Bizarre new fossil reptile had crest unlike anything seen before

A unique crest has signalled a change in our understanding about reptile evolution.

Belonging to a truly unusual animal with a beak-like mouth and prehensile tail, the bizarre structure is providing an incredible insight into how reptiles were experimenting more than 247 million years ago during the Triassic Period.

The crest has been described from a new species of reptile, named Mirasaura grauvogeli. The elongated feather-like structure running along its back was likely used to attract mates or deter predators.

But it is the how this structure is formed that has astounded scientists. Initially, it looked like the crest was made of feathers similar to those on birds or dinosaurs. Closer examination, however, revealed that it has a very different structure entirely.

The scientists who have studied the animal believe it is an example of convergent evolution, having evolved entirely independently from feathers. If this is the case, then similar characteristics could be found in other branches of the reptile family and may be much older than first thought.

Dr Stephan Spiekmanopens in a new window was the lead author of the study, which was published in the journal Nature.

“Developmental biology studies show that the genetic basis for the growth of complex skin appendages, such as feathers, probably originated in the Carboniferous Period more than 300 million years ago,” Stephan says.

“Mirasaura provides the first direct evidence that such structures formed early on in reptile evolution in groups not closely related to birds and extinct dinosaurs. The fact that we have discovered such complex skin appendages in such an ancient group of reptiles sheds new light on their evolution.”

What was Mirasaura’s life like?

The fossils of Mirasaura were initially uncovered between 1930 and 1978 in the Vosges Mountains of eastern France. They were found by prolific fossil collector Louis Grauvogel, who built up an extensive collection of Middle Triassic fossils.

At the time of their discovery, the striking crest was believed to be either the fin of a fish or possibly the wing of an insect. It was only after Louis’ daughter donated his collection to the State Museum of Natural History in Stuttgart, Germanyopens in a new window, that they were found to belong to a reptile.

In recognition of the fossil’s origins, the mystery animal was named Mirasaura grauvogeli, which translates as ‘Grauvogel’s Wonder Reptile’.

It’s a type of animal known as a drepanosaur, a bizarre group of Triassic reptiles that lived in trees. They had curiously bird-like skulls, a lizard-like body and a prehensile tail. Some species even had a claw on the end of their tail, which is thought to have helped them grasp branches as they climbed.

“There’s no living animal that’s a close analogue to the drepanosaurs,” Stephan says. “They’re sometimes described as chameleon-like, but I don’t think that fits. I think they’re best imagined as a reptile version of a pygmy anteater, using its tail and hindlimbs to hold onto the trees while its clawed forelimbs and snout were used to look for food.”

With big, forward-facing eyes and a dome-like skull, Mirasaura was likely an active insectivore hunting for early insects among the branches and leaves of trees.

These senses would also have allowed it to catch sight of other members of its species, which it’s believed to have signalled to using the extraordinary crest on its back.

Did other reptiles have a similar crest?

The crest of Mirasaura was made of 16 feather-like structures that together formed a fan longer than the animal’s torso. Out of the numerous fossils unearthed, the longest crest is 15 centimetres long, but it’s possible that the maximum length was even longer because none of the fossils are from adults.

What is so fascinating about this crest is that it evolved in a group of animals that branched off from the reptile family tree very early on in their evolution. This means that the crest of Mirasaura evolved entirely independently to feathers, something which is backed up by their different structure.

It’s set apart from feathers by the lack of a crucial characteristic known as barbs. In birds, these branch off from the feather’s central ridge to form the fluffy part of down feathers and the flight surface of wings. The feather-like structures in Mirasaura, however, seem to have been entirely solid.

The only parallel to these structures that the researchers could find was in a different species of enigmatic drepanosaur called Longisquama insignis. While direct evidence of a crest in this animal hasn’t survived, the outline of a structure has been preserved in some fossils.

It’s therefore possible that other drepanosaurs might have had similar crests too, but they haven’t been found yet.

“In Mirasaura, the skin appendages are associated with a hump formed by the vertebrae, and this hump is also present in other drepanosaurs,” Stephan explains. “It has even been suggested that some dark substance associated with the hump of Drepanosaurus could indicate the presence of a crest, but that’s currently inconclusive.”

“Personally, I’m not sure if many other drepanosaurs had crests like Mirasaura. It’s definitely possible, but it’s equally likely that it could have been unique to a relatively early lineage of drepanosaurs that includes Mirasaura and Longisquama.”

The team hope to answer questions like this as part of their future research into how these structures evolved.

“We know that hairs, scales and feathers all use partially similar genetic and developmental pathways to form, and it seems almost certain that Mirasaura also used these,” says Stephan.

“It’s also conceivable that the Mirasaura appendages employed some feather-specific genes, since these are present in living reptiles today. It’s very tricky to test that with the limited fossil remains that are available, but we have some ideas we want to investigate going forward.”