Washington:
A new study has overturned over 130 years of research on dinosaurs by shaking the family tree of the prehistoric reptiles, saying the monstrous creatures may have their origins in the northern hemisphere rather than the southern.
The dinosaur family tree, which was first created in 1888, may receive a revolutionary overhaul as scientists have proposed the same. Dinosaurs like the Tyrannosaurus rex (T rex) and Brontosaurus are likely to part ways because of incompatible differences.
The scientists came to this conclusion after they analysed that 75 species of the meat-eating group including the T. rex should not be endured with the long-necked, long-tailed, four-legged plant-eaters like Brontosaurus.
The new dinosaur family tree will have two reformulated categories, or clades, of dinosaurs that would replace the two that paleontologists have long recognised.
The research sends dinosaur origins back to relatively soon after a mass extinction on Earth 252 million years ago.
"We may be proved to be correct, we may not," said University of Cambridge paleontologist Matthew Baron, who led the research published in the journal Nature.
"But what has to happen now is a complete abandonment of old dogmatic views across the field because we have shown that rigorous and objective studies can pull apart age-old ideas, and that we as scientists should never got too comfortable with an idea when it can still be tested in new ways."
He said key skeletal differences indicate the meat-eating group called theropods, including giants like T. rex, Allosaurus, Giganotosaurus and Spinosaurus, and the long-necked group called sauropods, including huge Brontosaurus, Diplodocus and Argentinosaurus, should not be banded together.
Dinosaurs have long been organized into two clades by the scientists.
The so-called bird-hipped Ornithischia includes the herbivorous spiky-tailed stegosaurs, tank-like ankylosaurs, horned dinosaurs, duckbills and dome-headed dinosaurs. The so-called reptile-hipped Saurischia includes theropods including birds and the sauropods.
Two newly devised categories have been proposed by Baron – the first is called Ornithoscelida, which joins the theropods with all the current members of Ornithischia.
The current Saurischia group would lose the theropods but gain herrerasaurids, a strange, primitive group of two-legged carnivores.
The earliest dinosaur have been placed 242 to 247 million years ago by the analysis, a small Tanzanian species called Nyasasaurus. Dinosaurs were once the dominant land animals but an asteroid wiped them from Earth 66 million years ago.
"Our results strongly suggest that the ancestral dinosaur was a quick, two-footed, generalist feeder that would have eaten a mix of plants and meat," Baron said.
University of Maryland paleontologist Thomas Holtz, not involved in the study, praised the research, saying, "There is a very good chance that they are correct, even though it goes against decades of research pointing a different way."
