Prevalence of mineralized elements in the rostra of bats (Mammalia: Chiroptera)

The fleshy, movable tip of the snout of most mammals is supported by cartilaginous elements that provide leverage for muscles that control movement of the nose. Mineralization or ossification of the external nasal cartilages within the snout is thought to be associated with increased loading (e.g., in the snouts of pigs) or increased structural support of the snout (e.g., in taxa with elongated noses such as solenodons). However, little is known about the distribution of such structures across most groups of mammals, in part because they are easily overlooked during specimen preparation. Bats (Order Chiroptera) exhibit a diverse array of rostral forms, but have never been surveyed for evidence of mineralization or ossification of external nasal cartilages. We examined micro-CT scans of the heads of 83 fluid-preserved bat species representing 17 families. We observed mineralization of the external nasal cartilages within the snouts of only 5 species belonging to the families Pteropodidae, Molossidae, and Vespertilionidae, suggesting these elements are rare among bats. Mineralized elements varied in size, shape, location, and number among these 5 species, suggesting differences in function related to support and movement of the fleshy tip of the snout, or a role in echolocation.