Traquairius agkistrocephalus
This cochliodont holocephalan is the brother species to Traquairius spinosus. It
ranged to approximately 18 inches in length. It is extremely rare;
there is only one specimen known, a male, and we only found the front
half of it. The back half was probably eaten by some shark. T.
agkistrocephalus (the species name means fish hook head) is
armored with many plates, spines, enlarged denticles, and the tall
hooked spines on the head and at the position of the first dorsal fin.
Very fine and sparse scales were intermixed with enlarged scales on the
body. The spines may have served for protection, and sexual as well as
species recognition. The scale is in mm.
A small anterior paired upper tooth family and posterior tooth plates were used for crushing and grinding shelled animals.
The paired row of fish hook shaped spikes on the ethmoid and around the base of the dorsal fin plate are similar in shape to those of the much younger (Permian) Menaspis armata. The cranial plates and spines are grossly hypertrophied; some rows of scales on the head and certain scale rows on the body are also greatly enlarged. The tooth plates of this individual were almost completely worn out, showing that he was well past maturity when he died. The preservation of only his anterior half strongly suggests that he was bitten in half and only the less prickly posterior half was eaten.
Reference:
- Lund, R., and E.D. Grogan, 1997. "Cochliodonts from the Mississippian Bear Gulch Limestone Heath Formation; Big Snowy Group, Chesterian) of Montana and the relationships of the Holocephali." Dinofest International Symposium, Proceedings: 477-492.