The deciduous dentition and dental replacement in the Eocene bat Palaeochiropteryx tupaiodon from Messel: The primitive condition and beginning of specialization of milk teeth among Chiroptera

The deciduous dentition and tooth replacement pattern of Palaeochiropteryx tupaiodon from the early Middle Eocene of Messel, near Frankfurt, Germany, are described. Ontogenetic stares include fetuses to subadults. The posteri or portion of the deciduous dentition (dP3-4) still shows the primitive eut herian condition of molarization, while the anterior part (dI-dC) was alrea dy engaged in the evolution of the highly derived condition found in living bars for clinging to the mother's fur. A styliform and sharp anterior dent ition is considered a prerequisite in earliest chiropteran evolution. The g reatly modified milk teeth of all living bats developed in different clades by parallel evolution under high selective pressure. The tiny and, at init ial stages, poorly calcified teeth are substantiated by a newly developed m icroradiographic technique which is described in detail.