Before the dinosaurs Sensational Australian find turns reptile family tree on its head
New fossil finds from Australia show that the first reptile-like land animals colonized the mainland 350 million years ago, much earlier than previously thought.
No time? blue News summarizes for you
- Fossilized tracks from Australia prove the earliest appearance of reptiles 40 million years before previous findings.
- The research shifts the evolutionary origin of reptiles from the north (Europe, North America) to the southern primeval continent of Gondwana.
- The results suggest that the development of the four-legged land vertebrates was more rapid than previously assumed.
- The discovery shows how much untapped knowledge is still hidden in the Australian fossil record and revolutionizes our understanding of vertebrate evolution.
At first glance, it was "just" a fossilized sandstone slab, interspersed with depressions and traces. But when fossil hunters Craig Eury and John Eason discovered the slab in Mansfield, Australia, they had no idea that they were closing a 40-million-year-old gap in evolutionary history.
As palaeontologist John Long from Flinders University explained to the Guardian, the tracks are the oldest evidence of reptile-like land animals, known as amniotes.
These animals are characterized by the presence of a protective amniotic shell that allowed them to reproduce independently of water, an evolutionary milestone on the way to reptiles, birds and mammals.
Tracks from another time
The tracks that have now been dated are between 354 and 358 million years old and date from the early Carboniferous period. This makes them older than all previous amniotes found in Europe and North America, as the renowned scientific journal Nature writes.
Particularly striking are the clearly visible, fifteen-foot imprints with distinctive claws, a sure sign of true land vertebrates.
Long describes the discovery as "revolutionary". The tracks shift the origin of the amniotes to the southern supercontinent Gondwana, to which Australia also belonged at the time. "This is a fundamental rewriting of the evolutionary history of this group of animals," emphasizes Long.
From fish to reptiles: faster than expected
The new data also challenges the previous picture of the speed of vertebrate evolution. Long and his team suspect that the development of tetrapods, i.e. the transition from fish to land-living vertebrates, was much faster than previously assumed.
The fossil gap in the Devonian, a geological epoch around 419 to 359 million years ago, was previously regarded as evidence that the development of land vertebrates, i.e. those animals that first lived permanently on land, was very slow at the time.
But this impression may be deceptive. The supposed "brake" on evolution could simply be due to the fact that there are too few well-preserved fossil finds from this period. In other words: evolution continued, we just haven't found the evidence for it yet.
"Is that something?"
For John Long, the discovery is also a personal highlight. He has been researching in the region for over 45 years. Early on, he made close contact with a "dedicated group of fossil hunters from Mansfield", as he explains.
The decisive find was made by Craig Eury and John Eason, two of these local fossil collectors. They discovered the imprints on the banks of a river on the traditional land of the Taungurung, around 200 kilometers northeast of Melbourne. For Long, this find in particular underlines the value of such collaborations with amateurs: many eyes see more.
When Eason sent him a photo of the tracks by e-mail, Long was, in his own words, "stunned with amazement". With a twinkle in his eye, he remembers the simple question Eason asked at the time: "Is that something?"
Animals left claw marks
When he opened the photo, he immediately realized that it was something special: "It was a beautiful slab with not just one, but several interlocking tracks."
The surface covered in ancient raindrops was particularly striking - an unmistakable sign that open ground was once exposed here.
Later, land-dwelling animals crossed this area and left behind fifteen prints, some with clearly visible claw marks and scuff marks from digging.
More intensive research called for
Experts from Flinders University then took a close look at the find. Using high-resolution CT scans and detailed analyses of the tracks, they worked closely with international experts on early tetrapod tracks from Uppsala University in Sweden.
Their investigations ultimately confirmed the outstanding scientific significance of the find.
Long sees this as just the beginning: "Now we have the footprints - next we need the bones." Colleagues such as Dr. Erich Fitzgerald from Museum Victoria also describe the find as "groundbreaking" and call for more intensive research into Australia's fossil wealth.