Metacirolana jimlowryi, 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 : 409

Metacirolana jimlowryi sp. nov.

urn:lsid:zoobank.org:act:59704BC5-71E7-4358-9D90-E0C98ABA4CF4

Fig. 2

Electrolana madelinae Schädel, Hyžny & Haug, 2021: 21 , figs 2, 3, 8A, 10A (part, paratype only).

Holotype: Manca, NHMW 2017 /0052/0002 (specimen used for published figures of the paratype of E. madelinae 2017/0052/0002; Schädel et al., 2021; not examined in situ). Cretaceous of Myanmar.

Diagnosis. Body 2.4 as long as greatest width (at pereonite 4); pleon 21% total body length. Pleotelson as long as anterior width; lateral margins anteriorly sinuate, posteriorly straight, converging to narrowly rounded posterior margin without apical point; posterior margin robust setae not discernible. Coxae 6 not conspicuous in dorsal view, extending posteriorly to posterior of pleonite 2. Frontal lamina anterior margin rounded, with free anterior margin visible in dorsal view; clypeus with short anteroventral triangular blade. Antennular flagellum extending to anterior of pereonite 1. Antennal flagellum 2.0 as long as peduncle, extending to mid-pereonite 2. Pereopods typical of Metacirolana , pereopod 1 sub-prehensile, with slender dactylus and secondary unguis; pereopods 4–6 slender, distal margin not notably wider than proximally, distal and inferior margins of ischium and merus with few long acute robust setae (images indistinct). Uropod (details principally from left uropod) peduncle posterior lobe about 0.6 as long as endopod; rami extending clearly just beyond posterior margin of pleotelson, marginal setae in single tier; rami rounded, not bifid. Uropodal endopod lateral margin weakly convex, robust setae not discernible, mesial margin weakly convex, with 5 or 6 robust setae; lateral and mesial margins forming an angle of ca. 50°. Uropodal exopod apically broadly rounded; 0.9 as long as endopod, not extending to end of endopod, 2.9 times as long as greatest width; lateral margin straight, with 6 robust setae; mesial margin convex, setation not clear, with 3 or 4 robust setae.

Remarks. Metacirolana jimlowryi sp. nov. can be immediately distinguished from most other congeners by the uropodal rami having marginal robust setae and the uropodal exopod being posteriorly broadly rounded. Most species of Metacirolana , including all the Metacirolana “ serrata -group” lack robust setae on the margins of the pleotelson and uropods. Those species that do have these robust setae are otherwise very different from M. jimlowryi . Metacirolana spinosa ( Bruce, 1980) , M. halia Kensley, 1984 and M. riobaldoi ( Lemos de Castro & Brasil-Lima, 1976) all have a near continuous row of robust setae along the posterior margins of the uropodal endopod and pleotelson posterior margin. The large deep-water species, Metacirolana neocaledonica Bruce, 1996 and Metacirolana fornicata ( Mezhov, 1981) , size and habitat apart, have far more ornate body surfaces, and the uropodal endopods have subtruncate margins. There are no comparable fossil species of Metacirolana .

Etymology. The epithet honours the late James K. Lowry, recognizing his immense contribution to amphipod systematics, mentoring of students as well as the shared companionship both while at the Australian Museum and on the several field and other trips over the decades.

Figures

Figure 2. Metacirolana jimlowryi sp. nov.: A, dorsal view; B, pereopod 1; C, pereopod 6 (pereopod perspective partly reconstructed). Drawn from Schädel et al. (2021).