Crosnierocaris athanasoides Anker 2022, sp. nov.
Creators: name: Anker, Arthur
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Alpheidae
Crosnierocaris
Crosnierocaris athanasoides

description: Crosnierocaris athanasoides sp. nov.
(Figs. 1–5)
Type material. Holotype: ovigerous female (cl 4.6 mm), MNHN-IU-2017-451, Indian Ocean, Mozambique Channel, north of Grande Glorieuse Island, BIOMAGLO Sta. DW 4800, 11°28’S, 47°19’E, depth: 240–255 m, Warén dredge, decomposing sea grass accumulation with shells and pale sponges, leg. L. Corbari et al. (MNHN team), 4 January 2017 [HT-1].
Paratypes: 2 ovigerous females (cl 4.6 mm, 5.3 mm, MNHN-IU-2014-20458, same collection details as for holotype [PT-7, PT-5]; 2 males (cl 3.7 mm [rostrum broken], 4.3 mm), MNHN-IU-2014-20459, same collection details as for holotype [PT-3, PT-4]; 1 female (cl 4.7 mm), 2 ovigerous females (cl 4.7 mm, 5.0 mm), MNHN-IU-2014-20460, same collection details as for holotype [PT-9, PT-8, PT-10]; 1 ovigerous female (cl 5.2 mm), MNHNIU-2014-20461, same collection details as for holotype [PT-6, dissected]; 1 ovigerous female (cl 5.3 mm), MNHNIU-2014-20462, same collection details as for holotype [PT-11]; 1 male (cl 4.2 mm), MNHN-IU-2014-20463, same collection details as for holotype [PT-2].
Additional material. 17 specimens (most damaged or in poor condition, cl not measured), MNHN-IU-2014- 20464, same collection details as for holotype.
Description. Body not particularly compressed, not elongate (Fig. 1A). Carapace smooth, glabrous, unarmed dorsally and laterally (Fig. 1A, B). Rostrum elongate, acute, slightly lanceolate in dorsal view, very slender in lateral view, sloping down from dorsal plateau of carapace (most part of rostrum situated markedly below dorsal surface of carapace), its distal portion sometimes slightly ascending; rostral tip reaching far beyond distal margin of first article of antennular peduncle; rostral carina present, not extending posterior to rostral base, without teeth; ventral margin with sharp subdistal tooth; rostral length reaching or almost reaching half of carapace length in most individuals with complete rostrum (Fig. 1A–D). Anterolateral margin of carapace with strong, sharp, anteriorly projecting extra-corneal teeth, reaching at least to anterior margin of eyes, and less pronounced, blunt infra-corneal teeth (Fig. 1A–D). Pterygostomial angle produced in very stout, sharp tooth (Fig. 1A, B, D). Cardiac notch well developed, deep (Fig. 1A, B).
Pleon with first two pleura rounded ventrally; third, fourth and fifth pleura with distoventral margins armed with typically two, sometimes three or four, small, acute, well-spaced teeth; sixth pleuron with articulated subtriangular plate at ventrolateral angle, its posterolateral angle produced in small sharp tooth (Figs. 1A, 2A–D); preanal plate rounded posteriorly.
Telson slender, tapering towards posterior end, about 2.5 times as long as wide at proximal margin, without noticeable constrictions; dorsal surface not depressed, usually armed with two pairs of stout cuspidate setae situated at about 0.3–0.4 of telson length and 0.6–0.7 of telson length, respectively, rarely with additional cuspidate setae (up to seven in total, as in holotype); posterior margin rounded, with two pairs of spiniform setae of about same thickness, lateral being only slightly longer than mesial (Fig. 2E–G); anal tubercles absent.
Eyes well developed, largely visible in dorsal and lateral views, party concealed by proximolateral expansion of rostrum and extra-corneal teeth; cornea large, well pigmented (Fig. 1A–D). Each epistomial sclerite produced, forming sharp, mesially directed tooth.
Antennule with first article relatively slender, elongate, with well-developed, distally acute stylocerite, latter distinctly overreaching distal margin of first article of peduncle; ventromesial carina with stout, sharp, anteriorly directed tooth; characters of second and third article of antennular peduncle and flagella currently unknown (antennules broken between first and second article of antennular peduncle in most specimens, sometimes completely missing) (Fig. 1C–E). Antenna with basicerite relatively stout, quadrate, with sharp, projecting distolateral tooth; scaphocerite well developed, slender, with strong sharp distolateral tooth reaching far beyond relatively narrow blade; carpocerite relatively slender, not reaching distal third of scaphocerite; characters of flagellum unknown (broken in all specimens) (Fig. 1C, D, F).
Mouthparts typical for family (Fig. 3). Mandible with well-developed incisor and molar processes and two-articulated palp; incisor process with about six teeth on distal margin (Fig. 3A, B). Maxillule with palp bilobed distally, each lobe furnished with single stout seta (Fig. 3C). Maxilla with proximal (coxal) endite small, without setae; distal (basial) endite with deep cleft; palp (endopod) entire; scaphognathite rather narrow (Fig. 3D). First maxilliped with proximal (coxal) and distal (basial) endites without specific features, furnished with long setae; palp (endopod) subdivided into two articles, both with long plumose setae; exopod very long, caridean lobe poorly developed; epipod large, subtly bilobed (Fig. 3E). Second maxilliped with endopod of typical shape for family; exopod very long; epipod moderately developed, ovate (Fig. 3F). Third maxilliped relatively slender, pediform; coxa with small, auriform lateral plate above mastigobranch; antepenultimate article stouter than others, with some setae along ventrolateral and mesial surfaces; penultimate article cylindrical, about 2.7 times as long as wide; ultimate article tapering into corneous tip, with two stout subapical spiniform setae, their bases covered by short subacute projections; exopod very long, reaching well beyond penultimate article; arthrobranch moderately developed (Fig. 3G–K).
First pereiopods (= chelipeds) not particularly enlarged in both sexes, stouter but shorter than walking legs, equal in length, symmetrical in shape; ischium very short, unarmed; merus about three times as long as greatest width, slightly swollen; carpus subcylindrical, widening distally, mesial surface with four rows of serrulate setae; chela relatively small, not swollen, simple; fingers with cutting edges unarmed, except for one small bump near each fingertip (Fig. 4A–C).
Second pereiopod slender; ischium unarmed; merus as long as ischium; carpus with five subdivisions, first longest, ratio of carpal subdivisions equal to 3.2: 1: 1: 1.4: 1.7; chela simple, longer than distal-most carpal subdivision; cutting edges of chela fingers unarmed (Fig. 4D).
Third pereiopod generally slender; ischium armed with two cuspidate setae on ventrolateral surface; merus about eight times as long as wide, armed with four cuspidate setae on ventrolateral surface; carpus slenderer than merus, about 0.6 length of merus, unarmed, except for stout distolateral seta on ventral margin; propodus armed with numerous (about 20) spiniform setae inserted in two rows on ventrolateral and ventromesial margins, respectively, distal-most spiniform setae longest, including one pair adjacent to dactylus; dactylus about 0.3 length of propodus, gently curved, biunguiculate, secondary unguis small, subdistal (Figs. 4E, 5A–C).
Fourth pereiopod generally similar to third, slightly slenderer; ischium armed with two cuspidate setae on ventrolateral surface; carpus about 0.6 times as long as merus, unarmed; merus almost nine times as long as wide, armed with four or five cuspidate setae on ventrolateral surface; propodus armed with numerous (up to 15) spiniform setae inserted in single, somewhat irregular row along ventrolateral margins, distal-most spiniform setae longest, especially one pair adjacent to dactylus; dactylus biunguiculate, similar to that of third pereiopod (Figs. 4F, 5D).
Fifth pereiopod slenderest of all walking legs; ischium unarmed on ventrolateral surface; merus almost 11 times as long as wide; carpus slenderer than merus, about 0.8 length of merus, unarmed; propodus armed with numerous (about dozen) spiniform setae inserted in single row on ventromesial margin, distal-most spiniform seta adjacent to dactylus longest; cleaning brush on distolateral surface of propodus well developed, composed of at least six rows of serrulate setae increasing in size distally; dactylus biunguiculate, similar to that of third pereiopod (Figs. 4G, 5E).
Second male pleopod with appendix masculina almost three times as long as appendix interna, overreaching endopod, with few long stiff setae distally and subdistally (Fig. 2H). Second female pleopod with appendix interna only.
Uropod with lateral lobe of protopod produced in long sharp tooth; endopod narrower than exopod, elongate, oval-shaped; exopod with lateral portion of diaeresis strongly dentate, typically with eight large triangular teeth, not including one minute tooth in-between, dentition abruptly ending at about 0.6 length of diaeresis length; distolateral tooth acute; adjacent spiniform seta stout, strongly projecting, but not reaching distal margin of exopod (Fig. 2I–K).
Gill-exopod formula as stated for genus.
Colour in life. Unknown.
Etymology. The specific name of the new species is the combination of Athanas and the Greek suffix - oides (resemblence or like), alluding to its remarkable general resemblance to many species of the possibly distantly related genus Athanas.
Distribution. Presently known only from the type locality north of Grande Glorieuse Island in the northern Mozambique Channel, Indian Ocean.
Ecology. All specimens of Crosnierocaris athanasoides sp. nov. were found in the same dredge haul, which was made at a depth of 240–255 m, and contained numerous brown decomposing fragments of decomposing sea grass and possibly some algae, shell debris and some pale sponges. It is possible that C. athanasoides sp. nov. is restricted to this type of decomposing vegetation / debris, but more dredges in the type locality area would be needed to confirm this hypothesis.
Remarks. See remarks under the genus.
description: Published as part of Anker, Arthur, 2022, Crosnierocaris athanasoides gen. et sp. nov., a new deep-water alpheid shrimp from the Mozambique Channel (Malacostraca: Decapoda: Caridea), pp. 269-280 in Zootaxa 5105 (2) on pages 273-279, DOI: 10.11646/zootaxa.5105.2.6, http://zenodo.org/record/6332687