Morphologic study of the tympanoperiotic bones of cetaceans from the sub-order Odontoceti (Mammalia: Cetacea)

Abstract

Taxonomic or morphologic studies of tympanoperiotic bones, which composse the medium and internal ears of cetaceans, are scarce. The goal of this paper is to identify and to describe the structures that constitute the tympanoperiotic bones of six species of small cetaceans that occur off the coast of Ceará State, Brazil. Between January 1992 and July 1996, 22 sets of tympanoperiotic bones of six species were studied: 15 of Sotalia fluviatilis, 2 of Steno bredanenses, 1 of Stenella clymene, 2 of Tursiops truncatus, 1 of Peponocephala electra and 1 of Ziphius cavirostris. The auditive bules were coded and measured to the 0.05 mm precision, and 22 characteristics were recorded. A study of bilateral symmetry in S. fluviatilis was also performed comparing bule measurements using the Hotelling’s T² statistics. The results were non significant. Phylogenetic relationships among the six stiied species based on cluster analysis of tympanoperiotic bones measurements, were in agreement with phylogenetic trees based on mitochondrial DNA sequences.