The evolution and ontogeny of the dentition of Myotragus balearicus Bate, 1909 (Artiodactyla, Caprinae): evidence from new fossil data

Myotragus balearicus Bate 1909 is an artiodactyl Caprinae endemic re the Ba learic Islands (Spain), which became extinct more than 4000 years ago. It i s characterized by a series of very unusual apomorphies acquired throughout its insular evolution, one of which is the presence of a single evergrowin g incisor (with an open root) in each dentary. This incisor has been classi cally considered as I-1. The study of recently discovered fossils of this s pecies, which have been collected from die excavation of Holocene cave sedi ments in Cova Estreta (Pollenca, Mallorca) and in Cova des Moro (Manacor, M allorca), together with the reexamination of materials belonging both to th is species and to its ancestors, allowed us to study the ontogeny and evolu tion of the Myotragus dentition. The replacement of premolars differs only slightly from the pattern recorded in other bovids. Nevertheless, there are significant differences with other bovids regarding the incisiform series. Myotragus balearicus lacks secondary incisors. Through a neotenic process, which starred during the Upper Pliocene,.M. balearicus acquired a monophyo dontic incisiform dentition, reducing the number of incisiforms to only one , identified as dI(2). The richness of the finds allows us to describe the different steps in this evolution. The only incisiform that appears to have been lost is dI(3). The identification of the everproducing incisor of M. balearicus as dI(2) reinforces its convergence with rodents postulated by B ate and there is discussion regarding homologies of incisors of rodents and lagomorphs. (C) 1999 The Linnean Society of London.