Traquairius nudus
Traquairius nudus is a cochliodont holocephalan, and judging by the cranial plates, the spines, and the jaws and tooth plates, it is a sister species to other members of the genus Traquarius (T. agkistrocephalus and T. spinosus). The body of T. nudus is unknown.
We have a second head of the same proportions and the same cranial
plates, which bears a large median ethmoid tenaculum or clasper
(tenaculum in blue), and thus is a male. The clasper of this specimen
resembles the tenaculae of two distinctly and distantly related
holocephalans, Metopacanthus and Squaloraja, but is
quite different than the tenaculum of modern male chimaeroids.
The cranial spines and plates of T. nudus differ from those of the other species of the genus in positions, numbers, and sizes. No ethmoid spikes or spines are known, hence the species name nudus. The tooth whorls, tooth plates, and general features of the head are very similar to those of the other members of the genus, and are excellently displayed in this material. The proportions of the cranium are very close to those of modern chimaeroids.
Upper (left) and lower (right) jaws of an individual of Traquairius nudus. Note the impressions of the upper plates behind (above) the lower plates, and the wear of the upper plates.
References:
- 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.
- Lund, R., and E.D. Grogan, 2004. "Two tenaculum-bearing Holocephalimorpha (Chondrichthyes) from the Bear Gulch Limestone (Chesterian, Serpukhovian) of Montana, USA." part 1, p. 171-188 in Arratia, G., Wilson, M.V.H. and Cloutier, R. (eds), Recent advances in the origin and early radiation of vertebrates, Verlag Dr. Friedrich Pfeil, München.