In the Aftermath of Permian-Triassic Boundary Mass-Extinction: New Ostracod (Crustacea) Genus and Species from South Tibet Marie-Béatrice Forel, S
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In the aftermath of Permian-Triassic boundary mass-extinction: new ostracod (Crustacea) genus and species from South Tibet Marie-Béatrice Forel, S. Crasquin To cite this version: Marie-Béatrice Forel, S. Crasquin. In the aftermath of Permian-Triassic boundary mass-extinction: new ostracod (Crustacea) genus and species from South Tibet. Geodiversitas, Museum National d’Histoire Naturelle Paris, 2011, 33 (2), pp.247-263. 10.5252/g2011n2a3. mnhn-02326941 HAL Id: mnhn-02326941 https://hal-mnhn.archives-ouvertes.fr/mnhn-02326941 Submitted on 11 Dec 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. In the aftermath of Permian-Triassic boundary mass-extinction: new ostracod (Crustacea) genus and species from South Tibet Marie-Béatrice FOREL Sylvie CRASQUIN UPMC Université Paris 06, CNRS, UMR 7207 CR2P, Laboratoire de Micropaléontologie, T.46-56, E.5, case 104, F-75252 Paris cedex 05 (France) [email protected] [email protected] Forel M.-B. & Crasquin S. 2011. — In the aftermath of Permian-Triassic boundary mass- extinction: new ostracod (Crustacea) genus and species from South Tibet. Geodiversitas 33 (2): 247-263. DOI: 10.5252/g2011n2a3. ABSTRACT 46 samples were processed for a taxonomic ostracod study from the Lower- Middle Triassic (Smithian to Anisian) of South Tibet. Forty four species belong- ing to 15 genera are recognized. One genus and seven species are described as KEY WORDS Crustacea, new: Bairdia jeancharlesi Forel n. sp., Bairdia letangae Forel n. sp., Bairdiacypris Ostracods, combeae Forel n. sp., Petasobairdia collini Forel n. sp., Hungarella tulongensis Lower-Middle Triassic, Crasquin n. sp., Triassicindivisia tibetinella Crasquin n. gen., n. sp., Liuzhinia South Tibet, new genus, larmae Forel n. sp. Th e goal of this paper is to describe the new taxa as a pre- new species. liminary step to palaeoenvironmental reconstruction. RÉSUMÉ Après l’extinction en masse de la limite Permien-Trias : nouveau genre et nouvelles espèces d’ostracodes du sud Tibet. Quarante-six échantillons ont été analysés pour l’étude des ostracodes du Trias inférieur et moyen (Smithien à Anisien) du sud Tibet. Quarante-quatre espèces appartenant à 15 genres ont été identifi ées. Un genre et sept espèces MOTS CLÉS Crustacea, sont nouveaux : Bairdia jeancharlesi Forel n. sp., Bairdia letangae Forel n. sp., Ostracodes, Bairdiacypris combeae Forel n. sp., Petasobairdia collini Forel n. sp., Hungarella Trias inférieur et moyen, tulongensis Crasquin n. sp., Triassicindivisia tibetinella n. gen. n. sp., Liuzhinia sud Tibet, genre nouveau, larmae Forel n. sp. Le sujet de cet article est la description des nouveaux taxons espèces nouvelles. en prélude à une reconstruction paléoenvironnementale. GEODIVERSITAS • 2011 • 33 (2) © Publications Scientifi ques du Muséum national d’Histoire naturelle, Paris. www.geodiversitas.com 247 Forel M.-B. & Crasquin S. INTRODUCTION re-describe the section in detail. Th e following short presentation of the section (Fig. 2) is based GEOLOGICAL SETTING on Brühwiler et al. (2009). Th e Tulong section was located on the North Th e unit III corresponds to 9 m of mostly grey Indian margin during the Early Triassic. It crops limestone beds alternating with thin shale intervals. out near the village of Tulong (28°26’13’’N, It is subdivided in four sub-units. Th e sub-unit 86°08’09’’E; 4430 m) on the road from Lhasa to IIIa is composed of 1.60 m of red-weathering Nyalam (Fig. 1). Th is section is well known for dolomitized calcarenite and grey packstones and its Lower Triassic succession in South Tibet. It is Smithian in age (based on conodonts); this sub- was described by Garzanti et al. (1998) and more unit was not sampled. Th e sub-unit IIIb consists recently by Shen et al. (2006). More recently, of 20 m of thin-bedded, platy to nodular, grey to the Permian-Triassic interval in this area was light red limestones alternating with shale inter- restudied by a team from Zurich (Switzerland) beds and is Middle Smithian in age (conodonts). and the stratigraphic succession obtained from Th e sub-unit IIIc is 4 m thick and is composed of other outcrops allow establishment of an almost medium bedded grey limestone alternating with complete succession from the Upper Permian shales or very nodular marly limestone. Th e lower up to the Lower Anisian (Brühwiler et al. 2009). part of sub-unit IIIc contains middle Smithian Th e Tulong section corresponds to units III to VI ammonoids and the upper part late Smithian of the Tulong Formation and is very well dated ammonoids. Th e sub-unit IIId consists of 1 m by ammonoids and conodonts (Brühwiler et al. of massive very nodular marly limestone of latest 2009). It is beyond the scope of this paper to Smithian age (ammonoids and conodonts). Gyanyima Lhasa Lalung La TIBET area enlarged 28°30’N NEPAL BHUTAN INDIA Tulong Tong La Tu 28°24’ Yali Tso Lama am Nyal 5 km 86°10’ 86°20’E To thrust fault Palaeozoic Jurassic normal fault Crystalline Triassic FIG. 1. — Location map of the Tulong section (), South Tibet (after Brühwiler et al. 2009). 248 GEODIVERSITAS • 2011 • 33 (2) New ostracods (Crustacea) from South Tibet Ammonoid Units faunas Samples m Pseudodanubites 06Ti35 Gymnites 06Ti34 Anisian Middle Triassic 06Ti33 VI 06Ti32 06Ti31 06Ti30 06Ti29 Hellenites 06Ti28 06Ti27 15 06Ti26 06Ti25 Paragoceras 06Ti24 V Fengshanites 06Ti23 06Ti22 06Ti21 undescribed 06Ti20 albanitid b 10 Red shales 06Ti19 Green shales IV Shales Columbites a Nordophiceras 06Ti18b Shales with phosphatic nodules 06Ti18a Laminated limestone Early Triassic Early Triassic Xenoceltites d Glyptophiceras Nodular, laminated limestone 06Ti17 Wasatchites Dolomitic limestone Tulong Formation Tulong 5 06Ti16 White, recrystallised limestone Prionites 06Ti15 c 06Ti14 Fish teeth Ammonoids Owenites 06Ti13 06Ti12 III Arctoceratid B 06Ti11 Orthoceratids 06Ti10 06Ti09 06Ti08 Bivalves 06Ti07 Smithian06Ti06 Spathian 06Ti05 b Crinoids Arctoceratid A 06Ti04 Flemingitid A 06Ti03 Brachiopods 0 06Ti02 06Ti01 Foraminifera Na12 a Gastropods Ostracods Stromatactis cavities FIG. 2. — Log of the Tulong section, South Tibet, with the location of the studied samples (after Brühwiler et al. 2009). Th e unit IV corresponds to 4 m of shales of early Th e unit V is 6 m thick and consist of nodu- Spathian age (conodonts and ammonoids) subdivided lar, marly and bioturbated limestones of “am- into a lower green part and an upper red part. monitico rosso” facies (Garzanti et al. 1998) GEODIVERSITAS • 2011 • 33 (2) 249 Forel M.-B. & Crasquin S. and is middle Spathian in age (ammonoids and SYSTEMATIC PALAEONTOLOGY conodonts). Th e last unit, unit VI, consists of 1 m of thin- Class OSTRACODA Latreille, 1806 bedded yellowish nodular limestones overlain by less Subclass PODOCOPA Müller, 1894 than 1 m of grey and yellowish limestone. Th e last Order PODOCOPIDA Müller, 1894 beds contain early middle Anisian ammonoids. Suborder PODOCOPINA Sars, 1866 Superfamily BAIRDIOIDEA Sars, 1887 Family BAIRDIIDAE Sars, 1887 MATERIAL AND METHOD Genus Bairdia McCoy, 1844 Forty six samples, distributed through a 21 m thick sequence (Fig. 2), were processed by hot acetolysis TYPE SPECIES. — Bairdia curta McCoy, 1844. method (Lethiers & Crasquin-Soleau 1988; Cras- quin-Soleau et al. 2005) which allows the extraction of calcareous shells contained in calcareous rocks. Bairdia jeancharlesi Forel n. sp. Twenty-nine samples gave ostracods; three of them (Fig. 3I-L) yielded only indeterminable specimens. Except for several specimens, in most of cases, the TYPE MATERIAL. — Holotype: one complete carapace (P6M2607; Fig. 3J); paratype: one complete carapace preservation of ostracods is poor and the number (P6M2603; Fig. 3I). of specimens is low. Internal features were not observed. ETYMOLOGY. — Dedicated to Jean-Charles Forel, per- Forty four species belonging to 15 genera are sonal dedication. identifi ed and fi gured (Figs 3-8). Seven species MATERIAL EXAMINED. — 26 complete carapaces and 1 and one genus are new and described in detail single valve. in this paper. Other indicative species are also fi gured (Figs 3-8) and a complete list is available DIMENSIONS. — L = 435 to 1120 μm; H = 260 to 680 μm. Holotype: L = 453 μm; H = 276 μm. Paratype: in Table 1. L = 895 μm; H = 535 μm. All the specimens are deposited in the Université Pierre et Marie Curie, Paris (UPMC) collection TYPE HORIZON. — Sample 06Ti08, unit IIIb, Tulong (numbers: P6Mxx). Formation, Smithian, Lower Triassic. TYPE LOCALITY. — Tulong section, Southern Tibet. ABBREVIATIONS AB anterior border; OCCURRENCE. — Tulong section, southern Tibet. Samples ADB antero-dorsal border; 06Ti04, 06Ti08, 06Ti21, 06Ti27-31, 06Ti35, Tulong AVB antero-ventral border; Formation, units III, V and VI, Smithian to Anisian, DB dorsal border; Lower-Middle Triassic. H height; DIAGNOSIS. — A punctate species of Bairdia with faint L length; overlap, AB and PB with quite small radius of curvature, LV left valve; PDB, BD and ADB straight at RV. PB posterior border; PDB postero-dorsal border; DESCRIPTION PVB postero-ventral border; RV right valve; RV: PDB, DB and