Rostrocalanus, Markhaseva & Schulz & Arbizu, 2008
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publication ID |
https://doi.org/ 10.1080/00222930802254771 |
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persistent identifier |
https://treatment.plazi.org/id/03A087E4-FF9F-3476-FD91-3F9709816873 |
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treatment provided by |
Felipe |
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scientific name |
Rostrocalanus |
| status |
gen. nov. |
Genus Rostrocalanus gen. nov.
Diagnosis
Female. Small to medium-sized Clausocalanoida; prosome 3.4–5.1 times longer than urosome. Rostrum large, as rounded plate without filaments. Cephalosome and pediger 1 fused, pedigers 4 and 5 incompletely separate; posterior corners of prosome prolonged and obtusely rounded or acutely pointed. Antennule of 24 free segments. Antenna coxa without seta, basis with one small vestigial seta; endopodal segment 1 with one seta; exopod seven-segmented with 0, 3, 1, 1, 1, 0 and 3 setae. Gnathobase of mandible with keel, cutting edge bearing four to five teeth, one fork-like distally and tipped with three to four points; endopod segment 1 without seta, endopod segment 2 with six setae; basis with two setae, one very small; exopod foursegmented with 1, 1, 1 and 1 setae. Praecoxal endite of maxillule with nine terminal elements, four or five of them as thick spines, other setae modified (with swollen heads) or not; coxal endite with two setae, coxal epipodite with three to four setae, or setae absent; proximal basal endite with two setae; distal basal endite fused to endopod, with five setae (setal affiliation obscure); exopod with five or six setae. Proximal praecoxal endite of maxilla with one or two setal elements, distal with three setae; proximal and distal coxal endites with three setae each; proximal basal endite with four setae; endopod apparently three-segmented, with six long and slender worm-like sensory setae. Syncoxa of maxilliped without seta on proximal praecoxal endite, with one seta on middle endite and two setae on distal praecoxal endite; coxal endite bearing two setae. Setae of praecoxal endites poorly sclerotized but not aesthetasc-like. Basis with two medial setae, distal setae absent. Five-segmented endopod with 3, 2, 2, 3+1 and 4 setae.
P1 basis with or without medial distal seta; lateral lobe of endopod moderately developed. P5 uniramous, two-segmented; distal segment with three spine-like unarticulated extensions terminally.
Male. Unknown.
Type species Rostrocalanus peracutus sp. nov.
Etymology
The generic name is derived from the Latin rostrum meaning beak and refers to the pronounced beak-like ventral process on the cephalon lacking any filaments.
Remarks
In addition to the characters of the family, the new genus differs from the remaining bradfordians by: (1) A2 coxa without seta [shared with Brodskius , Undinella and some species of Tharybis (Tharybidae) ]; (2) setation of A2 exopod as 0, 3, 1, 1, 1, 0, 3 [shared with Grievella ; other bradfordian genera differ in A2 exopod setation by a more primitive type with one seta present on the first exopod proximal segment, or, for type with fewer setae on the second exopod proximal segment, see fig. 30 in Markhaseva and Ferrari (2005)]; (3) Md Enp2 with six setae [shared with Frigocalanus (placement of this genus is unclear) and some species of Diaixis (Diaixidae) , but usually nine setae in other bradfordian genera]; (4) Mx1 epipodite with fewer than five setae (shared with Frigocalanus , but usually nine setae in other bradfordians); (5) setae on the proximal praecoxal endite of maxilliped syncoxa absent [shared with Brodskius , Undinella and Pseudophaenna (latter genus is of uncertain familiar nomenclatural status]; (6) Mx2 proximal praecoxal endite with one or two setae (shared with some species of Undinella , but three to five setae in other bradfordians); (7) one seta on medial praecoxal endite of Mxp syncoxa [shared with Heteromalla ( Scolecitrichidae ?), vs two setae in other bradfordian genera]; (8) Mxp basis with two medial setae [shared with Undinella and Parkius (Parkiidae) , vs. three setae in other bradfordian genera]; (9) segment 1 of maxilliped endopod with three setae (shared with some species of Undinella , but four setae in other bradfordian genera).
Rostrocalanus peracutus sp. nov.
( Figures 1–3 View Figure 1 View Figure 2 View Figure 3 )
Material examined
Holotype. Adult female, dissected, body length 1.30 mm ( ZMH K-41628); tropical Atlantic, 17 ° 06 9 S, 004 ° 42 9 E, station 344, 25 July 2000, above the seabed at a depth of 5415 m. GoogleMaps
Paratypes. One adult female, dissected, body length 1.25 mm ( ZMH K-41629); two adult females, partly dissected, body length 1.30 mm ( ZIN 91091); same data as for holotype GoogleMaps .
Description
Adult female. Total length 1.25–1.30 mm; prosome 4.4–5.1 times as long as urosome. Rostrum ( Figure 1C, D View Figure 1 ) large, as rounded plate without filaments. Cephalosome ( Figure 1A, B View Figure 1 ) and pediger 1 fused, pedigers 4 and 5 incompletely separate; posterior corners ( Figure 1F View Figure 1 ) significantly prolonged into sharp points extending to urosome somite 3. Spermathecae ( Figure 1E View Figure 1 ) with distal part oval-shaped and directed anterodorsally. Genital double somite and urosome somites 2 and 3 with fringe of spinules along posterior borders. Caudal rami ( Figure 1G View Figure 1 ) with four terminal plus one small dorsolateral and ventral setae each.
Antennule reaching to posterior margin of pediger 3. Antennule ( Figure 1H–K View Figure 1 ) of 24 free segments, armature as follows: I 3s, II–IV 6s+1ae, V 2s+1ae, VI 2s, VII 2s+1ae, VIII 2s, IX 2s+1ae; X–XI 3s+1ae, XII to XIII 1s each; XIV 2s+1ae, XV 1s, XVI 2s+1ae, XVII to XIX 1s each, XX 2s, XXI 1s+1ae, XXII to XXIII 1s each, XXIV to XXVI 2s each, XXVII–XXVIII incompletely separate with 2s and 2s+1ae, respectively.
Antenna ( Figure 2A View Figure 2 ), coxa without seta; basis with one small vestigial seta; endopodal segment 1 with one seta, endopodal segment 2 with 13 setae; exopod seven-segmented with 0, 3, 1, 1, 1, 0 and 3 setae.
Mandible ( Figure 2B–E View Figure 2 ), gnathobase with keel, cutting edge with four teeth, one fork-like with four points; exopod of four segments with 1, 1, 1 and 1 seta; endopod segment 1 without seta, endopod segment 2 with six setae; basis with two setae, one very small.
Maxillule ( Figure 2F, G View Figure 2 ), praecoxal endite with nine terminal elements including five thick spines, one of which is shorter, and four soft setae distally swollen; coxal endite with two setae, coxal epipodite with four setae; proximal basal endite with two setae, distal basal endite fused to endopod, with five setae; exopod with six setae.
Maxilla ( Figure 2H, J View Figure 2 ), proximal praecoxal endite bearing one seta, distal with three setae; proximal and distal coxal endites with three setae each; proximal basal endite with four setae, endopod three-segmented, with six long and slender wormlike sensory setae.
Maxilliped ( Figure 3A, B View Figure 3 ), syncoxa without seta on proximal praecoxal endite, one seta on middle endite, and two setae on distal praecoxal endite; coxal endite with two setae; all setae of praecoxal endites poorly sclerotized but not aesthetasc-like. Basis with two medial setae; endopod five-segmented with 3, 2, 2, 3+1 and 4 setae.
P1 ( Figure 3C View Figure 3 ), basis with medial distal seta curved; endopod one-segmented with three medial and two terminal setae; lateral lobe well-developed, rounded and ornamented with spinules along distolateral margin; exopod three-segmented, segment 1 with lateral spine, segment 2 with lateral spine and medial seta, segment 3 with lateral spine, three medial setae and terminal spine. All lateral spines well developed, long, with spine on segment 1 shortest, on segment 3 longest and on segment 2 intermediate.
P2 ( Figure 3D View Figure 3 ), coxa with medial seta; basis with scattered spinules on posterior surface laterally; endopod two-segmented, segment 1 with one medial seta, segment 2 with two medial, two terminal and one lateral setae and furnished with spinules on posterior surface. Exopod three-segmented, segments 1 and 2 with lateral spine and medial seta each, segment 3 with three lateral spines, four medial setae and terminal spine.
P3 ( Figure 3E View Figure 3 ), coxa with medial seta; basis with scattered spinules on posterior surface laterally; endopod three-segmented, segments 1 and 2 with one medial seta each, segment 3 with two medial, two terminal and one lateral setae; segment 3 with scattered spinules on posterior surface; exopod three-segmented, segments 1 and 2 with lateral spine and medial seta each, segment 3 with three lateral spines, four medial setae and terminal spine.
P4 ( Figure 3F View Figure 3 ), coxa with medial seta; coxa, basis, endo- and exopod segments with scattered spinules on posterior surface; endopod three-segmented, segments 1 and 2 with one medial seta each, segment 3 with two medial, two terminal and one lateral setae; exopod three-segmented, segments 1 and 2 with one lateral spine and one medial seta each, segment 3 with three lateral spines, four medial setae and terminal spine.
P5 ( Figure 3G View Figure 3 ) uniramous, symmetrical, two-segmented; left coxa furnished with medial spinules; distal segment more than twice the length of coxa and with small patch of denticles posteriorly and three spine-like unarticulated extensions terminally.
Male. Unknown.
Etymology
The specific name is derived from the Latin peracutus meaning very sharp, and refers to the shape of the prosomal posterior corners of the species.
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