RESEARCHERS working in the far north of Canada have recovered the fossil remains of a unique seal-like creature that has paws rather than flippers. They believe it may be a "missing link" that fills in a huge gap in the family tree for seals and related animals, writes DICK AHLSTROM
Modern seals are ungainly on land, staggering along on short flippers not best designed for terrestrial use. Once in the water, however, seals and their cousins, sea lions and walruses, become graceful swimmers.
Scientists are excited about the find, made in a crater lake on Devon Island in Nunavut, Canada. Located well inside the Arctic Circle, due north of the Great Lakes, the near-complete skeleton dates back between 21 and and 24 million years. Devon Island today is under ice most of the time but back then it was a temperate haven, with a coastal climate much like Ireland’s today and covered with conifer forests.
The animal, Puijila darwini,measured about 110cm from head to the tip of its longish tail, and although it had a body and muzzle akin to a seal's, it had legs like an otter with webbed paws that were ideal for swimming. This meant it was swift of foot on land but also in the water, according to the research team from the Canadian Museum of Nature, the Carnegie Museum of Natural History in Pittsburgh and the American Museum of Natural History, who describe their findings this morning in in the journal Nature.
"The remarkably preserved skeleton of Puijilahas heavy limbs, indicative of well- developed muscles and flattened phalanges , which suggests that the feet were webbed but not flippers," according to Dr Mary Dawson, curator emeritus of Carnegie.
SEALS, SEA LIONSand walruses are part of a family known as the pinnipeds. The earliest known example, Enaliarctos, recovered along the north Pacific coast, already had flippers. But the authors note in their report that the modern seal also has physical characteristics that match up with land meat-eaters such as bears in one group or skunks, badgers, weasels and otters in another.
They believe that Puijilawas semi-aquatic and a carnivore.
“The discovery suggests that the evolution of pinnipeds included a freshwater transitional phase, and may support the hypothesis that the Arctic was an early centre of pinniped evolution,” they write.
The theory holds that the Puijilahunted on land but also swam about in the temperate lakes during the summer, though it may have had to travel further when these froze over during the winter. They probably made for the nearby coast to hunt for fish to sustain them during the winter.This, over time, could have caused a gradual transition from fresh water to salt water for the evolving pinnipeds, ultimately leading to the flipper adaptation, the authors maintain.
The finding fills in a gap in the family tree and provides useful evidence in arguing for this slow evolutionary modification, which changed the web-footed land animal into a wholly aquatic carnivore.
The creature was the first meat-eating carnivore found at the site, but it yielded up other interesting findings from the early Miocene epoch.
These included two families of freshwater fishes, one bird and four other mammalian groups, including shrews, rabbits, rhinoceroses and “artiodactyl”, small short-legged plant-eaters who were the early ancestors of modern giraffes and deer.
Puijila darwinitakes its name from Charles Darwin, appropriately so given this prescient observation, quoted by the authors from his On the Origin of Species by the Means of Natural Selection: "A strictly terrestrial animal, by occasionally hunting for food in shallow water, then in streams or lakes, might at last be converted in an animal so thoroughly aquatic as to brace the open ocean."