-Alvarez, J.R., Sánchez de Posada, L. C., Villa, E., 1982. Datos bioestratigráficos de la sucesión carbonífera (Turnesiense-Kasimoviense) de Las LLacerias, Picos de Europa, Norte de España. Trabajos de Geología de la Universidad de Oviedo 12, 187–193. Méndez, C.A., 1990. Conodontos del Carbonífero Superior de la Cordillera Cantábrica. Ph.D. Dis. (unpublished), Universidad de Oviedo 1–213. Méndez, C.A., 2002. Carboniferous conodonts of the Ponga and Picos de Europa units (Cantabrian Zone, North Spain). In: García-López, S., Bastida, F. (Eds.), Palaeozoic conodonts from northern Spain. Instituto Geológico y Minero de España, serie Cuadernos del Museo Geominero 1. pp. 207–227. Méndez, C.A., García López, S., Sánchez de Posada, L.C., 1998. Gondolellidae (Conodonta), del Carbonífero Superior de la Zona Cantábrica (N. de España). Sistemática e implicaciones paleotérmicas. Geobios 31, 337–348. Merrill, G.K., 1975. Pennsylvanian conodont biostratigraphy and paleoecology of northwestern Illinois. The Geological Society of America, Inc. Microform Publication 3, 1–128. Merrill, G.K., von Bitter, P.H., 1976. Revision of conodont biofacies nomenclature and interpretations of environmental controls in Pennsylvanian rocks of eastern and central North America. Life Sciences Contributions Royal Ontario Museum 108, 1–46. Pérez Estaún, A., Bastida, F., Alonso, J.L., Marquínez, J., Aller, J., Alvarez Marrón, J., Marcos, A., Pulgar, J.A., 1988. A thin-skinned tectonics model for an arcuate fold and thrust belt: the Cantabrian Zone. Tectonics 7, 517– 537. Rexroad, C.B., Wade, J.A., Merrill, G.K., Brown, L.M., Padgett, P., 2001. Conodont biostratigraphy and depositional environments of the Mecca Quarry Shale Member and the Velpen Limestone Member of the Linton Formation (Pennsylvanian, Desmoinesian) in the eastern part of the Illinois Basin, USA. Indiana Geological Survey Special Report 63, 1–17. Stauffer, C.R., Plummer, H.J., 1932. Texas Pennsylvanian conodonts and their stratigraphic relations. The University of Texas Bulletin 3201, 13–50. Swade, J.W., 1985. Conodont distribution, paleoecology, and preliminary biostratigraphy of the Upper Cherokee and Marmaton Groups (Upper Desmoinesian, Middle Pennsylvanian) from two cores in south-central Iowa. Iowa Geological Survey Technical Information Series 14, 1–71. Villa, E., van Ginkel, A.C., Leyva, F., Martínez-Chacón, M., Méndez, C., Rodríguez-González, R.M., Rodríguez, S., Sánchez de Posada, L.C., 1993. Fossil content of the Moscovian-Kasimovian boundary in a section of the Picos de Europa area (Carboniferous, NW Spain). Comptes Rendus XII ICC-P 2, 385–406. Villa, E., Alekseev, A.S., Barskov, A.S., Coquel, R., Davydov, V.I., van Ginkel, A.C., Goreva, N.V., Isakova, T.N., Kabanov, P.V., Kononova, L.I., Lazarev, S.S., Lebedev, O.A., Makhlina, M.K., Mamet, B., Martínez-Chacón, M.L., Méndez, C., Rodríguez, R.M., Rodríguez, S., Sánchez de Posada, L.C., Shkolin, A.V., 1997. Paleontological analysis and comparison of the Moscovian/Kasimovian boundary beds in the Moscow Basin (Russia) and in the Cantabrian Mountains (Spain). Prace Panstwowego Instytutu Geologicznego CLVII. Proceedings of the XIII ICC-P, Part 1, 173–185. Villa, E., van Ginkel, A.C., 2000. Some Late Moscovian and Kasimovian fusulinaceans from the Las LLacerias Section (Cantabrian Mountains, Spain). Journal of Foraminiferal Research 30, 219–243. von Bitter, P.H., Merrill, G.K., 1998. Apparatus composition and structure of the Pennsylvanian conodont genus Gondolella based on assemblages from the Desmoinesian of northwestern Illinois USA. Journal of Paleontology 72, 112–132.