Ichthyosaur - Marine Reptile

Fossil photo | Wed 14 Dec 2011  

The image depicts one of three bones found in association (featured in one of the video clips) in the lower (Albian) part of the Gearle Siltstone. The bone (assembled from five broken fragments) is identified as the right surangular bone of an ichthyosaur, approximately 4-5 metres in length. As preserved the bone is 16 cm long. The horizontal groove near the base of the bone fits into a ridge on a second bone which, we believe, is a fragment of the angular bone. A third bone fragment may represent part of the splenial bone and bears numerous shallow bite marks made by smaller sharks scavenging the dead ichthyosaur. The anterior part of the surangular bone is sheared off, possibly by a large Dwardius shark that may have bitten off the snout of the ichthyosaur in one single bite. The angular, surangular and splenial bones are part of the back end of the lower jaw. Together they form the walls of the enclosed Meckelian canal which houses the Meckelian cartilage. In chondrichtyans (sharks, rays and chimaeroids) the Meckelian cartilage is not surrounded by bone as it is in reptiles but is the sole element making up the lower jaw.

The image below depicts a typical ichthyosaur. These marine reptiles had very large eyes which enabled them to hunt squid and fish several hundred metres below the surface:

Fossil specimen of Ichthyosaurus sp.
Fossil specimen of an Ichthyosaurus sp. Photo by Ballista. Image under GNU Free Documentation License.