The link lacks the origin of seals, sea lions and walruses

US and Canadian scientists have discovered the fossil skeleton of a new carnivore, Puijila darwini. New research shows that Puijila is the missing link in the evolution of a group of animals today, including seals, sea lions and walruses .

The analysis and support for the hypothesis that fins animals originating from the Arctic are published in the April 23 issue of the journal Nature.

Seals, sea lions and walruses all have flippers - the adaptation of chi to swim in the water. This adaptability evolves over time as some terrestrial animals turn to habitats selling water. However, so far, morphological evidence for the transition from right to water is still very limited.

Mary Dawson, curator of the Carnegie Museum of Natural History, said: 'Puijila's very well preserved skeleton has heavy limbs, showing that muscles are growing well, and flattened, flattened fingers and fingers meaning that they have fins, not flippers. This animal adapts to both swimming in the water and walking on land. When swimming, they rowed both the back and the front limbs. Puijila is an evolving proof that we lacked for a long time . '

Part of the Puijila darwini specimen was discovered in 2007 in sediments at a volcanic crater in the Devon region, Nunavut, Canada. The next visit in 2008 brought basicranium (skull), an important structure in determining the classification relationship.

Illustration of Puijila darwini swimming. (Photo: Mark A. Klingler / Carnegie Natural History Museum)

Ancient botanical fossils show this place in the Miocene era with a cool climate, like the climate of New Jersey now. Freshwater lakes freeze in the winter, so Puijila moves out of the mainland to the sea in search of food. There have been many theories about the transition from freshwater to saltwater in mammals that sell water. The first hypothesis is that of Charles Darwin, with his natural selection theory in the book Origin of Species. ' An animal that only lives on land, sometimes looking for food in shallow water, then in streams or lakes, can eventually transform into a completely underwater animal .'

Natalia Rybczynski, who directs the excavation, said: ' This finding shows that the finnage has undergone a' freshwater 'stage in evolution. We also have an overview of the appearance of the fins animals before they evolve into flippers . '

The described animal has a long tail, the forelimbs are quite commensurate with today's terrestrial predators. This is the first mammal predator found in this area. Other fossils found include two freshwater fish, one bird, and 4 mammal species: shrews, rabbits, rhinos, and a small scorpion.

The most well-known finnage, Enaliarctos, is found in North America's North Pacific coast. There have been hypotheses that the evolution of fins is centered around the Arctic, and the discovery of Pujjila reinforces this hypothesis.

The co-authors of the study include Natalia Rybczynski, a scientist from the Canadian Museum of Nature, Ottwa, Ontario; Mary R. Dawson, who is in charge of paleontology at the Carnegie Natural History Museum, Pittsburgh, Pennsylavania; and Richard H. Tedford, curator of paleontology at the American Museum of Natural History, New York.

Refer:
Natalia Rybczynski, Mary R. Dawson & Richard H. Tedford.A semi-aquatic Arctic mammalian from the Miocene epoch and origin of Pinnipedia.Nature, 2009;458 (7241): 1021 DOI: 10.1038 / nature07985