Abstract

New cranial and postcranial (including shell and thin sections) material of the baenid turtle “Trinitichelys” maini is described and the species is taxonomically revised and referred to a new genus, Gehennachelys. The hypodigm of G. maini is expanded to include informative specimens allowing for a more comprehensive morphological understanding and shell reconstruction, as well as more thorough comparisons with confamilials.This taxon is phylogenetically placed at the base of Baenodda. Gehennachelys maini comb. nov. lacks a contribution of the posteriormost vertebral scale to the carapace margin and an omega-shaped femoral-anal sulcus, both historically regarded as baenodd synapomorphies, despite showing derived cranial characters for Baenodda. This inconsistency challenges the utility of these traits in diagnosing baenodds and highlights problems in resolving baenid relationships. Gehennachelys demonstrates that baenodds evolved as early as the middle Cenomanian, and it likely dispersed to southwestern Appalachia during a regression in the early Cenomanian, becoming the terminal baenid from the eastern North American landmass.