The first bird-like dinosaurs, completely covered in feathers, appeared with Archaeopteryx. It is known that feathers appeared much earlier in dinosaurs, but it is unclear if these features already covered their whole body. Scientists may have some answers with the discovery of a Psittacosaurus fossil.
Feathers, which adorn the bodies of our present-day birds, originated in dinosaurs around 250 million years ago, long before the first birds like Archaeopteryx evolved. This small avian dinosaur appeared about 150 million years ago, and fossils clearly show that it had feathers covering its entire body. The debate continues on the appearance of the first feathered dinosaurs. In other words: how did the transition occur from dinosaurs with scaly skin, like reptiles, to dinosaurs completely “feathered” like Archaeopteryx?
A Dinosaur with Only a Few localized Feathers
A new study could provide some answers to this question. Paleontologists from the University College Cork in Ireland have discovered tiny traces of skin on a new fossil specimen of Psittacosaurus. This small herbivorous theropod dinosaur, nicknamed “parrot lizard” because of its beak shape, lived in the early Cretaceous period around 135-120 million years ago, a critical time when the first birds appeared.
Some hints found on previous specimens suggest that Psittacosaurus had a line of fibers on the top of its tail, although it is unclear whether these were actual feathers or simply hollow hairs, and their purpose remains questioned.
Two Different Skin Types
The analysis of the new fossil, with results presented in the journal Nature Communications, reveals new details about the cellular structure of this dinosaur’s skin. Preserved in silica, the skin fragments of Psittacosaurus offer unprecedented insights into the characteristics of dinosaur skin during the transition to feathers.
Under light and UV light, the study reveals that the animal had two different skin textures. One resembling that of birds, only found in the area of the body with feathers. The rest of the body had scaly skin similar to reptiles.
This zoning suggests that feathers gradually appeared on dinosaur bodies, allowing them to retain the advantage of scaly skin while passing down the feather genes to their descendants. Scaly skin appears to be a more effective protective barrier than feathers against attacks, dehydration, and parasites, at least for these non-flying dinosaurs.