A new mesoeucrocodylian, Pachycheilosuchus trinquei, from the Lower Cretaceous (Albian) Glen Rose Formation, exhibits progressive caudal-to-cranial vertebral procoely. This modification is characterized by an intermediate semi-procoelous condition in which the posterior condyle is dimpled by a concavity. Pachycheilosuchus differs from all known crocodyliforms in having an expanded maxillary margin that displaces the tooth row medially, and in possessing a cervical shield formed by the complete fusion of six osteoderms. Phylogenetic analysis indicates a sister taxon relationship with the weakly defined Atoposauridae. The presence of variable procoely in both Pachycheilosuchus and the closely related atoposaurid Theriosuchus indicates convergent evolution of the character with Eusuchia. Sediments at the locality were deposited in near-shore, marine-to-brackish waters, suggesting that Pachycheilosuchus inhabited euryhaline marine environments.