Earliest land-walking fish
Tiktaalik roseae
375 million year(s)
Canada ()

The earliest fish potentially capable of walking on land is Tiktaalik roseae, a species of sarcopterygian that lived approximately 375 million years ago, during the late Devonian Period, in what is today the Canadian Arctic. Its pectoral fins possessed primitive wrist bones not seen in true fishes but present in tetrapods, and the fins themselves were notably muscular, with massively constructed scapulae and coracoids, as well as functional elbows, all of which would have enabled it to support itself upon them when standing in shallows, and moving about briefly on land if need be. Again, like tetrapods but unlike most fishes, its neck was capable of movement independent of its body, and its powerful ribcage coupled with spiracles on top of its head suggest that it possessed lungs as well as gills. Consequently, it is deemed to be a transitional fossil species, linking true fishes to tetrapod amphibians.

The earliest known land animal overall is Pneumodesmus newmani, a species of millipede known from a single fossil specimen, which lived c. 428 million years ago during the late Silurian Period. It was discovered in 2004, in a layer of sandstone near Stonehaven, in Aberdeenshire, Scotland, UK, by amateur palaentologist Mike Newman.
In 2010, a team of palaeontologists made public the discovery at Poland's Zachelmie Quarry of numerous fossilized tracks and individual footprints that they claimed were those of tetrapods, but which considerably pre-dated the existence of Tiktaalik, thereby indicating that the first tetrapods had already evolved long before the latter species. However, these claims are contentious as they have been disputed by a number of other palaeontologists, who have suggested such alternative identities for the tracks as fish nests and feeding traces, as well as tracks left by transitional forms analogous to Tiktaalik.