Dakosaurus

Dakosaurus is an extinct genus within the family Metriorhynchidae that lived during the Late Jurassic and Early Cretaceous. It was large, with teeth that were serrated and compressed lateromedially (flattened from side to side). The genus was established by Friedrich August von Quenstedt in 1856 for an isolated tooth named Geosaurus maximus by Plieninger. Dakosaurus was a carnivore that spent much, if not all, its life out at sea. The extent of its adaptation to a marine lifestyle means that it is most likely that it mated at sea, but since no eggs or nests have been discovered that have been referred to Dakosaurus, whether it gave birth to live young at sea like dolphins and ichthyosaurs or came ashore like turtles is not known. The name Dakosaurus means 'biter lizard', and is derived from the Greek dakos ('biter') and σαῦρος -sauros ('lizard'). When isolated Dakosaurus teeth were first discovered in Germany, they were mistaken for belonging to the theropod dinosaur Megalosaurus. In 1856 von Quenstedt made Plieninger's Geosaurus maximus teeth a new genus with the name Dakosaurus. He explained the etymology as Greek dakos 'Biss' in 1858 in German, adding 'denn wenige kommen seinem furchtbaren Gebiss gleich” . He gave the meaning of Greek dakos more correctly as 'Beisser' in another description in 1859 in which he classified Dakosaurus as a dinosaur. Fossil specimens referrable to Dakosaurus are known from Late Jurassic deposits from England, France, Switzerland, Germany, Poland, Russia, Argentina, and Mexico. Teeth referrable to Dakosaurus are known from Europe from the Oxfordian. The type species Dakosaurus maximus, meaning 'greatest biter lizard', is known from fossil discoveries in Western Europe (England, France, Switzerland and Germany) of the Late Jurassic (Late Kimmeridgian-Early Tithonian). Dakosaurus andiniensis, meaning 'biter lizard from the Andes', was first discovered in 1987 in the Neuquén Basin, a very rich fossil bed in the Vaca Muerta, Argentina. However, it was not until 1996 that the binomen Dakosaurus andiniensis was erected. Two recently discovered skulls have indicated that D. andiniensis is unique among the metriorhynchids (the family of stem-crocodilians most specialised for marine life) with its short, tall snout, which lent it the popular nickname 'Godzilla' in press reports about its description. This species has a fossil range from the late Jurassic to early Cretaceous (Late Tithonian-Early Berriasian). Dakosaurus nicaeensis, named in 1913 by Ambayrac, was mistakenly classified as a megalosaurid dinosaur; now it is assigned as the sole species in the genus Aggiosaurus. Buffetaut in 1982 demonstrated that it was in fact a metriorhynchid, closely related to, if not a member of Dakosaurus. As the type specimen is poorly preserved it is considered nomen dubium. In 2009, Young and Andrade published a re-description of Geosaurus, examining its relationships and the validity of species lumped into the genus. Incomplete skull specimens of Dakosaurus have been discovered in Kimmeridgian age rocks from Mexico. Dacosaurus is a misspelling of Dakosaurus, and thus a synonym.