Shaochilong (meaning “shark toothed dragon”) is a genus of carcharodontosaurid dinosaur from the mid Cretaceous (Turonian stage) Ulansuhai Formation of China (about 92 million years ago). The type species, S. maortuensis, was originally named Chilantaisaurus maortuensis, but was re-described and reclassified in 2009.
Phylogenetic analysis performed by Brusatte and coworkers indicate that Shaochilong is deeply nested within the carchorodontosaurids, the most derived group among the allosauroids. Shaochilong appears to be more closely related to the Gondwanan carcharodontosaurids (Tyrannotitan, Carcharodontosaurus, Mapusaurus, Giganotosaurus) than the Laurasian ones (such as Neovenator and Acrocanthosaurus). Shaochilong is the youngest known Laurasian allosauroid suggesting that basal tetanurans not tyrannosaurids, were still the dominant group of large-bodied theropods in Laurasian during the Mid-Cretaceous and that the rise of tyrannosaurids as the dominant group of large terrestrial predators was sudden and confined to the very end of the Cretaceous.
The fragmentary nature of Shaochilong resulted in it being included into the Chilantaisaurus genus, a theropod dinosaur also from the Ulansuhai Formation. However while fragmentary, the fossil remains for C. maortuensis were much larger that the estimated length of two and a half meters for other Chilantaisaurus material. Questions were first raised about its validity in 2001, thirty seven years after the initial description which placed the material within the Chilantaisaurus genus. In 2009 Brusatte et al. confirmed that the material was actually of a carcharodontosaurid dinosaur, a very significant discovery in itself as this was the first theropod of its kind known from Asia.
The material was renamed Shaochilong which translates to English as ‘shark toothed dragon’, a reference to the shape of its teeth (the carcharodontisaurid group is so named after the Carcharodon shark genus which include the great white shark) combined with ‘long’, a term that is increasingly used refer to dinosaurs from Asia just as the ancient Greek ‘saurus’ is used to describe dinosaurs in the Western World. The species name S. maortuensis is derived from the original classification of the Shaochilong material Chilantaisaurus, something which is standard procedure when splitting a species from an established genus into its own new genus.
Even though Shaochilong and Chilantaisaurus are now in their own separate genera, they are still related to one another, kind of like distant cousins. Their presence in the same fossil Formation also indicates that they were probably active at the same time and location as one another.