Journal of the Palaeontological Society of India ISSN 0522-9630 Volume 58(2), December 2013: 213-218 RECORD OF A LATE MIOCENE SUID, TETRACONODON INTERMEDIUS FROM THE BARIPADA BEDS (MAYURBHANJ, ORISSA): AGE IMPLICATIONS K. MILANKUMAR SHARMA* and RAJEEV PATNAIK* *DEPARTMENT OF GEOLOGY (C. A. S.), PANJAB UNIVERSITY, CHANDIGARH-160014 Corresponding e-mail: [email protected] ABSTRACT The highly fossiliferous marine deposits of the Baripada Beds have been assigned ages ranging from Eocene to Pleistocene primarily based on biostratigraphically long-ranging foraminfers, molluscs and selachians. We describe here a short ranging (Late Miocene) suid, Tetraconodon intermedius from these beds for the first time. A detailed comparison and biostratigraphic correlation of our finding with similar finds from the Nagri-Dhok Pathan transition of the Siwalik of Jammu and the Irrawaddy beds of Myanmar allows us to provide a smaller age window of ~10-8 Ma to these beds. Keywords: Tetraconodon, Late Miocene, Biostratigraphy, Baripada Beds INTRODUCTION The Baripada Beds, which are considered to be deposited as a consequence of marine transgression (Modak, 1952), are well known for their diverse fossil assemblages: selachians, spine of Rays and Skates, bony fishes, molluscs and foraminifers. However, the precise geological age of these fossiliferous marine deposits has remained contentious for a long period of time due to the presence of long-ranging taxa. The current paper describes an isolated tooth of Tetraconodon intermedius, which is known from the Nagri-Dhok Pathan transition in Jammu Siwalik (Pilgrim, 1926). The present specimen was collected from the bluish grey sandy shale bed overlying the limestone deposits of Itamundia (Fig. 1). This is overlain by a hard, compacted deposit of conglomerate bed of about 1.5 m thickness, which in turn is overlain by lateritic fresh water sediments of Quaternary age. The bluish grey sandy shale yielding Tetraconodon tooth is underlain by fossiliferous limestone bed of 1.5 m thickness. The lowermost bed comprises of green shales, the base of which is not exposed in the studied section. The Tetraconodon intermedius-bearing section has yielded bone fragments of turtles, diverse fossil remains of sharks such as Galaecerdo cuvier, Negaprion brevirotis, Carcharadon carcharias, Carcharodon mecalodon, Charcharias mylobatis sp., Charcharinus egertoni, Odontaspis tricuspidatus, Negaprion brevirostris, Myliobatis sp., Aetobatus sp., Dentex sp. and molluscs (bivalves and gastropods), etc., representing a shallow marine environment (Eames 1937; Modak, 1952; Sahni and Mehrotra, 1981). Various workers have assigned ages ranging from Eocene to Pleistocene to Baripada Beds, which are only 10-14 meters Fig. 1. A, Location map and B, Litho-section exposed at the Locality, thick and exposed on the banks of Burabalang River. The Itamundia, Baripada Beds, Orissa. offshore data from Mahanadi basin indicates presence of ~1903 m thick Miocene sequence (Fuloria et al., 1992). Hora (1939) Bhalla and Dev, 1972, 1975a; Tiwari and Awasthi, 1960; Singh proposed an age of Eocene to these beds based on the presence et al., 1976; Chatterjee, 1977; Mishra, 1985; Eames, 1936). Bhalla of siluroid and scomber fishes. Similar assertions were made and Dev (1975a, 1972) suggested a Lower Miocene age based by Ghosh (1956, 1959) who used the presence of batoids, on the presence of Ostrea which is known from the Gaj Beds Rhinoptera raeburni, Rhinoptera sherborni and Hypolophus (Lower Miocene) of Pakistan and Miocene beds of Burma. and indicated the possibility of a wider age range to these Sahni et al. (1971) opined an age not older than the lower beds. Most of the workers were in favour of a Miocene Age for Miocene and not younger than the Pleistocene based on the the Baripada Beds (Modak, 1952; Sarma, 1956; Mohanty, 1966; fish fauna. 214 K. MILAN KUMAR SHARMA AND RAJEEV PATNAIK Some worker, however, preferred a Plio-Pleistocene age limestone bed of Baripada Beds, Itamundia, Orissa. Dental for these beds. Chaudhuri (1958) combined mammals terminology and the method of measurements are followed (Potamochoerus and Gazella) and foraminifers, to assign after Thaung-Htike et al. (2005) (Fig. 2A). Dental measurements Baripada Beds a lower Pleistocene age. Chatterji and Adyalkar of the M3 of Tetraconodon intermedius specimen of Baripada (1962) also favoured an age of Plio-Pliestocene to the Beds have been compared with those of other Tetraconodon gravel deposits overlying the fossiliferous deposits of specimens of Thaung-Htike et al. (2005) and Made and Han Miocene age. (1994) (see, Table 1.) The mean dental measurements of Propotamochoerus wui recovered from the upper Miocene MATERIAL AND METHOD deposits of the East Asian site of Lufeng, China (Made and A diagnostic right upper third molar (RM3) (Fig. 2 B) was Han, 1994) that yielded Tetraconodon has been used here for collected from the bluish grey sandy shale just above the comparing ratios. Fig. 2: A, Dental terminology and measuring method of tetraconodontine teeth. Abbreviations: BL= Base line; L= Mesiodistal length; W = Bucco- 3 3 lingual width; W1 = first lobe width; W2 = Second lobe width; W3 = Third lobe width of M /3. (After, Thaung-Htike et al., 2005). B. M of Tetraconodon intermedius (mks/pal/pu.1020) and its dental terminology. Table 1: Dental measurements (mm) of the new Tetraconodon intermedius from Baripada Beds (Mks/pal/pu. 1020); T. intermedius (Thaung-Htike et al., 2005), T. cf. T. intermedius (Thaung-Htike et al., 2005) and mean measurements of Propotamochoerus wui (Made, 1994). Abbreviations: L = Mesiodistal length; W1 = first lobe width; W2 = Second lobe width; W3 = Third lobe width of M3; * ¼ estimate (Source, Thaung-Htike et al., 2005). Taxa Specimen M3 L W1 100(L/w1) W2 W3 T. intermedius Mks/pal/pu.1020 31 21.5 144 18 11 T. intermedius Thaung-Htike et al. 2005 GSI B 675 43* 32* 130 T.cf. intermedius Thaung-Htike et al. 2005 NMMP-KU-IR 0225 33.3 26.8 120 22.9 12.1 P. wui Made & Han (1994) Mean 7-28 spec 24.1 17.4 138 14.9 8 RECORD OF TETRACONODON INTERMEDIUS FROM THE BARIPADA BEDS 215 SYSTEMATIC PALAEONTOLOGY mesially; anterior cingulum is convex, protopreconule is not Family Suidae Gray, 1821 distinct, furchen are prominent in well developed paracone, Subfamily Tetraconodontinae Lydekker, 1876 protocone, hypopreconule, metacone and hypocone; Genus Tetraconodon Falconer, 1868 protocone is little bit larger than the paracone; pentapreconule (Type species Tetraconodon magnus Falconer, 1868) is tiny, pentacone is large and the surface is worn. The Type species: Tetraconodon magnum Falconer, 1868 measurements of the specimen and its comparison with other (including Tetraconodon mirabilis Pilgrim, 1926) described specimens are given in Table 1. Other included species : Tetraconodon minor Pilgrim, 1910; Tetraconodon intermedius Made, 1999; Tetraconodon COMPARISON malensis. A morphological comparison of the present specimen Diagnosis: The Genus Tetraconodon differs from the other shows that it is similar to the M3 of Tetraconodon intermedius 3-4 reported from Myanmar (Thaung-Htike et al., 2005). The Tetraconodontine genera in having extremely enlarged P /3-4, 3 comparison of the size with M3 teeth of other Tetraconodon simple and relatively small M /3, and thick and highly wrinkled 3-4 1-3 specimens show that the present specimen is little bit smaller enamel in P /3-4, and less wrinkled enamel in M /1-3. (Also see, Thaung-Htike et al., 2005). than those of Tetraconodon intermedius and T.cf. T. Tetraconodon intermedius Made, 1999 intermedius, described by Thaung-Htike et al. (2005) and larger (Fig. 2B) than P. wui (Made and Han, 1994) (see Table. 1). T. cf. T. Tetraconodon intermedius Thaung-Htike et al., 2005, p. 5, fig. 4 intermedius (Thaung-Htike et al., 2005) differs from the present Tetraconodon intermedius Made, 1999, p. 203-205. specimen in having a small minor cuspule at the lingual side 3 Tetraconodon mirabilis Pilgrim, 1926 (in part), p.16, p l. 3, ?g. 4. and small pentacone (Fig. 3). As the M s’ of Tetraconodon Tetraconodon cf. mirabilis Pilgrim, 1926, p. 16 – 17, pls. 4, 6. intermedius are rarely described in the previous literature, Diagnosis: Tetraconodon of intermediate size. interspecific variability of size of the teeth is not well known. Specimen: Mks/pal/pu. 1020, an isolated right upper M3. However, based on the morphological features as well as the Locality: Itamundia relative size of the tooth, the present specimen can be assigned Horizon and Age of the Locality: Baripada Beds, Late to Tetraconodon intermedius. Miocene The teeth of Tetraconodon minor are larger than that of Description: Mks/pal/pu. 1020 is a right upper third molar Conohyus but are smaller than Tetraconodon mirabilis (RM3). The tooth is elongated and narrower distally than (Thaung-Htike et al., 2005; Made, 1999). Tetraconodon minor Fig. 3. I. Bivariate plot (Length versus W1-width) for the M3 of Tetraconodontinae; II. Bivariate plot (L versus W2) for the M3 of Tetraconodontinae; III. Bivariate plot (L versus W3) for the M3 of Tetraconodontinae; IV. Bivariate plot (W2 versus W3) for the M3 of Tetraconodontinae. The indices in the figures is given as; A = Tetraconodon intermedius (Mks/pal/pu.1020), B = T. intermedius (GSI B 675) (Thaung-Htike et al., 2005), C = T. cf. T. intermedius (NMMP-KU-IR 0225) (Thaung-Htike et al., 2005), D = P. wui (Made, 1994). 216 K. MILAN KUMAR SHARMA AND RAJEEV PATNAIK had been considered to be the smallest and the most primitive The Genus Tetraconodon most probably originated from Tetraconodon (Pilgrim, 1926; Thaung-Htike et al., 2005; Made, Conohyus sindiensis, the oldest known Asian 1997; Colbert, 1935). However, teeth of Tetraconodon minor tetraconodontine, which occurs in the lower Middle Miocene are found to be three times larger than those of Conohyus (Kamlial or lower Chinji) of the Siwalik Group of Indo-Pakistan sindiensis (Thaung-Htike et al., 2005). An evolutionary and Nepal (Thaung-Htike et al., 2005).