A groundbreaking discovery in Australia has the potential to reshape our understanding of the early history of reptiles, mammals, and birds. Fossilized claw tracks found in Victoria, Australia, suggest that the group known as amniotes originated much earlier than previously believed, at least 35 million years earlier.
The study, published in Nature, reveals that early amniotes evolved to lay eggs on land, protected by an amniotic membrane that prevented them from drying out. Prior to this discovery, the earliest known amniote fossils were found in Nova Scotia, Canada, dating back to the mid-Carboniferous period, around 319 million years ago. However, the newly discovered tracks in Australia indicate that amniotes existed as far back as the early Carboniferous period, approximately 355 million years ago.
According to Steven Salisbury, a palaeontologist at the University of Queensland in Australia, this finding has significant implications for our understanding of tetrapod evolution. The claw tracks were unearthed in a sandstone block on the bank of the Broken River at Barjarg in Victoria, by non-professional scientists. The area, known as Berrepit to the Indigenous Taungurung people, has been dated to the early Carboniferous based on radiometric and tectonic evidence.
The tracks, which include clear footprints with claw indentations, suggest a reptile-like animal. John Long, a palaeontologist at Flinders University, notes that the presence of hooked claws indicates a reptilian origin. However, there is debate over whether the animals walked on land or in shallow water, as the absence of belly or tail drag marks raises questions about their locomotion capabilities.
The discovery also sheds light on the common ancestor of modern amphibians and amniotes, suggesting a divergence dating back to the Devonian period, around 380 million years ago. By using various dating methods, including geological evidence and molecular phylogenetics, researchers were able to estimate the timing of this split.
Moreover, the origin of amniotes may be linked to the Gondwana landmass, challenging previous beliefs that the group originated in North America. Further exploration of Australian fossil sites is needed to confirm this shift in origin and uncover more insights into the early evolution of amniotes.
This exciting discovery, first published in Nature, marks a significant milestone in our understanding of early reptilian history and highlights the importance of ongoing research in uncovering the mysteries of our planet’s past.
