Newly discovered fossil clues can rewrite the early history of reptiles
Fossilized claw clues discovered in Australia show that the animal group that includes reptiles, mammals and birds formed before expected
Illustration of an amniote animal that is believed to leave fossilized claw impressions in Victoria, Australia.
The fossil claw impressions found in Australia were probable by the first known members of the group that includes reptiles, birds and mammals, according to a study published in Nature Today. The findings suggest that the group, the amniotes, originated at least 35 million years before what was previously thought.
The first amniotes evolved to put eggs on the ground, because they were locked in an amniotic membrane that prevented them from drying. Before this study, the first known amniot fossils had found themselves in Nueva Scotia, Canada, and were dating the middle carboniferous period, about 319 million years ago. The last findings suggest that amniotas also existed in the early carboniferous period, about 355 million years ago.
“This discovery is exciting, and if the clues have interpreted the legs in the right way, the findings have important implications for our understanding of the evolution of the tetropods,” says Steven Salisbury, paleontologist at the University of Queens, Austia,.
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The clues
The traces of the claw were found in a sandstone block on the shore of the Broken River in Barjarg in the state of Victoria, by two co -authors of the newspaper who are not professional scientists. This area of the river is known as Berrepit for the Taungurung indigenous people who have the country.
The sandstone block is part of a larger structure that already had a leg with the early carboniferous at the base of radiometric and tectonic evidence. The fossilized clues of aquatic invertebrates and fish found in the same layer also dated this period of time.
The slab of the formation of the formation of snowy plains with traces and traces highlighted. Manus (Front foot) The impressions are shown in yellow; Pes (Rear foot) The impressions are shown in blue.
The three sets of tracks in the study have traces with claw attempts, a reptile characteristic but not amphibians. “Having claw thesis hooked on the roads indicates that they are definitely a reptile animal,” says John Long, paleontologist at the University of Flinders in Adelaide, Australia.
There are no scoring or queues drag marks, and the authors suggest that the amniotes left by the clues could keep their bodies and tails on the ground while walking on the country. But Salisbury questions that interpretation, because it would mean that animals had developed sophisticated structures for complex locomotion, which would be surprising given how early they are. “It seems more likely that the tracks were made by an animal that was ‘pointing’ in shallow waters, instead of walking on the ground,” he says.
Ancestor
Until now, the evidence suggested that the last common ancestor of modern and amniot amphibians lived about 352 million years ago. But if reptile ancestors existed as early carboniferous, their separation from amphibians must have happened the same before, Long says. The team quotes suggest that the groups diverged in the devonic period, about 380 million years ago.
To estimate the probable time of divergence, Long and his colleagues used several appointment methods. One included geological evidence of radioactive decomposition in layers of volcanic rock above and below fossil tracks. They also used molecular phylogenetics, which compares similarities and differentials in the DNA of living species to estimate their evolutionary relationship and how the last recent common ancestor lived.
The discovery could also change the origin of amniots to the mass of Gondwana earth. This formed the southern part of the Pangea Supercontinent and the increase in current land masses, including Africa and Australia. Previously, the first known amniotas were found in North America, which led paleontologists to think that the group originated in the northern hemisphere. But more evidence of Australian fossils is needed before definitely changing their site of origin, says Long. “Australia is a permanent area with less paleontologists on the ground,” says Long. “We have many more unexplored fossil sites where new things like this continue to appear.”
This article reproduces with permission and laundry. First published May 14, 2025.
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