Utatsusaurus hataii is the earliest-known ichthyopterygian which lived in the Early Triassic period (c. 245–250 million years ago).

[4] The fossils have been found from the Early Triassic Osawa Formation of Miyagi Prefecture, Japan and British Columbia, Canada.

[6][7] Utatsusaurus was a relatively small ichthyopterygian, measuring 2.5–3 m (8.2–9.8 ft) long and weighing 57.8 kg (127 lb).

They have longitudinal grooves and were first thought to be longer and more acute than Grippia, which is a closely related ichthyosaur.

First, the attachment of the pelvic girdle to the vertebral column was probably not robust enough to support the body on land unlike terrestrial amniotes.

They also used phylogenetic analyses and concluded that ichthyosaurs were a member of the Diapsida and the sister group of the Sauria.Additionally, in 2013, Cuthbertson and colleagues from the University of Calgary, Canada, using phylogenetic analyses, reported that Ichthyopterygia is a monophyletic group and Utatsusaurus and Parvinatator are a basal clade.

A museum (called Gyoryū-kan (魚竜館), literally translating as "a house of fish-dragons") was built to keep and display those fossils, and over sixty thousand people had visited there a year.