A new procolophonid and a new tetrapod of uncertain, possibly procolophonian affinities from the Upper Triassic of Virginia

ABSTRACT

Two jaw fragments of small tetrapods from the Turkey Branch Formation of the Richmond basin (Newark Supergroup; Upper Triassic: lower to middle Carnian) of Virginia have highly distinctive dentitions. The robust, transversely broadened, and bicuspid teeth of Gomphiosauridion baileyae, gen. et sp. nov. support its placement in the Procolophonidae. The two cusps are linked by a pronounced transverse ridge, which divides the occlusal surface of the crown into two deep fossettes. The cusps have strongly fluted enamel. The heterodont dentition of Xenodiphyodon petraios, gen. et sp. nov. comprises transversely broadened, tricuspid posterior teeth and transversely compressed anterior teeth with distinct apical ridges. The posterior teeth of Xenodiphyodon closely resemble those of the alleged trilophosaurid taxa Tricuspisaurus thomasi and Variodens inopinatus from Upper Triassic fissure-fillings in southwestern England and ?Trilophosaurus jacobsi from the Upper Triassic Chinle Formation of Arizona. The latter is clearly distinct from the archosauromorph Trilophosaurus buettneri and is made the type species of the new genus, Chinleogomphius. All four genera may prove referable to the Procolophonia.