Until the late 1990s, Captorhinus was diagnosed by the presence of multiple rows of marginal teeth on the maxillary and dentary bones.

[7]Although a subfamily of Captorhinidae, Moradisaurinae, also possessed multiple-tooth-rows, the best-known type species Captorhinus aguti clearly acquired multiple-rowed-teeth independently.

C. aguti likely practiced lateralized feeding, as enamel on the teeth of the upper and lower right jaws was more worn down than on the left side.

[13] Due to the shape of the distal femoral articulation, Captorhinus aguti would have had little capacity to compensate for lateral movement of the femur.

Unlike C. aguti, the femur of C. magnus possesses a concave proximal articular surface in both immature and mature individuals.

Without the presence of the femur or a tooth-bearing element, it would prove difficult to distinguish between C. magnus and C. aguti, although the two can likely be differentiated with size as the sole criterion.

[18] Possible remains of Captorhinus have been reported from the Pedra de Fogo Formation, Piauí, Brazil, but they are fragmentary and cannot be assigned to the genus with confidence.

[19] In 1882, Edward Cope described a fragmentary skull from the Lower Permian of Texas collected by W. F. Cummins at Coffee Creek as Ectocynodon aguti.

The comparatively small body size of basal captorhinids suggests that they were probably in competition for food with only the youngest of varanopids and sphenacodontids.

[22] Captorhinus is known from the Admiral, Belle Plains, Clyde, Arroyo, Vale, and possibly the Choza Formations, Lower Permian, of Texas.

[23] The genus is also known from the Lower Permian fissure deposits at Richards Spur, Oklahoma, and the Cutler Formation, Rio Arriba County, New Mexico.