DON’T GO IN THE WATER: NEW EVIDENCE THAT SOME DINOSAURS WERE STRONG SWIMMERS
Claw marks left on a river bottom in Sichuan, China are evidence for dinosaurs’ ability to swim relatively long distances. According to an international team of scientists in the journal Chinese Science Bulletin, theropod species of dinosaurs were able to travel in relatively deep bodies of water.
A theropod dinosaur walked on two legs. This group of dinosaurs was carnivorous, had grasping hands with fingers, and long necks. Tyrannosaurus rex, Velociraptor, and the chicken-sized Compsognathus were all theropods, which ranged in size. Living birds of today have common ancestors with theropods.
The researchers examined a section of land that was a major transportation route for dinosaurs due to the presence of abundant footprints. While examining the tracks of other Early Cretaceous dinosaur species, scientists noticed unusual claw marks made by what is thought to be a 1-meter-tall theropod in the sediment. These marks showed a left-to-right pattern akin to bipedal movement, as if the theropods’ claws were scratching into the soil on its toes; the gouging pattern left by the dinosaur is deeper in the front of the track than in the back. This pattern continued for about 15 meters in the section.
According to the researchers, the river must have had dry and wet cycles over 100 million years ago due to the presence of ripple marks and mud cracks in the soil. In addition to theropod tracks, there are those of sauropod dinosaurs as well. Sauropods were four-legged herbivores, and were found on all landmasses with the exception of Antarctica. Finally, there are ornithopod tracks in the sediment. Ornithopod dinosaurs were also plant-eaters and mostly walked on two legs. Their tracks were in parallel formations, indicating herding behavior in walking in pairs or groups. It is unclear whether these tracks were all made during the same time period, but the sauropod and theropod tracks were deposited on the same formation. All tracks were around the same depth and similar in size, so they could have been produced at the same time.
Since there are only claw marks for the theropods present, it is difficult to determine the exact type of species that produced them. The scientists think that the theropod could have been an early tyrannosaur or a Sinocalliopteryx, which were small predatory dinosaurs 2.5 meters in length. Both species of dinosaurs have been found in this region of China.
-Jeanne K.
Illustration by Nathan E. Rogers.
References: http://link.springer.com/content/pdf/10.1007%2Fs11434-013-5802-6
http://www.eurekalert.org/pub_releases/2013-04/uoa-ned040813.php
http://www.sciencedaily.com/releases/2013/04/130408123502.htm
http://www.ucmp.berkeley.edu/diapsids/saurischia/theropoda.html
http://www.ucmp.berkeley.edu/diapsids/saurischia/sauropoda.html
http://www.bbc.co.uk/news/science-environment-19426885
http://www.ucmp.berkeley.edu/diapsids/ornithischia/ornithopoda.html