Articullichirus chiltoni, Poore & Dworschak & Schnabel, 2022

Poore, Gary C. B., Dworschak, Peter C. & Schnabel, Kareen E., 2022, Articullichirus, a new genus of ghost shrimp (Crustacea: Axiidea: Callichiridae) with one new species, Memoirs of Museum Victoria 81, pp. 123-133 : 127-130

Articullichirus chiltoni sp. nov.

Figures 3 , 4

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Callianassa articulata .— Chilton, 1911: 551–552.

? Glypturus articulatus .— Sakai, 1999: 76–78, fig. 15 (Gilbert Is, Kiribati).

Glypturus collaroy . — Sakai, 2005:139–141, fig.29 ( New Zealand).

Material examined. Holotype. New Zealand, Kermadec Is, Sunday I. [now Raoul I.], rockpool, Captain Bollons, 1907, CMNZ AQ3372 (male, 14.7 mm).

Diagnosis. Maxilliped 3 basis with mesial spine; merus with tubercle on distal margin. Pereopod 1 coxa with mesiodistal hook. Uropodal endopod midlength about 1.5 times as long as wide, with broadly rounded apex, with submarginal dorsal cluster of setae midway along posterior margin, with 1 proximal tooth. Telson 1.4 times as wide as long, with excavate posterior margin; with transverse dorsal row of 12 or 13 pairs of contiguous spiniform setae plus 1 or 2 more lateral.

Description of holotype. Carapace length 0.28 of total length; cervical groove at 0.8 length of carapace; dorsal oval well defined; hepatic region with weakly sclerified line between dorsal oval and linea thalassinica. Rostrum and anterolateral carapace spines with unsclerified basal region; rostrum an anteriorly directed, acute spine nearly as long as eyestalk; anterolateral spines acute, set slightly back from rostrum, half as long as rostrum. Anterolateral branchiostegal lobe margin extending dorsal to linea thalassinica, with sclerified plate below linea thalassinica. Pleomere 1 (damaged) with weak transverse groove, with dorsolateral longitudinal setal row; pleomere 2 about 1.5 times as long as pleomere 1 tergite; pleomeres 3–5 scarcely expanded laterally, with dense setose areas; pleomeres 5 and 6 subequal in length, with posterolateral notch.

Eyestalks shorter than first article of antennular peduncle, without produced mesiodistal apex; cornea globular, distally placed. Antennular peduncle little shorter than antennal peduncle. Antennal peduncle with acute scaphocerite. Right maxilliped 3 (left missing) basis with recurved mesial hook; ischium with distinct crista dentata, teeth diminishing distally; merus width about 0.8 as long as ischium and merus together; merus slightly shorter than ischium, with blunt tooth on free distal margin; carpus articulating distolaterally on merus; propodus slightly wider than long, expanded as round lobe on lower margin; dactylus one third as wide as propodus, 0.7 times as long.

Pereopods 1 unequal, dissimilar; coxae with strong mesial hook. Major pereopod 1 (left cheliped) carpus-propodus upper margin 0.9 times carapace length; ischium lower margin with row of 6 spines, larger distally; merus lower margin with 3 proximal spines, upper margin strongly convex proximally; carpus 1.6 times as wide as long, with blunt tooth at end of upper and lower margins; propodus upper margin smooth, with submarginal carina on mesial face, palm slightly longer than wide, distomesial edge convex; fixed finger 0.5 times upper margin, cutting edge with broad tooth at midlength, proximally serrated; dactylus stout, slightly longer than fixed finger, with terminal tooth, cutting edge slightly concave, with blunt tooth at midlength; ratio of dorsal lengths, merus: carpus: propodus – 1: 0.76: 1.38.

Minor pereopod 1 (right cheliped) about 0.8 times length of major; ischium lower margin with 5 spines, larger distally; merus lower margin with 1 proximal spine; carpus subtriangular, 1.2 times as wide as long, with tooth at end of upper and lower margins; propodus upper margin about as long as greatest width; fixed finger 1.1 times upper margin, cutting edge with 2 teeth in distal quarter; dactylus as long as fixed finger, cutting edge smooth; ratio of dorsal lengths, merus: carpus: propodus – 1: 0.85: 0.92.

Pereopod 2 chelate. Pereopod 3 ischium slightly longer than wide, about half length of merus; carpus slightly shorter than merus; propodus 0.7 times length of carpus, lower margin broadly expanded proximally, densely setose; dactylus simple, about half length of propodus. Pereopod 4 propodus semichelate, with spiniform seta at base of finger; dactylus simple.

Male pleopod 1 uniramous, biarticulate; article 2 with small distolateral triangular lobe. Male pleopod 2 biramous; endopod with obsolete distomesial appendix masculina; exopod longer than endopod.

Uropod endopod 1.5 times as long as wide, anterior margin convex, without setae; posterior margin slightly concave, tapering to a narrowly rounded apex; marginal setae confined to distal and posterodistal margins; upper face with cluster of setae close to posterior margin, few scattered setae near anterior margin, with 1 proximal tooth. Exopod longer than endopod, subtriangular, as wide as anterior margin, upper face with proximal tooth; dorsal plate oblique, well separate from distal margin, armed with imbricating robust setae, posterodistal angle rounded, armed with imbricating robust setae.

Telson 1.4 times as wide as long, lateral margins evenly convex, posterior margin concave; with dorsal transverse row of spiniform setae, 1 or 2 robust setae placed laterally, remote from row of 12 (right) and 13 (left), separated medially by cluster of fine setae; posterolateral margin with row of setae.

Etymology. Named after New Zealand carcinologist Charles Chilton (1860–1929) who first reported this specimen from the Kermadec Islands.

Distribution. Kermadec Islands, New Zealand and possibly Kiribati; intertidal.

Remarks. The single specimen collected from the Kermadec Islands is more similar to Articullichirus collaroy than to A. articulatus . The new species differs from A collaroy and A. articulatus as follows: the transverse row of 28 spiniform setae on the telson exceeds those of the other species (<9), and the single or two spiniform setae placed laterally on the outside of the submedian ridges are absent in both A. collaroy and A. articulatus . The uropodal endopod has one distinct proximal spine on the dorsal surface, rather than two distinct spines as in both other species. Articullichirus chiltoni shares the distinct curved spine on the maxilliped 3 basis and the hook on the pereopod 1 coxa with A. collaroy ; these are absent or reduced in A. articulatus .

Sakai (2005) identified and partly illustrated two ovigerous females of “ Glypturus collaroy ” from Flax Bush Bay, New Zealand – these specimens cannot now be found ( R. Webber, pers. comm., 14 Dec 2021). Sakai (2005) specifically mentioned a spine on the merus of maxilliped 3 and a telson with a concave posterior margin. These features are consistent with Articullichirus but the upturned rostrum is enigmatic, more like that of Glypturus . Sakai (1999) recorded a very small male (cl. 4.5 mm) from Gilbert Is ( Kiribati) as “ Glypturus articulatus ”; this specimen (Swedish Museum of Natural History, SMNH 16226) cannot now be found (S. Stöhr, pers. comm., 7 Mar 2022). Sakai’s illustrations of the short excavate telson, uropodal endopod and maxilliped 3 resemble those of A. chiltoni . Minor differences, such as more teeth on the merus of the major cheliped, could be due to this specimen being only one third of the size of the holotype from New Zealand.

Figures

Figure 3. Articullichirus chiltoni sp. nov. New Zealand, CMNZ AQ3372 (holotype male, 14.7 mm). a, carapace, eyestalks, dorsal view; b, pleon, telson, dorsal view; c, anterior carapace, pterygostomium, eyestalk, antennular peduncle, antennal peduncle, lateral view; d, anterior carapace, eyestalk, antennular peduncle, antennal peduncle, dorsal view; e, thoracic sternite 7, pereopodal coxae 1–4, detail of right pereopodal coxa 1; f, maxilliped 3, outer view, detail of tooth on upper meral margin; g, maxilliped 3, inner view; h, major cheliped, left, lateral view; i, major cheliped, left,upper view; j, minor cheliped, right, lateral view. Scale bars = 1 mm.

Figure 4. Articullichirus chiltoni sp. nov. New Zealand, CMNZ AQ3372 (holotype male, 14.7 mm). a, left pereopod 2, outer view; b, left pereopod 3, inner view (setae not shown); c, left pereopod 3, outer view; d, left pereopod 4; e, left pereopod 4, detail of distal propodus and dactylus; f, pleopod 1; g, h, right and left pleopods 2; i, telson; j, uropodal endopod and exopod. Scale bars = 1 mm.