Dilatatiocauda, Harris, 2002

Harris, V. A., 2002, A New Genus Belonging to the Family Porcellidiidae (Crustacea: Copepoda: Harpacticoida) With Three New Species from Australia, Records of the Australian Museum 54, pp. 1-24 : 2

Genus Dilatatiocauda n.gen.

Diagnosis. Anterior of female cephalosome semicircular, rostrum prominent, projects beyond cephalosome; anterior of male cephalosome truncated, male rostrum not pointed anteriorly; hyaline border on cephalosome and metasomal epimera appears granular, ducts from marginal glands open dorsal to hyaline membrane; dorsal pits present, ornamentation of net-like or honeycomb-like ridges may be present on parts of dorsal surface; labrum (hyperstome) with two grooved plates (comb plates) located near tip of mandibular incisor process; female urosome broad, division into anterior and posterior lobes indistinct, usually indicated by feint scar, anterior lobe without lateral striations, posterior lobe rounded, typically bordered with setules, caudal arch deep (50% of urosome length); female caudal ramus elongate, rectangular (L/W ratio 3), tendency to widen distally, posterior border not pointed, bevelled or deeply notched at external corner, & setae close or very close (L/[]>5),

seta on posterior border, terminal setae T1 to T4 present, terminal setae T2 & T3 close together; male caudal ramus short (quadrate), widens distally, setation similar to female; male antennule without anterior comb on accessory lobe, dactylus (terminal segment of antennule) lobed or expanded at its base; maxillule endopod with six setae, exopod with two setae; maxilliped medial lobes (coxae) widely separated in mid-line, basis quadrate (not elongate), no fimbriate process on basis; P1 with conspicuous area of denticulate pegs on endopod; endopod of P3 and P4 with long straight plumulose or serrulate spinous terminal seta; female P5 exopod without ventral expansion, does not extend beyond urosome; male P5 with six terminal setae.

Remarks. The genus is characterised by the unusual shape and structure of the maxillipeds which are widely separated in the mid-line and lack both the characteristic fimbriate edge and fimbriate process common to all other genera (see Fig. 1A,D,E). The presence of labial comb plates (see Fig. 1C), shape and setation of the caudal rami ( Fig. 1B) as well as the unusual straight spine-like terminal seta on P3 and P4 endopod (see Fig. 8A,C) are also characteristic. The generic name Dilatatiocauda (gender feminine) has been compounded from Hicks’ (1971) trivial name dilatatum which refers to the distal widening of the caudal rami, (late L. dilatatio = expanded, enlarged + cauda = tail).

Species composition. Dilatatiocauda dilatata ( Hicks, 1971) n.comb., (synonym Porcellidium dilatatum Hicks, 1971: 94–98 , figs. 5–7), type species; D. multidenticulata n.sp.; D. medialis n.sp.; D. retroseta n.sp.; Dilatatiocauda tristanensis ( Wiborg, 1964) n.comb., (synonyms Porcellidium tristanense Wiborg, 1964: 18–19 , fig. 8; P. peniculiferum Tiemann, 1978: 235–241 , abb. 1–20; redescribed by Hicks, 1982: 51–59, figs. 1–17); Dilatatiocauda plana ( Tiemann, 1977) n.comb., (synonym Porcellidium planum Tiemann, 1977: 69–76 , abb. 1–22); Dilatatiocauda bipartita ( Kim & Kim, 1997) n.comb., (synonym Porcellidium bipartitum Kim & Kim, 1997: 142–148 , figs. 1–3).A key to the species of Dilatatiocauda is given below.