Stratodus

''Stratodus'' is a genus of giant prehistoric aulopiform fish found in Cretaceous-aged marine strata of Kansas, Alabama, Morocco, Israel, and Niger, Jordan. It has also been found in the Tamaguélelt Formation of Mali, dating to the Lower Eocene, indicating that ''Stratodus'' survived the Cretaceous-Paleogene extinction event. This sleek fish has an upper jaw filled with multiple rows of tiny teeth and was the largest aulopiform, reaching 5 meters in length.

History of Discovery

''Stratodus'' was initially described by Edward Drinker Cope in Kansas during 1872, naming the type species ''S. apicalis'', and described a second species in 1877, ''S. oxypogon'', both species being assigned to the family Stratodontidae. ''S. oxypogon'' is now often considered a synonym of ''S. apicalis'', and the family was shifted from Stratodontidae to Dercetidae, but now has gone back to Stratodontidae.

For the 19th and 20th centuries, ''Stratodus'' was only known from poor fossils, usually of the skull. It wasn't until 2008 that a nearly complete skeleton of ''S. apicalis'' in the Upper Niobrara Formation was uncovered along the bank of the Missouri River of Oacoma, South Dakota, and other well preserved remains have subsequently been found in the Muwaqqar Chalk Marl Formation of Harrana, Jordan. A second species, ''S. indamanensis'', was described from Niger. In 2019, fossils of ''S. apicalis'' were been found in Mali dating to the Eocene.

Description

''Stratodus'' in many respects is similar in appearance to other lizardfish but much larger, as ''S. apicalis'' could grow to over a meter while ''S. indamanensis'' could reach lengths of . The body is long and slender, anguiliform in shape, and is covered in thick, spiny scutes. An elongated dorsal fin runs down the back.

Perhaps the most striking feature of ''Stratodus'' were it's conical, inward pointing teeth. ''Stratodus'' possessed multiple rows of these teeth which could reach . These teeth were extremely numerous, with at least 6,000 being present in the fish's mouth, to the point that over 1,000 of the teeth are oriented outside of the jaws on the lips of the fish.

''Stratodus'' was related to '' Ministratodus'', a member of Stratodontidae with a similar body plan but smaller size.

Paleoecology

During the Late Cretaceous, ''Stratodus'' had a cosmopolitan distribution on both sides of the North Atlantic Ocean, along with North Africa and Arabia. It lived in shallow, epicontinental waters only a few meters deep. While modern aulopiformes are often ambush predators, ''Stratodus'' appears capable of active hunting, owing to a muscular and hydrodynamic body, and swam in an anguilliform-esque fashion. It's hunting strategy has been hypothesized to resemble that of billfish, using its external teeth to injure prey before returning to devour them, indicated by its external teeth and club-like protrusion at the end of its skull. It was likely a protogyneus hermaphrodite.

''Stratodus'' is one of the few large fish to exist on both sides of the K-Pg boundary, surviving the asteroid that caused the extinction of most other megafauna. In the Eocene, Stratodus inhabited brackish-to-marine tropical waters in the Trans-Saharan Seaway, living alongside animals like '' Palaeophis colossaeus'' and '' Rhabdognathus''.

References

{{Taxonbar, from=Q7622223

Prehistoric aulopiformes
Prehistoric ray-finned fish genera
Cretaceous bony fish
Cretaceous fish of Asia
Cretaceous fish of Africa
Cretaceous fish of North America
Mooreville Chalk
Fossils of Mali
Fossils of Morocco
Fossils of Israel
Fossils of Niger
Eocene Africa