IS IT a shark with legs? No, it鈥檚 a new species of dinosaur with a mysterious fin.
Concavenator corcovatus, which belonged to the theropod group of dinosaurs, has a pair of vertebrae five times longer than the others, which protrude midway along its back to make a triangular fin. 鈥淲e鈥檝e no idea what it is for,鈥� says Francisco Ortega of the National University of Distance Education in Madrid and head of the team that found the skeleton in Las Hoyas, Spain (Nature, ).
鈥淭he back fin is just plain weird,鈥� says at the University of Cambridge. Some later species of theropod had head crests and sails on their backs, he adds, which may have been used for signalling or display. Ortega suspects the bones supported a hump that stored energy as fat.
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Equally intriguing, the dinosaur may have had bird-like feathers. Its forearm bones have knob-like recesses that could have held feather quills. This pushes back the emergence of theropods with bird-like feathers by some 50 million years. 鈥淭his is hugely significant as it鈥檚 the first good evidence for feather-like structures in a primitive theropod lineage,鈥� says Benson.
