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New fossil discoveries solve enigma surrounding T-rex evolution

ByClaire Hutchison

Mar 23, 2016

Two archaeological discoveries have been made, shedding further light on the evolution of both the Tyrannosaurus Rex and living birds. Additionally, a study published in The Proceedings of the National Academy of Sciences revealed the discovery of a completely new species of dinosaur.
The horse-sized tyrannosaur has been named Timurlengia euotica and lived around 90 million years ago. Hans Sues of the Smithsonian’s National Museum of Natural History, and Alexander Averianov of the Russian Academy of Sciences, unearthed the fossils between 1997 and 2006 in the Kyzlkum Desert of Uzbekistan. A team from the University of Edinburgh, led by Geoscience lecturer Dr Steve Brusatte, was then responsible for studying the fossils and identifying the tyrannosaur.

Brusatte has explained that this new species is particularly important as, “it comes from the middle part of the Cretaceous period – a point where we have a huge gap in the fossil record”. Part of the T-Rex’s notoriety comes from the fact that its evolutionary nature is shrouded in mystery within the scientific community. The giant T-Rex stood at 13m from its head to its tail, and there has been much confusion about how it evolved to be so ginormous.

With the discovery of Timurlengia, a gap of around 20 million years in the fossil record has now been accounted for. This animal was very similar to the T-Rex in terms of its bone features and skull. Researchers were even able to determine the sensory abilities of the animal – which were noted to be incredibly high. Dr Bill Sellers of the University of Manchester noted that this fossil has helped scientists discover how “big brains and keen senses evolved early in the history of this group of dinosaurs and may have been what allowed tyrannosaurs to become such successful predators”.

The discovery means that scientists now know that the tyrannosaurs evolved very quickly near the end of their 70-million-year reign, growing from being small to gigantic in size. The evolution of high functioning brains has also been proven to be crucial in the T-Rex’s positioning at the top of the food chain around 70-80 million years ago.

Another equally ground-breaking discovery regarding the T-Rex has also been made recently. In 2005, Mary Schweitzer, a paleontologist at North Carolina State University, and her colleagues examined the fossil of a 68-million-year-old T-Rex found in Montana. The specimen was uncovered by Bob Harmon of the Museum of the Rockies, Montana. Schweitzer and her team published a study in Science Magazine in 2005 that claimed that the dinosaur found was both female and pregnant.

This was a very interesting claim, considering that the gender of dinosaurs cannot typically be deduced from the fossil record. What was interesting about this dinosaur was that it contained a medullary bone within its thigh bone. This is a distinctive feature of female living birds, which is only produced before they lay an egg. The observation was based on the fact that birds and dinosaurs are very similar genetically – as birds evolved from dinosaurs. However, there was speculation in the scientific community that this dinosaur merely had osteopetrosis.

It was only in more recent years that technology became available to prove this claim without doubt. Schweitzer tested the tissue using CT scans to determine the chemical composition. With this information, it could be confirmed that the T-Rex did have a medullary bone, and therefore was pregnant. The discovery is important as it will aid the scientific community in its understanding of the evolutionary processes behind the egg laying of modern birds.


Image: Scott Robert Anselmo

By Claire Hutchison

Science & Technology Editor and Secretary of The Student, 4th year Environmental Geoscience student.

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