Priority of the slipper lobster genus Crenarctus Holthuis, 2002, over Antipodarctus Holthuis, 2002 (Crustacea, Decapoda, Scyllaridae).

In revising the Indo-Pacific scyllarine lobsters, Holthuis (2002) proposed a new genus, Antipodarctus, for Scyllarus aoteanus Powell, 1949 (type locality: Great Barrier Island, New Zealand), and a new genus, Crenarctus, for two species, Scyllarus bicuspidatus De Man, 1905 (type species; type locality: Flores Sea, Indonesia) and S. crenatus (Whitelegge, 1900) (type locality: off Wata Mooli (= Wattamolla), New South Wales, Australia). According to Holthuis (2002), Antipodarctus is distinguished from Crenarctus only by the presence of an additional carina on the fourth antennal segment. Examination of the male holotype of A. aoteanus in 2009 (Auckland War Memorial Museum, registration number MA76171) revealed that the original diagnosis of Antipodarctus was incorrect — A. aoteanus does not have an additional carina on the fourth antennal segment and is indistinguishable from C. crenatus. Moreover, a recent molecular phylogenetic study of the slipper lobsters (Yang et al. 2012) showed that Antipodarctus and Crenarctus are indistinguishable and that A. aoteanus and C. crenatus are conspecific. Being conspecific, A. aoteanus and C. crenatus must also be congeneric and so both genera cannot be maintained. In the online appendix to their paper (Appendix A. Supplementary material, doi:10.1016/j.ympev.2011.09.019), Yang et al. (2012) assumed that the name Antipodarctus had priority over Crenarctus on the basis of page priority in Holthuis (2002) (p. 551 for Antipodarctus, p. 659 for Crenarctus) (see discussion in Nemésio 2007). According to Article 24.2.2 of the International Code of Zoological Nomenclature (ICZN 1999), however, priority of taxon names simultaneously published in the same paper is determined by the deliberate choice of the first reviser and not by order of appearance in the original publication. Additionally, the appendix of Yang et al. (2012) was only published as online supplementary information, rather than as part of the main printed article. In any case, the ‘action’ in the appendix would not be nomenclaturally valid because it was simply stating what the authors thought to be a Code requirement rather than being a deliberate First Reviser action (Article 24.2, ICZN 1999). The status of Antipodarctus and Crenarctus thus remains unresolved because no formal (Code-compliant) action has been taken to fix name priority. Selection of one genus over the other has consequences for nomenclatural stability. If Antipodarctus is selected over Crenarctus, new generic combinations for both species of Crenarctus would be required and Antipodarctus aoteanus would be replaced by a new combination, A. crenatus. Conversely, giving priority to Crenarctus over Antipodarctus would require fewer nomenclatural changes: the current combinations, C. bicuspidatus and C. crenatus would continue to be used unchanged, and the names Antipodarctus and A. aoteanus would simply fall from use. Priority of Crenarctus over Antipodarctus would also enable the original diagnosis and composition of Crenarctus to remain unchanged (since A. aoteanus is a junior synonym of C. crenatus) and the revised classification would remain more consistent with the taxonomy used in the main text of Yang et al. (2012) in which the Crenarctus, C. bicuspidatus and C. crenatus were used as valid names alongside Antipodarctus and A. aoteanus. Therefore, in the interests of nomenclatural stability, we herein take First Reviser action and select Crenarctus over Antipodarctus. The following taxonomic changes are made: