The claw marks are from dinosaurs, which arose far earlier than thought
The Trackway Record Reveals New Taxa and Evolutionary Sequences in Early Tetrapod Formations: A Case Study: Berrepit, Victoria
There are three sets of tracks in the study and all of them have clear footprints and claw marks. Long says they are definitely a reptile-like animal because of their hooked claws.
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. There were fossils of fish and aquatic invertebrates found in that same layer.
The claw tracks were found in a sandstone block on the bank of the Broken River at Barjarg in the state of Victoria, by two co-authors of the paper who are not professional scientists. The Berrepit is a land where the Taungurung people own the land.
The trackway record gives further information on this phenomenon. All the records of the Amphibians, synapsids, sauropsids and limbed stemtetrapods are known as “HemiNorecords7”. It is well known from later parts of the fossil record, that trackway assemblages often capture taxa that are not seen in the associated body fossils. Taxa that are not represented by body fossils are present in the early high-diversity fossil from Blue Beach, Canada. The Mansfield Group contains no known tetrapod body fossils14,15,16,17. This is also the case for the two Middle Devonian formations that contain published tetrapod tracks, the Givetian Valentia Slate Formation of Valentia Island, Ireland, and the Eifelian Wojciechowice Formation of Zachełmie, Poland; the former yields only fish49,50, the latter no body fossils at all. The trackway record thus provides direct evidence of the incompleteness of the body-fossil record, and in turn has a key part to play in fleshing out the picture of early tetrapod diversity, even though it is also quite meagre.
There is a substantial time interval between the tetrapod and amniote crown-group, which is a universal feature of the recent phylogenies. These age differences are inferred from branch lengths that in turn reflect base substitutions recorded in the genomes of extant animals, and are thus not susceptible to the distorting effects of gaps in the fossil record. Even though the exact ages vary between phylogenies, depending both on the fossil calibrations and phylogenetic algorithms used, the substantial age separation between the amniote and tetrapod crown-group nodes is consistent and must be real; these cladogenetic events were separated by tens of millions of years.
Early amniotes evolved to lay eggs on land, because they were encased in an amniotic membrane that stopped them drying out. Before this study, the earliest fossils were found in Nova Scotia, Canada and were from the mid-Carboniferous period. The latest findings suggest that amniotes also existed in the early Carboniferous period, around 355 million years ago.
A series of body-fossil discoveries over the past four decades lend indirect support to this contention, by providing evidence for previously unsuspected diversity and morphological disparity among Devonian tetrapods43,44,45,46,47. The fact that every new locality has at least one new tetrapods is a striking contrast to the widespread distribution of associated fishes such as Holoptychius and Bothriolepis. Nevertheless, the complete absence so far in the Devonian body-fossil record of any crown-group tetrapods, or crownward stem-group clades such as colosteids and baphetids, indicates that this record markedly under-samples the living diversity.
Researchers from Victoria, Australia, found that tetrapod tracks known as trackways contain new taxa and evolutionary Sequences in Early Tetrapod Formations. The tracks of two Middle Devonian formations contain published tetrapod tracks, but both contain no known tetrapod body fossils. Taxa present in Blue Beach, Canada’s early high-diversity fossil are not seen in the associated body fossils.