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15 June 2011, 08:58
A new species of dinosaur has been discovered by two University of Portsmouth palaeontologists - it could be the world's smallest.
The tiny dinosaur, nicknamed the Ashdown Maniraptoran, was identified by Dr Darren Naish and Dr Steve Sweetman and was found in one of the pits at Ashdown Brickworks, north-west of Bexhill in East Sussex.
The new specimen is a bird-like carnivorous or omnivorous dinosaur. The palaeontologists estimate that the Ashdown maniraptoran was between 33 and 40cm in total length, making it one of the smallest dinosaurs yet reported from the Mesozoic era, which began approximately 250 million years ago.
The dinosaur has been identified from only a single neck vertebra, which contains enough information to show it was part of the large group that included all of the two-legged, meat-eating dinosaurs called theropods.
The palaeontologists found the new dinosaur has clear similarities with maniraptorans, the group of theropods that includes birds and other bird-like, feathered theropods, making it likely to belong to this group.
Dr Steve Sweetman said: "This is such an exciting find as it represents the smallest dinosaur we have yet discovered in the European fossil record. Originally it was identified as the vertebra of a snake but once I saw it I knew straight away it was far more likely to be the vertebra of a tiny theropod. My colleague Darren is a theropod expert so I borrowed the specimen, showed it to him, and we concluded that it was in fact a tiny adult theropod dinosaur."
The pair were able to confirm that the remains are definitely from a fully grown dinosaur because the main body of the neck vertebra is fully fused to the arch-shaped part of the vertebra that sits on top, meaning that it was skeletally mature. The whole vertebra has a total length of just 7.1mm.
Dr Naish said: "Determining the total length of the specimen from just a single bone is highly speculative but we used two techniques to provide a rough estimate of size."
The first method involved duplicating digital versions of the vertebra to make a complete neck. The digital vertebrae were modified because vertebrae within a neck are not all the same length. The neck was then positioned within the silhouette of a maniraptoran. This technique suggested a total length for the Ashdown maniraptoran of about 45 cm, similar in size to a jay or magpie.
Dr Naish said: "This method is more art than science because it relies on the assumption that the silhouette is correct to begin with but it gives us a reasonable idea of roughly what length the specimen could have been."
The second method also involved using the reconstructed digital neck, but this time data from neck length in other maniraptorans was used to calculate a possible total length for the animal. This technique suggested a total length for the Ashdown maniraptoran of somewhere between 33 and 50 cm, with the lower estimate being most likely.
The tiny dinosaur was discovered by local fossil collector Dave Brockhurst, who works at the Brickworks. The dinosaur-bearing rocks at the site have yielded lots of other fossils including the remains of salamanders, frogs, lizards, turtles, crocodiles, and various kinds of large dinosaur.