Upper Moscovian-middle Kasimovian conodonts (Pennsylvanian, Carboniferous) from the Las LLacerias Section (Cantabrian Zone, north Spain)

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Geobios 39 (2006) 245–254

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Upper Moscovian-middle Kasimovian conodonts(Pennsylvanian, Carboniferous) from the Las LLacerias

Section (Cantabrian Zone, north Spain)

Conodontes du Moscovien supérieur-Kasimovien moyen

dress:

- see fr.geobio

(Pennsylvanien, Carbonifère) de la coupe de Las

Carlos A. Méndez

Departamento de Geología, Universidad de Oviedo, Campus de LLamaquique, 33005 Oviedo, Asturias, Spain

Received 10 June 2004; accepted 15 November 2004Available 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 con-tinuous) Upper Moscovian-Kasimovian succession in the Pennsylvanian of the Cantabrian Zone. The section consists almost entirely of lime-stones, and conodonts are scarce in general, but some Myachkovian levels are significantly more productive. Most specimens recovered are Papectiniform elements, and are generally well preserved. Idiognathodus, Streptognathodus, Gondolella, and Neognathodus are the most significantgenera and Ubinates and Hindeodus are present. Idiognathodus is the dominant genus. Most of the idiognathodids differ morphologically fromthose elsewhere, and one, Idiognathodus covadongae, is formally recognized a new species. The presence of Idiognathodus eccentricus in theupper part of the Kreviakinian levels suggests a correlation with the lower Missourian of the United States. Neognathodus disappears in the upperpart 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 thelower 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’Es-pagne. La coupe est composée en grande partie de calcaires, en présentant la meilleure succession (essentiellement continue) du Moscoviensupérieur–Kasimovien du Pennsylvanien de la Zone Cantabrique. Les conodontes y sont rares en général mais quelques niveaux myachkoviensen 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 dumonde. Une des espèces, en particulier, Idiognathodus covadongae nov. sp., est ici formellement proposée comme une nouvelle espèce. Laprésence d’Idiognathodus eccentricus dans la partie supérieure des niveaux kreviakiniens suggérerait une corrélation avec le Missourien inférieurdes États Unis. Neognathodus disparaît dans la partie supérieure des couches myachkoviennes. Gondolella pohli fut récoltée dans un intervallepeu étendu dans la partie supérieure du Myachkovien. Les conditions paléoécologiques dans la partie inférieure des niveaux myachkoviensreprésenterait une sédimentation marine normale, sommaire, ouverte du biofaciès d’Idiognathodus.© 2006 Elsevier SAS. All rights reserved.

[email protected] (C.A. Méndez).

ont matter © 2006 Elsevier SAS. All rights reserved.s.2004.11.002

C.A. Méndez / Geobios 39 (2006) 245–254246

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 ofnorthern Spain (Fig. 1) have been investigated since 1958.

The Mississippian Alba Formation (Late Tournaisian-Na-murian) provides the richest and, in general, best preservedconodont fauna in the region. In contrast, Pennsylvanian con-odonts are scarce but well preserved, although some levels canbe significantly more productive.

Moscovian to Gzhelian (Pennsylvanian) conodonts have notbeen as extensively studied throughout the world as those ofthe lower part of Mississippian and their utility for biostratigra-phy may be significant, once their systematic instability is re-solved.

For several years the conodont research of the author hasconcentrated on the Upper Moscovian-Gzhelian levels of thePicos de Europa Unit of the Cantabrian Zone (northern Spain)

Fig. 1. Geological map of the Iberian Variscan Belt. The Cantabrian Zone issituated 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’aprèsJulivert et al., 1972).

(Fig. 2), although other units are under study. The Picos deEuropa Unit is well differentiated with good exposure of theCarboniferous succession comprising mainly marine lime-stones that have proved to be favourable for conodont recovery(chiefly in the Moscovian levels) (Méndez, 1990, 2002; Mén-dez in Villa et al., 1993 and in Villa et al., 1997).

2. Stratigraphy

The Las LLacerias Section is in the western part of the Pi-cos de Europa Unit (Fig. 2) in the locality of Las LLaceriasnear the village of Covadonga, within the Picos de Europa Na-tional Park. The series is shown on sheet 55 (Beleño) of theGeological Map of Spain (1:50 000) (Julivert and Navarro,1984). The section is exposed along a footpath, which leadsfrom the Covadonga Lakes local road to the cattle sheds ofLas LLacerias (Fig. 3).

The studied interval constitutes the best, and essentiallycontinuous Upper Moscovian-Kasimovian succession in thePennsylvanian of the Cantabrian Zone. Outcrops are discontin-uous and covered by vegetation in many places. Where pre-sent, the limestone outcrops lie on both sides of the path andcross it.

Lithostratigraphic units of the interval studied (Figs. 3 and4) include the massive member (uppermost part) of the Picosde Europa Formation (Maas, 1974) followed by the Las LLa-cerias Formation (Villa and van Ginkel, 2000). The intervalstarts with a red crinoidal limestone, which is about 480 mabove the base of the Picos de Europa Formation and can betraced easily in the field. Above it lie grey, sometimes redlimestone beds, which are massive in places. The Las LLacer-ias Formation consists of grey, thin-bedded limestones withsome marly limestone intervals and a few levels of sandy lime-stone near the top.

The age of the succession is middle Myachkovian-Khamo-nivkian based on fusulinoideans (Villa et al., 1997; Villa andvan Ginkel, 2000). The Moscovian-Kasimovian boundary lieswithin the sequence at the lower part of Interval 5 (Fig. 4),along which a succession of Protriticites (fusulinoideans) fau-nas from primitive to typical forms occur.

3. The conodont fauna and comments about correlation

Conodonts are scarce in general in the Las LLacerias Sec-tion, but some Myachkovian levels in the Upper Moscovianare significantly more productive. A major reduction in thenumber of conodont elements occurs in the Kasimovian (Kre-viakinian and Khamonivkian) beds (Fig. 4). Specimens recov-ered are mainly Pa pectiniform elements and are generally wellpreserved. Other elements of the conodont apparatus are notvery well preserved nor are they common.

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 PérezEstaún et al., 1988).

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Idiognathodus, Streptognathodus, Gondolella, and Neog-nathodus are the most significant genera present for biostrati-graphy. Ubinates and Hindeodus are also present.

Idiognathodus is the dominant genus and extends from themiddle Myachkovian into the Khamonivkian, but is muchmore abundant in Myachkovian beds. The idiognathodids aremorphologically different from those elsewhere, exceptI. eccentricus. At least one of the different forms is a new spe-cies, Idiognathodus covadongae, nov. sp. However, half showaffinities with species from the Moscow Basin and the DonetsBasin. These forms are Idiognathodus aff. I. podolskensis Gor-eva, I. aff. I. trigonolobatus Barskov and Alekseev, and I. aff.I. sagittalis Kozitskaya.

We found I. eccentricus (sample LL-9030, Fig. 4) in theupper part of the Kreviakinian levels 16 m below the entry ofthe fusulinoidean species Montiparus, that is, the base of Kha-monivkian. In their provisional conodont zonation for the LatePennsylvanian in North American Midcontinent Region, Bar-rick and Heckel (2000) propose the Idiognathodus eccentricusZone (lowest Missourian) to extend from the first appearanceof the nominate species up to the first appearance of Streptog-nathodus cancellosus. In North America, I. eccentricus rangesinto the Streptognathodus cancellosus Zone. These data sug-gest the correlation of a level within the upper part of the Kre-viakinian beds in Las LLacerias Section with the lower Mis-sourian.

Idiognathodus covadongae, nov. sp. is a form with a bios-tratigraphic range potentially restricted to the Myachkovian,below the extinction of the genus Neognathodus.

The rest of idiognathodids are placed in open nomenclatureas Idiognathodus sp. The morphology of these specimens isdistinctive, and at the same time, highly variable, so it is notpossible at the moment to assign the material to a species leveltaxon with certainty.

Streptognathodus, which is relatively scarce, appears in theupper Myachkovian a few metres above the extinction ofNeognathodus and it ranges to the Khamonivkian near thetop of the studied interval. In this part of the series Idiognatho-dus and Streptognathodus are the only conodonts recovered,although idiognathodids are more diversified and a little moreabundant than streptognathodids.

With the exception of Streptognathodus aff. S. subexcelsus,whose position in the upper Myachkovian in LLacerias Sectionis near to that of the entry of Streptognathodus subexcelsus inthe Donets Basin, the material recovered is assigned to thegenus without specific determination; the low number of speci-mens prevents any definitive consideration beyond the genericlevel.

Gondolella is recorded from the middle to upper Myachko-vian, and is represented by Gondolella laevis, Gondolella poh-li, and specimens of Gondolella sp. We have recently recov-ered G. pohli from a short interval in the upper portion of theMyachkovian levels. This species was reported in North Amer-ica from the middle to ? upper Desmoinesian (von Bitter andMerrill, 1998) in northwestern Illinois, western Indiana andsouth-central Iowa, and from the middle Desmoinesian(Barrick et al., 2002) in the Midcontinent. Therefore, the baseof the Missourian could be correlative, not with the base of

Fig. 3. Geological sketch map of the zone around Las LLacerias Section (afterMarquínez et al., 1982).Fig. 3. Géologie détaillée près de la localité de Las LLacerias (d’aprèsMarquínez et al., 1982).

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Kasimovian, but higher as suggested by some authors (for ex-ample: Villa and van Ginkel, 2000).

Neognathodus ranges through most of the Myachkovian le-vels, until the genus disappears in the upper part of Interval 4with the loss of Neognathodus aff. N. inaequalis (Fig. 4). Thistaxon was reported from the Myachkovian of the Donets Ba-sin, and from the Podolskian to Myachkovian of the MoscowBasin. Neognathodus is not recorded in levels higher thanMoscovian in the Moscow Basin or Donets Basin. The sameholds in the Las Llacerias Section, where Neognathodus is notrecovered in beds dated as Kasimovian.

Several specimens are assigned to Hindeodus sp. due to lownumbers and poor preservation.

About one half of the conodont taxa identified at specieslevel show affinities with those of the Moscow Basin and Do-nets Basin, except Idiognathodus trigonolobatus Barskov andAlekseev, reported from the Moscow Basin only.

4. Systematic paleontology

The material illustrated and/or described is deposited in theDepartment of Geology (Paleontology) of the University ofOviedo (DPO).

Genus Gondolella Stauffer and Plummer, 1932.Type species: Gondolella elegantula Stauffer and Plummer,

1932.

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; carinawith several denticles situated in the centre of the platform;cusp inclined in posterior direction very close to the posteriorend of the unit.

In lower view, basal cavity very broad, deep, and situated ina posterior position; this structure is bordered by a loop, backclosed, and continues to the anterior end of the unit like agrooved keel.

No microsculpture has been observed.Remarks: The characteristics of the Gondolella laevis ma-

terial from this locality and those of the Río Nevandi Sectionwere dealt with in Méndez et al. (1998).

The general features of the Pa element of this species arelike 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, respec-tively, Picos de Europa Formation).

Remarks: This species is quite similar to Gondolella laevis,from which it is distinguished by a “significantly wider Pa ele-ment platform” (von Bitter and Merrill, 1998).

The platform in our material is very well developed, likethat of Gondolella pohli von Bitter and Merrill, 1998 fromthe Desmoinesian of northwestern Illinois (USA).

The outline of the posterior half of the platform in one ofour specimens (Fig. 5B) resembles a specimen figured and de-scribed by Swade (1985) as Gondolella sp. 1 (Fig. 18: 45)

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 LasLLacerias 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 LasLLacerias dans la coupe stratigraphique de Las LLacerias. 1–10 = intervalles sédimentologiques distingués par Villa et al. (1993) (d’après Méndez, 2002, modifié).

C.A. Méndez / Geobios 39 (2006) 245–254 249

from the Verdigris Formation (Demoinesian) in the Midconti-nent 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 lan-

ceolate, most of the outer margin of platform convex, innermargin relatively straight, both margins join posteriorly to pro-

duce a moderately pointed form; a couple of short, nodose ad-carinal ridges are present anteriorly; poorly defined eccentrictrough in the posterior part of the platform cuts several well-developed transverse ridges; carina of moderate length, a fewirregular 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, thelobes on both sides of this structure, together with the relativelylong carina permit us to assign this specimen to Idiognathoduseccentricus (Ellison). We agree with the concept of Barrick andWalsh (1999) for this species, as the holotype figured by Elli-son (1941) is early Missourian in age, and distinct from the lateMissourian to early Virgilian eccentric Pa elements.

On the other hand, our specimen shows some similarity toone figured by Barrick and Boardman (1989: Pl. 1, Fig. 8)

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, lowerview, × 38. Picos de Europa Formation, sample S-370 (DPO 38518). 3a, 3b. Gondolella laevis Kossenko and Kozitskaya, 1975. 3a, upper view, × 48, 3b, lowerview, × 50. Picos de Europa Formation, sample S-230 (DPO 38519). 4. Streptognathodus aff. S. subexcelsus Alekseev and Goreva, 2001, upper view, × 54. Picos deEuropa Formation, sample S-232 (DPO 38520). 5. Idiognathodus sp., upper view, × 29. Las LLacerias Formation, sample LL-9030 DPO (38521). 7. Neognathodusaff. N. inaequalis Kozitskaya and Kossenko, 1978, upper view, × 68, Picos de Europa Formation, sample S-232b (DPO 38529). 8, 9. Streptognathodus sp. 8, upperview, × 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. Idiognathoduseccentricus (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). Universityof Oviedo.Fig. 5. 1, 6. Idiognathodus covadongae nov. sp., 1, vue supérieure, × 52, holotype. Formation Picos de Europa, échantillon S-230 (DPO 38517) ; 6, vuesupérieure, × 62, paratype. Formation Picos de Europa, échantillon S-231 (DPO 38536). 2a, 2b. Gondolella pohli von Bitter et Merrill, 1998. 2a, vue

C.A. Méndez / Geobios 39 (2006) 245–254250

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from upper Salesville core shale (lower Missourian) of north-central 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 Forma-tion); the rest are paratypes from the same formation: DPO38533 (sample S-370); DPO 38534-38538 (sample S-231).

Locus typicus: Near Covadonga Village. Left side of thefootpath that leads from the Covadonga Lakes local road tothe cattle sheds of Las LLacerias, down to the road, in themiddle of the meadow (Fig. 3).

Stratum typicum: Level of red crinoidal limestone. At thebase 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 fieldof numerous transverse ridges; field of transverse ridges sub-rhombic in outline and slightly depressed, greatest width nearanterior one third.

Description: In upper view platform lanceolate, outline sub-triangular, inner margin slightly bent, outer margin rounded;unit posteriorly pointed; adcarinal ridges converge towards car-ina anteriorly in the platform then diverge, develop and goaway tending to fuse with the free blade; inner adcarinal ridgemore developed in some specimens showing short ridges; fieldwith numerous transverse ridges on platform, sub-rhombic inoutline and slightly depressed, greatest width near anterior onethird; carina short; lobes not equally developed, situated to-wards the anterior termination of platform, the inner more de-veloped with several relatively abundant organised nodes semi-circular in outline, the outer with a row of a few nodes.

Remarks: Idiognathodus covadongae shows some similar-ity with Idiognathodus podolskensis Goreva, 1984, recordedfrom the Podolskian of the Moscow Basin and the Myachko-vian of the Donets Basin. However, our species has a moreelongate platform and the field of transverse ridges is sub-rhombic, not subtriangular like that of Russian species.

Another species that shows some similarity with ours isIdiognathodus obliquus Kossenko and Kozitskaya, 1978, re-

supérieure, × 43, 2b, vue inférieure, × 38. Formation Picos de Europa, échantillon S-vue supérieure, × 48, 3b, vue inférieure, × 50. Formation Picos de Europa, échantiGoreva, 2001, vue supérieure, × 54. Formation Picos de Europa, échantillon S-2LLacerias, échantillon LL-9030 (DPO 38521). 7. Neognathodus aff. N. inaequalis Kéchantillon S-232b (DPO 38529). 8, 9. Streptognathodus sp. 8, vue supérieure, ×supérieure, × 34. Formation Picos de Europa, échantillon LL-9022 (DPO 38524). 10.S-230 (DPO 38528). 11. Idiognathodus aff. I. trigonolobatus Barskov et Alekseev(DPO 38526). 12. Idiognathodus sp. B, vue supérieure, × 46. Formation Picos de EGoreva, 1984, vue supérieure, × 31. Formation Picos de Europa, échantillonsupérieure, × 52. Formation Las LLacerias, échantillon LL-9030 (DPO 38532). 15,Formation Las LLacerias, échantillon S-236-K (DPO 38540), 16, vue supériTous les spécimens figurés sont des éléments Pa à l’exception du 10 (élément X) ed’Oviedo (DPO).

corded from Podolskian to Myachkovian from the Donets Ba-sin and from Kashirian to Myachkovian from the Moscow Ba-sin. Nevertheless the Spanish species has a more bent innermargin, a more elongate platform, a more depressed ridgedfield of the platform, and less developed lobes than in the Rus-sian 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, subtriangu-

lar, outer margin convex, inner margin straight or relativelystraight, both margins join posteriorly giving way to an acutetermination; platform with a slightly concave subtriangularfield of numerous transverse ridges, greatest width in the ante-rior one-half; adcarinal ridges approach to carina near the ante-rior termination of platform then diverge, the inner giving wayto a parapet-like structure (with short ridges in the adult figuredspecimen); carina very short; lobes not equally developed, si-tuated near the anterior termination of platform, outer lobepoorly developed with several nodes, inner lobe semi-circularwith several irregular coarse nodes.

Remarks: Our material resembles Idiognathodus podols-kensis Goreva, 1984, from the Podolskian of the Moscow Ba-sin and the Myachkovian of the Donets Basin, but differs by itsmore elongate platform.

Distribution: middle to upper Myachkovian.

Idiognathodus aff. I. sagittalis Kozitskaya in Kozitskaya etal., 1978.

(Pa element).Fig. 5 (15, 16).Material: Five specimens with acceptable preservation:

DPO 38531, DPO 38540, DPO 38541 and DPO 38542 (sam-ple S-236-K, Las LLacerias Formation); DPO 38543 (sampleS-238, Las LLacerias Formation).

Description: In upper view, platform resembles an arrow-head, inner margin slightly convex, outer margin more convex;unit posteriorly pointed; adcarinal ridges (when present) con-verge near anterior termination of platform, then diverge and

370 (DPO 38518). 3a, 3b. Gondolella laevis Kossenko et Kozitskaya, 1975. 3a,llon S-230 (DPO 38519). 4. Streptognathodus aff. S. subexcelsus Alekseev et32 (DPO 38520). 5. Idiognathodus sp., vue supérieure, × 29. Formation Lasozitskaya et Kossenko, 1978, vue supérieure, × 68. Formation Picos de Europa,46. Formation Picos de Europa, échantillon LL-9022 (DPO 38523), 9, vueUbinates sp., vue latérale interne, × 30. Formation Picos de Europa, échantillon, 1976, vue supérieure, × 33. Formation Picos de Europa, échantillon LL-9026uropa, échantillon S-230 (DPO 38527). 13. Idiognathodus aff. I. podolskensisS-371 (DPO 38530). 14. Idiognathodus eccentricus (Elison, 1941), vue16. Idiognathodus aff. I. sagittalis Kozitskaya, 1978. 15, vue supérieure, × 38.eure, × 38. Formation Las LLacerias, échantillon S-236-K (DPO 38531).t ont été déposés au Département de Géologie (Paléontologie) de l’Université

C.A. Méndez / Geobios 39 (2006) 245–254252

go away for some distance before fusing with free blade, inneradcarinal ridge more developed with very short ridges from theanterior termination of platform until their fusion with freeblade; field of transverse ridges on platform mostly triangular,with a variable number (but never much) of poorly developedridges in a couple of specimens (Fig. 5: 15, 16), the posteriormost are interrupted, greatest width in anterior one-half; carinashort in general; lobes well developed in more adult specimens,the inner usually with several nodes situated on a flaring struc-ture, the outer with fewer nodes in a variable arrangement.

Remarks: Our material resembles Idiognathodus sagittalisKozitskaya in Kozitskaya et al., 1978, recorded from Kasimo-vian of the Russian Platform and the Donets Basin. The differ-ences are in the more narrow outline of platform and moreelongate 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 (sam-

ple LL-9026, Picos de Europa Formation).Description: In upper view, platform with irregular outline,

inner margin strongly convex in anterior half and moderate inposterior half, outer margin mostly straight with a strong cur-vature near the anterior termination of platform; unit poster-iorly pointed; inner adcarinal ridge moderately developed,short, continues anteriorly like a ridged parapet from the termi-nation of platform until its fusion with free blade; field oftransverse ridges on the platform sub-rhombic with a moderatenumber of ridges, some of them poorly defined and broken intonodes, greatest width in anterior one half; lobes not equallydeveloped, occupy much of the platform, inner lobe notrounded, very developed, showing a flaring structure withtwo different node sizes arranged in rows, outer lobe rounded,very poorly defined, fused to the platform with a few coarsenodes.

Remarks: Our specimen resembles Idiognathodus trigono-lobatus Barskov and Alekseev, 1976, recorded from Myachko-vian to Kreviakinian in the Moscow Basin. However, the Rus-sian species has a convex outer platform margin, triangularfield of transverse ridges on the platform, rostral ridges thatare 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 EuropaFormation).

Description: In upper view, moderately curved, long, sub-triangular platform, posteriorly pointed; inner margin mostlystraight, can be concave about the middle or irregular, outermargin convex, more strongly near the anterior termination;

short adcarinal ridges initiate near the anterior termination ofthe platform and extend anteriorly like nodose or ridged para-pets, although fusion with the free blade does not take place inall specimens (when visible), standing as free edges, inner ad-carinal ridge more developed; field of numerous transverseridges on the platform mostly sub-rhombic, greatest width inanterior one-half; short strong carina; lobes in general inte-grated into the platform, mostly well developed, sub-roundedinner lobe with abundant nodes that tend to be arranged inrows, sometimes fused, outer lobe, slightly droping, shoulder-like, extending posteriorly, giving a robustness to the platform,nodes on outer lobe sometimes abundant.

Remarks: The long platform, short, strong, carina, well-de-veloped adcarinal ridges, and shape of outer lobe are the maincharacteristics of this form, which probably represents a newspecies, although the modest number of specimens and absencein other samples prevent a formal definition.

The subtriangular shape of the platform, development of theouter lobe, and non-depressed field of transverse ridges on theplatform are major differences with Idiognathodus covadongaenov. sp. described in this paper.

The non-depressed field of transverse ridges on the plat-form, development of the lobes, shape of the outer lobe, andmore abundant nodes in relation to the adult specimen of Idiog-nathodus aff. podolskensis are the main differences with thelatter.

Distribution: middle Myachkovian.

Genus Neognathodus Dunn, 1970.Type species: Polygnathus bassleri Harris and Hollings-

worth, 1933.

Neognathodus aff. N. inaequalis Kozitskaya and Kossenkoin 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, Picosde Europa Formation).

Description: In upper view, platform slightly bowed, sub-lanceolate, posteriorly pointed, directed downwards in the adultspecimen, greatest width in anterior one-third; blade continuesposteriorly on platform as a strong, high carina that terminatesnear to the posterior end of the unit, ends as a few nodes exceptin juveniles where this structure is unbroken, carina higher thanplatform in adult and in one larger juvenile specimen; outerside of platform is a slightly steep parapet with short ridges,not very wide and reduced near its posterior termination tothe end of the unit, essentially parallel to carina, separated fromit by a slight sulcus crossed by a few ridges near the posteriorend of the unit; in most juvenile specimens outer parapet re-duced or absent; inner side of platform developed like the outerin a very much wider structure, steeper with developed radiat-ing ridges, moderate sulcus separates the carina from inner sideof platform; both parapets converge at the posterior end of theunit.

C.A. Méndez / Geobios 39 (2006) 245–254 253

Remarks: The morphology displayed by our specimens re-sembles that of Neognathodus inaequalis Kozitskaya and Kos-senko in Kozitskaya et al., 1978, recorded from the Myachko-vian of the Donets Basin and from Podolskian to Myachkovianof the Moscow Basin, but have a wider and less triangular plat-form.

Distribution: upper Myachkovian.

Genus Streptognathodus Stauffer and Plummer, 1932.Type species: Streptognathodus excelsus Stauffer and

Plummer, 1932.

Streptognathodus aff. S. subexcelsus Alekseev and Gorevain 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, tongue-like, slightly depressed towards the middle in the surface pos-terior to the end of carina, where several transverse ridges ex-ist, surface of platform mostly directed downwards; carina,short, ending near the anterior termination of the platform; ad-carinal ridges, not very long, fused with the free blade, devel-oped towards its anterior part in wide, steep, structures orna-mented with short ridges; lobes situated near the anteriortermination of the platform in the more adult specimen, outerlobe poorly developed, with one or few nodes, inner lobe, welldeveloped, showing a variable number of coarse nodes.

Remarks: The material described resembles Streptognatho-dus subexcelsus Alekseev and Goreva in Makhlima et al.,2001, from the Kreviakinian of the Moscow Basin and Myach-kovian to Kreviakinian of the Donets Basin. Differences exist,however, such as the wider, not subtriangular, depressed areaof the platform, and the less well-developed outer lobe in theSpanish form.

Distribution: upper Myachkovian.

Streptognathodus spp.(Pa Elements).Fig. 5(8, 9).Material: Nineteen specimens: DPO 38546 to 38551 (sam-

ple S-232, Picos de Europa Formation); DPO 38552 and DPO38553 (sample S-234, Picos de Europa Formation); DPO38523 to 38525 (sample LL 9022, Picos de Europa Forma-tion); DPO 38554 (sample LL-9026, Picos de Europa Forma-tion); DPO 38555 to 38557 (sample S-239, Las LLacerias For-mation); DPO 38558 to 38560 (sample S-240, Las LLaceriasFormation).

Remarks: The specimens assigned to this genus (some ofthem juveniles) that were recovered in the studied intervalshow several types of morphologies, including forms with longcarinae, present or absent inner lobe, and a variable number oftransverse ridges below the carina. An additional another dif-ferent morphology also exists. It’s possible that all of these

belong to a few species, but the paucity of material precludesany 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 com-

pressed, deflected downward, denticles on the process, the sec-ond from the cusp is the largest; posterior process sinuouslydeflected, one discrete denticle preserved only; pit expandedinward.

Remarks: The unique element we recovered, although notvery well preserved, shows in general the same features de-scribed for the Aethotaxis, X element by Baesemann (1973),the author who erected the genus. That name was later changedto 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 sedimenta-tion characterizes the lower part of the studied interval. Paleoe-cological conditions derived from the conodonts are best lim-ited to the lower part, where the number of specimens ishigher.

The absence of Adethognathus shows us that nearshore bio-facies must be excluded.

Idiognathodus is the dominant genus throughout the intervalstudied. An Idiognathodus-biofacies is present from the levelS-230 to the level S-231, in the lower part of the Myachkovianbeds (Fig. 4), where the number of the specimens of that genusis higher.

According to Merrill and von Bitter (1976), the Idiognatho-dus-biofacies is one that dominates most Pennsylvanian sedi-mentary rocks, and represents shallow, open, normal marineoffshore deposits.

Sedimentological data from Leyva (in Villa et al., 1993) in-dicate a platform-lagoon in the levels with abundant Idiog-nathodus (sedimentological intervals 1–3, Fig. 4). A more re-cent sedimentological study from Bahamonde et al. (2000)indicates a shallow, flat-topped platform environment with apoorly rhythmic character for the same intervals.

Acknowledgements

This work has been supported by Spanish government fund-ing through Project BTE 2003-01012. The paper benefitedfrom referees’ comments by Dr. James E. Barrick, Texas TechUniversity and Dr. Hans P. Schönlaub, Geologische Bundesan-salt, Viena. Thanks are also due to Dr. Lance L. Lambert, Uni-versity of Texas at San Antonio, for his revision of the English

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C.A. Méndez / Geobios 39 (2006) 245–254254

language and useful suggestions, Dr. J.L. García-Alcalde, Uni-versidad de Oviedo, for his revision of the French language ofthe abstract and Dr. C. Brime, from the same university, for herhelp with the figures format. The author wants to thank Mr.Severino Méndez for his valuable help in the field work.

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