Named By: Richard Lydekker - 1889.
Classification: Chordata, Reptilia, Diapsida, Ichthyopterygia, Ichthyosauria, Temnodontosauridae.
Species: T. platyodon (type), T. eurycephalus, T. nuertingensis, T. trigonodon, T. acutirostris.
Diet: Cephalopods like ammonites.
Size: Up to 12 meters long.
Known locations: Europe including British Isles and Germany.
Time period: Hettangian through to Toarcian of the Jurassic.
Fossil representation: Several specimens.
is one of the oldest and largest ichthyosaurs
known to science, and
while there are a few species associated with the genus, the most
obvious differences between these are the size and proportions of the
jaws. Temnodontosaurus fossils have been so well
preserved that they
reveal stomach contents of ammonites and cephalopods like squid.
Juvenile specimens have also been reported inside Temnodontosaurus
remains, but in a position that suggests they were waiting to be born
rather than being digested. Live birth in ichthyosaurs like
Temnodontosaurus has long been suspected as their
fusiform bodies that
are so much like fish would make it impossible for them to climb onto
land.Study of other genera such as Ophthalmosaurus amongst others have
helped to confirm the theory of live birth in ichthyosaurs. Like most
large ichthyosaurs, Temnodontosaurus
is thought to
have been a marine reptile of deep water, mostly rising to the
surface just to breathe in fresh air.
Temnodontosaurus had large eyes that were roughly twenty centimetres across. These large eyes would have enabled Temnodontosaurus to see better when in deep water where most of the above sunlight could not penetrate. The large eyes providing a greater catch area for the little available light would allow Temnodontosaurus to distinguish ammonite forms against the dim oceanic backdrop. Aside from ammonites found inside Temnodontosaurus fossils, further support for this hunting behaviour comes from study of the teeth which reveals that they had robust roots so that they could withstand the stresses of cracking shells without breaking off.
Ammonites would have been a plentiful food supply back in the Jurassic oceans, and one that could not have required a great amount of energy expenditure to catch. This suited the large body of Temnodontosaurus as it would require large amounts of a stable food supply to keep going. It is hard to say how the large size came about however but a larger body can carry more oxygen for Temnodontosaurus to stay hunting down in the depths for longer. It’s possible that the earlier ancestors of Temnodontosaurus came across the plentiful supply of deep water cephalopods and grew larger to take better advantage of it. However this greater size also brought a greater reliance upon them, a specialisation that could bring the end of the genus with the disappearance of the prey.
- A revision of the longipinnate ichthyosaurs of the Lower Jurassic of England, with descriptions of two new species (Reptilia: Ichthyosauria) - C. McGowan - 1974.
- Temnodontosaurus risor is a Juvenile of T. platyodon (Reptilia: Ichthyosauria) - C McGowan - 1995.
- A longirostrine Temnodontosaurus (Ichthyosauria) with comments on Early Jurassic ichthyosaur niche partitioning and disparity - J. E. Martin, V. Fischer, P. Vincent & G. Suan - 2012.