Dietary adaptations of two goat ancestors and evolutionary considerations

Abstract

A comparative tooth microwear data base of twenty extant ungulates (eight browsing species, four mixed feedingspecies, and eight grazing species) was established and analyzed. The three dietary categories are reflected by the tooth microwear results, as browsers have more pits and fewer total scratches, and grazers have fewer pits and more total scratches. The data of the mixed feeders form bimodal distributions, consisting of a browsing group and a grazing group, which indicates that they either graze or browse. Based on the tooth microwear results, Pachytragus crassicornis, one of the extinct ancestors of modern Caprini (goats and sheep) found on the Miocene localities of Samos in Greece (7.2 – 8.5 Ma), was most likely a mixed feeder. Pachytragus laticeps was a grazer. The masticatory morphology of both Pachytragus species are similar to a few mixed feeders, such as Tragelaphus scriptus and Gazella grunti. According to the local biostratigraphy at Samos, the horn core morphology of several species, and the tooth micowear data, P. laticeps most likely evolved from P. crassicornis. In P. crassicornis, the masticatory morphology was synchronized with the dietary adaptation, in P. laticeps, which evolved rapidly, it was not. The origin of Capra may be best related to Pachytragus solignaci, which is 17 Ma. Sheep and goats may have had distinct origins prior to 17 Ma. The tribe Pseudotragini is revived and includes Protoryx carolinae, Protoryx enanus, Pseudotragus capricomis, Caprotragoides potwaricus, Sporadotragus parvidens, Pachytragus solignaci, Pachytragus laticeps and Pachytragus crassicornis.