Sivatherium Falconer and Cautley, 1835 giganteum

KUMAR, SURESH, 2022, New Fossils Of Sivatherium Giganteum (Giraffidae, Mammalia) From The Upper Siwaliks Of The Indian Subcontinent, Acta Palaeontologica Romaniae 18 (2), pp. 85-92 : 88-91

Species Sivatherium Falconer and Cautley, 1835 giganteum

Holotype: NHMUK-15283 , a skull.

Type Horizon: Upper Siwaliks.

Additional Material: PUA/SK - 07/49 , a half right maxillary second molar;

PUA/SK- 06/ 34 , a left mandibular fragment with partial M 2 and M 3.

Horizon: Tatrot Formation of the Upper Siwaliks.

Locality: About 1km north of Gobindpur Village.

Description PUA/SK-07/49

The present specimen is a half right maxillary second molar. The tooth preserves its complete mesial half and only a small part of the distal half of the molar. The occlusal aspect of the preserved part of the molar shows two major cusps in the anterior half, namely, mesio-buccally, the metacone, and mesio- lingually, the protocone. The metacone is broad in the middle with a strongly developed median rib and sloping anterior and posterior ridges. The anterior ridge is united with the parastyle whereas the posterior ridge is connected with the anterior ridge of the metacone, which is completely broken. The lingual part of the specimen displays a roughly crescent-shaped protocone the mesial limb of which extends up to the mesiolingual aspect of the metacone.

The metacone and protocone are separated by a deep and broad pre-fossette, in the mesial half of the molar. Only a small part of the mesial portion of the hypocone is preserved. The molar displays a median basal pillar on its lingual side which extends up to one third the height of the crown. A moderately developed cingulum can be seen around the base of the lingual side of the protocone, extending from the basal pillar to the middle of the mesial side. A strong facet is visible on the mesial side of the molar. The enamel is thick and rugose. The tooth shows slight wear. The colour of enamel is dark brownish yellow and that of dentine is dull brown.

PUA/SK- 06/34

The specimen under description is a left mandibular fragment with partially preserved M 2 and M 3. The preserved portion of the mandibular ramus is deep. It is eroded on the lingual face, exposing portion of the roots of the third molar, while distal to the third molar is laterally compressed.

M2

The molar is half broken and badly preserved. The crown details cannot be clearly demarcated as all the major cuspids as well as stylids are missing. The tooth shows heavy wear.

M3

This molar is highly worn and is roughly rectangular in outline. The crown displays only two cuspids, the mesiolingual metaconid and the mesio-buccal protoconid. In the mesial half, the paraconid and the protoconid are separated by a crescent-shaped pre-fossettid. The distal aspect of the tooth is badly damaged therefore the major cuspids in this area, namely, the metaconid, hypoconid, and entoconid as well as the stylids such as the paratstylid, mesostylid, and metasylid, are completely missing.

Only a trace of the mesial part the post-fossettid is preserved. The hypoconulid is also broken. Only a trace of cingulum can be seen at the mesio-buccal border of the protoconid. On the lingual side the roots of M 3 are visible; these extend up to the lower one-third of the ramus. The colour of enamel is yellow-greyish brownish while the dentine is medium brown in colour.

DISCUSSION AND COMPARISONS

Several genera of fossil giraffids, namely, Giraffa , Giraffokeryx , Sivatherium , Hydaspitherium , Helladotherium , and Bramatherium , are known from the Siwaliks of India and Pakistan. Several workers in the past, such as Lydekker (1876, 1878), Pilgrim (1910, 1911), Matthew (1929), Gaur (1987), Nanda & Shukla (2001), Akhtar et al.(1991), Khan & Sarwar (2002), and Khan et al. (2011), respectively, have reported fossil Siwaliks giraffids. Although the Upper Siwaliks of the study area have yielded many mammalian fossils, those of Sivatherium giganteum are very rare when compared to other mammals of the fauna ( Kumar, 2009). So far, Sivatherium giganteum is the only known species of the genus Sivatherium from the Upper Siwaliks of the Indian Subcontinent ( Gaur, 1987). The earliest occurrence of the genus Sivatherium was reported by Falconer & Cautley (1835; see also Bohlin, 1926; Colbert, 1935; Gaur, 1987). The present discovery is significant in the sense that it represents the first report of Sivatherium giganteum from the Tatrot Formation of the Upper Siwaliks of Indian Subcontinent. As yet, there is no published report of the Sivatherium giganteum from the Tatrot Formation of the Upper Siwaliks of the Indian Subcontinent. The problem of the boundary between the Pliocene and the Pleistocene is still very doubtful both from geological and faunal viewpoints. Accordingly, due to the paucity of relevant fossil material and to limited magnetostratigraphic studies in the present study area, it is not possible to comment about the precise age of the genus Sivatherium in the Siwaliks. Hence, it is necessary to extensively explore the Siwaliks in order to solve this problem.

The Siwalik giraffids can be grouped according to their size into larger-bodied and smaller-bodied forms, respecttively ( Colbert, 1935; Solounias, 2007; Harris et al. 2010). The group of large forms includes Sivatherium giganteum , Bramatherium megacephalum , and Hydaspitherium megacephalum . whereas smaller forms include Giraffa punjabiensis and Giraffokeryx punjabiensis . According to ( Colbert, 1935, see also Geraads and Gülec, 1999), Siwalik giraffids can be distinguished on the basis of their dentition, separating the genera Sivatherium , Bramatherium , and Hydaspitherium with large- sized teeth in comparison with the genera Giraffa and Giraffokeryx with small teeth.

The studied specimens (PUA/SK-07/49 and PUA/SK-06/34) show large- sized teeth with moderate height, and with a thick and rugose enamel, both of which are typical characteristic features of the genus Sivatherium (Table 1). According to Falconer & Cautley (1836), in the genus Sivatherium the protocone is truly crescentic with its praeprotocrista projected backward. The specimen PUA/SK-07/49 can be differentiated from the genus Bramatherium which has an L-shaped protocone; whereas in Sivatherium the protocone is crescent-shaped. According to Gentry (1997), the size of teeth is the only criterion to differentiate the Siwalik giraffid species in addition to the presence of styles/stylids, obliteration in the central fossettes, and the rugosity.

The present specimens differ from Giraffa punjabiensis and Giraffokeryx punjabiensis in their overall size (Table 1). These can be also differentiated from Hydaspitherium megacephalus which is smaller than Sivatherium giganteum . The above comparisons of the specimens suggest show close morphological and dimensional similarities with Sivatherium giganteum . Moreover, S. giganteum is the only species of the genus Sivatherium known from the Upper Siwaliks of India ( Gaur, 1987) Hence these specimens are assigned to Sivatherium giganteum .