The development of nasal turbinal morphology of moles and shrews

Abstract

The phylogenetic relationships of major groups within the Order Eulipotyphla was once highly disputed, but the advent of molecular studies has greatly improved our understanding about the diversification history of talpids, soricids, erinaceids, and solenodontids. Their resolved phylogenetic relationships now allow us to revisit the turbinal and lamina evolution of this group. The inner structure of the nasal cavity of mammals is highly complicated and the homologies of the turbinals among mammalian species are still largely unsettled. In this regard, investigation on fetal anatomy and ontogenetic changes of the nasal capsule allows us to evaluate the homologies of the turbinals and laminae. We observed various fetuses and adults of talpids and soricids using high-resolution diffusible iodine-based contrast-enhanced computed tomography (diceCT) and reviewed previous reports on erinaceids, solenodontids, and other laurasiatherians. Although the turbinal and lamina morphology was previsouly considered to be similar among eulipotyphlans, we found phylogenetic patterns for talpids and soricids. The nasoturbinal of the common ancestor of talpids and soricids was most likely rostrocaudally elongated. The epiturbinal at the ethmoturbinal II disappeared in soricids independently. Finally, we propose two possible scenarios for the maxilloturbinal development: 1) the maxilloturbinal of talpids and soricids became small independently with a limited number of lamellae as a result of convergent evolution, or 2) the common ancestor of talpids and soricids already had a small and simple maxilloturbinal.