Marine reptiles from Svalbard
Plesiosaurs and ichthyosaurs are two groups of marine reptiles that inhabited the Earth's oceans in the Mesozoic - the plesiosaurs being most diverse in the Jurassic and Early Cretaceous, while the ichthyosaurs dominated the Triassic and diminished throughout the Jurassic and Cretaceous. Like today's whales and seals, plesiosaurs and ichthyosaurs descended from land-living animals that adapted to a life in water. The evolutionary path to this life is reflected in the anatomy of the body. Both groups had four flippers of which, in plesiosaurs, all four were used for locomotion, whereas in the dolphin-like ichthyosaurs the hind flippers were reduced and a fish-like tail propelled the animal forward, while the fore flippers were used for steering.
Pliosaur hunting ichthyosaurs.
On Svalbard the first remains of these animals are of Triassic ichthyosaurs found over a century ago. The first Jurassic fossil - a plesiosaur - was found in 1913 on Spitsbergen near the mountain Janusfjellet. In 1931 the postcranial remains of another plesiosaur was found by an American group of medical doctors studying the spread of the common cold in Longyearbyen. This material was later described and named Tricleidus svalbardensis.
With the exception of one isolated plesiosaur limb, no new material from Jurassic rocks were recorded until 2001 when an excursion of Norwegian scientists and students came across the remains of a marine reptile weathering out of the black shale in the Slottsmøya Member of the Agardhfjellet Formation (Tithonian, Upper Jurassic). The find was reported to Dr. Jørn Harald Hurum at the Natural History Museum in Oslo , who in 2004 led a team into the field to collect the specimen, which turned out to be a partial plesiosaur skeleton. While in the field, Dr. Hurum's team found an astounding nine additional occurrences including a large complete ichthyosaur skull (which was also collected and is being prepared).
Since then, the Svalbard expedition group has been mapping and excavating marine reptiles for eight summers, and more than 40 specimens have been collected. The research on these animals is ongoing, and several new spcecies of plesiosaurs and ichthyosaurs have been described, along with their ecosystem. An international research group led by Dr. Jørn H. Hurum and Dr. Hans Arne Nakrem from the Natural History Museum, Oslo, scientifically published their findings October 12 2012 in a special volume of the Norwegian Journal of Geology.
In 2014 the expedition continued, and the group went to Isfjorden on Svalbard to map older marine reptiles, from the Triassic. Many ichthyosaurs from this time period on Svalbard are well known from before, however are there many remaining questions linked to their early evolution and their environment, as well as the early radiation of the plesiosaurs. The 2014 expedition was a huge success, and is the foundation for excavations and research in many years to come.
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Hurum, Druckenmiller & Knutsen demonstrating the powerful wind at Knorringfjellet, 2008
May-Liss Knudsen preparing the ichthyosaur skull, Natural History Museum, Oslo