Name: Ichthyosaurus
(fish lizard).
Phonetic: Ick-thee-oh-sore-us.
Named By: William Daniel Conybeare & Henry
De la Beche - 1821.
Classification: Chordata, Sauropsida,
Ichthyosauria, Ichthyosauridae.
Species: I. communis
(type), I. anningae, I.
breviceps, I. conybeari, I. intermedius, I. larkini, I.
somersetensis.
Diet: Piscivore.
Size: Most known specimens about 2 meters long, but
largest individuals up to 3.3 meters long.
Known locations: Europe including, Belgium,
England, Germany and Switzerland.
Time period: Hettangian to Sinemurian of the
Jurassic.
Fossil representation: Many hundreds of specimens,
some articulated. Skin impressions have also been recovered in some
specimens. These reveal features such as the dorsal and caudal
(tail) fins that are not often preserved.
The
most
well-known of the ichthyosaurs,
Ichthyosaurus
itself is almost always
included in books about dinosaurs and other prehistoric creatures.
While it may look superficially like a prehistoric dolphin,
Ichthyosaurus wasn't even closely related, in fact
Ichthyosaurus
wasn't even
a mammal like a dolphin is, it was a reptile. Also,
Ichthyosaurus was not in the same group of reptiles
as the dinosaurs,
although it did live at the same time as many of them.
With
its distant ancestors
being terrestrial reptiles going back to an aquatic lifestyle,
Ichthyosaurus ended up with an extremely different
morphology to other
land living reptiles. This 'fish' appearance is a result of the
fact that the basic fish morphology is the most streamlined and
efficient form for submerged locomotion. It also means that
Ichthyosaurus was never able to return to the land,
instead leading
an entirely pelagic life in the oceans.
As
an ocean going hunter,
the main diet of Ichthyosaurus would have been
primarily if not
exclusively piscivorous. Study of coprolites has confirmed the
presence of both fish and squid in its feeding habits. Although
Ichthyosaurus appears to have relied upon its sight
for feeding, the
solid bone structure of the ear drums suggests that they could have
'heard' their prey from a distance by their vibrations in the water.
Some
specimens have shown
smaller Ichthyosaurus remains inside larger ones in
positions that
appear to be within a uterus of a parent animal and some even appear
to
have been in the process of being born. This means that Ichthyosaurus
almost certainly did not lay eggs, but was instead viviparous,
giving birth to live young. As with other viviparous air breathing
marine organisms, the young emerged from the mother tail first so
that they did not drown while being born.
Further reading
- Additional notices on the fossil genera Ichthyosaurus
and
Plesiosaurus - Transactions of the Geological
Society of London, Series
2 1:103-123 - W. D. Conybeare - 1822.
- A large skull of Ichthyosaurus (Reptilia:
Ichthyosauria) from the
Lower Sinemurian (Lower Jurassic) of Frick (NW Switzerland) - Swiss
Journal of Geosciences 101: 617-627 - M. W. Maisch, A. G. Reisdorf , R.
Schlatter & A. Wetzel - 2008.
- An Ichthyosaurus (Reptilia, Ichthyosauria) with
gastric contents from
Charmouth, England: First report of the genus from the Pliensbachian -
Paludicola 8 (1): 22–36 - Dean R. Lomax - 2010.
- A new specimen of Ichthyosaurus communis from
Dorset, UK, and its
bearing on the stratigraphical range of the species - Proceedings of
the Geologists' Association 123:146-154 - S. P. Bennett, P. M. Barrett,
M. E. Collinson, S. Moore-Fay, P. G. Davis & C. P. Palmer -
2012.
- A new species of Ichthyosaurusfrom the Lower Jurassic of West Dorset,
England, U.K. - Journal of Vertebrate Paleontology: e903260. - Dean R.
Lomax & Judy A. Massare - 2015.
- Two new species of Ichthyosaurus from the lowermost Jurassic
(Hettangian) of Somerset, England. - Papers in Palaeontology. - Dean R.
Lomax & Judy A. Massare - 2016.
- On the largest Ichthyosaurus: A new specimen of Ichthyosaurus
somersetensis containing an embryo. - Acta Palaeontologica Polonica. -
D. R. Lomax & S. Sachs - 2017.