Changes in inner ear canal morphology over time suggest that mammalian ancestors called mammaliamorphs evolved warm-bloodedness around 233 million years ago during the late Triassic period, according to research published yesterday (July 20) in Nature. The analysis provides new clues to the outstanding question of when mammals switched from relying on external heat to regulate their body temperatures (ectothermy) to generating their own heat (endothermy).
Inside ears, semicircular ducts filled with a fluid called endolymph help animals perceive head motion to improve motor coordination, balance, and spatial awareness, the study authors write. But not all inner ears are created equal.
“Mammals have very unique inner ears,” study coauthor Ricardo Araújo, a vertebrate paleontologist at the University of Lisbon, tells Science News. This led Araújo and his team to hypothesize that because endolymph is more viscous in warm-blooded animals, their canal structures may have evolved differently than in ectotherms, the outlet ...
