Dry season at the Mygatt-Moore Quarry showing Ceratosaurus and Allosaurus fighting over the desiccated carcass of another theropod. Illustration by Brian Engh.

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Dinosaur diaries: Oldest evidence of cannibal dinosaurs uncovered

In our Dinosaur diaries series, the Museum's experts share some of the latest science news and views from across the world of palaeontology.

This week they discuss the biggest findings from the last fortnight, including the oldest recorded incident of cannibalism in dinosaurs, Chinese sauropods and long-legged theropods.

A mounted specimen of Allosaurus showing it's large head and jaw

A mounted specimen of Allosaurus in the Houston Museum of Natural Science. Image via Wikimedia Commons.


Evidence of cannibalism in theropod dinosaurs

Theropod dinosaurs, including the iconic T. rex, were ferocious predators but it is often difficult to know what they ate, partly because evidence of their bite marks is rare. However a new study led by Stephanie Drumheller at the University of Tennessee shows how theropods ate, and scavenged, other dinosaurs - including members of their own species, in a form of prehistoric cannibalism.

A bone-ridden quarry near the Utah-Colorado border contains fossil of animals that lived 150 million years ago. These were examined carefully for evidence of feeding behaviour and 29% of them were found to have bite marks.

This abundance of bite-marked bone is extraordinarily high for a dinosaur site, and it isn't clear why this is the case. One suggestion is that the environment of the quarry, which would have alternated between wet and dry seasons, would have given plenty of time for the dinosaur carcasses to be scavenged, particularly for the large-bodied sauropods. This is backed up by the high number of bites found on the bony, less-meaty parts of the animals, including the toes, which are generally only eaten if nothing else is left.

Evidence of cannibalism was found at the site. Many of the bite marks were made by sharp, serrated teeth, suggesting that Allosaurus, the most common theropod at the quarry, was the perpetrator. Intriguingly, many of these bite marks were found on fossils of Allosaurus, meaning this is the first evidence of Allosaurus cannibalism in the fossil record. Cannibalism in dinosaurs is rare and has only previously been seen in the theropods T. rex and Majungasaurus, meaning this is the oldest recorded incident of dinosaurs munching one of their own.

An artist's impression of Klamelisaurus in a conifer forest. Image via Wikimedia Commons.


Dippy's Chinese cousins

We all love sauropods - especially our own Dippy the Diplodocus, whose species lived in modern-day America. But did you know that sauropods were members of a successful, abundant group that lived from the Late Triassic to the end of the Cretaceous and whose remains have been found on every continent except Antarctica?

A new paper led by Andrew Moore of Stony Brook University (and including the Museum's Paul Barrett) provides the first detailed description of the poorly-known Middle Jurassic sauropod, Klamelisaurus gobiensis.

This obscure animal is known from a single skeleton which was collected in 1982 from a remote desert region in China, on the slopes of the Kelameili Mountains in the Gobi desert. It was named by Chinese dinosaur expert Zhao Xijin in 1993 but it was never fully described and its relationships to other sauropods remained unknown.

Although the skull of Klamelisaurus is missing, many of the vertebrae and limb bones are well preserved. Following extensive comparisons with other sauropods from China and elsewhere, Moore and his team were able to show that Klamelisaurus was a close relative of several poorly-understood species from the Chinese Jurassic and Cretaceous, including Mamenchisaurus, Omeisaurus and Euhelopus.

Together, these animals form a distinct sauropod group. Although they retain the distinctive sauropod body, most of them have exceptionally long necks, some of which include up to 19 individual vertebrae (for comparison, Diplodocus has 15 and humans have seven).

Many other sauropods have been named from the Jurassic rocks of China, but most have not yet been fully described. This work on Klamelisaurus marks a small step on a long road. However, unlocking this information will be crucial if we are to undercover the factors underpinning the global success story of these impressive animals.

A summary of the main findings of this study. Image courtesy of Thomas Holtz Jr., University of Maryland. Silhouettes from Phylopic.org.


Size matters in long-legged theropods

If you've seen the movie Jurassic Park, you'd be forgiven for thinking that all dinosaurs, especially the mostly carnivorous theropods, were agile, fast and dynamic animals.

Theropods were the top predators of the Mesozoic Era and include iconic dinosaurs ranging from the small Compsognathus and Velociraptor, to the very large Allosaurus and Tyrannosaurus.

Palaeontologists have tried to figure out how fast these species could have moved, how they caught prey and escape predators. Researchers study fossil trackways and measure the distances between footprints, looked at the bones of the back legs, and even built complex virtual models.

A new publication by Alex Dececchi, from Mount Marty College, investigated how the running ability of theropods is influenced by how big they were. The team found that there was little correspondence between various hind limb bone measurements and ratios and estimates of top speeds when size was also factored into their comparisons.

The study concluded that small and large theropods with hind legs of similar length relative to their overall size would not be expected to reach similar top speeds, because the mechanical and energetic constraints of large body sizes would slow the larger animals down. Instead, longer legs in small theropods helped them to achieve bursts of high speed to catch prey and avoid becoming prey, while the long legs of larger theropods would have increased their energy efficiency when walking for large distances foraging for food.

Tyrannosaurids had much longer legs than other big theropods, which would have made them more effective at finding, pursuing and capturing prey. Over the course of a year this might add up to saving an amount of energy equivalent to several tones of meat.