The External Nasal Cartilages in Chiroptera: Significance for Intraordinal Relationships

Abstract

Detailed description and comparison of the prenatal and postnatal morphology of the external nasal cartilages across bats and their relatives have identified morphological characters that contribute to the resolution of phylogenetic conflicts concerning the relationships among bat subgroups. In this study, I include observations on the morphology of the cupula nasi anterior and of the processus alaris superior in chiropteran species not previously examined, including members of the Rhinolophidae and Megadermatidae. Contrary to recent results, based on analysis of single-copy DNA hybridization and DNA sequence data from nuclear and mitochondrial genes, morphology of the nasal cartilages supports the traditional view that Microchiroptera is monophyletic and that Rhinolophoidea is more closely related to other microchiropteran families than it is to Pteropodidae. A dorsal apertura nasi externa diagnoses the grouping Megadermatidae + Rhinolophidae and Rhinopomatidae and the presence of a cartilago accessoria appears to be a putative synapomorphy of the clade Rhinolophidae + Megadermatidae. Most Microchiroptera share a commissura alicupularis and a shell-shaped processus alaris superior. The few extant Microchiroptera that lack the shell-shaped processus alaris superior show a very different form of the anterior nasal capsule and superior alaris process: the processus alaris superior is integrated as part of the cupular side wall (e.g., emballonurids, megadermatids), or has a half-tube shape (rhinolophids). Based on observations of a sickle-shaped superior alaris process in Megachiroptera and other potential relatives of the Chiroptera, it seems most likely that a shell-shaped processus alaris superior is a synapomorphy of the living microchiropteran bats.