Scientists are filling in the gaps in their knowledge thanks to a dinosaur fossil discovered in Mississippi that resembles an ostrich and is about the height of a giraffe.
By examining fossilized remains excavated from the Eutaw Formation of Mississippi, scientists have filled in a significant gap in North America's fossil record. They have discovered large-bodied specimens of the ornithomimosaur, which may have been the world's fastest dinosaur.
The Ornithomimosaur
Tom Cullen, an author of the study, explained that a particular class of bipedal dinosaurs, the majority of which resemble ostriches in appearance, is referred to as an ornithomimosaur. Long arms with fairly large clawed hands, large eyes, a long tail, long legs, and either small or no teeth are typical features of them. To be clear, later ornithomimosaurs lack teeth and instead have a keratinous beak to aid in food processing.
The dinosaurs that resembled birds are believed to have roamed the Northern Hemisphere somewhere around 145 million to 66 million years ago.
Cullen said that they would probably occupy a similar position in the food chain as ostriches or emus: they are medium-sized, mostly herbivorous animals that are swift on their feet.
The earliest ornithomimosaur species were all small-bodied and weighed around 26 pounds. According to Chase Brownstein, a research associate from the Stamford Museum and Nature Center, larger species started to evolve. Brownstein was not involved in the study.
The Hexing qingyi, a Chinese species of about 125 million years old, is the smallest species which is barely more than a meter long. In contrast, the biggest species, the Deinocheirus mirificus, from about 72 million years ago, was hump-backed with enormous armed species from Mongolia and measures more than 33 feet in length.
Filling the Gaps
Cullen said that North American knowledge of the evolution of this dinosaur with bird-like characteristics has been rather fragmentary up until recently. Western North America has significantly more extensive deposits of rocks than eastern North America, which helps to preserve the environments where dinosaurs once lived. As a result, western North America's dinosaurs are better understood than those that once roamed the eastern half of the continent.
Cullen continued to explain that as a result, there are gaps in our understanding of the species, and it can take a long time to identify the species that were present in eastern North America from the relatively few records that do exist.
The Western Interior Seaway, a significant body of water, served as the dividing line between North America during this time.
Brownstein explained that around 90 million years ago, when the American interior was flooded, creating the Western Interior Seaway, eastern North America was cut off from western North America, resulting in the formation of Appalachia. As with western North American dinosaurs, little is known about the Appalachian dinosaurs, so any information is crucial.
Even with the abundance of fossil evidence from western North America, there remains a gap in our knowledge of the evolution of the dinosaurs that resembled ostriches from 100 million to 83 million years ago.
Cullen said ornithomimosaurs were once present in North America, but there is only a patchy record of them. Some of them were probably quite large. Following this time interval, western North America has a fairly extensive record of ornithomimosaurs, almost all of which are small-bodied. In the data presented by Prehistoric Wildlife, ornithomimosaurs, sometimes called 'ostrich dinosaurs', were prevalent in North America and Asia, with some possible spreads in Eurasia.
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1 Species, 2 Species
In their most recent study published in Plos One, Cullen and his team estimated the body mass range of the individuals using femur bone fossils taken from two different ornithomimosaur specimens.
According to Cullen, they were able to determine whether they were working on two different species or simply the juvenile versus adult individuals of the same species by using the growth rings retained in these bones. The fact that the small specimen was older than 7 but was only half as big as the large specimen, who was older than 10, gave them a reason to believe they were dealing with two different species. They found no proof that the growth rates rose high enough during that interim period to compensate for the size difference seen.
According to their research, small and large ornithomimosaur species coexisted during this time. This information fills in a knowledge gap for the team, which previously knew there were both small and large ornithomimosaurs at different times. However, they were unaware of what was happening during this specific time during the Cretaceous in North America.
Cullen said that their discovery contributes to the completion of a previously unsolved puzzle regarding the evolutionary as well as the biogeographic history of the dinosaurs called ornithomimosaurs, Newsweek reports.
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