Data from: Cranial anatomy and phylogenetic affinities of Bolosaurus major, with new information on the unique bolosaurid feeding apparatus and evolution of the impedance-matching ear

Resolving the phylogenetic relationships of early amniotes, in particular
stem reptiles, remains a difficult problem. Three-dimensional
morphological analysis of well-preserved stem-reptile specimens can reveal
important anatomical data and clarify regions of phylogeny. Here, we
present the first thorough description of the unusual early Permian stem
reptile Bolosaurus major, including the first comprehensive description of
a bolosaurid braincase. We describe previously obscured details of the
palate, allowing for insight into bolosaurid feeding mechanics. Aspects of
the rostrum, palate, mandible, and neurocranium suggest that B. major had
a particularly strong bite. We furthermore found B. major has a
surprisingly slender stapes, similar to that of the middle Permian stem
reptile Macroleter poezicus, which may suggest enhanced hearing abilities
compared to other Paleozoic amniotes (e.g., captorhinids). We incorporated
our new anatomical information into a large phylogenetic matrix (150 OTUs,
590 characters) to explore the relationship of Bolosauridae among stem
reptiles. Our analyses generally recovered a polyphyletic ‘Parareptilia,’
and found Bolosauridae to diverge from the reptile stem after
Captorhinidae + Araeoscelidia. We also included Bolosaurus major within a
smaller matrix (10 OTUs, 27 characters) designed to explore the
interrelationships of Bolosauridae and found all species of Bolosaurus to
be monophyletic. While reptile relationships still require further
investigation, our phylogeny suggests repeated evolution of
impedance-matching ears in Paleozoic stem reptiles.