Bats (Chiroptera) are one of the most successful extant mammalian orders, uniquely capable of powered flight and laryngeal echolocation. The timing and evidence for evolution of their novel adaptations have been difficult to ascertain from the fossil record due to chronological gaps and the fragmentary nature of most fossil bat material. Here, we quantify the quality of the bat fossil record using skeletal and character completeness metrics, which respectively document for each taxon what proportion of a complete skeleton is preserved, and the proportion of phylogenetic characters that can be scored. Completeness scores were collected for 441 valid fossil bat species in 167 genera from the Eocene to the Pleistocene. All metrics record similar temporal patterns: peak completeness in the Lutetian stage reflects the presence of Lagerst€ atten, while subsequent stages have very low completeness, except an Aquitanian high and a Pleistocene peak in skeletal completeness. Bat completeness is not correlated with intensity of sampling through geological time but has a weak negative correlation with publication date. There is no correlation between taxonomic richness and completeness, as the bat record predominately consists of diagnostic but isolated teeth. Consequently, bat skeletal completeness is the lowest of any previously assessed tetrapod group, but character completeness is similar to parareptiles and birds. Bats have significantly higher character completeness in the northern hemisphere, probably due to heightened historical interest and presence of Lagerst€ atten. Taxa derived from caves are more complete than those from fluviolacustrine and marine deposits, but do not preserve highly complete specimens.

Proterosuchids are an important group of carnivorous basal archosauriforms characterized by a bizarre and enigmatic downturned premaxilla that overhangs the lower jaw. They are particularly significant because they radiated in the immediate aftermath of the Permian–Triassic mass extinction and represent one of the best known ‘disaster taxa’ following that event. While traditionally considered to be semi‐aquatic, recent histological studies and geological data have suggested that it is more likely that they inhabited terrestrial environments. By using computed tomographic (CT) data, we virtually reconstruct the brain endocast and endosseous labyrinths of two adult specimens of Proterosuchus fergusi from the earliest Triassic of South Africa, in an attempt to understand its life habits within the context of basal archosauriform evolution. Endocasts reveal that the brain cavity is tubular in shape and the endosseous labyrinths are highly pyramidal. The angle of the lateral semicircular canal suggests that P. fergusi naturally held its head upwards ~17°, while the length of the cochlear duct suggests its auditory abilities were specialized towards low‐frequency sounds. Furthermore, beam theory analysis suggests that the rostrum of P. fergusi is highly resistant to both bending and torsion when compared to modern crocodilians, although this resistance is neither enhanced nor reduced by the overhanging premaxilla. Comparative anatomical analyses suggest P. fergusi was probably a semi‐aquatic, generalist apex predator capable of surviving the harsh environmental perturbations of the Early Triassic.

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