Possible New Common Ancestor Shakes Up Dinosaur Family Tree
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The evolution of evolution just took a new twist that may shake the branches of the dinosaur family tree all the way down to the single seed it grew from. While some are calling it a “This changes everything” discovery, others are warning not to melt down and reshape your plastic dinosaur collection just yet.

Matt Baron, a paleontology doctoral student at the University of Cambridge in England, is the author of the study published in Nature that began with his Ph.D. work on Ornithischian dinosaurs – so called because early paleontologist thought their hips structures resembled those of modern birds even though they weren’t birds, bird-like or even bird ancestors. That discrepancy prompted him to switch to studying the entire classification system of dinosaurs to see if it was correct or if a better one could be developed. Although this could be considered heretical among paleontologists, Baron got support from his superiors to proceed.

This better be good

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The current family tree was developed by paleontologist Harry Seeley in the late 19th century. He divided dinosaurs into Ornithischia (bird-hipped – included the Stegosaurus) and Saurischia (lizard-hipped), which he then broke down into Sauropodomorpha (long-necks like Brachiasaurus and Theropoda (T. Rex). Paleontologists as well as dinosaur aficionados wondered why actual bird ancestors of the Theropoda T. Rex types weren’t in the bird-hipped group, but conventional wisdom prevailed.

Enter Matt Baron. He spent three years visiting museums with dinosaur fossils and making note whether they had or didn’t have each of 457 diagnostic anatomical features. He fed that simple binary data set into a computer program called TNT which came up with 32 billion possible trees before settling on the best one.

TNT agreed with those who thought some therapods belonged in the Ornithischia group, prompting Baron to suggest combining them into a new category — .Ornithoscelida. This led to an even more tree-shaking conclusion, says Baron.

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The carnivorous theropods were more closely related to the herbivorous ornithischians and, what’s more, some animals, such as Diplodocus, would fall outside the traditional grouping that we called dinosaurs. This meant we would have to change the definition of the ‘dinosaur’ to make sure that, in the future, Diplodocus and its near relatives could still be classed as dinosaurs.

Change the definition of ‘dinosaurs’? Heresy! Or is it? Nineteenth century biologist Thomas Huxley, known as “Darwin’s Bulldog,” also thought Ornithischia and theropods should be grouped together and is the originator of the term “Ornithoscelida.” However, other questions raised by Baron’s study may change a different category of “everything we know.”

The new tree suggests that dinosaurs emerged 247 million years ago, which is earlier than past t estimates. Moreover, Baron notes that a dinosaur-like creature found in Scotland called the Saltopus elginensis might now be considered the first dinosaur, which upends the common belief that dinosaurs first appeared in South America.

Saltopus elginensis

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Does this change everything we’ve come to know and believe about dinosaurs? Co-author Dr. David B. Norman has this to say:

The proposed new family tree of dinosaurs has a lot of statistical support. That doesn’t mean it’s right, just that it’s the best we can do with the data we’ve got at the moment.

In other words, get your plastic dinosaurs out of the microwave … for now.