New Study Shakes Up The Dinosaur Family Tree

Posted: Mar 23 2017, 1:41am CDT | by , Updated: Mar 23 2017, 2:00am CDT, in News | Latest Science News

 
New Study Shakes up the Dinosaur Family Tree
The revised family tree of dinosaurs. Credit: Nature.com

The findings from new study go against 130-year-old theory about origin and evolution of dinosaurs

The family tree of dinosaurs may need to be rewritten, redefined or rearranged after an extensive analysis of hundreds of fossil skeletons.

Since 1888, dinosaurs have been divided into two major categories based on the structure of their hip bones, Ornithischia for bird-hipped dinosaurs and Saurischia for dinosaurs with reptile-like pelvic bones. But a new careful analysis of dinosaur’s ancestry and shared features suggests that many of those species are more closely related to others species than the originally assigned ones. For instance, theropods such as Tyrannosaurus rex are not closely linked to Brontosaurus from sauropod infraorder as they were under previous classification. Researchers beleive that T. rexes are more closely related to the Ornithischia line than Saurischia.

While Brontosaurus remains in Saurischia but they are grouped with another early carnivorous dinosaur called Herrerasauridae,suggesting that the long-accepted dinosaur groupings may, in fact, be wrong and prompting call for an overhaul of 130-year-old roots of dinosaur family tree.

These conclusions are based on the analysis of 75 different species of dinosaurs that lived within the first 100 million years of dinosaurs’ era. The oldest known dinosaur fossil goes back as far as 243 million years ago while the last dinosaurs date back to 66 million years ago.

“When we started our analysis, we puzzled as to why some ancient ornithischians appeared anatomically similar to theropods. Our fresh study suggested that these two groups were indeed part of the same clade. This conclusion came as quite a shock since it ran counter to everything we’d learned,” said lead study author Mathew Baron from University of Cambridge.

“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.”

The new study also reached another unexpected conclusion. For many years, it was thought that dinosaurs originated in the southern hemisphere on the ancient continent known as Gondwana as the oldest dinosaur fossils have been recovered from South America. But new findings suggest that dinosaurs may have been originated in Northern Hemisphere, possibly in the area that now comprises Britain. Also, the first dinosaurs might have appeared around 247 million years ago, slightly earlier than previously thought.

“The results of this study challenge more than a century of dogma and recover an unexpected tree topology that necessitates fundamental reassessment of current hypotheses concerning early dinosaur evolution, palaeoecology and palaeobiology.” Authors wrote in the study.

The new effort is revolutionary and detailed but its findings cannot be accepted immediately. However, they certainly worth a closer look because of involvement of the largest and most comprehensive dataset of dinosaur species analysis to date. If accepted, it will lead to radical regroupings of dinosaurs in existing family tree and altering the names inside them.

“This study radically redraws the dinosaur family tree, providing a new framework for unraveling the evolution of their key features, biology and distribution through time,” said Co-author, Professor Paul Barrett from Natural History Museum. “If we're correct, it explains away many prior inconsistencies in our knowledge of dinosaur anatomy and relationships and it also highlights several new questions relating to the pace and geographical setting of dinosaur origins".

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