[2] It can be distinguished from other elasmosaurids by the following characteristics: there is a long distance between the eye sockets and nostrils; the interclavicles and clavicles are fused, and the anterior edge is bent; the humerus is relatively long; and the femora are slim and show prominent muscle scars.

The type specimen of Futabasaurus was found in the Irimazawa Member of the Tamayama Formation, in the Futaba Group of Fukushima Prefecture, Japan.

[1] Many of the bones of the type specimen show signs of apparent scavenging or predation by sharks,[1] specifically Cretalamna.

[1] The name "Futabasaurus" has also been used for an unrelated theropod dinosaur, from the Late Cretaceous Ashizawa Formation of Japan.

[4] The following cladogram shows the placement of Futabasaurus within Elasmosauridae following an analysis by Rodrigo A. Otero, 2016:[5] Eromangasaurus carinognathus Callawayasaurus colombiensis Libonectes morgani Tuarangisaurus keyesi Thalassomedon haningtoni CM Zfr 115 Hydrotherosaurus alexandrae Futabasaurus suzukii Kaiwhekea katiki Alexandronectes zealandiensis Morturneria seymourensis Aristonectes parvidens Aristonectes quiriquinensis Terminonatator pointeixensis Elasmosaurus platyurus Albertonectes vanderveldei Styxosaurus sp.