Cerviniella mirabilipes Smirnov, 1946.

Cerviniella abyssalis Apostolov, 2011, C. arctica Kihara & Martínez Arbizu, 2012, C. bodini Coull, 1973, C. brodskayae Por, 1969, C. danae Kihara & Martínez Arbizu, 2012, C. hamata Coull, 1973, C. hitoshii Kihara & Martínez Arbizu, 2012, C. lagarderei Bodin, 1968, C. langi Bodin, 1968, C. longifurcata Apostolov, 2011, C. peruana Becker, 1974, and C. talpa (Por, 1964).

The Yellow Sea; 34°59'40.14"N, 125°00'2.82"E; 88 m depth.

Holotype. One ♀ preserved in a vial with 80% ethanol (MABIK CR00253873); collected from the type locality, 20 April 2019. Paratypes. One ♀ (MABIK CR00253868) dissected on 11 slides, three ♀♀ (MABIK CR00253869–00253871) each dissected on 10 slides, six ♀♀ (MABIK CR00253874) and eight ♀♀ (MInRB-Hr88-L001) preserved in a vial with 80% ethanol, collection data as in holotype; S.L. Kim leg.

Female (based on the holotype and paratypes). Body length from anterior margin of rostrum to posterior margin of caudal rami (paratype, MABIK CR00253868, in lateral view, telescoping of somites not considered) 797 μm (range: 694–797 μm, n = 11, holotype: 765 μm).

Habitus (Fig. 1A, B) subcylindrical, gradually tapering towards posterior caudal rami, with unclear separation between prosome and urosome. Prosome (Fig. 1A, B) slightly longer than urosome, comprising cephalothorax with completely fused first pedigerous somite, and three free pedigerous somites; posterior margins finely serrated. Cephalothorax bell-shaped, slightly longer than wide, ~ 28% of body length; integument covered with several sensilla, numerous minute pits and striped pattern (discernible under high resolution); rim with anastomosing patterns. P2-bearing somite longer than following two prosomites, with well-developed pleural area. Pleural areas of P3- and P4-bearing somites with pointed posterolateral corners.

Urosome (Figs 1A, B, 3D) comprising P5-bearing somite, genital double-somite, and three free abdominal somites; integument of tergites covered with minute spinules and posterior margins finely serrated except for anal somite. Genital somite and third urosomite separated dorsally and laterally, but completely fused ventrally, forming genital double-somite (Figs 1A, B, 3D), with one pair of hook-like lateral projections on original genital somite; ventral surface with striations. Genital apertures (Fig. 3D) located far anteriorly, closed off by a single plate, on both sides with an outer vestigial seta and an inner bare seta, representing P6 (Fig. 4E; based on holotype). Copulatory pore located in median depression at level of gonopores. Anal somite (Figs 1A, 3D) as long as two preceding urosomites combined, ~ 2× as long as the caudal rami, with one pair of sensilla; semicircular operculum ornamented with minute spinules; anal sinus wide.

Caudal rami (Figs 1A, B, 3D) cylindrical, ~ 1.7× as long as wide; surface covered with fine spinules; with one pore on ventro-distal surface; with seven setae: ventro-lateral seta I pinnate, short, inserted in proximal third of ramus, dorso-lateral seta II pinnate, twice as long as seta I; seta III pinnate, arising from outer ventro-distal corner, as long as caudal ramus; terminal setae IV and V well-developed, with internal fracture plane proximally, both setae fused basally, of which seta V longest, ~ 4× as long as seta IV; seta VI shortest, spiniform, located on ventro-posterior margin; tri-articulate seta VII plumose, issuing from dorsal surface subdistally.

Rostrum (Fig. 1A, C) completely fused to cephalothorax, triangular, subdistally with paired sensilla and one ventral tube pore; anterior tip slightly concave.

Antennule (Fig. 2A) robust, short, five-segmented, covered with diminutive dots (or denticles) as shown in Fig. 2A. First segment with a blunt conical process on outer distal corner. Second segment longest, with a distal peduncle bearing an aesthetasc fused to a seta. Forth segment shortest. Fifth segment distally with a small aesthetasc fused to a pinnate seta. Armature formula: 1 - [1 pinnate], 2 - [12 pinnate + 2 pinnate spine + (1 pinnate + ae)], 3-[3 pinnate], 4-[3 pinnate], 5-[6 pinnate + (1 pinnate + ae)].

Antenna (Fig. 2B) three-segmented, comprising coxa, allobasis, and one-segmented endopod. Coxa small (not figured). Allobasis elongated, covered with various-sized spinules on surface, and with long spinules along abexopodal margin and a patch of denticles near base of exopod as shown in Fig. 2B; with one subdistal abexopodal seta. Endopod distinctly shorter than allobasis, with long spinules on inner and outer margins and rows of minute spinules along inner distal margin; lateral armature comprising one plumose and two pinnate elements; distal armature consisting of four serrate spines and three setae, of which outermost spine fused to one seta. Exopod two-segmented, proximal segment longer than distal segment, with two setae; distal segment with two lateral and three apical setae.

Mandible (Fig. 2C). Coxa proximally with rows of spinules; gnathobase well-developed, with several multi-cuspidate teeth and one pinnate seta; outermost tooth largest; with two rows of minute spinules proximally and one row of spinules subdistally. Palp biramous, consisting of basis, three-segmented exopod, and one-segmented endopod; basis with four plumose setae distally, covered with spinules on surface, and with one row of setules on lateral margin. Exopod smaller than endopod; exp-1 and exp-2 each with one plumose lateral seta, and exp-3 with three plumose (one lateral and two apical) setae. Endopod with two lateral and five apical plumose setae, of which two apical setae fused at base (indicated by arrowhead in Fig. 2C).

Paragnaths (Fig. 3A) with well-developed chitinized lobes; distal and lateral margins covered with numerous spinules; posterior face with five strong spinules and one row of tiny spinules.

Maxillule (Fig. 2D). Praecoxa ornamented with outer and subdistal spinules; arthrite well-developed, with two juxtaposed anterior setae, ten distal elements, and two pinnate posterior setae; posterior surface with patch of spinules. Coxa ornamented with outer spinules; cylindrical endite with one pinnate and five bare setae. Basis and endopod fused, with spinules on anterior and posterior surface; distal margin with 13 setae. Exopod represented by three pinnate setae.

Maxilla (Fig. 3B). Syncoxa (damaged) large, with one row of stout spinules and one row of setules along outer margin, and five groups of spinules on anterior and posterior surfaces; with four endites: proximal praecoxal endite one-segmented, with two pinnate and two bare setae distally; distal praecoxal endite small, incorporated basally into syncoxa, with one pinnate and two bare setae distally; proximal coxal endite large, with one row of spinules subdistally, and one bare and two pinnate setae distally; distal coxal endite cylindrical, with one row of spinules subdistally, and one pinnate spine and two setae (one bare and one pinnate) distally. Allobasis large, with one stout spine and two setae distally; inner part drawn out into a curved strong claw accompanied by one stout pinnate spine and two setae. Endopod small, three-segmented; first segment with two bare setae; second segment with one bare and one geniculate seta; distal segment with one geniculate and three bare setae.

Maxilliped (Fig. 3C) three-segmented, composed of protopod, and two-segmented endopod. Protopod elongate, with two rows of long outer setules, one row of posterior spinules; with four endites ornamented with inner and anterior spinules: three syncoxal endites represented proximal to distal by one pinnate spine and one pinnate seta, one pinnate spine and two plumose setae, and one pinnate spine and one plumose seta; basal endite represented by one pinnate spine and one plumose seta. Endopod small; first segment with one row of outer spinules and one plumose subdistal seta; second segment with two pinnate distal spines and two pinnate lateral setae, of which proximal one plumose proximally.

P1 (Fig. 4A). Intercoxal sclerite transversely elongated and narrow, with surface reticulation distally. Praecoxa with spinules on anterior surface. Coxa with various-sized spinules and setules on anterior surface. Basis larger than coxa, with one anterior pore and several rows of anterior spinules; with one long plumose outer and one pinnate inner seta; rami set far away from each other. Exopod one-segmented, with a row of setules on inner margin, and rows of spinules on outer proximal margin and around bases of outer setae; with three inner, two apical, and five outer setae. Endopod one-segmented, with one anterior pore medially, setules along inner and outer margins, and anterior spinules around distal margin; with one inner, one outer, and two apical setae.

P2 (Fig. 4B) larger than other thoracic legs. Intercoxal sclerite well-developed, cordiform; anterior surface with conspicuous reticulation, distally with one pair of rows of long setules; distal margin concave. Praecoxa small, with minute spinules along distal margin. Coxa with several rows of various-sized anterior spinules and three rows of long outer spinules. Basis with one anterior pore and numerous rows of various-sized anterior spinules; distal margin with one small acute process between rami; plumose outer seta shorter than those of P1 and P3. Exopod one-segmented, with one anterior pore distally and several rows of setules along inner and outer margins; with five serrate outer spines, increasing in size distally, one serrate apical spines, one plumose apical seta, and four plumose inner setae; outer and distal margins with four acute and three small processes near base of spines. Endopod two-segmented, shorter than exopod; enp-1 with three outer rows of setules and two distal rows of minute spinules, outer margin drawn out into a chitinous process bearing weakly concave tip and inner margin with one plumose seta; enp-2 longer than preceding one, ~ 1.6× as long as wide, with one outer, two apical, and four inner pinnate setae, outer and distal margins with two acute processes.

P3 (Fig. 4C) smaller than P2. Intercoxal sclerite well-developed, subrectangular, with surface reticulation; distal margin concave, with long setules. Praecoxa small, with two distal rows of minute spinules. Coxa with numerous rows of various-sized anterior spinules. Basis with numerous minute anterior spinules and row of inner setules, and one small acute process between rami; anterior pore larger than that of P2; outer seta plumose and ~ 3× as long as outer margin of basis. Exopod one-segmented, with one row of outer spinules and several rows of outer and inner setules; outer margin with two blunt and five acute processes; with five serrate outer spines, increasing in size distally, one serrate apical spine and one pinnate apical seta, and three plumose inner setae. Endopod two-segmented, distinctly shorter than exopod; enp-1 with three groups of outer spinules and one plumose inner seta, outer corner drawn out into a chitinous blunt process; enp-2 oval, ~ 2.3× as long as wide, with one plumose apical seta, outer and inner margins with row of setules.

P4 (Fig. 4D) rudimentary, uniramous, comprising outer setophore and exopod, fused basally to fourth pedigerous somite, covered with various-sized spinules; outer setophore cylindrical, longer than exopod, with long plumose seta. Exopod one-segmented, with one apical and one outer setae. Endopod absent.

Armature formulae of P1–P4 as follows:

P5 (Fig. 3D) bilobate as in P4, fused to somite, covered with minute spinules; outer setophore cylindrical, with one plumose seta. Exopod slightly exceeding setophore, with one plumose outer and one plumose apical seta, the latter ~ 2.5× longer than outer seta.

Male. Unknown.

The morphological variation in Cerviniella bisegmenta sp. nov. appears in the armature formula of thoracopods. P2 enp-2 presumably has four inner setae in the normal condition, but the P2 enp-2 of some specimens (four of 18 specimens) has two or three inner setae.

Abnormal exopod and endopod of P2 were observed in one specimen (paratype, MABIK CR00253869) (Fig. 4F, G). In comparison with the normal condition of P2 (Fig. 4B), the abnormal exopod has a seta in place of the proximal fourth outer spine and a spine in place of the proximal third inner seta (Fig. 4F, indicated by arrowheads), and the enp-2 lacks a small pointed protrusion on either side of the two apical setae (Fig. 4G, indicated by arrowheads). In addition, paratype (MABIK CR00253868) displayed two setae (the normal condition) on one of the exopods of P4 (Fig. 4D) and three setae on the other exopod (Fig. 4D’).

The specific name bisegmenta is derived from a combination of the Latin prefix bi-, meaning ‘having two parts’ and the Latin noun segmentum, meaning ‘cutting’ or ‘piece’, and refers to the two-segmented antennary exopod, which is an autapomorphy of this species. It is a noun in the nominative plural.

Based on the presence or absence of the P4 endopod, Apostolov (2011) subdivided the genus Cerviniella into the brodskayae and mirabilipes groups. Cerviniella bisegmenta sp. nov. lacks the ramus and can be classified within the mirabilipes group, which includes C. danae, C. lagarderei, C. langi, C. mirabilipes, and C. talpa.

The segmentation of the female antennule is useful for differentiating among species of Cerviniella. Cerviniella bisegmenta sp. nov. has an advanced five-segmented antennule, shared in C. danae and C. hitoshii, but the latter species is in the brodskayae group. The other 11 Cerviniella species have a six- or seven-segmented antennule (see discussion below).

Cerviniella bisegmenta sp. nov. can be easily distinguished differs in several characters from the same group, C. danae. First, the antenna of C. bisegmenta sp. nov. has a two-segmented exopod, compared with the four-segmented antennary exopod of C. danae. Second, the mandibular endopod of C. bisegmenta sp. nov. has two lateral setae, whereas the mandibular endopod of C. danae has three lateral setae. Third, the basis and endopod of the maxillule of C. bisegmenta sp. nov. have a total of 13 setae, compared with 14 setae in C. danae. Fourth, the syncoxa of the maxilliped of C. bisegmenta sp. nov. has nine setae and spines, compared with the seven elements of C. danae. Fifth, the P1 endopod of C. bisegmenta sp. nov. has four setae, compared with six setae in C. danae. Sixth, the P3 exopod of C. bisegmenta sp. nov. has three inner setae, compared with two inner setae in C. danae. Finally, the caudal ramus of C. bisegmenta sp. nov. is short with a 1.7-fold length relative to width, compared with a 3.5-fold length for C. danae. The first and seventh aforementioned characteristics provide conclusive evidence for the identification of C. bisegmenta sp. nov. In all species of Cerviniella, except C. bisegmenta sp. nov., the antennary exopod is four-segmented, and the length of the caudal rami is > 3-fold to width and longer than the length of the anal somite.

The Yellow Sea; 35°00'05.44"N, 125°59'44.49"E; 88.1 m depth.

Holotype. One ♀ preserved in a vial with 80% ethanol (MABIK CR00253875); collected from the type locality, March 02, 2022. Paratypes. One ♀ (MABIK CR00253872) dissected on 10 slides, two ♀♀ (MABIK CR00253876) preserved in a vial with 80% ethanol, collection data as in holotype; J.G. Kim leg.

Female (based on the holotype and paratypes). Body length from anterior margin of rostrum to posterior margin of caudal rami (paratype, MABIK CR00253872, in lateral view, telescoping of somites not considered) 857 μm (range: 857–886 μm, n = 4, holotype: 861 μm).

Habitus (Fig. 5A, B) subcylindrical, gradually tapering posteriorly, with unclear separation between prosome and urosome.

Prosome (Fig. 5A, B) slightly longer than urosome, comprising cephalothorax (with completely fused first pedigerous somite) and three free pedigerous somites. Cephalothorax bell-shaped, slightly longer than wide, ~ 31% of body length; surface embossed with numerous minute dots (or denticles) and striped pattern (discernible under high resolution), covered with several sensilla and pores; rim with anastomosing patterns; ventro-posterior margins with row of fine spinules and posterior margin weakly serrate. Pedigerous somites bearing P2–P4 with several sensilla, minute spinules and pores as shown in Fig. 5A, B. Pleural areas of P2-bearing somite more extended than those of other prosomites, P2- and P3-bearing somites with pointed posterolateral corners; posterior margins distinctly serrate.

Urosome (Figs 5A, B, 6A) comprising P5-bearing somite, genital double-somite, and three free abdominal somites; surface covered with striation and minute spinules (or denticles); posterior margins finely serrated except for anal somite, pore pattern on dorsal surface as indicated in Fig. 5A. Genital somite and third urosomite separated dorsally and laterally, but completely fused ventrally forming genital double-somite (Figs 5A, B, 6A), with one pair of hook-like lateral projections on original genital somite. Genital apertures (Fig. 6A) located far anteriorly; closed off by single plate, on both sides with an outer vestigial seta and an inner bare seta, representing P6 (Fig. 6A). Copulatory pore located in the middle. Anal somite (Figs 5A, B, 6A) slightly shorter than two preceding urosomites combined; as long as caudal rami; with one pair of sensilla dorsally and one pair of pores laterally; with semicircular operculum ornamented with minute spinules; lateral margin of anal opening with spinules row and a spinous process.

Caudal rami (Figs 5A, B, 6A) cylindrical, ~ 4× as long as greatest width, surface covered with stripes and fine spinules; with pairs of pores on dorsal and ventral surface; with seven setae: ventro-lateral seta I bare, short, inserted in proximal third of ramus, dorso-lateral seta II pinnate, ~ 1.5× longer than seta I; seta III missing (this seta missing in all specimens), arising from outer subdistal corner; terminal setae IV and V well-developed, with internal fracture plane proximally, both setae fused basally, seta V longest (but damaged in all specimens); seta VI shortest, spiniform, located on ventro-posterior margin; tri-articulate seta VII plumose, issuing from dorsal surface subdistally.

Rostrum (Fig. 5A, C) completely fused to cephalothorax, triangular, subdistally with one pair of sensilla and one ventral tube pore; apical tip blunt.

Antennule (Fig. 6B) robust, short, seven-segmented, covered with numerous diminutive dots (or denticles) as shown in Fig. 6B. First segment largest. Third segment with one peduncle bearing a seta fused to an aesthetasc. Fourth to sixth segments small. Seventh segment subdistally with a pinnate seta fused to an aesthetasc. Armature formula: 1-[1 pinnate], 2-[5 pinnate + 3 spine], 3-[2 + 4 pinnate + 2 spine + (1 pinnate + ae)], 4-[1 + 1 pinnate + 1 pinnate spine], 5-[1 pinnate + 1 pinnate spine], 6-[2 pinnate], 7-[1+ 5 pinnate + (1 pinnate + ae)].

Antenna (Fig. 6C) three-segmented, comprising coxa, allobasis, and one-segmented endopod. Coxa small, with long outer spinules. Allobasis elongate, covered with several group of minute spinules, outer margin with one group of setules, and inner margin with two rows of long setules and two rows of spinules; area close to the insertion of exopod swollen; with one subdistal abexopodal seta. Endopod distinctly shorter than allobasis, with one row of outer setules, one row of inner setules, and one row of minute distal spinules; lateral armature composed of one serrate spine and two pinnate setae; distal armature consisting of four serrate spines, one pinnate seta, one plumose seta, and one bare seta; outermost serrate spine fused basally to neighboring seta. Exopod four-segmented, covered with minute spinules; proximal segment longer than other segments, with two pinnate lateral setae; second and third segments each with one pinnate lateral seta; distal segment distally with one pinnate and one plumose seta.

Mandible (Fig. 7A). Coxa well-developed, proximally with four rows of various-sized spinules and subdistally with one row of minute spinules; gnathobase well-developed, with one uni-cuspidate and four multi-cuspidate teeth, of which outermost tooth largest, and one pinnate seta. Palp biramous, consisting of basis, three-segmented exopod, and one-segmented endopod; basis covered with minute spinules, subdistally with one pinnate and three plumose setae, of which subdistal one distally bare and proximally plumose. Exopod shorter than endopod; exp-1 longer than other two distal segments combined, covered with minute spinules, with one small plumose seta laterally and one long plumose seta subdistally; exp-2 small, with one pinnate seta; exp-3 small, with three plumose setae distally. Endopod 1.4× longer than exopod, laterally with one pinnate and two bare setae, and distally with one pinnate and six bare setae, of which two bare setae fused at base (indicated by arrowhead in Fig. 7A).

Paragnaths (Fig. 7B) (damaged during dissection process, one side figured) with well-developed chitinized lobes; distal margin with numerous spinules; posterior face with five strong spinules and one row of tiny spinules; lateral margin with tiny spinules.

Maxillule (Fig. 7C). Praecoxa ornamented proximally with several rows of outer spinules and subdistally with three rows of anterior spinules and two rows of posterior spinules; arthrite well-developed, with two juxtaposed pinnate setae anteriorly (one missing seta indicated by the dotted line in Fig. 7C), seven spines and three pinnate setae distally, and two pinnate setae posteriorly (one missing seta indicated by the dotted line in Fig. 7C); posterior surface with several rows of spinules. Coxa with one row of outer spinules and three rows of posterior spinules; endite cylindrical, with one pinnate and five bare setae subdistally or distally. Basis broad, with several rows of posterior spinules and ten distal setae. Exopod represented by one pinnate and two plumose setae. Endopod completely fused basally to basis, represented by three setae.

Maxilla (Fig. 7D). Syncoxa large, with numerous rows of spinules anteriorly and posteriorly and one row of long outer setules; with four endites: proximal praecoxal endite separated basally from syncoxa, with four pinnate setae distally; distal praecoxal endite rudimentary, represented by three bare setae; proximal coxal endite cylindrical, with three bare setae distally; distal coxal endite also cylindrical, with one pinnate spine and two setae distally (one bare and one pinnate). Allobasis with one unipinnate stout spine and two bare setae distally; inner part drawn out into a curved strong claw accompanied by one unipinnate stout spine and two bare setae. Endopod small, three-segmented; first segment with one bare and one geniculate seta; second segment with two geniculate setae; distal segment with one geniculate and three bare setae.

Maxilliped (Fig. 7E) three-segmented. Protopod elongate, with two and three rows of long setules along outer and inner margins and numerous rows of spinules on anterior and posterior surfaces; with four endites: syncoxal endites represented proximal to distal by two pinnate spines, three pinnate spines, and one pinnate spine and one plumose seta; basal endite represented by one pinnate spine and one plumose seta. Endopod two-segmented, with one row of outer setules on first segment, the latter with one plumose seta; second segment with two pinnate spines distally, and one unipinnate and one plumose seta laterally.

P1 (Fig. 8A). Intercoxal sclerite transversely elongated and narrow, with weak surface reticulation distally. Praecoxa (damaged) small, with anterior and distal spinules. Coxa wide, with various-sized spinules anteriorly and distally. Basis wide, somewhat larger than coxa, with one anterior pore and several rows of spinules anteriorly and distally; outer setophore with one row of anterior spinules and one plumose seta; inner distal corner produced, with one pinnate seta slightly exceeding end of exopod. Exopod one-segmented, elongate, with rows of outer and inner setules and two groups of anterior spinules, and several groups of spinules at bases of outer and distal setae; with two plumose inner, two pinnate apical, and five pinnate outer setae. Endopod one-segmented, ~ 1/2 exopod length, with two rows of outer setules and one outer and two apical setae.

P2 (Fig. 8B) larger than other legs, anterior surface covered with striated patterns (not figured). Intercoxal sclerite well-developed, cordiform, slightly concave distally, with surface reticulation, two pairs of anterior spinular rows and one pair of distal setular rows. Praecoxa small, triangular, with one row of minute spinules anteriorly and one row of minute spinules distally. Coxa large, wide; anterior surface with one pore, one row of large spinules and numerous rows of minute spinules; distal margin with one row of minute spinules. Basis large, with numerous rows or groups of fine spinules anteriorly and one row of setules distally; distal margin with small process between rami, and outer margin with one pore and one plumose seta. Exopod one-segmented, expanded distally; with five serrate outer spines, of which proximal third one shortest, one serrate apical spine, one pinnate apical seta, and four plumose inner setae; outer and distal margins with one blunt and five acute processes at bases of spines; anterior surface with one small pore and several rows of spinules; outer margin with one row of fine spinules and one row of setules; posterior surface with several rows of spinules (not figured). Endopod two-segmented, reaching distal fourth of exopod; enp-1 with several minute anterior spinules, two rows of outer setules, one plumose inner seta and one distal pore; outer corner drawn out into a chitinous process with weakly bifid tip; enp-2 with one plumose outer seta, one plumose apical seta, one small pinnate apical spine, and four plumose inner setae, and two anterior pores; distal and outer margins each with two acute processes.

P3 (Fig. 8C) smaller than P2; anterior surface covered with striated patterns (not figured). Intercoxal sclerite well-developed, subrectangular, with surface reticulation and one row of long distal setules. Praecoxa small, with one row of minute spinules distally. Coxa large, with one large pore, one group of spinules and one row of minute spinules on anterior surface, and one row of minute spinules along distal margin. Basis larger than coxa; anterior surface with one large pore and several rows of fine spinules; outer setophore with one long plumose seta; inner margin with one rounded protrusion bearing one row of setules; distal margin with one small process between rami and one row of setules. Exopod one-segmented, expanded, with five serrate outer spines, of which proximal third one shortest, one serrate apical spine, one pinnate apical seta, and three plumose inner setae; outer and distal margins with four acute and three small processes; anterior surface with several fine spinules and one small pore; posterior surface with several spinules (not figured); inner and outer margins with one and two rows of setules, respectively. Endopod two-segmented, slightly exceeding 1/2 of exopod length; enp-1 as in P2, with outer chitinous process, two rows of outer setules, and one plumose inner seta; enp-2 elongate, 3× as long as wide, with one row of outer setules, one pinnate apical seta, and one plumose outer seta.

P4 (Fig. 8D) visibly reduced, composed of outer setophore and exopod, fused basally to supporting somite. Outer setophore larger than exopod, covered with minute anterior spinules, with one long pinnate seta apically and one small inner protrusion subapically. Exopod one-segmented, small, with one pinnate apical and one pinnate outer seta. Endopod absent.

Armature formulae of P1–P4 as follows:

P5 (Fig. 8E) fused basally to supporting somite as in C. bisegmenta sp. nov. Outer setophore cylindrical, covered with small denticles, with one long pinnate seta. Exopod small, fused basally to baseoendopod, covered with small denticles, with one plumose apical and one pinnate outer seta; apical seta 1.8× longer than outer seta.

Male. Unknown.

The specific name permixta is derived from the Latin adjective permixtus, meaning ‘mixed’ or ‘confused’, and refers to the fact that several diagnostic characteristics of Cerviniella species are mixed in this species. It is in the nominative singular. Gender: feminine.

Cerviniella permixta sp. nov. lacks a P4 endopod and is placed in the mirabilipes group as C. bisegmenta sp. nov. described above. This new species can be distinguished from C. bisegmenta sp. nov. on the basis of several morphological differences. Cerviniella permixta sp. nov. is characterized by the presence of numerous minute pits on the cephalothorax surface, whereas C. bisegmenta sp. nov. is characterized by numerous minute dots or denticles. Cerviniella permixta sp. nov. has a blunt rostral tip, whereas C. bisegmenta sp. nov. has a concave tip. The antennule has seven segments in C. permixta sp. nov. and five segments in C. bisegmenta sp. nov. The P1 enp-1 lacks the inner seta and P3 enp-2 has two setae in C. permixta sp. nov., whereas the P1 enp-1 has an inner seta and P3 enp-2 has one seta in C. bisegmenta sp. nov. The caudal ramus of C. permixta sp. nov. is relatively long, with a 4-fold length relative to width, compared with a 1.7-fold length for C. bisegmenta sp. nov.

In the mirabilipes group, the species with a seven-segmented antennule are C. lagarderei, C. langi (but illustrated as six-segmented in the original description (Bodin 1968: pl. III); see discussion below), C. mirabilipes, C. talpa, as well as C. permixta sp. nov. However, C. permixta sp. nov. is different from these four species in several characteristics. First, C. permixta sp. nov. has two setae on the distal exopodal segment of the antenna, compared with three setae in C. langi. Second, C. permixta sp. nov. has a three-segmented mandibular exopod, compared with a one-segmented mandibular exopod in C. mirabilipes and four-segmented in C. lagarderei and C. langi. Third, the P1 enp-1 of C. permixta sp. nov. has three setae, compared with six in C. lagarderei and C. talpa, and seven in C. langi. Fourth, the P2 enp-2 apical margin has a spine-like element in C. permixta sp. nov., compared with a seta-like element in the remaining four species. Fifth, the P3 enp-2 of C. permixta sp. nov. has two setae, compared with four setae in C. langi and C. talpa, and three setae on the one-segmented P3 endopod in C. lagarderei. Finally, the reduced P4 exopod of C. permixta sp. nov. has two setae, compared with four setae in C. talpa and five setae in C. mirabilipes; C. lagarderei has the well-developed and two-segmented ramus with ten setae/spines.