Cirolana madelinae ( Schädel, Hyžny & Haug, 2021 ) Bruce & Rodcharoen, 2023

Bruce, Niel L. & Rodcharoen, Eknarin, 2023, Electrolana Schädel, Hyžný & Haug, 2021 (Crustacea: Isopoda: Cirolanidae), a Junior Synonym of Cirolana Leach, 1818 and a New Species of Metacirolana Kussakin, 1978 from Cretaceous Amber of Myanmar, Records of the Australian Museum (Rec. Aust. Mus.) 75 (4), pp. 405-412 : 407

Cirolana madelinae ( Schädel, Hyžny & Haug, 2021) comb. nov.

Fig. 1

Electrolana madelinae Schädel, Hyžny & Haug, 2021: 21 , figs 4, 5, 6, 7A (part, holotype only; not paratype figs 2, 3, 10A = Metacirolana jimlowryi sp. nov).

Holotype: Published figures ( Schädel et al., 2021), NHMW 2017 /0052/0001.

Diagnosis. Body 2.8 as long as greatest width (at pereonite 5); pleon 19% total body length. Pleotelson 1.2 as long as anterior width; lateral margins evenly convex, converging to broadly rounded posterior margin with apically bifid median point; posterior margin with 10 robust setae (as 5+5; as counted from Schädel et al., 2021: fig. 4A, RS present and notches where RS are missing). Coxae 6 and7 prominent, conspicuous in dorsal view, with prominent oblique carina, posteriorly acute; coxae 6 ventral and posterior margin forming angle of ca. 40°, coxae 7 ca. 30°; coxae 7 extending posteriorly to mid-pleonite 5. Frontal lamina broad, ventrally flat, ca. 3.0 as long as posterior width; anterior margin obscured, narrowly rounded or acute. Antennular flagellum extending to mid-pereonite 1. Antennal flagellum ca. 1.8 as long as peduncle, extending to posterior of pereonite 6. Pereopods typical of Cirolana , distal and inferior margins of ischium and merus with short robust setae (images indistinct), distal margin noticeably wider than proximal; pereopod 1 dactylus robust with robust unguis and secondary unguis. Uropod (details principally from left uropod) peduncle posterior lobe about 0.7 as long as endopod; extending to or very slightly beyond posterior margin of pleotelson, marginal setae in single tier, apices sub-acute. Uropodal endopod apically sub-bifid; lateral margin distally convex, without prominent excision, with 3 robust setae, mesial margin strongly convex, with 6 robust setae; lateral and mesial margins forming an angle of ca. 45°. Uropodal exopod apically sub-bifid; 0.8 as long as endopod, not extending to end of endopod, 2.5 times as long as greatest width; lateral margin weakly convex, setation not clear, with 4 widely-spaced robust setae; mesial margin convex, setation not clear, with 3 or 4 robust setae; lateral and mesial margins forming an angle of ca. 37°.

Remarks. Cirolana madelinae was not described as such by Schädel et al. (2021), but rather the specimen was described using primarily absolute measurements taken from both the holotype and paratype, together with higher-taxon characters; a short differential diagnosis was also given. The diagnosis, also based on the holotype and paratype, included several errors in interpretation of the specimens and consisted of a mixture of higher-taxon characters, non-differential characters as well as some species-level information. Specifically, pleonite 5 was misinterpreted as having free lateral margins, when pleonite 5 is clearly laterally overlapped by pleonite 4 ( Schädel et al., 2021: fig. 4A); further, the pleopod 5 endopod is described as lacking marginal setae, but pleopod 5 is not visible in the holotype and, in any case, that is a family level character for the Cirolanidae and therefore uninformative at genus and species level.Although not stated, the “differential diagnosis” appears to include characters of both specimens, and thereby combines characters of two species in different genera. The species diagnosis presented here is based on a standard cirolanid taxonomic character data seta as used, for example, by Sidabalok & Bruce (2017, 2018a) and Bruce et al. (2017) and as such does not include higher-taxon characters.

Several large and definable groups of species exist within the large genus Cirolana (157 species; 144 extant and 13 fossil species to date; Boyko et al., 2021). One such group of species is the Cirolana “ parva -group” ( Bruce, 2004; Sidabalok & Bruce, 2017). All “ parva -group” species have a rostrum that folds ventrally and posteriorly and makes contact with the anterior point of the pentagonal frontal lamina. Whereas the ventral rostral characters are not visible in the specimen, the frontal lamina, while not clear, does appear to be pentagonal. Several other character states of the “ parva -group” are present in C. madelinae : the antennal flagellum extending posteriorly to or beyond pereonite 4; unornamented body surfaces; and more significantly, pleonite 4 strongly produced, extending posteriorly to or beyond pleonite 5, and while pleonite 3 is not as clearly visible, it also appears strongly posteriorly produced and acute; the linguiform pleotelson with an apical point; the pattern of robust setae on the pleotelson; and the shape of the uropodal rami, notably with acute apices and at least sub-bifid apices (apices appear at least partly damaged). Cirolana madelinae differs from all species in the “ parva -group” by the long acute coxae on pereonites 4–7, those of pereonite 7 extending posteriorly to pleonite 5. A further point of distinction is that the pleon in C. madelinae is relatively longer than all other species of the “ parva -group” (19% total body length versus 10.4–13.2%).

Fourteen species of fossil Cirolana have been described (including Cirolana tomhurleyi (Wilson in Wilson, Paterson & Kear, 2011) comb. nov. Each of these species can be excluded by having either rounded uropodal endopods, or the uropodal endopod being apically acute, with the rami extending clearly beyond the posterior margin of the pleotelson (e.g., Bruce et al., 2021).

Figures

Figure 1. Cirolana madelinae (Schädel, Hyzny & Haug, 2021), comb. nov.: A, dorsal view; B, pereopod 1; C, pereopod 6 (partly reconstructed). Drawn from Schädel et al. (2021).