Impedance-Matching Hearing in Paleozoic Reptiles: Evidence of Advanced Sensory Perception at an Early Stage of Amniote Evolution

摘要: Background Insights into the onset of evolutionary novelties are key to understanding amniote origins and diversification. The possession an impedance-matching tympanic middle ear is characteristic all terrestrial vertebrates with a sophisticated hearing sense adaptively important feature many modern vertebrates. Whereas ears seem have evolved multiple times within tetrapods, especially among crown-group members such as frogs, mammals, squamates, turtles, crocodiles, birds, presence true has never been recorded in Paleozoic amniote, suggesting they fairly recently history. Methodology/Principal Findings In present study, we performed morphological examination phylogenetic analysis poorly known parareptiles from Middle Permian Mezen River Basin Russia. We recovered well-supported clade that characterized by unique cheek morphology indicative tympanum stretching across large parts temporal region extent not seen other amniotes, fossil or extant, braincase specialized showing modifications clearly related increase auditory function, unlike any tetrapod. In addition, estimated ratio area relative stapedial footplate for basalmost taxon clade, which, at 23∶1, close correspondence amniotes capable efficient hearing. Conclusions/Significance Using analogues, these suggests ecological adaptations potentially living dim-light environments. More importantly, our results demonstrate already early stage diversification, prior Permo-Triassic extinction event, complexity vertebrate ecosystems had reached level proved advanced sensory perception be notable adaptive significance.