Callomon J.H., Donovan S.K., Van den Hoek Ostende L.W. (2009) Zenostephanus, a new name for the genus Xenostephanus Arkell & Callomon, 1963 (Mollusca, Cephalopoda), preoccupied by Xenostephanus Simpson, Minoprio and Patterson, 1962 (Mammalia) // Palaeontology. Vol. 52. Part 3. P.671–672.
Arkell and Callomon (1963, pp. 226, 232) described a new subgenus of perisphinctid ammonite, Aulacostephanus (Xenostephanus), from the Jurassic (Lower Kimmeridgian, Mutabilis Zone) of Lincolnshire, eastern England (drift) and of Scotland (in situ). The type species is A. (X.) ranbyensis; the holotype is from Ranby, Lincolnshire. However, the name Xenostephanus had already been used in only the previous year for a new genus of toxodont notoungulate from Mendoza Province, western central Argentina. The type species of this genus, which was tentatively included in the Oldfieldthomasiidae, is Xenostephanus chiottii Simpson et al., 1962, from the mid Cenozoic. Authors therefore propose the name Zenostephanus nom. nov. as a replacement for Xenostephanus Arkell and Callomon, 1963, not Simpson et al., 1962. The new name attempts to preserve the sense of the original by a minor modification of the spelling. The type species of Zenostephanus is Aulacostephanus (Xenostephanus) ranbyensis Arkell and Callomon, 1963, by original designation.