CHARACTERS AND ANATOMY
plan of a typical ichthyosaur
Above: This ichthyosaur
in the Bristol City Museum has the remains of an embryo
preserved along side
indicated by an arrow (see below).
Above: The ichthyosaur
embryo: The vertebrae, ribs, jawbone and an eye socket are clearly
Above: The sclerotic
ring is found in most vertebrates, except mammals, crocodiles,
and some others. In ichthyosaurs they were very well developed,
so we can take accuarate measurements and use them as a relaible
proxy for eyeball size. Ichthyosaurs had quite flat eyeballs so
the sclerotic rings may have been usefull in maintaining their
shape. Relative to body size, ichthyosaurs had huge eyes, possibly
up to a metre in the largest species.
The vertebrae of fish shaped ichthyosaurs (left) are flattened,
resembling hockey pucks. In contrast, those in lizard shaped ichthyosaurs
(right) are more elongate, and so resemble camera film cases.
HOW DID ICHTHYOSAURS SWIM?
Lizard shaped ichthyosaurs had a slender body,
and thin backbone with many vertebrae, which suggests they swam
in an eel like motion, as do modern lizards when in water. Fish
shaped ichthyosaurs had a thicker body and a thicker backbone
so probably swam like tuna or mackerel sharks.
Author: P. T. Hadland
Last updated: Date 21st November 2005
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