Fossil found of earliest known animal
Posted: Thursday, July 4, 2002
AP - A fossil found in Scotland in 1971 has been newly identified by scientists as the earliest known animal built to walk on land, a salamander-like creature that marked a previously unknown stage in the evolution of fish into the ancestors of all vertebrates alive today.
British scientists say the toothy animal, Pederpes finneyae, lived between 348 million and 344 million years ago in what is today's Scotland. It was perhaps a metre long and probably split its time between the water and land where it walked on four feet, said Jenny Clack, of the Cambridge University Museum of Zoology. "It trudged through the swamp catching anything that moved," Dr Clack said. She formally described Pederpes in this week's edition of the journal, Nature. The creature's nearly complete fossil skeleton had lain, mislabelled as a fish, in a Scottish museum since its discovery 31 years ago. Further work on the fossil in the 1990s revealed it had legs.
The identification helps close a hole in the early fossil record of a group of creatures called tetrapods. The gap, or Romer's Gap - named after the late Harvard paleontologist Alfred Sherwood Romer - had stumped scientists charting the evolution of the first four-limbed creatures with backbones. Tetrapods were the first animals known to walk the Earth and are the ancestors of today's mammals, reptiles, amphibians and birds.
"The discovery of a nearly complete skeleton in the middle of Romer's Gap should help in establishing the pattern of evolutionary change among early tetrapods," wrote Robert Carroll, of Montreal's Redpath Museum, in an accompanying commentary.
The earliest tetrapods appeared roughly 365 million years ago when scientists believed they used their paddle-like feet to move around underwater. Only later did they emerge to use their rudimentary feet to walk on land.
Scientists knew of no other fossils, until Pederpes, that represented any sort of intermediate stage between the aquatic and terrestrial tetrapods. The fossil record picks up again 20 million to 30 million years later with more modern-looking animals with feet and legs that were clearly for walking on land.