How ancient reptile footprints are rewriting the history of when animals evolved to live on land
By CHRISTINA LARSON AP Science Writer WASHINGTON AP Scientists in Australia have identified the oldest known fossil footprints of a reptile-like animal dated to around million years ago The discovery suggests that after the first animals emerged from the ocean around million years ago they evolved the ability to live exclusively on land much faster than previously assumed We had thought the transition from fin to limb took much longer disclosed California State University paleontologist Stuart Sumida who was not involved in the new research Previously the earliest known reptile footprints detected in Canada were dated to million years ago The ancient footprints from Australia were located 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 feet centimeters long and may have resembled a modern monitor lizard The findings were published Wednesday in Nature This image provided by Prof Per Erik Ahlberg shows a slab of sandstone detected near Melbourne Australia preserving fossil footprints from a reptile-like animal that lived around million years ago The footprints are highlighted in yellow front feet and blue back feet and show the movements of three similar animals researchers say Grzegorz Niedzwiedzki Prof Per Erik Ahlberg via AP The hooked claws are a crucial identification clue explained investigation co-author and paleontologist Per Ahlberg at Uppsala University in Sweden It s a walking animal he commented 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 Related Articles Bright auroras on Jupiter are captured by Webb Space Telescope The researchers charged with defending the planet against asteroids Chimpanzees drum with regular rhythm when they beat on tree trunks a form of ancient communication US infant mortality dropped in Experts partly credit RSV shots Dog material may help track dangerous syndrome for humans 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 This is the earliest evidence we ve ever seen of an animal with claws noted Sumida At the time the ancient reptile lived the region was hot and steamy and vast forests began to cover the planet Australia was part of the supercontinent Gondwana The fossil footprints record a series of events in one day Ahlberg reported One reptile scampered across the ground before a light rain fell Particular 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 Fossil trackways are beautiful because they tell you how something lived not just what something looked like explained co-author John Long a paleontologist at Flinders University in Australia The Associated Press Vitality and Science Department receives help from the Howard Hughes Health Institute s Science and Educational Media Group and the Robert Wood Johnson Foundation The AP is solely responsible for all content
