STUDIES OF EVOLUTIONARY TRENDS IN DENTITION OF THE SIWALIK TRAGULIDS

The tragulids belonging to the siwaliks of Pakistan are studied in detail, and a very comprehensive systematic has been worked out, which reveal the status and position of the two genera of family tragulidae i.e, Dorcatherium and dorcabune. The genus dorcatherium includes three species, I ) Dorcatherium magus, ii) dorcatherium minus and iii) docrcatherium minimus from the Siwalik Hills of Pakistan . Dorcatherium majus is characterized by its large size very prominent hypsodonty. The upper molars bear strongly developed styles and cingulum, whereas the lower molars have well developed median basal pillars. Dorcatherium minus on the other hand is distinguished by its small size and subhypsodonty. Its upper molars have well developed styles and cingulum whereas the lower molars are characterized by moderately developed or vestigial median basal pillar. Third species Dorcatherium minimus was erected by West (1980), on the basis of only one specimen and after which no other specimen is reported so far which makes the validity of this species doubtful.\ud \ud The genus dorcabune includes four species, i ) dorcabune anthracotherioides,ii ) Dorcabune hyaemoschoides, iii) Dorcabune nagrii and iv) Dorcabune latitens. Dorcabune anthracotherioides is characterized by bunodonty as well as selenodonty. The upper molars are with very much pronounced median rib, strong parastyle and mesostyle and weakly developed metastyle. Protocone is more pyramidal and displays three strong folds. The species dorcabune hyaemoschoides is found synonymous with dorcabune anthracotherioides (Colbert, 1935). The species dorcabune nagrii is well distinguished by small size and weakly developed cingulum. Dorcabune latidens is found synonymous with dorcabune nagrii (Colbert, 1935). Hence according to Colbert (1935) only two species of the genus dorcabune are valid, which are i) Dorcabybe anthracotherioides and ii) Dorcabune nagrii.\ud \ud A trend towards increase in thickness of enamel as well as in size of the dentition of Dorcadtherium majus from chinjian to Dhokpathanian Formation has been studied. In Docatherium minus there is a tendency towards decrease in prominence of cingulum from chinji to Dhokpathan Formation. As far as dorcabune anthracotherioides is concerned it reveals a tendency toward decrees in size with slight deviations from lower siwaliks to the Middle sewaliks. Dorcabune nagrii is very similar to docrcabune anthracotherioides. This species is differentiated by its small size, faint cingulum and less defined posterior inner fold of protoconid. It exhibits a trend towards decrease in size from Nagri Formation to Dhokpathan Formation