Invalidity of the proposed neotype for Sousa chinensis by Porter (2002)
Article 75 of the International Code of Zoological Nomenclature(ICZN 1999) comprises the rules and conditions governingneotype designation. Article 75.2 states that, “A neotype is not to be designated as an end in itself, or as a matter of curatorial routine, and any such neotype designation is invalid”. The reasons for neotype designation appear to have been misinterpreted by Porter (2002).There is no debate that taxonomic confusion has existed within Sousafor decades or even centuries (Jefferson & Rosenbaum 2014). However, the taxonomic issues are not due to confusion with defining the nominal taxon (Sousa chinensis) or its type locality, both of which are not contentious.There was also no taxonomic controversythat required a neotypeof Sousa chinensisto resolve – this is evidenced by the near absence of the reference to the neotypein recent taxonomic studies on Sousa,including papers co-authored by Porter (see Jefferson & Van Waerebeek 2004; Frère et al. 2008, 2011; H. Chen et al. 2008; Wang et al. 2008a; L. Chen et al. 2010; Lin et al.2010, 2012; Mendez et al. 2013; Jefferson & Rosenbaum 2014). Moreover, some authors specifically recommended against comparisons to this specimen because of the unreliable information presented (see Jefferson & Van Waerebeek 2004;Jefferson & Rosenbaum 2014). In contrast, the description by Flower (1870) hascontinued toserve as a very useful reference for the species.
Article 75.3 states that “A neotype is validly designated when there is an exceptional need” and when seven qualifying conditions are met. As shown above, there was no “exceptional need” for a neotype. Three of the qualifying conditions were also not satisfied: 75.3.1 (the purpose of designating a neotype was to clarify the taxonomic status or the type locality of the nominal taxon), 75.3.2 (describing the characters that differentiate the nominal taxon from other taxa) and 75.3.5 (demonstrating theneotype is consistent with the previous name-bearing type of the original description and other sources). As shown above, there was no issue with the type locality or status of the nominal taxon. A statement of characters that differentiated Sousa chinensis from other taxa was not presented by Porter (2002), who only made comparisons with the specimen of Flower (1870) and eight others collected from the waters in or near the type localityeven thoughsubstantial data exist for specimens outside the region. Lastly, the proposed neotypewas not consistent with what is known of the species (see below). Although a neotype can be an individual of a different life stage “if necessary or desirable to secure stability of nomenclature” [Art. 75.3.5], this was not the case for the proposed neotype,because this immature specimen (and with its description being very different from all known specimens of the species) added more confusionunnecessarily.Thus, the designation of the neotype by Porter (2002) can only be viewed as a curatorial exercise (thatwas also poorly executed) and as such, the proposed neotypeis invalid.
Other issues with the information in Porter (2002)
Porter’schoiceof an immature specimen was baffling because with the “many strandings of Sousa chinensis in Hong Kong waters”and a strong bias towards very young and old individuals in the stranding records of Hong Kong (Jefferson et al. 2006),several adult specimens were available.Taxonomic studies of small cetaceans often exclude non-adult specimens because developmental issues can obscure or confound results.Due to its immaturity, the colouration of the proposed neotype was also inconsistent with the original “snow-white” and “milky white” descriptions of the species by Osbeck(1765) and Robert Swinhoe (in Flower 1870), respectively.
The description of the postcranial skeleton ofthe proposed neotype was internallyinconsistent and inconsistent with the data in Flower (1870) as well as allpublished data on specimens from mainland Chinese waters(see table below). The obviously ankylosedatlas and axis were also reported as being unfused and the unit was called the “atlas” while the bone labelled as the “axis” was actually an anterior thoracic vertebra. These (and other) glaring issues contradict Porter’s claim that the proposed neotype specimenwas not “significantly different” from Flower’s “holotype” and leave little confidence in the information presented.
Additional References
Jefferson TA, Hung SK,Lam PKS(2006)Strandings, mortality and morbidity of Indo-Pacific humpback dolphins in Hong Kong, with emphasis on the role of organochlorine contaminants. J Cetacean Res Manage 8:181–193
Reported vertebral and chevron counts of Indo-Pacific humpback dolphins. The different reported counts in the text, table2 and appendix of Porter (2002) are shown separately.
Porter (2002) / Other ChineseVertebrae / Text / Table 2 / Appendix / Flower (1870) / Specimens**
Cervical / 7 / 7 / 7 / 7 / 7
Thoracic / 12 / 12 / 12 / 12 / 12 or 13
Lumbar / 23 / 12 / 12 / 10 / 9-11
Caudal / 18 / 18 / 18 / 22 / 21-24
Total / 60 / 49 / 49 / 51 / 50-53
Chevrons / 8 / 8 / 7 / 14 / 12-14
**Data from Wang (1999), Zhou (2004), Jefferson Van Waerebeek (2004) and Jefferson Rosenbaum (2014).