Occupying the role of primary consumer and having an early–middle Permian age range, caseids (Caseasauria, Synapsida) are fundamental to the interpretation of the early history of terrestrial vertebrate ecosystems. Despite this importance, no comprehensive, species-level phylogenetic study of Caseidae has yet been performed. Herein, we present a phylogenetic analysis of the group, using gap weighting to include poorly known taxa. Besides the description and comments on the resultant topologies, some more general issues concerning cladistic methodologies are briefly addressed. This study highlights the importance of a total-evidence approach, including as many within-group taxa and characters as possible. Continuously varying characters, in the form of indices derived from measurement of individual skeletal elements, proved to be highly important, adding significantly to the resolution of, and support for, recovered trees. The utility of the postcranial skeleton in understanding relationships among basal synapsids is highlighted.

Appendix S1 - Specimens direct analyzed and used for the construction of morphometric charactersList of specimens direct analyzed and used for the construction of morphometric charactersAppendix S2-Character listList of characters used in the cladistic analysisAppendix 2-Character list.pdfAppendix S3- Data MatrixData MatrixAppendix S4-Analysis of individual nodes and cladesAnalysis of individual nodes and cladesAppendix S5-Morphometric characters considered in phylogenetic analysisMorphometric characters considered in phylogenetic analysisAppendix 5-Morphometric characters considered in phylogenetic analysis.pdfAppendix S6 - PlatesPlatesAppendix S7: analysis including Eocasea martiniAppendix S7: analysis including Eocasea martiniAppendix S7.pdfMatrix, Nexus formarMatrix, Nexus formatRomano&Nicosia.nex