HORN CORES OF SIVOREAS (BOVIDAE) FROM THE MIOCENE OF PAKISTAN AND UTILITY OF THEIR TORSION AS A TAXONOMIC TOOL

The torsion (T) of the horn cores of Sivoreas, which was measured in d egrees per 10 cm, increased with time. T-values for Sivoreas from the lower Chinji equivalent strata range from 143 to 188. The same values for Sivoreas eremita from middle and upper Chinji equivalent strata re ach the maximum of 240. One Sivoreas horn core from the still younger member D of the Ngorora Formation in Kenya has a T-value of 243. Sivor eas from the Lower Chinji Formation represents a new species, S. sonda ari. The T-values of Protragocerus horn cores also increased with time (lower Chinji 40 less-than-or-equal-to T less-than-or-equal-to 95 ; m iddle and upper Chinji 97 less-than-or-equal-to T less-than-or-equal-t o 119). Other early Boselaphini have little torsion. Therefore, it is likely that Sivoreas and Protragocerus evolved from a boselaphine with horn cores with little torsion. In the course of evolution, the torsi on in the horn cores of both genera increased at different rates.