‘Parrot lizard’ dinosaur sheds light on how reptile scales became bird feathers

A feathered dinosaur with a parrot-like beak is helping shed new light on how reptile scales became bird feathers, according to scientists.

Psittacosaurus – a plant-eating creature about the size of a large dog – roamed the forests of China, Russia and Mongolia somewhere between 135 and 120 million years ago.

Palaeontologists have now discovered the creature, often known as the “parrot lizard”, had reptile-like skin in areas of the body without feathers.

They said the findings, published in the journal Nature Communications, is helping unlock the mysteries of evolutionary transition from scales to feathers.

The researchers said they also discovered something unexpected – the dinosaur skin fossil they analysed was composed of silica, the same compound that is used to make glass.

Scientists at the University College Cork (UCC) in Ireland teamed up with experts in Nanjing University in China to analyse a fossil specimen of a juvenile Psittacosaurus unearthed in northeastern China.

Describing the fossil as a “hidden gem”, Dr Zixiao Yang, of UCC’s School of Biological, Earth and Environmental Sciences and the first author on the study, said the preserved skin cannot be seen with the naked eye.

He said: “Only under UV (ultraviolet) light is the skin visible, in a striking orange-yellow glow.

“What is really surprising is the chemistry of the fossil skin. It is composed of silica – the same as glass.

“This type of preservation has never been found in vertebrate fossils.

“There are potentially many more fossils with hidden soft tissues awaiting discovery.”

Feathers are highly complex structures that require specific skin adaptations to help with feather growth, flight, and regulating body heat.

This makes feathered skin distinct from scaley, reptilian skin, the researchers said.

While feathers are thought to have evolved in dinosaurs, birds’ extinct ancestors, not much is known about the transition between the two skin types.

When the researchers analysed the samples from the Psittacosaurus fossil, it showed two layers of skin which strongly resembled that seen in living reptiles.

The team also found the preserved skin pigment to be consistent with that seen in the scales of reptiles, like crocodiles.

The researchers said their findings suggest Psittacosaurus’s skin had “zoned development”, with reptile-style scales in some areas – such as the torso – and bird-like skin with feathers in other areas – such as the tail.

Professor Maria McNamara, of UCC’s School of Biological, Earth and Environmental Sciences and a senior author on the study, said: “The evolution of feathers from reptilian scales is one of the most profound yet poorly understood events in vertebrate evolution.

“While numerous fossils of feathers have been studied, fossil skin is much more rare.

“Our discovery suggests that soft, bird-like skin initially developed only in feathered regions of the body, while the rest of the skin was still scaly, like in modern reptiles.

“This zoned development would have maintained essential skin functions, such as protection against abrasion, dehydration and parasites.

“The first dinosaur to experiment with feathers could therefore survive and pass down the genes for feathers to their offspring.”