Erpetonyx

Erpetonyx Temporal range: Gzhelian (Late Pennsylvanian), 303.7–298.9 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Illustration of the holotype fossil
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	†Parareptilia
Order:	†Procolophonomorpha
Clade:	†Bolosauria
Genus:	†Erpetonyx Modesto et al., 2015
Type species
†Erpetonyx arsenaultorum Modesto et al., 2015

Erpetonyx is an extinct genus of bolosaurian parareptile from the Gzhelian stage of the Carboniferous period, with a single known species: Erpetonyx arsenaultorum. It is known from a single articulated and mostly complete specimen from Prince Edward Island in Canada. Phylogenetics has predicted that parareptiles first evolved in the Carboniferous, parallel to eureptiles ("true reptiles"). However, Hylonomus, the oldest eureptile known from fossil evidence, lived millions of years before parareptiles appeared in the fossil record. The discovery of Erpetonyx helped to shorten this gap between parareptile and eureptile fossils, as Erpetonyx lived in the Late Carboniferous and is one of the oldest known parareptiles (though Carbonodraco is now known to be older). However, it was not closely related to ancestral parareptiles, so its discovery also indicated that the initial diversification of parareptiles occurred earlier in the Carboniferous. Erpetonyx was a small reptile, with the entire skeleton about 20 to 25 centimeters (7.9 to 9.8 inches) in length.^[1][2] It was likely carnivorous, and could be characterized by a variety of skeletal features, including a relatively elongated body and large claws with powerful tendon attachment points.^[1]