Platevindex Baker, 1938

Goulding, Tricia C., Bourke, Adam J., Comendador, Joseph, Khalil, Munawar, Quang, Ngo Xuan, Tan, Shau Hwai, Tan, Siong Kiat & Dayrat, Benoît, 2021, Systematic revision of Platevindex Baker, 1938 (Gastropoda: Euthyneura: Onchidiidae), European Journal of Taxonomy 737 (1), pp. 1-133 : 35-36

Genus Platevindex Baker, 1938

Type species

Onchidium coriaceum Semper, 1880 , by original designation ( Baker 1938: 88).

Diagnosis

Body dorso-ventrally flattened. Notum hard. No dorsal gills. Dorsal eyes present (in most species) or absent (only in two species). Dorsal eyes occur individually, never in groups. Eyes at the tip of short ocular tentacles. Foot narrow, approximately ¼ to ⅓ of total width. Pneumostome median, on ventral hyponotum. Intestinal loops of types I, II or III. Accessory penial gland absent. Male opening below two ocular tentacles, almost centered, but slightly to right side (in dorsal view). Rectal gland present. Penis composed of two regions: rigid proximal region and flexible distal region. Penial hooks in distal region present (in most species) or absent.

Gender

The gender is masculine (ICZN Article 30.1.1). The generic name Platevindex was formed from the family name of the German zoologist Dr. Ludwig H. Plate (1862–1937), professor at Jena, who described several onchidiid species. No gender was specified in Baker’s (1938) original publication of the generic name Platevindex . However, Baker (1938: 88) changed the ending of the specific name coriacea (combined with the generic name Oncis Plate, 1893 ) to coriaceus , indicating that he considered Platevindex to be of masculine gender. Also, the Latin word ‘ vindex ’, meaning ‘protector’ or ‘champion’, is masculine. As a result, the ending of all specific names transferred to Platevindex must become masculine (e.g., Onchidium luteum becomes Platevindex luteus ).

Distinctive diagnostic features

Platevindex slugs can easily be identified in the field by their dorso-ventrally flattened body, firm notum and very narrow foot (one third of the total width or less when the animal is not active). However, no combination of internal characters is unique to Platevindex . Slugs with a rectal gland and no accessory penial glands are also found in Melayonchis and Onchidina . Also, among Platevindex , Melayonchis and Onchidina slugs, intestinal loops of type I are found only in Platevindex , but intestinal loops of type II are found in all three genera and intestinal loops of type III are found in both Platevindex and Melayonchis . The lateral radular teeth of Platevindex are characterized by a slight protuberance on their inner lateral margin (e.g., see arrows on Figs 18B , 34C , 48C , 57C , 66C ). This kind of radular protuberance is unusual among onchidiids. Apart from in Platevindex , it has been observed only in Marmaronchis , in which the protuberance is also slight ( Dayrat et al. 2018), and in Melayonchis , where it is much more conspicuous and sharp ( Dayrat et al. 2019c).

Remarks

Several of the species that belong to Platevindex were classified in Plate’s genus Oncis . Baker (1938) established the generic name Platevindex as a replacement name for Oncis Plate, 1893 , which he treated as a junior homonym of Oncis Herrmannsen, 1847 . However, Oncis Herrmannsen, 1847 was a mere nomenclator entry (“ Oncis - vid. Onchis ”) which referred to Onchis Férussac, 1822 , an available generic name, and which Herrmannsen treated as a full entry. Because Oncis was not treated as the valid name of a taxon by Herrmannsen (1847), it is not an available name under ICZN Article 11.5.

Regardless of the nomenclatural status of Oncis Herrmannsen, 1847 , the generic name Oncis Plate, 1893 is not available because it is a junior objective synonym of Onchis Férussac, 1822 . Indeed, under ICZN Article 33.2.1, one reason for a change in the original spelling of a name to be interpreted as “demonstrably intentional” is “when two or more names in the same work are treated in a similar way.” In his revision of the onchidiids, Plate (1893) changed the original spelling of Onchidium to Oncidium , that of Onchidina to Oncidina , and that of Onchidella Gray, 1850 to Oncidiella . It is thus obvious that Plate (1893) considered that Oncis was a “demonstrably intentional” spelling change from Onchis . The generic name Oncis Plate, 1893 is thus an emendation of Onchis Férussac, 1822 , but it is an unjustified emendation because Plate’s (1893) correction was not made in accordance with Article 32.5. As an unjustified emendation, Oncis Plate, 1893 is a junior objective synonym of Onchis Férussac, 1822 and it enters in homonymy (Article 33.2.3). The fact that Plate (1893: 164) claimed that Oncis was a new generic name does not change the fact that, according to the Code, it is treated as an unjustified emendation of Onchis Férussac, 1822 . Interestingly, several authors already treated Oncis Plate, 1893 as a junior objective synonym of Onchis Férussac, 1822 . For instance, according to Woodward (1894: 57), Oncis Plate, 1893 is a “ nom. preocc. Onchis (i.e., Oncis ), Fér., = Peronia, Blainv. ”. Also, Woodward (1894: 57) designated Oncis coriacea as the type species of Oncis . Regardless, being a junior objective synonym of Onchis Férussac, 1822 , Oncis Plate, 1893 is objectively invalid. Oncis Plate, 1893 actually refers to the taxon of which the type species is Onchidium peronii Cuvier, 1804 (i.e., the type species of Onchis Férussac, 1822 ), and thus refers to the genus Peronia Fleming, 1822 , not Platevindex ( Dayrat et al. 2020) . As a result, the valid generic name for the genus revised here is Platevindex , which Baker (1938) rightly established as a new generic name to refer to the taxon erroneously named Oncis by Plate (1893), even though the justification provided by Baker was not completely appropriate. Finally, Baker (1938: 87) correctly pointed out that the generic name Semperella Labbé, 1934 was a junior homonym of Semperella Gray, 1868 (Porifera) . Baker (1938: 87) considered Semperella Labbé as a subjective synonym of Platevindex but provided no explanation; Semperella Labbé was later replaced by Semperoncis Starobogatov, 1976 , which refers to a genus of terrestrial onchidiids ( Dayrat 2009, 2010).

Distribution

Platevindex is broadly distributed in the Indo-West Pacific from the eastern coast of South Africa (~ 32° South) to New Ireland, Papua New Guinea and eastern Australia in the Pacific (~ 21° South). It has been documented up to 33° North in southern Japan ( Takagi et al. 2019). The known geographic range of each species is illustrated in Fig. 10 .

Figures

Fig. 18. Platevindex coriaceus (Semper, 1880), posterior reproductive system. A. Platevindex coriaceus coriaceus unit #2, Philippines, lectotype (ZMB/Moll 39028a). B. Platevindex coriaceus coriaceus unit #2, Bohol, Philippines [3356] (PNM 041240). C. Platevindex coriaceus coriaceus unit #1, Vietnam [5629] (ITBZC IM 00014). D. Platevindex coriaceus darwinensis Goulding & Dayrat subsp. nov., Northern Territory, Australia [1690] (NTM P.57606). Abbreviations: dd = deferent duct; fgm = female gland mass; hd = hermaphroditic duct; hg = hermaphroditic gland; ov = oviduct; rs = receptaculum seminis; sp = spermatheca. Scale bars = 2 mm.

Fig. 34. Platevindex luteus (Semper, 1880), reproductive system. A. Posterior reproductive system, Ambon, Indonesia [2837] (UMIZ 00089). B. Anterior, male copulatory apparatus (ZMB/Moll 39031a). C. Anterior, male copulatory apparatus, same as A. Abbreviations: dd = deferent duct; fgm = female gland mass; hd = hermaphroditic duct; hg = hermaphroditic gland; ov = oviduct; ps = penial sheath; rm = retractor muscle; rs = receptaculum seminis; sp = spermatheca; v = vestibule. Scale bars: A = 2 mm; B–C = 1 mm.

Fig. 48. Platevindex burnupi (Collinge, 1902) comb. nov., digestive system, dorsal view, intestinal loops of type II, with a transitional loop oriented at 7 o’clock. A. South Africa, lectotype (NHMUK 1905.4.12.33). B. Madagascar [3150] (MNHN-IM-2019-1398). Abbreviations: ddg = dorsal digestive gland; i = intestine; pdg = posterior digestive gland; rg = rectal gland; st = stomach. Scale bars = 2 mm.

Fig. 57.Platevindex martensi (Plate, 1893), penial hooks.A. Penis everted with hooks outside, Peninsular Malaysia, Penang [964] (USMMC 00029). B. Australia, Darwin [1711] (NTM P.57611). Scale bars: A = 50 μm; B = 30 μm.

Fig. 66. Platevindex amboinae (Plate, 1893), digestive system, dorsal view, intestinal loops of type III. A. Transitional loop oriented at 2 o’clock, Seram, Indonesia [2883] (UMIZ 00105). B. Transitional loop oriented at 6 o’clock, Sulawesi, Indonesia [#1] (SMF 333602). Abbreviations: ddg = dorsal digestive gland; i = intestine; pdg = posterior digestive gland; rg = rectal gland; st = stomach. Scale bars: A = 4 mm; B = 3 mm.

Fig. 10. Geographic distributions of species of Platevindex. Colored areas correspond to hypothetical ranges proposed based on all known records, and the colors are the same as those used for each species in the phylogenetic trees (Figs 1–5). Distinct colors are used for each subspecies and mitochondrial unit in P. coriaceus (Semper, 1880) as well as for each subspecies of P. burnupi (Collinge, 1902). Black dots show sites sampled for this study and red dots (China and Japan) show localities of previously published genetic sequences included in the phylogenetic analyses. A. Platevindex luteus (Semper, 1880), P. applanatus (Simroth, 1920), P. burnupi. B. Platevindex tigrinus (Stoliczka, 1869), P. coriaceus coriaceus (units #1, #2, and #3) and P. coriaceus darwinensis subsp. nov. C. Platevindex martensi (Plate, 1893), P. aptei Goulding & Dayrat sp. nov., P. amboinae (Plate, 1893) and P. latus (Plate, 1893).