| Stethacanthus productus|
Fossil range: Late Devonian - Early Carboniferous
| Scientific classification
Stethacanthus productus is the largest known stethacanthid shark of the genus Helicoprion. Adults are estimated, based on the few remains known, to have exceeded 9 feet in length. They were the largest known predatory sharks of the Mississippian, and were certainly apex predators.
Isolated teeth and large fecal masses filled with fish bones are presumed to be from these sharks; these are not uncommon in the Bear Gulch Limestone. One complete early subadult male is also known, as well as jaws of other individuals of varied sizes. Most of these remains, however, are from young individuals rather than large adults. It appears that S. productus visited the Bear Gulch bay to feed.
Scales were limited to patches along the ventral flanks of the abdomen.
Very large, sharp multicuspid cladodont teeth on large bony bases were mounted on strong well braced jaws that had ample room for the origin of the adductor muscles of the jaws. As in the rest of the Stethacanthidae, males developed the first dorsal fin and spine at puberty (~ 1 meter), along with denticles on the top of the head and associated with the top of the fin.
- Lund, R. 1984. "On the spines of the Stethacanthidae (Chondrichthyes), with a description of a new genus from the Mississippian Bear Gulch Limestone." Geobios, 17, fasc. 3: 281-295.
- Lund, R. 1985. "Stethacanthid elasmobranch remains from the Bear Gulch Limestone (Namurian E2b) of Montana." Amer. Mus. Nat. Hist. Novitates, 2828: 1-24.