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Download Full Article in PDF Format Triconodont mammals from the Jurassic Kota Formation of India Guntupalli V. R. PRASAD Department of Geology, University of Jammu, Jammu 180 006 (India) [email protected] Brijesh K. MANHAS 463, Sector E, Sainik Colony, Jammu (India) Prasad G. V. R. & Manhas B. K. 2002. — Triconodont mammals from the Jurassic Kota Formation of India. Geodiversitas 24 (2) : 445-464. ABSTRACT New mammalian teeth recovered from the Lower/Middle Jurassic Kota Formation, Pranhita-Godavari valley, peninsular India, are described. In its gross morphology, VPL/JU/KM/13 compares well with Dyskritodon amazighi Sigogneau-Russell, 1995, an Early Cretaceous triconodont from Morocco. Based on size and some morphological differences, this tooth is referred to a new species Dyskritodon indicus n. sp. Another fragmentary tooth (VPL/JU/KM/14) is assigned to Triconodonta indet. with possible affinities to morganucodontids. Re-examination and comparison of Kotatherium yada- girii Prasad & Manhas, 1997, previously documented from the same forma- KEY WORDS tion, with various Mesozoic mammalian groups reveal that K. yadagirii is not Mammalia, triconodonts, a symmetrodont, more likely a triconodont (family Morganucodontidae). Jurassic, Therefore, a new genus Paikasigudodon n. gen. is established for this Kota Formation, taxon. Indotherium pranhitai Yadagiri, 1984 is retained in the family India, new genus, Morganucodontidae, but the type tooth as well as the attributed tooth new species. (VPL/JU/KM/11) are now considered as upper molars. GEODIVERSITAS • 2002 • 24 (2) © Publications Scientifiques du Muséum national d’Histoire naturelle, Paris. www.mnhn.fr/publication/ 445 Prasad G. V. R. & Manhas B. K. RÉSUMÉ Mammifères triconodontes de la Formation Kota, Jurassique de l’Inde. Cet article présente la description de nouvelles dents de mammifères décou- vertes dans la Formation Kota, du Jurassique inférieur/moyen, vallée de Pranhita-Godavari, Inde péninsulaire. VPL/JU/KM/13 montre de grandes ressemblances, dans sa morphologie générale, avec Dyskritodon amazighi Sigogneau-Russell, 1995, triconodonte du Crétacé inférieur du Marocain. La nouvelle espèce, Dyskritodon indicus n. sp., est définie par une différence de taille, d’âge et quelques particularités de structure. Un autre fragment de dent (VPL/JU/KM/14) est attribué à un Tricododonta indet., peut-être affine avec les morganucodontides. Par ailleurs, un nouvel examen de Kotatherium yadagirii Prasad & Manhas, 1997, décrit précédemment de la même forma- tion, et sa comparaison avec divers groupes mammaliens du Mésozoïque, ont MOTS CLÉS montré que K. yadagirii n’est pas un symmétrodonte, mais plus vraisembla- Mammalia, triconodontes, blement un triconodonte (famille Morganucodontidae). Un nouveau genre, Jurassique, Paikasigudodon n. gen., est créé pour cette forme. Quant au taxon Formation Kota, Indotherium pranhitai Yadagiri, 1984, il est maintenu dans la famille des Inde, nouveau genre, Morganucodontidae, mais le spécimen type ainsi que la dent attribuée nouvelle espèce. (VPL/JU/KM/11) sont ici considérés comme des molaires supérieures. INTRODUCTION malian fauna from this formation puts into ques- tion the Early Jurassic age assignment. Age diag- In India, Mesozoic mammals have been docu- nostic palynofossils might prove useful in this mented from the Upper Triassic Tikhi Formation respect. Even assuming an age slightly younger (Datta & Das 1996), the Lower/Middle Jurassic than the Lower/Middle Jurassic, the Kota Kota Formation (Datta 1981; Yadagiri 1984, Formation represents an important geological 1985; Prasad & Manhas 1997), and from the time period during which the early radiations of Upper Cretaceous Deccan intertrappean beds mammals were taking place. (Prasad & Sahni 1988; Prasad et al. 1994; Prasad The Kota Formation has been well known for its & Godinot 1994; Godinot & Prasad 1994; Das vertebrate fauna since the second half of 19th cen- Sarma et al. 1995; Krause et al. 1997). Among tury. Despite the long history of vertebrate fossil these micromammal-yielding stratigraphic levels, collections including fishes, crocodiles, pterosaurs, the Kota Formation of the Upper Gondwana and dinosaurs (Egerton 1851, 1854; Owen 1852; Group, Pranhita-Godavari valley (peninsular King 1881; Jain et al. 1962; Jain 1973, 1974a, b, India), assumes great significance because of the 1983; Yadagiri & Prasad 1977; Yadagiri et al. time frame during which it was deposited. This 1979), mammals were discovered from this for- formation has traditionally been considered as mation only at the beginning of the 1980s (Datta Lower Jurassic in age based on semionotid (Jain et al. 1978; Datta 1981). The first mammalian 1973), coelacanth (Jain 1974a), and pholi- tooth recovered from the Kota Formation was dophorid (Yadagiri & Prasad 1977) fishes, referred to a then new genus and new species, pterosaurs (Jain 1974b) and palynofossils Kotatherium haldanei Datta, 1981, of uncertain (Prabhakar 1986), despite an alternative Middle familial affinities within Symmetrodonta (Datta Jurassic age favoured by other works based on 1981). Yadagiri (1984) described two other sup- ostracodes (Govindan 1975; Misra & Satsangi posed lower molars of symmetrodonts from this 1979). The present study of the micromam- formation and placed each of them in a new 446 GEODIVERSITAS • 2002 • 24 (2) Mammals from the Jurassic of India 79° 25' 79° 30' G a n Cave g a p Temple TUNGADA RESERVED FOREST u r Erra worre N Vagu Gangapur Dharmaram u ag Paikasigudem REBBANA ki V Bo IB PWD 19° REBBANA 15' Nambal MUMBAI Narlapur HYDRABAD Fossil Cart Track Railway Track CHENNAI locality Fossil locality Unmetalled Road 0 2 km Metalled Road Tanks broken ground 0 400 79° 25' 79° 30' FIG. 1. — Location map of mammal-bearing section of the Kota Formation. taxon: Trishulotherium kotaensis and Indotherium sil yielding site is located about 10 km east of the pranhitai (family incertae sedis). Subsequent to nearest town, Rebbana (Fig. 1). Except for K. hal- this, Yadagiri (1985) reported as new an amphi- danei (Manganapalli dinosaur site), all the mam- dontid symmetrodont, Nakunodon paikasiensis malian taxa reported until now from the Kota Yagadiri, 1985, from this formation. Prasad & Formation come from this site. The Kota Manhas (1997) described an upper molar under a Formation is primarily composed of sandstones, new species of Kotatherium, K. yadagirii, and limestones, clays, and mudstones, and is consid- included the two species of Kotatherium and ered to have been deposited in a lacustrine envi- Trishulotherium kotaensis in the symmetrodont ronment (Yadagiri & Rao 1987). The family Tinodontidae. The type of Trishulotherium microvertebrate assemblage recovered from the kotaensis Yadagiri, 1984, originally described as a Paikasigudem site also includes two new taxa of lower molar, has recently been considered as an sphenodontid reptiles (Evans et al. 2001) and one upper molar (Sigogneau-Russell & Ensom 1998). new taxon of agamid lizard (Evans et al. in press) Prasad & Manhas (1997) discussed the taxonom- as well as theropod and ornithischian dinosaur ic position of Indotherium pranhitai and tentative- teeth. In the present paper, the newly discovered ly referred it to the order Triconodonta, as closely triconodont teeth are described, and the systemat- allied to morganucodontids. Continued search for ic position of VPL/JU/KM/10, originally assigned early mammals from the Kota Formation has led to Kotatherium yadagirii (family Tinodontidae) to the recovery of a few additional teeth referable and of VPL/JU/KM/11 (Indotherium pranhitai) to docodonts and triconodonts from a stream sec- mistakenly thought to be a lower molar (Prasad & tion exposed west of Paikasigudem village, Manhas 1997), are re-examined. All the described Adilabad District, Andhra Pradesh State. The fos- specimens are deposited in the vertebrate palaeon- GEODIVERSITAS • 2002 • 24 (2) 447 Prasad G. V. R. & Manhas B. K. tological collections of Jammu University. DIAGNOSIS.— Dyskritodon indicus n. sp. differs from Measurements of the specimens were taken with a the type species D. amazighi Sigogneau-Russell, 1995 in its smaller size (length of lower molar = 1.24 mm, Mitutoya TM measuring microscope. maximum width = 0.46 mm), in having cusp b hardly lingual to a-c line; almost equally developed cusps e ABBREVIATIONS and f enclosing a relatively broader anterior notch. BMNH The Natural History Museum, London; MNHN Muséum national d’Histoire naturelle, DESCRIPTION Paris; The tooth is well-preserved except for the break- VPL/JU/KM Vertebrate Palaeontology Laboratory, age of the tips of cusps a and c. The crown is Jammu University, Jammu, Kota transversely narrow with three principal cusps in Mammals; GSI/SR/PAL Regional Palaeontological Laboratory, line anteroposteriorly. Cusp formula for this Geological Survey of India, Southern tooth is a>c>d>b. Cusp a is the largest cusp, Region, Hyderabad. anterior in position, and is connected to a small cusp b at its anterior base. Although the tips of a and c are broken, it seems that the posterior bor- SYSTEMATICS der of these cusps is slightly longer than the ante- rior one. Cusp d is much smaller than c and is Order TRICONODONTA Osborn, 1888 placed perpendicular to the line of a and c, with a Family incertae sedis flat anterior face and a convex posterior face, both faces being separated by a crest ascending Genus Dyskritodon Sigogneau-Russell, 1995 from the lingual cingulum. Cusps a, c, and d are separated from each other by V-shaped notches. TYPE SPECIES.— Dyskritodon amazighi Sigogneau-
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