Copytus Skogsberg, 1939

Coimbra, João Carlos, Bergue, Cristianini Trescastro & Ramos, Maria Inês Feijó, 2020, Is Copytus Skogsberg, 1939 (Crustacea: Ostracoda) a neocytherideid? With description of a new family and two new species, Zootaxa 4729 (2), pp. 177-194 : 179-181

Copytus Skogsberg, 1939 vs. Neocopytus Külköylüoðlu, Colin & Kiliç, 2007

In the ‘Introduction’ of their publication, Külköylüoðlu et al. (2007, p. 980) assert that Neocopytus was described as a new genus based on morphological differences of both carapace and soft parts with other three Neocytherideidae genera. On page 986 of the same work the authors declare that the comparison of Neocopytus to other neocytherideids was based only on the original description of Copytus caligula Skogsberg, 1939 , and those presented by

Athersuch (1982) for Neocytherideis subulata (Brady) and Sahnicythere retroflexa (Klie) . However, in their Table 1 , the authors added another source, Athersuch et al. (1989). Neocopytus and Copytus were considered the morphologically closer genera (see Fig. 7 of Külköylüoðlu et al. 2007).

Neocopytus was distinguished from Copytus mostly by a few differences in the soft parts anatomy, especially in details of the hemipenis distal processes of C. caligula Skogsberg and Neocopytus cylindricus (Brady) , the last one being the type-species of Neocopytus that was partially redescribed by Külköylüoðlu et al. (2007, p. 993). According to Table 1 (p. 989) and a discussion of the hemipenis of neocytherideids by Külköylüoðlu et al. (2007), it is dorsally rounded in all genera of the family Neocytherideidae , but in C. caligula the hemipenis ends with a boot-like process antero-proximally, whereas it ends with a gun-like process in N. cylindricus . Other differences in the soft parts between this two species are mainly related to proportions and number of setae of the appendages. However, it is noteworthy that, as already previously discussed, Athersuch et al. (1989) considered only the carapace morphology for the separation of the genera of Neocytherideidae .

Regarding to the hard parts, the alleged dissimilarity in the hinge morphology and in the central muscle scars pattern between Copytus and Neocopytus , is neither shown in the figures nor in Table 1 of Külköylüoðlu et al. (2007). The hinge in both genera is conspicuously adont, while the central muscle scars of Neocopytus are referred as “similar to Copytus ” ( Table 1 , p. 989). Externally, they considered Neocopytus more similar to Neocytherideis than Copytus “by the presence of thin, subparallel anterior marginal ribs and an acuminate anteroventral outline, Copytus being entirely smooth and having a more regularly rounded anterior margin” (p. 986).

Külköylüoðlu et al. (2007, p. 983) assigned nine other species to Neocopytus : Copytus novaezealandiae (Brady) , Copytus aff. rara McKenzie (in: Hartmann 1978), Copytus cf. rara McKenzie (in: Jain 1978, Gopalakrishna et al. 2007), Neocytherideis boomeri Dingle , Neocytherideis cf. cylindrica (Brady) (in: Jellinek 1993), and the South Atlantic species Copytus sp. 1, Copytus sp. 2 and Neocytherideis impudicus [ impudica ] Whatley, Moguilevsky, Chadwick, Toy & Ramos 1998, registered by Machado et al. (2005) off Cabo Frio town (Rio de Janeiro State, Brazil) as isolated valves, being N. impudicus originally described for Argentinian waters. It is noteworthy that none of the species mentioned above has the appendices described. Therefore, the species attributed by Külköylüoðlu et al. (2007) to the new genus Neocopytus were based exclusively on carapace morphology, i.e. the features of the appendices in fact are non-diagnostic.

It is surprising that Külköylüoðlu et al. (2007) reallocated Copytus novaezealandiae , Neocytherideis impudicus [ impudica ] and Neocytherideis boomeri in the new genus Neocopytus . As stated on p. 991, they agreed with Athersuch (1982) who described the central muscle scars of Neocytherideis as follows: “oblique row of four adductor muscle scars separated from kidney- or heart-shaped frontal scar by conspicuous fulcral notch”. Moreover, on the same page (see also Table 1 ) Külköylüoðlu et al. (2007) wrote the following: “In Neocopytus , the hinge is weakly lophodont, but it is more robust in Neocytherideis ; adont in Copytus ”. Besides other features of Neocytherideis , these two key characteristics are present in the first two species mentioned above. Thus, N. impudica is herein maintained in the original genus, while C. novaezealandiae is reallocated to Neocytherideis . Although Swanson (1969, 1979 a,b), Eagar (1971) and Külköylüoðlu et al. (2007) considered Copytus rara a junior synonym of C. novaezealandiae , they have different sizes and outlines, C. rara being larger and protruded anteroventrally. In turn, N. boomeri is a junior synonym of Copytus fusiformis ( Yassini, 1979) . (See also chapter ‘A critical synthesis of the study on Copytus Skogsberg, 1939 and its type species’).

Neocopytus cylindrica ( Brady, 1868) , the type-species of Neocopytus , shows most features as Neocytherideis . Although Külköylüoðlu et al. (2007, p. 989, Tab. 1 ) stated that the central muscle scars of Neocopytus are “similar to Copytus ”, they illustrated an oblique row of four adductor scars for the type-species of Neocopytus (their Fig. 3c), i.e. central muscle scars typical of Neocytherideis . On page 994, they present Copytus fusiformis ( Yassini, 1979) as a junior synonym of Neocopytus cylindrica ( Brady, 1868) . However, according to Witte (1993, p. 40) in C. fusiformis “the scars are clustered forming a small round group, such as reported by Skogsberg (1939) for the genus Copytus .”

Concerning the external morphology of the carapace, different from what was reported by Külköylüoðlu et al. (2007, p. 986), not all Copytus species present both ends rounded and a smooth surface. In some species, such as the two described below, the anterior end is protruded in the ventral half and the surface is faintly ornamented by striae and/or ribs.

Although the soft parts morphology is important for distinguishing genera in some families, this is not a rule in the classification of ostracods. Moreover, there is not a single case in podocopid taxonomy where a genus is diagnosed exclusively on soft parts anatomy. This subject has already been discussed at different levels by many authors, but here we especially remember Benson (1977, p. 26): “The value of carapace characters or the value of soft part characters is not predetermined as sacrosanct in the classification of ostracodes. It is only by attempting to group ostracode genera and species by their evolutionary history of phyletic proximity relative to their distribution can we approach a realistic ordering diversity. I say ‘attempt’ because no classification is more than a postulated relationship.”

Therefore, we conclude that the new genus proposed by Külköylüoðlu et al. (2007) is invalid since the authors included in their new genus both Copytus and Neocytherideis species.