Scientists in Australia have identified the oldest known fossil footprints of a reptile-like animal, dated to around 350 million years ago, around 100 million years before the earliest dinosaurs. The discovery suggests that after the first animals emerged from the ocean around 400 million years ago, they evolved the ability to live exclusively on land much faster than previously assumed, the AP reports. "We had thought the transition from fin to limb took much longer," says California State University paleontologist Stuart Sumida, who was not involved in the new research. Previously, the earliest known reptile footprints, found in Canada, were dated to 318 million years ago.
The ancient footprints from Australia were found on a slab of sandstone recovered near Melbourne and show reptile-like feet with long toes and hooked claws. Scientists estimate the animal was about 2½ feet long and may have resembled a modern monitor lizard. The findings were published Wednesday in Nature.
- The hooked claws are a crucial identification clue, says study co-author Per Ahlberg at Uppsala University in Sweden. "It's a walking animal," the paleontologist says. Only animals that evolved to live solely on land ever developed claws. The earliest vertebrates—fish and amphibians—never developed hard nails and remained dependent on watery environments to lay eggs and reproduce. But the branch of the evolutionary tree that led to modern reptiles, birds, and mammals—known as amniotes—developed feet with nails or claws fit for walking on hard ground.
- Study co-author John Long, a Flinders University paleontologist, says two other people listed as co-authors, builder Craig Eury and winemaker John Eason, spotted the slab while fossil hunting, the Australian Broadcasting Corporation reports. "They hit the mother lode with this trackway," Long says. "This is the oldest evidence in the world of amniote trackways—the lineage that will eventually end up as humans. It's huge."
- At the time the ancient reptile lived, the region was hot and steamy, and vast forests were beginning to cover the planet. Australia was part of the supercontinent Gondwana. The fossil footprints record a series of events in one day, Ahlberg says. One reptile scampered across the ground before a light rain fell. Some raindrop dimples partially obscured its trackways. Then two more reptiles ran by in the opposite direction before the ground hardened and was covered in sediment.
- "Footprints are fossil movie clips of living animals. You're not looking at dead remains," Ahlberg says, per the Washington Post. "You're looking at live animals doing their stuff."
- Food sources for creatures that could adapt to life on land at the time would have included plenty of insects, Long says. He says the 28-foot-long sharks in the oceans would also have been a big incentive to remain on land full time. "The rivers also had the biggest, most terrifying fishes ... with teeth the size of bananas," Long says, per the Post. "They would have driven a lot of animals onto shore."
(More
discoveries stories.)
,
uBlock 
,
and
Ghostery 
)
