Evolution of the amphibian tympanic ear and the origin of frogs

Recent anurans plus all but the most primitive temnospondyl labyrinthodont amphibians are proposed as a monophyletic taxon, based on shared stapedial characters which are derived with respect to all other tetrapods. Within temnospondyls, the mostly Lower Permian dissorophoids are proposed as most closely related to Recent anurans, based on interpretation of the dissorophoid dorsal quadrate process and the anuran tympanic annulus as sequential steps in a character transformation series. The otic features described here reinforce the concept of the amphibian tympanic ear as a prior "invention" with no genealogical relationship to amniote tympanic ears.