Name: Hybodus
(Humped
tooth).
Phonetic: Hy-bo-dus.
Named By: Louis Agassiz - 1837.
Classification: Chordata, Chondrichthyes,
Elasmobranchii, Selachimorpha, Hybodontiformes, Hybodontoidea,
Hybodontidae.
Species: H. houtienensis, H. chuanjieensis, H. xinzhuangensis.
Type: Type: Carnivore.
Size: Up to 2 meters long.
Known locations: Worldwide.
Time period: Changhsingian of the Permian through to
the Berriasian of the Cretaceous.
Fossil representation: Usually teeth and sometimes
the dorsal spike, fossilised imprints have also been found.
Hybodus
is
instantly recognisable by the spike that rises up in front of its
dorsal fins. The purpose of this has been explained as a form of
defence
from larger predators to display. With fossils dating back from the end
of the Permian to the early Cretaceous and a cosmopolitan distribution,
Hybodus must have been a highly successful predator.
The
teeth inside the mouth of
Hybodus were arranged into two groups. At the front
were sharper
pointed teeth, very useful for seizing prey items like fish and squid.
The teeth towards the back were more rounded, making them suitable for
crushing the shells of crustaceans. Working together, the only animals
that would not be on the menu were those too large to fit into its
mouth.
Hybodus
also displays sexual
dimorphism in that males have a pair of 'claspers' on the underside of
their bodies. These are used to transfer sperm into the females, and
are still present in the sharks
swimming the oceans today.
Sharks
are all known to have
cartilaginous skeletons which usually decompose upon death. Hybodus
however seems to have had highly ossified cartilage making it more like
solid bone. This has meant that impressions have been quite well
preserved revealing the morphology of the living animal.
Many
species have been
attributed to Hybodus but only H.
houtienensis is accepted universally.
The validity of other species have been called into question by
different sources, and further study of Hybodus is
required for further
clarification.
Further reading
- Recherches Sur Les Poissons Fossiles. Tome III (livr. 8-9).
Imprim�rie de Petitpierre, Neuchatel viii-72 - L. Agassiz - 1837.
- Description of the Mouth of a Hybodus found by
Mr. Boscawen Ibbetson
in the Isle of Wight - Quarterly Journal of the Geological Society -
Sir Philip Malpas de Grey Egerton, Bart. M.P. F.R.S. F.G.S.
- A Tooth of Hybodus grossicornis from the Inferior Oolite - Nature 58,
p390 - Thos. Beacall - 1898.
- On A Dorsal Fin-Spine of Hybodus From
Northwestern Kansu - Bulletin
of the Geological Society of China vol 14, issue 1, p 53-55 - C. C.
Young - 1935.
- Cranial anatomy of the Lower Jurassic shark Hybodus
reticulatus
(Chondrichthyes: Elasmobranchii), with comments on hybodontid
systematics. American Museum Novitates 2878:1-19 - J. G. Maisey - 1987.
- On the Hybodus (Euselachii) from the Early Jurassic of Anina (Caraş
Severin district, Romania) - Studia Universitatis Babeş-Bolyai,
Geologia, 2006, 51 (1-2), 51 - 54 - Emanual Paul Dica & Vlad
Codrea - 2006.