|Keywords (Extracted from title, table of contents and abstract of thesis)
neogene murine rodents, potwar plateau, zoogeographic diversification, stratigraphic implications, neogene siwalik mammal fauna, mammal assemblages, rodentia, muridae, cricetidae, rhizomyidae, himalayan molasses, miocene
One of the most important aspects of the continuing research for the last two decades on the Neogene Siwalik mammal fauna of Pakistan is the recovery of rich small mammal assemblages from almost the entire Siwalik sequence. Rodentia, in general, and its three families, namely the Muridae, Cricetidae, and Rhizomyidae, in particular, have been studied in fair details. Muridae have been found to be the dominant rodent group in the siwalkis and the ancestor-descendant relation of its various species establishes South Asia as the center of origin and subsequent diversification-dispersal for the family Muridae.
Although broad speciation patterns in Muridae from the early Middle Miocene to the present-day diversity in south Asia have been established, yet, important gaps for precise documentation of various speciation events still exits. This study is an attempt to redress the lacuna and a better temporally constrained murid phylogeny is presented based upon four selected time periods, which have been sampled from four different localities in the Powtar Plateau.
A small mammal assemblage from the middle part of the Chinji Formation, locality PMNH 8608 near Bin Amir Khatoon village in southern Potwar contains at least thirteen species that represent nine rodent and insectivore families plus a single specimen of Chiroptera. Cricetids are represented by three species, which resemble those reported from the Banda Daud Shah assemblage. Antemus chinjiensis is the only murid recognized but specimens referred to this species include three molars that are apparently atypical in being and having extra cuspules (morphologic variants as yet unrecorded). Prokanisamys benjauni and kanisamys indicus constitute typical Middle Miocene rhizomyids encountered in the Siwalik sequence. Palaeotupaia sp. Perhaps is a separate species from affinities with the Greek species and has been assigned to G. aff. Symeonidisi species probably had short longevities and hence their application in biochronology provide precise faunal dating. The PMNH 8608 locality fauna closely resembles the Daud Khel small mammal fauna and both are correlated with the Late Astracian age of the European sequence.
Isolated deposits near Jalapur, southeastern Potwar Plateau is the second locality, which yielded a diverse small mammal fossil assemblage. The fossil locality, JAL-101, contains a particularly good sample of a primitive species of the early murid progonomys, which is named herein as P, hussani. This and other elements of the fauna (Cricetidae, Rhizomyidae) argue for an age younger than that of Chinji Formation sites at the Chinji stratotype in southern potwar, consequently JAL-101 is important because it improves the sample of fossils representing early Late Miocene time in the Siwaiks. The fauna of 13 mammal species can be used to make an age estimate for JAL-101 by correlation to the Potwar microfauna sequence. Temporal ranges of rodent species, as presently known, constrain JAL-101 to ca. 11 Ma.
Small mammals from tow mid policene localities in Azad Kashmir produce a modern shrew comparable to living suncus and murids assignable to three genera. These are Golunda Kelleri, a species described previously from an early Pleistocene locality in northern Pakistan, cf. Hadromys sp. And Mus. Sp. The murids date to about 3 Ma and thus include the oldest record of Golunda and the Hadromys Lineatge.
The lehri fossil locality, PMNH 93128 in eastern potwar plateau contains important material of extinct species earlier based on a few specimens from an early Pleistocene locality in the Pabbi Hills, Pakistan. The material includes upper dentition of Golundda kelleri, named for a few lower molars, and lower dentition of Hadromys loujacobsi, first known by upper molars. These fossibls are slightly older, probably only 300,000 years, than the respective hypodigms, and are geographically close. They indicate the likely morphology of the complementary elements of each species. They help to put into focus other material from Pliocene localities in India, and suggest that Golunda and Hadromys both had complex phylogenetic histories. The locality also produced smaller murids, including at least one species of Cremnomys and mouse near Mus jacobsi. The fauna is like other Late Pliocene assemblages encountered across the Indian subcontinent and indicating zoogeographic ties to East Africa.