Bony Fish

Fossil photo | Wed 14 Dec 2011  

Tail-bones of a large bony fish, found in the 95 million years old, uppermost part of the Gearle Siltstone. The bony rods forming the tail are held together with the soft mineral gypsum. The flaky bone texture is typical for fishes and quite different from the spongy bone (underneath a dense outer layer of cortical bone) of marine reptiles like ichthyosaurs, turtles and plesiosaurs. The only large bony fish from the uppermost Gearle Siltstone positively identified at this stage is Pachyrhizodus (image below) based on a diagnostic premaxilla bone.

Pachyrhizodus caninus skeleton taken at the North American Museum of Ancient Lif
Photo of a fossil cast of a Pachyrhizodus caninus skeleton taken at the North American Museum of Ancient Life. Photo by Ninjatacoshell. Image under Creative Commons license.

The partial tail found in 2011 however shows greater resemblance to the tail of the giant Xiphactinus (image below). Isolated vertebrae found in the uppermost Gearle Siltstone are very similar to those of Xiphactinus but not quite as large. Several complete skeletons of Xiphactinus have been found in 85 million-year-old rocks in Kansas, USA, and some of them measure more than 5 metres in length.

Xiphactinus audax skeleton taken at the North American Museum of Ancient Life.
Photo of a fossil cast of a Xiphactinus audax skeleton taken at the North American Museum of Ancient Life. Photo by Ninjatacoshell. Image under Creative Commons license.