Caecoserolis Wägele, 1994

Bruce, Niel, 2009, New genera and species of the marine isopod family Serolidae (Crustacea, Sphaeromatidea) from the southwestern Pacific, ZooKeys 18 (18), pp. 17-76 : 70-71

Caecoserolis Wägele, 1994

Caecoserolis Wägele, 1994: 10 (not Caecoserolis of Poore and Brandt 1997: 161; = Myopiarolis gen. n.)

Type species. Serolis brinki Kensley, 1978 ; original designation ( Wägele 1994).

Description. Head lateral lobe mesial margin with single concavity; anterolateral lobes forming of continuous margin with pereonite 1; anterior submarginal ‘ridge’ absent; posterior margin without ornamentation. Eyes absent. Pereonites all entire, articulating; pereonite 1 anterior margin not strongly bent dorsally, dorsally without tubercles. Coxae of pereonites 2–4 articulated, with dorsal sutures; 2–4 and pereonite 6 entirely lacking coxal keys; distal margin truncate; coxae 6 wide, laterally or distally broad, extending proximal to insertion of uropod peduncle. Ventral coxal plates 2–4 meeting midline; simple, smooth; plates 6 and 7 entirely separate. Pleonites distally narrow or acute, laterally overlapped by coxae 6, extending posteriorly along pleotelson. Sternites 5–7 visible, fused. Sternal plates of pleonites 1–3 3-cornered, with acute median point, without median ridge. Pleotelson dorsal surface not vaulted, with weak median longitudinal carina, without paired sublateral carinae; pleotelson posterior margin evenly rounded, without distinct exit channel.

Antennule flagellum 1.2–2.0 as long as peduncle articles 3 and 4, extending to pereonite 2. Antenna peduncle articles 4 and 5 broad, article 5 less than 5 times as long as greatest width; flagellum three-quarters as long as peduncle article 5.

Epistome evenly rounded. Mandible incisor with two posterior cusps; left mandible lacinia mobilis three-quarters as wide as incisor or larger, right lacinia mobilis distally multicuspid; mandibular spine distally serrate. Maxilliped palp with 3 articles; article 3 cordiform, longer than wide.

Pereopod 1 carpus RS–state not known (pilose vs serrate); propodal palm setae all RS, alternating straight and flattened, wide RS finely pilose, narrow RS distally bifid, with simple flagellum. Pereopod 2 propodus inferior margin without heel; palm straight; unguis simple, blunt.

Penial openings narrowly separated.

Pleopods 1–3 peduncles subquadrate. slightly narrower distally, pleopods 1–3 peduncles with coupling setae. Pleopod 2 endopod lamellar part slightly shorter than ramus.

Uropods Biramous, inserted on pleotelson mid-laterally, positioned laterally, not forming part of continuous body outline; less than one-third as long as pleotelson, endopod distally rounded.

Remarks. Caecoserolis belongs with the group of genera characterised by having a distal stem on pleopod 2 endopod, approximating to the ‘Group B’ of Wägele (1994). The genus can be identified by the flat (or weakly domed) pleotelson that lacks lateral carinae, antenna with broad peduncular articles 4 and 5, pleopod peduncles that are sub-quadrate (slightly narrower distally than proximally) and by the short uropods inserted mid-laterally on the pleotelson; another less precise character is that Caecoserolis has a flatter body than related genera.

All but the type species of Caecoserolis have been transferred to the Myopiarolis gen. n. Th e characters that most readily separate these two genera (in parentheses for Myopiarolis ) include antenna peduncle articles 4 and 5 broad with article 5 less than 5 times as long as greatest width (slender, elongate, 4.6–6.3 and 8.6–10.3 as long as wide respectively), pleopods 1–3 peduncles quadrate or subquadrate (triangular), pereonite 1 anterior margin anterior margin weakly indented (distinctly indented), pereonites all with visible entire sutures (pereonites 5–7 sutures medially fused), simple and flat pleotelson that lacks sub-lateral carina (pleotelson vaulted, with sub-lateral carinae), coxae 6 not extending posteriorly to pleonites (extending posteriorly to pleonites) and penial openings narrowly separated (fused in all species of Myopiarolis ).

Distribution. The genus is monotypic, with one western Indian Ocean species, off the Natal coast of South Africa.