Evolution of the skull in arvicoline cricetids (Rodentia) according to 3D morphometric insights: Part 1. Morphological disparity of the palato-spheno-pterygoid complex

Our paper is the first contribution to the comprehensive analysis of the complicated evolution of cranial and mandibular parts connected by pterygoid muscles, as part of more global investigation into adaptive evolution of Arvicolinae. The analysis was performed on 90 micro-computed-tomography-scanned specimens from 33 species from 19 genera of Arvicolinae as well as two species from two genera of Cricetinae as an outgroup. We revised 11 morphological traits of the "palato-spheno-pterygoid" complex, including key features of the palatine that are highly important for defining Arvicolinae taxa according to the micro-computed-tomography data. We also homologized characters of the posterior palatal margin and categorized the composition of the palatal elements into two main morphotypes: morphotype "A" is unique to Clethrionomyini and morphotype "B" was subdivided into three additional types and was found to occur in the outgroup (cricetines), voles (B2), and lemmings (B3). Morphospace analysis of the palato-spheno-pterygoid complex by means of the three-dimensional dataset revealed a mode of transformation of morphotype "A" into morphotype "B2." A separate task was the development of a protocol for the preparation of morphological data for subsequent evaluation of genotype-phenotype relationships using specialized software applications (e.g., RERconverge).