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), Williston (1905), Delair (1960), Delair (1960), Macfadyen (1970), Brokenshire and Clarke (1994); it was synonymized subjectively with Ornithopsis leedsi by Zittel (1890), Mansel-Pleydell (1902); it was recombined as Pelorosaurus humerocristatus by Lydekker (1890), Lydekker (1893), Lydekker (1893), Sauvage (1895), Sauvage (1897), Sauvage (1898), Sauvage (1898), Van Den Broeck (1900), Sauvage (1900), Sauvage (1900), Sauvage (1902), Sauvage (1914), Huene (1927), Lapparent (1967), Steel (1970), Paton (1975), Cuny et al. (1991), Delair (1993); it was considered a nomen dubium by Blows (1995); it was recombined as Duriatitan humerocristatus by Barrett et al. (2010), Mocho et al. (2016), Torcida‑Fernández Baldor et al. (2020).