Dinosaur family tree
The new family tree structure is shown. CREDIT: University of Cambridge

A new study is calling for rearrangement, redefinition and renaming of family groupings of dinosaurs as these huge animals may have originated in the Northern Hemisphere and not the Southern.

The study published in the journal Nature derives its findings from analysis of dinosaurs and its near relatives. For over a century scientists studying dinosaurs have classified them in two distinct categories: Ornithischia and Saurischia. However, scientists at the University of Cambridge and Natural History Museum in London claim that these family groupings could be wrong and the naming convention that we have followed until now needs to be completely changed.

The initial classification of dinosaurs started during the Victorian times. Subsequently with discovery of more and more fossils, various species were named and identified. Scientists realised that dinosaurs were anatomically diverse and attempts were then made to classify them into groups that shared particular features with scientists then classifying them into two distinct groupings, or clades; Saurischia or Ornithischia.

As more dinosaurs were described it became clear that they belonged to three distinct lineages; Ornithischia, Sauropodomorpha and Theropoda. However, the new study concludes that the ornithischians need to be grouped with the theropods, to the exclusion of the sauropodomorphs. It has long been known that birds (with their obviously ‘bird-like’ hips) evolved from theropod dinosaurs (with their lizard-like hips). However, the re-grouping of dinosaurs proposed in this study shows that both ornithischians AND theropods had the potential to evolve a bird-like hip arrangement- they just did so at different times in their history.

The revised grouping of Ornithischia and Theropoda has been named the Ornithoscelida which revives a name originally coined by the evolutionary biologist, Thomas Henry Huxley in 1870.

While analysing the dinosaur family trees the team arrived at another unexpected conclusion. For many years, it was thought that dinosaurs originated in the southern hemisphere on the ancient continent known as Gondwana. The oldest dinosaur fossils have been recovered from South America suggesting the earliest dinosaurs originated there. But as a result of a re-examination of key taxa it’s now thought they could just as easily have originated on the northern landmass known as Laurasia, though it must be remembered that the continents were much closer together at this time.

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