A new study pro­poses a mas­sive shake-up of the di­nosaur fam­ily tree.

The Denver Post - - NEWS - By Seth Borenstein

wash­ing­ton» Tyran­nosaurus Rex and his bud­dies could be on the move as a new study pro­poses a mas­sive shake-up of the di­nosaur fam­ily tree.

Sci­en­tists who took a deeper look at di­nosaur fos­sils sug­gest a dif­fer­ent evo­lu­tion­ary his­tory for di­nosaurs, mov­ing theropods such as T. Rex to a new branch of the fam­ily tree and hint­ing at an ear­lier and more north­ern ori­gin for di­nosaurs.

The re­vised di­nosaur tree makes more sense than the old one, ini­tially de­signed more than a cen­tury ago based on hip shape, said Matt Baron, a pa­le­on­tol­ogy doc­toral stu­dent at the Univer­sity of Cam­bridge in Eng­land. He is the lead au­thor of the study in Wed­nes­day’s jour­nal Na­ture.

“If the au­thors are cor­rect, this re­ally turns our long­stand­ing un­der­stand­ing of di­nosaur evo­lu­tion up­side down,” Kristi Curry Rogers, a pa­le­on­tol­o­gist at Ma­calaster Col­lege in Min­nesota who wasn’t part of the study, said.

Di­nosaurs are split into two groups. One group has bird-like hips and is called Or­nithis­chia. It in­cludes the stegosaurus. The group with rep­tile-like hips is called Sau­rischia and in­cludes the bron­tosaurus.

Theropods, which in­clude T. Rex and the type of di­nosaurs that later evolved into mod­ern day birds, were con­sid­ered an off­shoot from the group that in­cludes the bron­tosaurus. The new study moves them to the group that in­cludes the stegosaurus, but on a dif­fer­ent branch.

“It means that an­i­mals that we’ve al­ways thought were very closely re­lated to each other might not be,” said Rogers, who praised the study, say­ing it prompts a whole bunch of new ques­tions.

Baron and col­leagues looked at 450 char­ac­ter­is­tics of 75 di­nosaur species. They used com­puter sim­u­la­tions to try to group to­gether those with sim­i­lar char­ac­ter­is­tics, cre­at­ing tens of thou­sands of po­ten­tial di­nosaur fam­ily trees. The pro­posed one com­bines the 80 most likely sce­nar­ios, he said.

It may sound like an aca­demic ex­er­cise, but it’s im­por­tant to un­der­stand how big an­i­mals changed with time, said Baron said, not­ing that the di­nosaurs ruled Earth for more than 150 mil­lion years.

His re­search sug­gests that di­nosaurs popped up 247 mil­lion years ago — 10 mil­lion years ear­lier than the stan­dard the­ory says — with a di­nosaur from Tan­za­nia in East Africa. It’s called Nyasasaurus and was 6 to 10 feet tall and a plant-eater.

He also found an an­i­mal that’s not quite a di­nosaur but as close as you can get — a rep­til­ian an­ces­tor. And it was in Scot­land. Pre­vi­ous the­o­ries pointed to di­nosaurs first evolv­ing out of the South­ern Hemi­sphere, and many out­side sci­en­tists said there wasn’t enough ev­i­dence to sup­port Baron’s north­ern con­cept.

Nikki Kahn, Wash­ing­ton Post file

The skele­ton of a tyran­nosaurus rex is ar­ranged to sim­u­late the de­vour­ing of a tricer­atops at Re­search Cast­ing In­ter­na­tional in Trenton, On­tario. Sci­en­tists are sug­gest­ing a dif­fer­ent evo­lu­tion­ary his­tory for di­nosaurs, mov­ing theropods such as the tyran­nosaurus to a new branch of the fam­ily tree.

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