The anatomical description of the osseous inner ear of tapirus and the evolution of the petrosal in perissodactyla

Abstract

The petrosal is an important and complex bone of the basicranium that houses the organs of balance and orientation in space (vestibule) and hearing (cochlea) together with the associated tissues related with these functions. Among ungulates, it is extensively applied in Artiodactyla phylogenetic studies, however it is still poorly known and used to study Perissodactyla internal relationships, mainly among the extant representatives. Also, the evolution of the petrosal of perissodactyls, although barely mentioned in literature, was never described and/or accurately analyzed. This study will be the first morphological description of the petrosal of the living species Tapirus kabomani Cozzuol, et al., 2013, Tapirus indicus Desmarest, 1819 and the extinct Tapirus cristatellus Winge, 1906; as well as extend the knowledge of the ear region of genus Tapirus Brisson, 1762. It will be also a major contribution to the analysis of the petrosal of Perissodactyla available in literature. Besides to contribute to the descriptive collection of petrosal of the order Perissodactyla we will trace the evolution of some petrosal characters among Perissodactyla, with emphasis in Tapiridae, investigating the evolutionary similarities and differences between the petrosal of some extinct and extant perissodactyls representatives and tracing how some petrosal characters behave when added to a existing phylogeny