Scottish quarry fossils belong to long-toed lizard-like creature, experts say | Paleontology

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A stubby creature that was half a meter long and boasted a surprisingly long toe on each of its hind legs has been discovered by experts analyzing fossils from a prehistoric lake in Scotland.

The creature is believed to have lived around 330 million years ago – a time when what is now Scotland sat on the equator and had not only a warm climate but a wealth of vegetation and even volcanic eruptions.

Dr Timothy Smithson, co-author of the research at the University of Cambridge, said the rocks the fossils were found in were deposited in an isolated lake, but the animal would have lived on land because the lake would have been too hot, or had an improper chemical balance, to sustain life.

“There were no fish or other aquatic animals in the lake until much later,” he said, adding that a wide range of fossils had already been recovered from the quarry, including scorpions, centipedes, and a limbless snake-like creature.

“They appear to have fallen or been chased into the lake, couldn’t get out, died either because it was hot water or chemically unsuitable for survival, or they drowned and then sank in the background,” Smithson said.

Writing in the journal Communications BiologySmithson and his colleagues report that they named the newly discovered creature Termonerpeton makrydactylus.

The nickname means ‘boundary caterpillar’ and ‘elongated toe’, and refers to the boundary walls near the East Kirkton quarry where the late Scottish fossil collector Stan Wood is thought to have found the specimen in the middle. from the 1980s, and the exceptionally long fourth. toe of the creature’s hind legs.

A Mississippian tetrapod showing early diversification of the hind limbs. Photography: National Museums of Scotland

Smithson said the creature would have looked a bit like a lizard, with large feet but stubby legs, adding that the creature’s long toe was unusual for an animal of that era.

“A similar long fourth toe is found in living lizards where it is thought to extend the length of the stride and thus allow them to cover ground more quickly. It may also help the animal negotiate a variety of substrates, from firm ground with pebbles and sand,” he said. “It may also have been advantageous for Termonerpeton, helping him to escape predators and negotiate an area prone to volcanic ashfall as well as firm ground and leaf litter.”

Smithson added that the creature lived before the two modern groups of tetrapods – amphibians such as frogs and newts, and amniotes such as reptiles and mammals – evolved.

“He was on the line leading to reptiles, birds and mammals but was not a direct ancestor of any of them,” he said.

The fossil of the long-toed creature, which includes the bones of the ribs, pelvis and left leg and hind foot, among other features, is believed to have sat in a drawer after being donated by Wood to the University Museum of Cambridge Zoology in the 1990s, and when first examined it was thought to be an example of another animal that had already been discovered. But the new analysis reveals that it is something different.

“It’s exciting because it shows for the first time that early tetrapods were experimenting with different ways of growing their feet to cope with walking on land,” Smithson said.

“The finds at the East Kirkton quarry represent the world’s first evidence of terrestrial tetrapods, animals that have apparently lived their entire lives on land,” he added. “They had no evidence of amphibious habits – although we have no evidence of how they might have reproduced.”

Dr Nick Fraser of National Museums Scotland, which houses one of the other fossils from the East Kirkton quarry but was not involved in the study, said the finds were exciting not least because they showed that the evolution of terrestrial locomotion in early tetrapods was complex. , and did not follow a regular pattern.

“To me, this also suggests that amniotes started thriving a bit earlier than previously thought,” he said. “We see a greater diversity of different types from this period.”

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