Hybodus

Hybodus (from Greek: ύβος hybos, 'crooked' and Greek: ὀδούς odoús 'tooth')[2] is an extinct genus of shark that, in a strict sense, only lived during the Early Jurassic epoch.[1] It is a wastebasket taxon that is 'broadly polyphyletic' and requires reexamination.[3][4][1] 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.

Hybodus
Temporal range: Early Jurassic[1]
Hybodus hauffianus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Superorder: Selachimorpha
Order: †Hybodontiformes
Family: †Hybodontidae
Genus: †Hybodus
Agassiz, 1837
Type species
†Hybodus reticulatus
Agassiz, 1837
Species[1]
  • †H. reticulatus
  • †H. hauffianus

Description

Hybodus species grew to about 2 metres (6.6 ft) in length, and are believed to have been opportunist predators. 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. The mouth was not large, and rather than ruthlessly hunt large prey, Hybodus, was capable of eating a wide range of foods. They had several distinct features that made them stand apart from other primitive sharks. Firstly, they had two different types of teeth, suggesting a wide diet. The sharper teeth would have been used to catch slippery prey, while the flatter teeth probably helped them crush shelled creatures. Secondly, they had a bony blade on their dorsal fin that probably served a defensive function. The males also possessed claspers, specialized organs that directly insert sperm into the female, and which are still present in modern sharks.[5]

Species Status

Several Hybodus species, including H. butleri, H. rajkovichi, and H. montanensis, were later reassigned to Meristodonoides.[6] H. basanus and H. fraasi is now included in the genus Egertonodus.[7] H. obtusus represents a junior synonym of Asteracanthus ornatissimus.[8] A new species from Spain, H. bugarensis, is described in 2013.[9] Two new species from China, H. xinzhuangensis and H. chuanjieensis are named in 2018, and H. houtienensis is considered,[10] while other species from China and Thailand are no longer part of the genus and requires reassessment.[11] However, Hybodus sensu stricto only refers to the type species H. reticulatus and the other species H. hauffianus.[1] The problem is that even those two species require reassessment.[12]

Media depictions

Hybodus was depicted in the third episode of the 1999 BBC television series Walking with Dinosaurs and within the 2003 BBC series Sea Monsters: A Walking with Dinosaurs Trilogy (Chased by Sea Monsters in the United States).[13]

References
  1. Maisch, M. W., & Matzke, A. T. (2016). A new hybodontid shark (Chondrichthyes, Hybodontiformes) from the Lower Jurassic Posidonienschiefer Formation of Dotternhausen, SW Germany. Neues Jahrbuch Für Geologie Und Paläontologie - Abhandlungen, 280(3), 241–257. https://doi.org/10.1127/njgpa/2016/0577
  2. Roberts, George (1839). An etymological and explanatory dictionary of the terms and language of geology. London: Longman, Orme, Brown, Green, & Longmans. p. 79. Retrieved 30 December 2021.
  3. Leuzinger, L., Cuny, G., Popov, E., & Billon-Bruyat, J.-P. (2017). A new chondrichthyan fauna from the Late Jurassic of the Swiss Jura (Kimmeridgian) dominated by hybodonts, chimaeroids and guitarfishes. Papers in Palaeontology, 3(4), 471–511. https://doi.org/10.1002/spp2.1085
  4. Korneisel, D., Gallois, R. W., Duffin, C. J., & Benton, M. J. (2015). Latest Triassic marine sharks and bony fishes from a bone bed preserved in a burrow system, from Devon, UK. Proceedings of the Geologists’ Association, 126(1), 130–142. https://doi.org/10.1016/j.pgeola.2014.11.004
  5. Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 28. ISBN 978-1-84028-152-1.
  6. Underwood, Charlie J.; Cumbaa, Stephen L. (July 2010). "Chondrichthyans from a Cenomanian (Late Cretaceous) bonebed, Saskatchewan, Canada". Palaeontology. 53 (4): 903–944. doi:10.1111/j.1475-4983.2010.00969.x.
  7. Maisey, J. G. (1987). "Cranial anatomy of the Lower Jurassic shark Hybodus reticulatus (Chondrichthyes: Elasmobranchii), with comments on hybodontid systematics". American Museum Novitates. 2878: 1–39.
  8. Stumpf, Sebastian; López‐Romero, Faviel A.; Kindlimann, René; Lacombat, Frederic; Pohl, Burkhard; Kriwet, Jürgen (2021-01-13). Cavin, Lionel (ed.). "A unique hybodontiform skeleton provides novel insights into Mesozoic chondrichthyan life". Papers in Palaeontology: spp2.1350. doi:10.1002/spp2.1350. ISSN 2056-2799.
  9. Pla, Cristina., Márquez-Aliaga, Ana. & Botella, Héctor. (2013). The chondrichthyan fauna from the Middle Triassic (Ladinian) of the Iberian Range (Spain), Journal of Vertebrate Paleontology, 33:4, 770-785, https://doi.org/10.1080/02724634.2013.748668
  10. SUN Baidong, WANG Wei, LIU Junping, SONG Donghu, LÜ Boye, XU Yunfei, WANG Lu. (2018). New fossil materials of hybodus (Chondrichthyes) in the Middle Jurassic found in Chuanjie Basin of central Yunnan Province[J]. Geological Bulletin of China, 37(11): 1991-1996.
  11. Cuny, G., Mo, J., Amiot, R., Buffetaut, E., SUTEETHORN, S., Suteethorn, V., & Tong, H. (2017). New data on Cretaceous freshwater hybodont sharks from Guangxi Province, South China. Research & Knowledge, 3(1), 11–15. https://doi.org/10.14456/randk.2017.4
  12. 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
  13. "Sea Monsters: A Walking With Dinosaurs Trilogy". BBC.

Sources
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