Cetiosaurus humerocristatus was named by Lydekker (1888). Its type specimen is BMNH R44635, a limb element (left humerus), and it is a 3D body fossil. Its type locality is Smallmouth Sands (BMNH), which is in a Kimmeridgian marine claystone in the Kimmeridge Clay Formation of the United Kingdom.

It was synonymized subjectively with Ornithopsis leedsii by Mansel-Pleydell (1888); it was recombined as Ornithopsis humerocristatus by Lydekker (1888), Lydekker (1888), Woodward and Sherborn (1890), Delair (1960) and Brokenshire and Clarke (1994); it was recombined as Pelorosaurus humerocristatus by Lydekker (1890), Lydekker (1893), Sauvage (1895), Sauvage (1897), Sauvage (1898), Sauvage (1900), Sauvage (1902), Sauvage (1914), Huene (1927), Lapparent (1967), Steel (1970) and Delair (1993); it was synonymized subjectively with Ornithopsis leedsi by Mansel-Pleydell (1902); it was misspelled as Ceteosaurus humerocristatus by Lydekker (1904); it was considered a nomen dubium by Blows (1995); it was recombined as Duriatitan humerocristatus by Barrett et al. (2010).