The Brachyura (Crustacea: Decapoda) described by Sidney Irving Smith: checklist, dates of publication and bibliography, with a discussion on Xantho stimpsoni A. Milne-Edwards, 1879, and X. stimpsonii Smith, 1869 Author Low, Martyn E. Y. Author Ng, Peter K. L. text Zootaxa 2012 3359 43 54 journal article 10.5281/zenodo.281631 22cee26c-9001-4d1e-8145-263e8f928860 1175-5326 281631 Xantho stimpsonii Smith, 1869 , an overlooked objective synonym of Xantho stimpsoni A. Milne- Edwards, 1879, and Xantho multidentatus Lockington, 1877 : reversal of precedence Smith (1869a: 275) , in a footnote to his discussion on Xantho denticulata White, 1848 , wrote: “Stimpson, being apparently unaware of White’s species, has described (Annals Lyc. Nat. Hist., N. Y ., vol. VII, p. 207, 1860) an allied species from Cape St. Lucas, as Xantho denticulata , which I will here designate as Xantho stimpsonii ”. No material of this species was described or figured by Smith (1869a) . The only subsequent publication using the name Xantho stimpsonii Smith, 1869 , is Miers (1886: 125) who listed “ Xantho stimpsonii , Smith = Xantho multidentatus , Lockington ”. A decade later, A. Milne-Edwards (1879: 252, footnote) proposed the name Xantho stimpsoni for “ Xantho denticulata (non White), Stimpson, Notes on North American Crustacea, p. 79 ( Annals of the Lyceum of Natural History of New York , 1860)” stating “Stimpson, pour désigner ce Xanthe, s’est servi du nom de Xantho denticulata , déjà employé White pour l’espèce précédente; par conséquent, cette dénomination ne peut être conservée et je proposerai d’appeler cette espèce Xantho stimpsoni , pour rappeler le nom du naturaliste qui, le premier, l’a fait connaitre”. It is clear that both Smith (1869: 275) and A. Milne-Edwards (1879: 252) were replacing the preoccupied name Xantho denticulata Stimpson, 1860 . The apparent discrepancy in the references to the original description of Xantho denticulata Stimpson, 1860 , by Smith (1869a: 275) who cited page 207, and A. Milne-Edwards (1879: 252) who cited page 79, can be easily explained by the former citing the page number of Stimpson’s (1860) paper as published in the Annals of the Lyceum of Natural History of New York , while the latter was citing the page number from the separate of the same paper (see Manning & Holthuis 1981 : 377; Rathbun 1930 : 315). Article 72.7 (ICZN 1999: 78) states that “[i]f an author proposes a new species-group name expressly as a replacement (a nomen novum ) for an earlier available one, then the two names are objective synonyms; both the nominal taxa they denote have the same name-bearing type despite any simultaneous restriction or application of the new replacement name ( nomen novum ) to particular specimens or any contrary designation of type , or any different taxonomic usage of the new replacement name”. Xantho stimpsonii Smith, 1869 , is thus a senior objective synonym of Xantho stimpsoni A. Milne-Edwards, 1879 . As such, the topotypic specimen described and figured by A. Milne-Edwards (1879: 252, 253, pl. 46, fig. 2, 2b) has no name-bearing value. The simultaneous type (s) of Xantho denticulata Stimpson, 1860 , Xantho stimpsonii Smith, 1869 , and Xantho stimpsoni A. Milne-Edwards, 1879 , is thus the unspecified number of specimens on which Stimpson (1860: 207) based his description, some of which are known to be extant (see Evans 1967 : 407). Xantho multidentatus Lockington, 1877 , was listed as a synonym of Xantho stimpsoni A. Milne-Edwards, 1879 (by Rathbun 1910 : 168, 1930: 315), and of Xantho stimpsonii Smith, 1869 (by Miers 1886 : 125). It should be noted that Rathbun (1930: 315) stated that the name Xantho multidentatus Lockington, 1877 , was a nomen nudum , citing Lockington (1877b: 99) . We agree. The name Xantho multidentatus was accompanied by a description in another publication by Lockington (1877a: 42) and the name is available from this work. All subsequent authors have followed the opinion of Rathbun (1910 : 168, 1930: 315) in regarding the names Xantho stimpsoni A. Milne- Edwards, 1879, and Xantho multidentatus Lockington, 1877 , as synonyms, with the former being used as the valid name (e.g., Hendrickx 1995: 150, Ng et al . 2008: 205). The name Xantho multidentatus Lockington, 1877 , has not been used as a valid name since its description. The descriptions of Xantho multidentatus Lockington, 1877 , agree very well with those of Xantho denticulata Stimpson, 1860 , and Xantho stimpsoni A. Milne-Edwards, 1879 ; and as such, we follow Rathbun’s (1910: 168, 1930: 315) conclusion that Xantho multidentatus Lockington, 1877 , is a senior subjective synonym of Xantho stimpsoni A. Milne-Edwards, 1879 . Xantho stimpsoni A. Milne-Edwards, 1879 , was transferred to the genus Xanthodius Stimpson, 1859 , by Rathbun (1930: 315) and the name Xanthodius stimpsoni (A. Milne-Edwards, 1879) , is in relatively widespread and current usage (see Appendix 2). The placement of Xantho stimpsonii A. Milne-Edwards, 1879 , in Xanthodius Stimpson, 1859 , was questioned by Guinot (1968a: 712) who indicated that Xantho denticulatus White, 1848 , and Xantho stimpsoni A. Milne-Edwards, 1879 , were atypical members of Xanthodius Stimpson, 1859 , and may not belong there (see also Ng et al . 2008). Recently, Reuschel & Schubart (2006) provided molecular evidence to suggest Xanthodius Stimpson, 1859 , was polyphyletic, with the type species, Xanthodius sternberghii Stimpson, 1859 , and Xanthodius inaequalis ( Olivier, 1791 ) , coming out in a separate clade from Xanthodius denticulatus (White, 1848) . Števčiċ (2005: 134) subsequently established the genus-group Olivioxantho for Xantho denticulatus White, 1848 , but as noted by Ng et al . (2008: 205), Olivioxantho Števčiċ, 2005 , is a nomen nudum . Števčiċ (2011: 138) recently resolved this by designating Xantho stimpsoni A. Milne-Edwards, 1879 , as the type species of the new genus Williamstimpsonia . Conceptually, Williamstimpsonia Števčiċ, 2011 , and the nomen nudum Olivioxantho Števčiċ, 2005 , are identical, although they have different type species. Although Števčiċ (2011: 138) did not discuss the composition of the genus Williamstimpsonia , or elaborate on why he decided not to validate the name Olivioxantho , or explain the reasons for his choice of type species, we recognise this separate genus for Xantho denticulatus White, 1848 , and Xantho stimpsoni A. Milne-Edwards, 1879 , on the arguments presented in Guinot (1968a) and Reuschel & Schubart (2006) . As discussed, the prevailing usage of the name Xantho stimpsoni A. Milne-Edwards, 1879 (now Williamstimpsonia stimpsoni ) is threatened by the senior objective synonym Xantho stimpsonii Smith, 1869 , and senior subjective synonym Xantho multidentatus Lockington, 1877 , since the Principle of Priority (Article 23 of the Code) requires that the oldest available name for a taxon must be used. However, the Principle of Priority is mediated by Article 23.9.1 of the Code that allows for a reversal of precedence of a junior synonym when the senior synonym has not been used as a valid name after 1899 (Article 23.9.1.1) and the junior synonym “has been used for a particular taxon, as its presumed valid name, in at least 25 works, published by at least 10 authors in the immediately preceding 50 years and encompassing a span of not less than 10 years” (Article 23.9.1.2). Xantho stimpsonii Smith, 1869 , and Xantho multidentatus Lockington, 1877 , have not been used as valid names since 1899, thus fulfilling Article 23.9.1.1. In Appendix 2, we list 25 publications written by 35 different authors in the past 45 years that have used the name Xantho stimpsoni A. Milne-Edwards, 1879 , thereby fulfilling Article 23.9.1.2. As both requirements of Article 23.9.1 are met, and in accordance with Article 23.9.2 of the Code, Xantho stimpsoni A. Milne-Edwards, 1879 , is here regarded as a valid name and takes precedence over Xantho stimpsonii Smith, 1869 , and Xantho multidentatus Lockington, 1877 , whenever the three names are regarded as synonymous. Xantho stimpsoni A. Milne-Edwards, 1879 , now becomes a nomen protectum , and Xantho stimpsonii Smith, 1869 , and Xantho multidentatus Lockington, 1877 , nomina oblita .