File:Day 26 - Tyrannosaurus Rex (8026022305).jpg

"Stan" Tyrannosaurus Rex (LL.12821)

"Stan" is one of the most iconic exhibits of the Manchester Museum's collection. It is a cast a Tyrannosaurus rex from the Upper Cretaceous, excavated in South Dakota in 1992.

This skeleton of was excavated by the Black Hills Institute in 1992, after its discovery by an amateur palaeontologist, Stan Sacrison (after whom it has been named!). The fossil remains were found near Buffalo in the USA. The excavation required the removal of the rock above the specimen, called overburden, then knives, scribes and brushes were used to expose the fossil bones and teeth, while glues and other chemicals were applied to stabilise and preserve the surface of the fossils. Before removal of the fossils, each one was drawn on a 'map' using a grid set over each section of the site. The fossils were then covered with aluminium foil and encased in a field jacket, layered burlap and plaster, so they could be moved without breakage. All excavated material was then transported to the lab for specialised cleaning, called preparation.

Abundant well-preserved leaves and a few palm fronds found with Stan have given palaeontologists new information about the environment and climate in which he lived. Other evidence from the site shows that Stan's body probably remained exposed for a few months before a flood scattered a variety of bones and buried his skeleton, entombing it for 65 million years. The excavation was carefully documented with photographs, video and scientific notations for future study of the specimen and public education. The continuing excavation has yielded several more bones and additional material. To date 199 of Stan's bones have been found - 70% of a complete skeleton - making Stan the second most complete T.rex found so far.

After the bones were prepared it became clear that this specimen included the best skull of all the Tyrannosaurus rex specimens ever collected.

Stan's skeleton preserves a number of pathologies (evidence of injury or disease), including healed injuries. One terrible injury gave Stan a very stiff and painful neck and, probably, horrible headaches. Two of his neck vertebrae were fused together and a great deal of extra bone had grown around the injury. The cheeks (jugals) and lower jaws reveal the presence of irregular openings that are not duplicated on the opposite side. One possible explanation for these holes is that they were puncture wounds received in battles with another T. rex. Smoothed edges around the holes indicate that the wounds healed in time. Perhaps the most interesting pathology is found at the back of the skull on the bones that make up part of the braincase. A portion of the top of the crest, where the powerful neck muscles once attached is missing. Below this we find a round hole that is a perfect match for a tooth from the lower jaw of another T.rex. Despite very serious injuries, Stan healed and lived to fight another day.

Cranial kinesis is the technical term for movement of the joints between the bones in the skull. It is cranial kinesis that allows a snake to swallow things larger than its head. Careful examination of Stan's disarticulated skull shows that T.rex had a kinetic skull. There are hinge, screw, and slip joints that allowed Stan to open wide both the upper and lower jaws, greatly increasing bite area. These joints also acted as shock absorbers, protecting both the bones of the skull and Stan's teeth from breakage when biting through the bones of prey.

Reconstructing dinosaurs