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Posts Tagged ‘Cretaceous period’

Asian fossil discovery may help explain how tyrannosaurs became dominant predators

June 17, 2016 Leave a comment
Timurlengia euotica - March 2016 - courtesy

This artist’s conception shows the tyrannosaur Timurlengia euotica in its environment 90 million years ago, accompanied by two flying reptiles (Azhdarcho longicollis). The fossilized remains of a the horse-sized dinosaur help explain how Tyrannosaurus rex and its close relatives became top predators. The paper describing the discovery was published in March in the Proceedings of the National Academy of Sciences. Illustration by Todd Marshall.

Researchers have discovered 90 million-year old fossils of an early tyrannosaur that may help improve scientists’ understanding of how that group of dinosaurs evolved into the predatory giants that later roamed North America.

The horse-sized animal, which would have likely weighed about 250 kilograms, apparently had impressive hearing ability. Its capacity to hear low frequency sounds can be deduced from an elongated cochlear duct.

Named Timurlengia euotica, the newly-identified tyrannosaur helps fill a gap in knowledge about how the relatively small theropods, which had to compete with larger allosaurs, evolved into some of the largest land predators ever known.

The discovery indicates that the tyrannosaur clade probably gained the sensory tools needed to become apex predators before late Cretaceous enormity took hold.

“Tyrannosaurs had to get smart before they got big,” Dr. Stephen L. Brusatte, a paleontologist at the University of Edinburgh in the United Kingdom and lead author of the paper describing the discovery, said.

Enormity on the scale so obviously presented by later tyrannosaurs like Tyrannosaurus rex, which stood about five meters tall and about 12 meters long and weighed about 3,600 kilograms, evolved during the last 20 million years of the dinosaurs’ dominance of Earth.

Researchers found a brain case, which they then subjected to a computed microtomography (CT) scan. That scan revealed not only the animal’s inner ear structure, but also likely similarities between T. euotica‘s brain and the brain of Tyrannosaurus rex.

Brusatte wrote in The Conversation that these features likely helped T. euotica become a very skilled tracker of prey.

“Their intelligence and sharp senses made tyrannosaurs perfectly equipped to swoop into the top-predator role,” he wrote.

As the tyrannosaur head became larger, it became more useful for hunting.

“Their heads became giant killing machines and their arms, now unnecessary, shrunk down to nubbins,” Brusatte wrote in The Conversation feature.

The fossilized braincase, along with a variety of other bones, had been stored in a museum for about ten years. Brusatte and his colleagues examined them in 2014.

Reconstructed T. euotica skeleton

This is a reconstructed skeleton of Timurlengia euotica with discovered fossilized bones, highlighted in red, and other bones remaining to be discovered inferred from other related species of tyrannosaurs in white. Individual scale bars for the pictured fossilized bones each equal 2 centimeters. The fossilized remains of T. euotica may reveal how Tyrannosaurus rex and its close relatives became top predators. Graphic (c) National Academy of Sciences.

“Working on Timurlengia has been one of the highlights of my career,” Brusatte said. “It gives us a glimpse of what the ancestor of T. rex was – a tyrannosaur right on the cusp of becoming huge.”

The fossils were found in the remote Kyzylkum Desert of Uzbekistan. Their significance was described in a paper published in March in Proceedings of the National Academy of Sciences.

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Fossils of largest-ever marine crocodile found in Africa

April 28, 2016 Leave a comment

Scientists have found evidence that a ocean-dwelling crocodile about 10 meters long once roamed the area we now know as north Africa.

The beast, which also likely weighed at least three tons, lived about 120-130 million years ago.

Dubbed Machimosaurus rex, the crocodile is the largest known of its kind. A marine reptile, it thrived at a time in Earth’s geologic history when the land now known as north Africa was submerged under an ocean.

machimosaurus-rex-reconstruction

Machimosaurus rex was a marine reptile, about 12 meters long, that swam in Cretaceous oceans. Illustration courtesy University of Alberta, illustration (c) Davide Bonadonna. All rights reserved.

Researchers discovered the species in 2014 when a skull measuring almost two meters in length was unearthed in Tunisia. The specimen has teeth that are are shaped like bullets, which the creature may have used to crush the carapaces of marine turtles.

The length of the animal is an estimate, based on the dimensions of similar organisms within the animal’s genus that lived during the Jurassic and Cretaceous periods.

“We have been digging in that area since 2011 because the rocks there are nothing like other places,” Federico Fanti, a paleontologist at the University of Bologna in Italy and lead author of the paper documenting the find, said in a statement. “Globally, good fossils are rare from this age—130 million years ago.”

Fanti and his team later found more of the specimen, including vertebrae, but were not able to remove those parts of the fossil because of ongoing unrest in the country.

The species is part of a larger genus that was first discovered in the nineteenth century. Among M. rex‘s close relatives are crocodilians that roamed Jurassic and Cretaceous period seas that then covered the part of Earth now known as Europe.

M. rex was the largest of the teleosaurids (marine crocodiles) in its genus.

While large, the croc is not the largest known from the planet’s long history of life. At least several species of freshwater crocodile that lived during the time of the dinosaurs, Sarcosuchus imperator and those in the genus Deinosuchus, were more imposing than M. rex.

S. imperator was about two meters longer than M. rex, while some Deinosuchus species may have been only slightly longer than M. rex.

The paper documenting the discovery of M. rex was published online in the Jan. 10, 2016 edition of Cretaceous Research.

 

 

 

 

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