A study published in Evolutionary Biology earlier this year has made headlines after claiming that the fearsome dinosaur Tyrannosaurus rex might have been three species, namely Tyrannosaurus regina, dubbed as "queen of dinosaurs," and Tyrannosaurus imperator.
It opened lots of debates from experts until scientists from the American Museum of Natural History re-analyzed the dinosaur fossils of the said types of T. rex. Now, they are refuting the claims of the earlier study. The researchers did not find sufficient evidence that splits T. rex into three iconic species.
T. rex Remains the One True King of Dinosaurs
Paleontologists at the American Museum of Natural History and Carthage College find that the theory about T. regina and T. imperator does not have enough evidence to support it, Phys.org reported. Study co-author Steve Brusatte, a paleontologist at the University of Edinburgh, stressed in their new study that T.rex "remains the one true king of the dinosaurs."
They re-analyzed nearly 40 fossilized Tyrannosaurus skeletons, including the complete tyrannosaurus skeleton named Sue currently at the Field Museum of Natural History in Chicago, as well as dinosaur fossils classified as AMNH 5027 that were found at Big Dry Creek Montana in 1908.
The team studied the physical differences of the femur, dental structures, and other bones of the specimens that the earlier study claims to be indications that there were three species of Tyrannosaurus species. They suggested that the larger specimens were believed to have been from the T. imperator, which means tyrant lizard emperor, and the smaller and slender specimens were attributed to T. regina.
Brusatte pointed out that the dinosaur fossils may vary in size and shape, but these variations are minor and cannot be used as evidence to say that there are three different species of T. rex. Their data also discussed 112 species of living dinosaurs, also known as birds, and four non-avian theropod dinosaurs, showing that the previous argument was based on a limited comparative sample, non-comparable measurements, and improper statistical techniques used.
Boundaries Between Species are Hard to Define
According to MailOnline, researchers of the new study tried to replicate the results of the previous study but failed to do so and even had different findings when they took their measurements of the dinosaur fossils. More so, they were skeptical about how the previous study identified the breakpoints for each new species.
In the new study published this month in Evolutionary Biology, researchers wrote that they used a different technique to determine how many groups were in the data and came up with just a single group.
Study co-author Thomas Holtz from the University of Maryland and the National Museum of Natural History said that the boundaries of living species are hard to identify and much more in determining differences in ancient species that were only known from a small number of specimens.
He added that growth, region, sex, and individual difference were some of the sources that cause these variations that should all be rejected before someone could identify a new species.
Given their findings, they think the hypothesis of three T. rex species is not the best explanation for the two sets of specimens. Although, they are not closing the possibility that other T. rex species are yet to be found and would need strong evidence to prove such claims.
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