Dinosaur fact file (6/28/2008)

Student identifies new dinosaurs

The upper jaw of Carcharodontosaurus saharicus from Morocco, the closest living relative to Carcharodontosaurus iguidensis - Photo by Steve Brusatte

Carcharodontosaurus iguidensis was probably 13-14 metres long, making it taller than a double-decker bus. It had a skull about 1.75 metres long and its teeth were the size of bananas. The newly-found fossils include several pieces of the skull - parts of the snout, lower jaw and braincase - as well as part of the neck. They were discovered in the Republic of Niger and showed a number of differences from previously identified Moroccan material, allowing Steve Brusatte, an MSc student in the department, to name the dinosaur as a new species.

Two other mega carnivores are known to have inhabited the same Saharan ecosystem during the Cenomanian, about 95 million years ago: Spinosaurus, a sail-backed creature which may have grown up to 18 metres in length, and a smaller abelisaurid theropod that only grew to about nine metres. But recognition of C. iguidensis reveals a diversity among these theropods that was previously unknown. The presence of distinct species in the Cenomanian of Niger and Morocco suggests localised faunal differentiation, possibly the result of shallow continental seas that may have acted as temporary barriers between these areas. Each of these large-bodied carnivores has very distinctive cranial and dental morphology, suggesting that their coexistence may have been enabled by dietary niche partitioning.

Two new meat-eating dinosaurs unearthed in the Sahara

A few months later, Brusatte was again in the news with more discoveries from the Niger, this time from a formation thought to be about 112 million years old (Mid-Cretaceous). The finds turned out to be the earliest records of two of the major carnivore groups that would go on to dominate Africa, South America and India during the next 50 million years. Eocarcharia dinops, an early relative of C. iguidensis, represents one of the oldest known carcharodontosaurids, and Kryptops palaios is the oldest African abelisaurid and the oldest confirmed abelisaurid on any continent.

Abelisaurids have played a prominent role in helping to determine the time when Africa separated from Gondwanaland, a super-continent that formed in the southern hemisphere some 500 million years ago. Ten years ago it was suggested that the absence of abelisaurids in Africa and their presence in South America, India and Madagascar provided evidence of the separation of Africa from Gondwanaland about 120 million years ago. Their subsequent discovery in Africa, however, points to the final separation of South America and Africa being around 100 million years ago, significantly later than previously thought.

Pygmy dinosaur inhabited Bristol's tropical islands

CT Scan of the elongate skull of Baryonyx - Photo by Emily Rayfield

Remains of the celebrated Bristol Dinosaur, Thecodontosaurus, were first excavated back in 1834 from the limestone quarries of Durdham Down, in Clifton, Bristol. In 1975, the remains of at least 11 other individuals were uncovered in a quarry at Tytherington, north of Bristol. Many people have subsequently worked on the specimens and The Bristol Dinosaur Project was set up four years ago to develop an interactive exhibit, displaying the dinosaur and the environment in which it lived.

A collaboration between two palaeontologists - the University's Dr David Whiteside, an authority on extinct reptiles, and Professor John Marshall, an expert on fossil pollen from the University of Southampton - revealed that Thecodontosaurus lived more recently than was previously thought. The research involved a microscopic study of marine algae and fossil pollen.

It shows that rather than inhabiting the arid uplands of the Late Triassic as previously thought, the dinosaurs lived just before the Jurassic on lushly vegetated islands around Bristol. The outlines of these islands can still be seen today in the shape of the land; for example, Bristol's famous Downs was one such island.

The discovery that the Bristol dinosaur lived on small islands is very important as it could explain the dinosaur's small size (two metres) in relation to its giant (ten metres) mainland equivalent, Plateosaurus. Geological mapping indicates that the islands were quite small in size. This suggests that, like other species trapped on small islands, such as the recently found hominoid Homo floresiensis, dubbed the 'hobbit' of Flores, and the pygmy elephants of Malta, the Bristol Dinosaur may have been subjected to island dwarfing.

Unusual British dinosaur had crocodile-like skull

Another British dinosaur, Baryonyx walkeri, was also the subject of a collaboration between experts at different institutions. Dr Angela Milner from the Natural History Museum, who first described the dinosaur, originally thought that the unusual skull of Baryonyx indicated that it might be a fish-eater, but it was the computer modelling techniques - more commonly used to discover how a car bonnet buckles during a crash - employed by Dr Emily Rayfield in the Department of Earth Sciences, which confirmed that to be the case.

Rayfield used an engineering technique called 'finite element analysis' that reconstructs stress and strain in a structure when a load is placed on it. The Baryonyx skull bones were CT-scanned by a colleague at Ohio University, USA, and digitally reconstructed so she could view the internal anatomy of the skull. She then analysed digital models of the snouts of four different animals - a theropod dinosaur, an alligator, an Indian gharial crocodile and Baryonyx - to see how each snout stressed during feeding.

The biomechanical data showed that the eating behaviour of Baryonyx was markedly different from that of a typical meat-eating theropod dinosaur or an alligator, and most similar to the gharial. Since the bulk of the gharial diet consists of fish, Rayfield's study suggests that this was also the case for Baryonyx back in the Cretaceous. This evidence was supported by the fact that on excavation, partially digested fish scales and teeth were found in the stomach region of the animal, demonstrating that at least some of the time this dinosaur ate fish. Through quirks in their evolutionary history, Baryonyx and the gharial have evolved independently to feed in a similar manner. This demonstrates that in some cases there is more than one evolutionary solution to the same problem.

Note: This story has been adapted from a news release issued by Bristol University

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