Ctenospondylus had a long tail, short back spines, and a very deep yet narrow skull with massive jaws that had sharp teeth.

The generic name, from Greek κτείς, kteis, "comb", and σφόνδυλος, sphondylos, "vertebra", referred to the form of the back sail.

[2] The fossil had been found in Archer County at the Slippery Creek site in the Belle Plains Formation, dating from the Artinskian.

The specific name refers to the Niniveh Limestone Member of the Greene Formation, dating from the Sakmarian where it was found at Clark Hill in Monroe County, Ohio.

Berman considered C. ninevehensis more basal than Ctenospondylus casei and only referred the second species to the genus because of the similar spine length.