The claw marks show that the reptiles came before thought

Trackway assemblages of aquatic invertebrates, synapsides and limbed stem tetrapods dated to the early Carboniferous

The three sets of tracks in the study have clear footprints with indentations from claws, a feature of reptiles but not amphibians. “Having these hooked claws on the trackways indicates they’re definitely a reptile-like animal,” says Long

The sandstone block is part of a larger structure that had already been dated to the early Carboniferous on the basis of radiometric and tectonic evidence. Fossilized tracks of aquatic invertebrates and fish found in the same layer were also dated to this time period.

The claw tracks were found by two co-authors of the paper who aren’t professional scientists and are on the bank of the Broken River in Victoria. There is an area of the river called Berrepit that is owned by the Taungurung people.

There’s more to this phenomenon that the trackway record sheds light on. The oldest records of salamanders, synapsids and limbed stem tetrapods are currently in the collection of the ichnorecords. It is well known that trackway assemblages capture taxa that are not found in body fossils, which also applies to the Devonian and Carboniferous record. Taxa that are not depicted among the associated body fossils were found in the early part of the trackway from Canada’s Blue Beach. The Mansfield Group contains no known tetrapod body fossils14,15,16,17. The Givetian Valentia Slate Formation of the Island of Ireland and the Eifelian Wojciechowice Formation of the Poland are both known to contain published tetrapods. The trackway record has direct proof of the incomplete body-fossil record, and it can be important in fleshing out the picture of early tetrapods, even though they are quite meager.

Fossil claw prints found in Australia were probably made by the earliest known members of the group that includes reptiles, birds and mammals, according to a study published in Nature today1. The findings suggest that this group — the amniotes — originated at least 35 million years earlier than previously thought.

Early amniotes evolved to lay eggs on land, because they were encased in an amniotic membrane that stopped them drying out. In Nova Scotia, Canada, amniote fossils were found in the mid-Carboniferous period, about 319 million years ago. The findings show that amniotes existed in the early Carboniferous period around 355 million years ago.

The search for temporal and spatial patterns of distribution can be difficult due to the poor fossil record. With the discovery of the Snowy Plains Formation tracks, the crown-group amniote record of northeastern Gondwana now predates that of Euramerica by about 30 million years, but we cannot rule out that earlier representatives may eventually be found in Euramerica as well. The mid- to late- Serpukhovian amniote tracks from Silesia have advanced claws and narrow digits, which suggests that the evolutionary history of this group is nested deeper in time. The palaeomagnetic reanalysis of the northern path of the Australia51,52 pole path has shown that the continent was much further north during the Famennian than had been thought. At the time of deposition of the Mansfield Group, the trackway locality lay at a latitude of approximately 17° south, at the southern edge of the tropics. This is quite similar to the Euramerican Notalacerta localities, and does not give a strong case for a difference between tropical and temperate faunas being a factor in early amniote distribution.