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Bos (Mammalia: Bovidae) from the Pinjor Formation of Sardhok, Pakistan.

Byline: Muhammad Khaled Siddiq, Muhammad Akbar Khan and Muhammad Akhtar

ABSTRACT

The new Bovini remains, referred to the genus Bos, are recovered from the Sardhok Pleistocene of Northern Pakistan. Bos appears for the first time in the Plio-Pleistocene of the Siwaliks. The best record of Bos acutifrons is found in the Siwaliks of Pakistan and India. Recently excavated Bos material in the Middle Pleistocene locality of Sardhok (Gujrat, Punjab, Pakistan) includes a complete horn-core that provides a better knowledge of the taxon's morphology.

Key words

Artiodactyls, Bovini, Pleistocene, Pinjor, Siwaliks.

INTRODUCTION

The Upper Siwalik subgroup of the subcontinent was inhabited by early bovines: Hemibos, Proamphibos, Bison, Bos and Leptobos (Rutimeyer, 1878; Pilgrim, 1939; Khan et al., 2010; Siddiq et al., 2014). Bos was widespread in the Siwaliks and Eurasia during Pleistocene (Pilgrim, 1939; Martinez-Navarro et al., 2007). In the Siwaliks, the oldest record of the genus is from the Tatrot Formation (3.5-2.6 Ma) of the Siwaliks (Pilgrim, 1939). The first occurrence of Bos coincides with those of Equus and Elephas in the Siwaliks. Nevertheless, Bos is a highly derived genus of the tribe Bovini.

The Sardhok village is located in the Gujrat district of Pakistan (Fig. 1). The outcrops coordinates are Lat. 32 49' 39" N: Long. 73 43' 51" E and vernacularly, the deposits are named Pabbi Hills. The low altitude land surface is furnished by water channels (locally called Kas), representing flash-flood conditions. The sediments comprise brown to grayish-brown, fine, medium to coarse-grained sandstones with pebbles and large-scale cross stratifications, brown mudstones, and embedded conglomerates (Dennell, 2008; Dennell et al., 2008; Siddiq et al., 2014). Chronologically, the Sardhok outcrops are dated to Pleistocene (2.6-0.6 Ma) (Cande and Kent, 1995; Dennell et al., 2006; Nanda, 2002, 2008) and yielded early bovines of this age.

Remains of Bos have been found in many sites in the Plio-Pleistocene of Pakistan (Lydekker, 1877; Pilgrim, 1939; Hooijer, 1958; Akhtar, 1992; Dennell et al., 2008). However, previously reported assemblages that retain horn-cores were badly preserved. A new partially complete horn-core from the middle Pleistocene of the Siwaliks in Pakistan is now more informative. The horn-core indicates the main diagnostic features of species.

MATERIALS AND METHODS

The measurements are in millimeters (mm). The inventory number on the specimen represents the collection year (numerator) and serial number (denominator) of that year. The comparative study was made with the material in the Natural History Museum at London, United Kingdom (BMNH), the Geological Museum at Leiden, Netherland (Coll. Dub.), and Dr. Abu Bakr Fossil Display and Research Center, Department of Zoology, University of the Punjab, Lahore, Pakistan (PUPC).

The studied specimen is housed in the Dr. Abu Bakr Fossil Display and Research Center, Department of Zoology, University of the Punjab, Lahore, Pakistan. The terminology of horn-core follows Pilgrim (1939).

SYSTEMATIC PALAEONTOLOGY

Suborder Ruminantia Scopoli, 1777

Family Bovidae Gray, 1821

Subfamily Bovinae Gray, 1821

Genus Bos Linnaeus, 1758

Bos acutifrons Lydekker, 1877

Stratigraphic range

Upper Siwaliks (Plio-Pleistocene).

Locality

Sardhok (S VII), district Gujrat, province Punjab, Pakistan.

New material

PUPC 10/80, right horn-core.

Description

The slight torsion of the horn-core is counter clockwise as indicated by heavy longitudinal grooves along the posterior surface (Fig. 2). The curvature is upward representing strong forward flexion. The cross section is pyriform (subtriangular) at the base and almost elliptical at the apex. The posterior keel is prominent. The sinuses are present. The horn-core is rather slender and decrease gradually in diameter towards the tip, moderately compressed dorso-ventrally and slightly narrow anteriorly.

Longitudinal furrows regularly ornament the horn-core. The length of the horn-core along the outer curve is 455 mm and along the inner curve is 356 mm. The total length along the chord is 385 mm. The antero-posterior diameter (DAP) at the base is 67 mm and the transverse diameter (DT) at the base is 92.5 mm giving an index of compression 72 (index of compression followed by Hooijer, 1958). The antero-posterior diameter (DAP) at the apex is 50 mm and the transverse diameter at the apex is 62 mm giving an index of compression 81 (Table I).

Table I.- Comparative measurements (mm) of Bos acutifrons with Epileptobos groeneveldtii and Leptobos. *: the studied specimen. The compression index is followed by Hooijer (1958).

Taxa###Inventory No.###Description###Measurement

B. acutifrons###PUPC 10/80*###Length along the outer curve###455

###Length along the inner curve###356

###Antero-posterior diameter (DAP) at the base###67.0

###Transverse diameter (DT) at the base###92.5

###Index of compression (DAP x 100/DT) at the base###72.0

###Antero-posterior diameter (DAP) at the apex###50.0

###Transverse diameter (DT) at the apex###62.0

###Index of compression (DAP x 100/DT) at the base###81.0

###Total length along the chord###385

L. falconeri###BMNH 48037###Length along the outer curve###ca 500

###Antero-posterior diameter (DAP) at the base###77.0

###Transverse diameter (DT) at the base###85.0

###Index of compression (DAP x 100/DT)###91.0

L. etruscus###Length along the outer curve###500

###Antero-posterior diameter (DAP) at the base###73.0

###Transverse diameter (DT) at the base###79.0

###Index of compression (DAP x 100/DT)###92.0

L. vallisarni###Length along the outer curve###330

###Antero-posterior diameter (DAP) at the base###77.0

###Transverse diameter (DT) at the base###88.0

###Index of compression (DAP x 100/DT)###88.0

L. stenometopon###Length along the outer curve###420

###Antero-posterior diameter (DAP) at the base###58.0

###Transverse diameter (DT) at the base###72.0

###Index of compression (DAP x 100/DT)###81.0

###Coll. Dub. No. 2833###Length along the outer curve###890

###Antero-posterior diameter (DAP) at the base###82.0

###Transverse diameter (DT) at the base###111

###Index of compression (DAP x 100/DT)###74.0

###Coll. Dub. No. 1696###Length along the outer curve###-

###Antero-posterior diameter (DAP) at the base###79.0

###Transverse diameter (DT) at the base###95.0

###Index of compression (DAP x 100/DT)###83.0

###Coll. Dub. No. 2765###Length along the outer curve###660+

###Antero-posterior diameter (DAP) at the base###86.0

###Transverse diameter (DT) at the base###102

###Index of compression (DAP x 100/DT)###84.0

###Coll. Dub. No. 2775###Length along the outer curve###-

###Antero-posterior diameter (DAP) at the base###84.0

###Transverse diameter (DT) at the base###97.0

###Index of compression (DAP x 100/DT)###87.0

###Coll. Dub. No. 2791###Length along the outer curve###-

###Antero-posterior diameter (DAP) at the base###78.0

###Transverse diameter (DT) at the base###90.0

###Index of compression (DAP x 100/DT)###87.0

###Coll. Dub. No. 2767###Length along the outer curve###-

###Antero-posterior diameter (DAP) at the base###87.0

###Transverse diameter (DT) at the base###99.0

###Index of compression (DAP x 100/DT)###88.0

###Coll. Dub. No.2622###Length along the outer curve###750

###Antero-posterior diameter (DAP) at the base###79.0

###Transverse diameter (DT) at the base###88.0

###Index of compression (DAP x 100/DT)###90.0

###Coll. Dub. No.2770###Length along the outer curve###590+

###Antero-posterior diameter (DAP) at the base###86.0

###Transverse diameter (DT) at the base###95.0

###Index of compression (DAP x 100/DT)###91.0

###Coll. Dub. No.8474###Length along the outer curve###-

###Antero-posterior diameter (DAP) at the base###80.0

###Transverse diameter (DT) at the base###88.0

###Index of compression (DAP x 100/DT)###91.0

###Coll. Dub. No.2813###Length along the outer curve###-

###Antero-posterior diameter (DAP) at the base###78.0

###Transverse diameter (DT) at the base###85.0

###Index of compression (DAP x 100/DT)###92.0

###Coll. Dub. No.2796###Length along the outer curve###-

###Antero-posterior diameter (DAP) at the base###76.0

###Transverse diameter (DT) at the base###83.0

###Index of compression (DAP x 100/DT)###92.0

###Coll. Dub. No.2766###Length along the outer curve###650

###Antero-posterior diameter (DAP) at the base###89.0

###Transverse diameter (DT) at the base###94.0

###Index of compression (DAP x 100/DT)###95.0

###Coll. Dub. No.2829###Length along the outer curve###-

###Antero-posterior diameter (DAP) at the base###82.0

###Transverse diameter (DT) at the base###86.0

###Index of compression (DAP x 100/DT)###95.0

Comparison and discussion

The indication of sinuses in the horn-core associates this specimen to the bovine group Taurina (e.g., Bos, Leptobos, Bison) in distinction to the Bubalina group (e.g., Hemibos, Amphibos, Proamphibos) (Gentry, 1992). The absence of sharp keels excludes the horn-core from those of Hemibos, Proamphibos and Bubalus that are characterized in having the sharp keels. Bibos is also different in having flattened horn-cores at their bases (Pilgrim, 1939, 1947; Hooijer, 1958). The two primary keels are almost disappeared in Leptobos, Bison and Bos. Nevertheless, the primitive form of Bos represents a keel. Bos is also different in having strong forward flexion horn-cores.

The studied horn-core shows similar morphological characters with that of Bos in having strong forward flexion and posterior keel which is one of the characters of Bos primitive form. The studied horn-core represents the persistence of a vestigial posterior keel. The overall pattern of the described horn-core is clearly different from that of Epileptobos, Leptobos and Bison and much more similar to the pattern observed in the Siwalik Bos primitive form Bos acutifrons (Pilgrim, 1939). Comparison with other Siwalik form (i.e. B. namadicus) also indicates great difference, as the later form shows circular cross section, almost disappearance of keels. Morphological and metric features of the Sardhok horn-core coincide with the Siwalik Bos primitive form, Bos acutifrons.

Originally, all Bovini employed the genus Bos. Earlier many bovine forms like Leptobos, Bison, Eobison and Bibos were considered the subgenera of Bos (Pilgrim, 1939). Later on, Pilgrim (1939) attributed the genus Bos to living B. taurus or allied fossil forms, and Leptobos, Bison, Eobison and Bibos were ranked to the generic level. Because the horn-cores of these bovines show a significant difference e.g., Bison forms show a clear double flexion and a significantly stronger upward curvature, Eobison shows strong dorso-ventral compression, Probison represents an obvious twisting and stronger curvature and Leptobos represents disappearance of keels (Hooijer, 1958; Shani and Khan, 1968; Bukhsianidze, 2005; Khan et al., 2010).

CONCLUSIONS

The new specimen of horn-core from Sardhok (PUPC 10/80) is attributed to Bos acutifrons. This species represent the primitive form of the genus Bos in having a vestigial posterior keel. Numerous records of B. acutifrons exist from the late Pliocene (Tatrot Formation) through the Pleistocene of the Siwaliks. Bos acutifrons at Sardhok is limited by a single horn-core and offered good evidence on the existence of this species in the Siwalik Pleistocene.

Statement of conflict of interest

Authors have declared no conflict of interest.

REFERENCES

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Shani, M. R. and Khan, E., 1968. Probison dehmi n. g. n. sp., a recent find of the Upper Siwalik bovid. Mitt. Bayer. Staatssamml. Palaont. Hist. Geol., 8: 247-251.
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Publication:Pakistan Journal of Zoology
Article Type:Report
Geographic Code:9PAKI
Date:Aug 31, 2016
Words:2487
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