Dinosaur family tree is being redrawn

Based on 77 dinosaur fossils with hair, feathers, or scales, a computer model has calculated the likely features of a plumed ancestor. Not only did the model reveal that the ancestor most probably had scales, it suggests that the entire dinosaur family tree should be reconstructed. Dinosaur ancestor unlikely to have had feathers

1 Pterosaurs have their own branch of the family tree, and are hence more closely related to the dinosaurs’ common ancestor than other species.

The computer simulation was based on a pterosaur which had some kind of feathers across its entire body. The simulation’s conclusion was that even with a wellfeathered pterosaur that is directly related to the common ancestor, the likelihood of a feathered original form is low compared to one with scales.

Feathered dinosaurs originated several times

2 The computer model was also fed the few species in the group of armoured and horned dinosaurs (to which Triceratops and Stegosaurus belong) that have been found with feather-like growths. These examples, including Psittacusaurus and Kulindadromeus, have outgrowths that are very different from other types of feathers. According to the computer model, this means either that feather-like growths originated independently several times, or that the horned dinosaurs should be repositioned with the predatory dinosaurs on the family tree.

Longnecks and T. rex must be separated

3 Saurischia is a group with two subgroups that are surprisingly varied: predatory dinosaurs (which include birds), and the big long-necked sauropod herbivores. Originally they were united on the family tree due to their hip structures, which share common features. But there are also distinct differences. According to the computer model, the sauropodmorphs should be a separate group, because featherlike growths have been found in predatory dinosaurs, but not in sauropodmorphs.