Scientists are pushing back the date that the first land-walkers stepped foot on solid ground. Thanks to the discovery of prehistoric footprints from an 8-foot-long animal, scientists now say creatures strolled the Earth 20 million years earlier than previously thought. The prints were made by tetrapods—animals with backbones and four limbs—and could rewrite the history of when, where, and why fish evolved limbs and first walked onto land, the study says [National Geographic News]. The researchers published their results in the journal Nature.
Dozens of the fossilized footprints were found in an abandoned quarry in Poland, and the researchers say that the area was probably a lagoon or an intertidal flat when the tetrapod wandered across it about 395 million years ago. Researchers say the footprints in such old rock was a big surprise: They’re about 10 million years older than body fossils of creatures such as Tiktaalik and Panderichthys, … believed to represent the transition from lobe-finned fish to creatures fully adapted to life on land [Science News].
A new study of a the fossilized remains of the Tiktaalik, the “walking fish” that illuminates how swimming fish evolved into land-dwelling amphibians, shows that there was more to the transition than the switch from fins to limbs. The study shows that the head and braincase were changing, a mobile neck was emerging and a bone associated with underwater feeding and gill respiration was diminishing in size, a beginning of the bone’s adaptation for an eventual role in hearing for land animals [The New York Times].
The creature, dubbed Tiktaalik roseae — or, to be less formal, Fishapod — lived 375 million years ago 600 miles north of the Arctic Circle in a subtropical floodplain that eventually became Ellesmere Island, where it was discovered in 2004 [Wired News]. The fishapod has already earned its reputation as a “missing link” in evolutionary history due to its sturdy, jointed fins and its dual breathing system, with both gills and lungs. But the new study suggests that changes to the animal’s head and the development of the first neck also played a critical role in its evolution.
Researchers have found the first small finger-like bones in the fins of a fish that lived 380 million years ago, about 15 million years before the first four-footed creatures, called tetrapods, clambered onto the land.
The finding upends the most recent theory of the evolution of digits: The need to adapt to swampy marshlands and terra firma, the theory went, is what drove the gradual shift through natural selection from fish fins suitable only for swimming to weight-bearing limbs with articulated joints. The study, however, reveals that rudimentary fingers were already present inside the fins of the shallow-water Panderichthys, a transitional species that was nonetheless more fish than tetrapod [The Daily Telegraph].
Around 365 million years ago, a fishy, finned creature that resembled a small alligator clambered up on a sandbank and earned its place in evolutionary history. Researchers who recently discovered fossils of the animal, named Ventastega curonica, say it’s the most primitive four-legged creature ever found. While it wasn’t the first “fishapod” to lurch out of the water (that honor goes to the Tiktaalik, which accomplished the feat about 375 million years ago), its more primitive evolutionary stage gives researchers new information about the earliest four-legged creatures, or tetrapods.
Ventastega was first described from a few bone fragments unearthed in Latvia in 1994, but it took additional years of excavation and the discovery of remains from many more individuals before scientists had a good idea of what the creature looked like. The latest portrait to emerge, from an especially well-preserved find, reveals an animal with a part-fish, part-tetrapod skull and a full-fledged tetrapod body. It would have spent the majority of its time on water and been clumsy on land [National Geographic News].