Redescription and phylogenetic relationships of Solenodonsaurus janenschi Broili, 1924, from the Late Carboniferous of Nýřany, Czech Republic
Abstract. The basal tetrapod Solenodonsaurus janenschi Broili, 1924, from Nýřany (Westphalian D, Late Carboniferous), Czech Republic, is redescribed and its phylogenetic position reevaluated. A distinct groove at the base of the maxillary teeth is regarded as an autapomorphic character, which is present in both the large and small specimens. Other characteristic features, which are not unique to S. janenschi, are: an extension of the lacrimal that forms the anteroventral margin of the orbit; a long posterior extension of the jugal; spool-shaped vertebrae, and small, wedge-like intercentra. A phylogenetic analysis based on the data matrix of Ruta, Coates and Quicke suggests that S. janenschi is the sister taxon of the Lepospondyli. Shared characters include the shape of the vertebrae, non-swollen neural arches, and absence of an intertemporal. Although nested within the amniote stem, S. janenschi is not as closely related to basal amniotes as previously suggested. A rather long, slender humerus argues for a predominantly terrestrial mode of life, and the curved, slender ribs, as well as the comparatively small skull, suggest costal ventilation of the lungs similar to that in amniotes, rather than buccal pumping. The morphology of the shallow squamosal embayment in which an ossified dorsal margin is absent, renders the presence of a tympanum unlikely.