Labidosaurus hamatus (Cope 1895, Case 1911) Artinskian, Early Permian, ~280 mya, ~75 cm in length, was derived from a sister to Eocaptorhinus and was a sister to Captorhinus.
Distinct from Eocaptorhinus, the skull of Labidosaurus had a straight and horizontal rostral profile and a deep premaxillary notch greater than 45 degrees. The skull roof was flat. The jawline descended. The ventral naris is bordered chiefly by the maxilla. The frontals were longer than the nasals, as in more basal captorhinids. The paraoccipital angle was 20-40 degrees. The supratemporals were transverse in orientation. The quadratojugal was robust. The teeth retained sharp tips as in more basal taxa. The dentary did not contribute to the coronoid.
Gastralia were present.
The scapula and coracoid were subequal in size. The femur and humerus were subequal. All the metacarpals and metatarsals were elongated. All the digits were more gracile.
Metatarsal I is longer than 75 percent of mt III and IV. Metatarsal V is the shortest metatarsal.