Thursday 16 August 2012

A giant Monitor Lizard from the Miocene of Samos, Greece.

Monitor Lizards, Varanidae, are carnivorous Lizards noted for their large size and aggressive behavior. While the majority of the group are not exceptionally large, the largest members are bigger than any other Lizards. The extant Komodo Dragon reaches 3 m in length, and the extinct Giant Australian Monitor is thought to have reached lengths of around 7 m. Among the Squamates (the group that includes Snakes and Lizards) only the Boas, Pythons and extinct Mosasaurs (a group of fully marine Reptiles that went extinct at the end of the Cretaceous) are larger, and among Lizards the only species that reach comparable sizes are the limbless Amphisbaena and Glass Snakes. More remarkably still, the Monitor Lizards appear to have repeatedly evolved large forms in places where they were in direct competition with carnivorous Mammals; the Boas and Pythons, in contrast, evolved large sizes before the evolution of large Mammals, and have simply remained large.

In a paper published in the journal PLoS One on 10 August 2012, Jack Conrad of the Anatomy Department at the New York College of Osteopathic Medicine, and the Department of Vertebrate Paleontology at the American Museum of Natural History and Ana Balcarcel and Carl Mehling, also of the Department of Vertebrate Paleontology at the American Museum of Natural History, describe a new species of Monitor Lizard from the Miocene of Samos, Greece.

The new specimen was collected by the famous palaeontologist Barnum Brown (discoverer of Tyrannosaurus rex, amongst other things) in the 1920s, and have lain undescribed in the collection of the American Museum of Natural History ever since. It was found in the Turolian (Late Miocene) Mytilini Formation of northern Samos, making it 6.9–7.6 million years old.

Map of Greece with Samos enlarged. Circle indicates the locality where the Monitor fossil was found. The star indicates Athens. Conrad et al. (2012).

The new species is placed in the extant Monitor Lizard genus Varanus, and given the specific name amnhophilis, meaning 'lover of lamb', in reference to the tendency of large monitors to take Mammalian prey. The remains from which it is reconstructed are extremely fragmentary, but it is thought that it would have been about 70 cm in length, making it the earliest known large member of the genus Varanus.

Reconstructions of Varanus amnhophilis, based upon the available material. (Top) Complete animal. (Bottom) Head. Conrad et al. (2012).

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