Horn cores of Sivoreas (Bovidae) from the Miocene of Pakistan and utility of their torsion as a taxonomic tool

Abstract

The torsion (T) of the horn cores of Sivoreas, which was measured in degrees 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 reach 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. Sivoreas from the Lower Chinji Formation represents a new species, S. sondaari. The T-values of Protragocerus horn cores also increased with time (lower Chinji 40≤T≤95; middle and upper Chinji 97≤T≤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 torsion in the horn cores of both genera increased at different rates.