What is "futabasaurus"

Futabasaurus is a genus of plesiosaur from the Late Cretaceous of Fukushima, Japan. Described and named in 2006, it was assigned to the family Elasmosauridae.

"Futabasaurus" is an informal name for a genus of theropod dinosaur from the Late Cretaceous of Japan, known only from a partial shin bone discovered in the Coniacian-age Ashizawa Formation of the Futaba Group. It was coined by David Lambert in 1990 as a conversion from the Japanese nickname "Futaba-ryu", for an undescribed theropod. Dong Zhiming and coauthors briefly discussed the fossil shin bone it was based on that same year, publishing a photograph. They considered the bone to belong to an indeterminate tyrannosaurid. If the specimen is eventually described and named, it will require a different name, because the name Futabasaurus has since been used for a genus of plesiosaur.