''Hybodus'' (from el, ύβος , 'crooked' and el, ὀδούς 'tooth') is an extinct genus of hybodont, a group of shark-like elasmobranchs that lived from the Late

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

to the end of the Cretaceous. Species closely related to the type species ''Hybodus reticulatus'' lived during the Early Jurassic epoch. Numerous species have been assigned to ''Hybodus'' spanning a large period of time, and it is currently considered a wastebasket taxon that is 'broadly polyphyletic' and requires reexamination. The first fossilized teeth from ''Hybodus'' were found in England around 1845; since then teeth (and dorsal spines) have been recovered from Europe. During the Triassic, Jurassic, and Cretaceous periods, the hybodonts were especially successful and could be found in shallow seas around the world. For reasons that are not fully understood, the hybodonts became extinct near the end of the Late Cretaceous period.

Description

''Hybodus'' species grew to about in length. It was not very big, but had the classic streamlined shark shape, complete with two dorsal fins that would have helped it steer with precision. As in other Hybodontiformes, dentinous fin spines were present on the dorsal fins of ''Hybodus''. The fin spines of ''Hybodus'' exhibit a rib-like ornamentation located towards the tip of the spine, with rows of hooked denticles present on the posterior side. The spines may have played a role in defending the animal from predators. ''Hybodus varied dentition would have allowed it to opportunistically exploit a variety of food sources; sharper teeth would have been used to catch slippery prey, while the flatter teeth probably helped them crush shelled creatures. The males also possessed claspers, specialized organs that directly insert sperm into the female, and which are still present in modern sharks.

Species

Several ''Hybodus'' species, including ''H. butleri'', ''H. rajkovichi'', and ''H. montanensis'', were later reassigned to '' Meristodonoides''. ''H. basanus'' and ''H. fraasi'' is now included in the genus '' Egertonodus''. ''H. obtusus'' represents a junior synonym of '' Asteracanthus ornatissimus''. A new species from Spain, ''H. bugarensis'', is described in 2013. Two new species from China, ''H. xinzhuangensis'' and ''H. chuanjieensis'' are named in 2018, and ''H. houtienensis'' is considered, while other species from China and Thailand are no longer part of the genus and requires reassessment. However, the only two species that should be retained within the genus ''Hybodus'' are the type species ''H. reticulatus'' and the other species ''H. hauffianus''. The problem is that even those two species require reassessment.Stumpf, S., & Kriwet, J. (2019). A new Pliensbachian elasmobranch (Vertebrata, Chondrichthyes) assemblage from Europe, and its contribution to the understanding of late Early Jurassic elasmobranch diversity and distributional patterns. ''PalZ, 93''(4), 637–658. https://doi.org/10.1007/s12542-019-00451-4

References

Sources

* * Hybodontiformes Prehistoric shark genera Permian sharks Triassic sharks Jurassic sharks Cretaceous sharks Prehistoric fish of Africa Cretaceous fish of Asia Fossils of Uzbekistan Bissekty Formation Prehistoric fish of Europe Hasle Formation Prehistoric fish of South America Taxa named by Louis Agassiz {{Jurassic-fish-stub