INTRODUCTION

The Chitarwata Formation of western Pakistan is a thick rock sequence recording the late Oligocene and early Miocene geological and biological history of the western Himalayan Foreland. Near Dalana in the Zinda Pir Dome region west of Dera Ghazi Khan (Figure 1a) the Chitarwata Formation is over 400 m thick and represents deposition in marginal marine settings (Downing et al. 1993; Downing and Lindsay, this issue). Vertebrate remains have not been recovered from the thick eolian sandstones comprising the middle unit of the Chitarwata Formation. However, a diverse small and large mammal fauna, described by Flynn and Cheema (1994), Lindsay (1995), Baskin (1996), and Lindsay et al. (this issue), has been recovered from numerous fossiliferous levels within the Chitarwata Formation’s lower and upper units. However, the remains of very large mammals have been sparse in the Chitarwata Formation in the Zinda Pir area, although specimens of deinotheres, gomphotheres, rhinocerotoids, and chalicotheres have been collected (Lindsay and Downs 2000). Near the base of the lower unit of the Chitarwata Formation (locality Z153) hyracodontid (Indricotheriinae) fossils have been found. Evidence of rhinocerotoids in the Chitarwata Formation at Zinda Pir Dome area is typically limited to enamel fragments of teeth or isolated postcranial remains.

By comparison, an exceptionally diverse Oligocene and early Miocene record of rhinocerotoids has been developed for the Bugti Hills localities in Baluchistan over the last 160 years since fossils were reported by Vickary in 1846. Early collections and study by Lydekker (1881), Pilgrim (1912), and Forster-Cooper (1934) have been recently augmented by the Mission Paléontologique Française au Balouchistan (Welcomme et al. 2001). The classic “Bugti fauna” and its diverse rhinos have been collected in two primary areas of the Bugti Hills region, the “Dera Bugti Valley” and the Gandoi Plain. The localities Lundo Chur and Paali Nala in the Gandoi plain have yielded the Oligocene giant hyracodontid, Paraceratherium, the amynodontid Cadurcotherium and the rhinocerotid Epiaceratherium (Welcomme and Ginsburg 1997; Antoine et al. 2003a). In younger deposits in this area Aprotodon, Cadurcotherium, and smaller varieties of Paraceratherium, are recovered. The early Miocene Dera Bugti Valley rhinos from Dera Bugti 4 and Kumbi 4b-c and 4f, include Aprotodon, two species of Dicerorhinus, Protaceratherium, Plesiaceratherium, Brachypotherium, Hoploaceratherium, as well as the small elasmotheriine, Bugtirhinus (Welcomme et al. 1997; Antoine and Welcomme 2000; Welcomme et al. 2001). The late Miocene Sartaaf locality in the Dera Bugti Valley has produced Alicornops (Antoine et al. 2003b).

This report examines new rhinocerotid fossils recovered from two localities in the upper unit of the Chitarwata Formation at Zinda Pir Dome, Z143 and Z147 (Figure 1b) near stratigraphic sections D and E (Lindsay et al. this issue). The upper unit was considered to represent the interval from approximately 17.4 to 19 Ma based upon magnetostratigraphy (Lindsay and Downs 2000), but reassessment of this information in light of additional fossil localities, sections, and magnetostratigraphic sampling (Lindsay et al. this issue) supports a provisional age of 19.5 Ma (chron C6n) for the Chitarwata Formation-Vihowa Formation contact in the southern end of Zinda Pir Dome and two possible ages 23.5 Ma (chron C6Bn) or 27.0 Ma (chron C8n) for the base of the upper unit.

Specimens from Z143 were recovered about 100 m stratigraphically above the contact of the middle and upper units of the Chitarwata Formation as float in close proximity to one another and derived from a fine-grained sand with an iron-rich cement. They are presumed to be from one individual based on the context of recovery, similarity of the fossils’ preservational condition, and tooth wear state. The only other notable vertebrate fossils observed near Z143 were abundant crocodile remains several meters stratigraphically below the Z143 locality. The Z147 molar was found in isolation about 20 m above the contact of the middle the upper unit of the Chitarwata Formation in coarse sand also with iron-rich cement. Based upon the chronostratigraphic age estimates for the contact between the middle and upper units of the Chitarwata Formation described above, the rhinoceros teeth are late Oligocene or early Miocene in age. The upper unit of the Chitarwata Formation is characterized by local concentrations of marine molluscs and is interpreted as a tidal flat-tidal channel environment (Downing et al. 1993). Presumably this rhino’s habitat included lowland forests near the coastal plain and may have been similar to the habitat of the modern Javan Rhinoceros.