With subsequent discoveries, Crassigyrinus is now known from three skulls, one of which is in articulation with a fairly complete skeleton, and two incomplete lower jaws.

Some paleontologists have even considered it as the most basal crown group tetrapod, while others hesitate to even place it within the Tetrapoda superclass.

Studies have shown that Crassigyrinus may have been able to open its mouth as wide as 60 degrees, which suggests that it was a powerful predator with a strong bite.

Several thickened bony ridges ran along the dorsal midline of the snout and between the eyes, and several paleontologists have suggested that they helped the skull to withstand stress when the animal bit prey.

[5][6] The hindlimbs were much larger than the forelimbs, and in the pelvis the ilium lacked a bony connection to the vertebral column (a classic feature of aquatic tetrapods).