Chorisquilla excavata ( Miers, 1880 )

Ahyong, Shane T., 2017, Stomatopod Crustacea of the Austral and Gambier Islands, French Polynesia, Zootaxa 4286 (4), pp. 555-564 : 560-561

Chorisquilla excavata ( Miers, 1880)

( Fig. 1 C, 3)

Gonodactylus excavatus Miers, 1880: 123 , pl. 3, figs. 11–12 [type locality: unknown]. Protosquilla excavata . — Brooks 1886: 78.

Chorisquilla excavata .— Manning 1969b: 159; 1975: 254–255, fig. 1a, c.— Moosa 1991: 163.— Ahyong & Harling 2000: 635.— Ahyong 2001: 88, 91.

Material examined. Holotype: NHM 62.35, male (TL 22 mm), locality unknown, coll. H.M.S. Herald.

AUSTRAL ISLANDS: Tubuai Islands : MNHN IU- 2016-9518, 1 male (TL 23 mm), 5 females (TL 17–29 mm), Président Thiers Bank, 24°38.16'S, 146°00.82'W, 50–90 m, BENTHAUS stn DW1926, 13 November 2002 .

SOCIETY ISLANDS: AM P64480, 1 male (TL 13 mm), Pointe Venus , Baie de Matavai , Tahiti, Society Islands, French Polynesia, 17°29.60'S, 149°29.95'W, 20 m, on scuba, FRP-75, coll. J. Lowry & M. Arakino, 27 August 1991.

Diagnosis. Rostral plate sharply trispinous, each spine slender. Mandibular palp 2-segmented. Abdominal somite 5 mid-dorsal surface smooth, with few well-spaced pits; lateral margins with 2 low ridges above marginal carina. Abdominal somite 6 with smooth, glabrous submedian and intermediate bosses; lateral boss with posterolateral spine. Telson with 2 pairs of fixed primary teeth; submedian bosses elongate, margins smooth or at most slightly eroded, weakly sinuous, extending posteriorly to base of submedian primary teeth, well beyond base of median excavation of telson; median boss short, pyriform, margins smooth; lateral margins of telson relatively straight to rounded; submedian denticles present in adults. Uropodal protopod with dorsal spine at articulation with exopod; without upright spines on dorsoproximal surface adjacent to articulation with abdominal somite 6. Proximal segment of uropodal exopod with blunt, obsolete lobe lateral to articulation of distalmost movable spine.

Remarks. Despite being the type species of Chorisquilla Manning, 1969b , C. excavata has had a somewhat unstable taxonomic history. Manning (1975) re-evaluated prior records of the species and described a new species, C. andamanica from the Andaman Sea, and C. pococki from the Indo-Malay archipelago and South China Sea. Subsequently, Moosa (1986) synonymized C. pococki and C. andamanica with C. excavata , but Ahyong (2001) showed all three species to be valid in addition to describing a new closely related species, C. convoluta from northwestern Australia. Chorisquilla excavata sensu stricto and has only ever been minimally figured ( Miers 1880: pl. 3, figs. 11–12; Manning 1975: fig. 1a, c). Other published figures attributed to C. excavata represent C. andamanica (see Kemp 1913: pl. X, figs. 122–123) or C. pococki (see Hansen 1926: pl. II, 4a; Moosa 1986: fig. 4).

In view of the fluid taxonomy of C. excavata , and because it has never been adequately figured, the species is rediagnosed and refigured here.

Characteristic of C. excavata is the combination of posterolateral spines on abdominal somite 6 and elongate, smooth submedian bosses of the telson in which the margins are at most slightly eroded, rather than distinctly eroded or fissured as in C. pococki Manning, 1975 and C. convoluta Ahyong, 2001 . Chorisquilla andamanica lacks the posterolateral spine on abdominal somite 6. Chorisquilla excavata appears to occur largely on oceanic islands and reefs ranging from New Caledonia to Fiji and now the Austral Islands, whereas C. pococki occurs in the South China Sea and neighbouring localities. Chorisquilla andamanica and C. convoluta both occur in the Indian Ocean, the former from the Andaman Sea and the latter from Western Australia .

Specimens of Chorisquilla excavata in the present series agree well with the holotype in diagnostic features. Allometric change is evident in the telson shape: the lateral margins are relatively straight in the smallest specimens, becoming increasing curved with size.

As with the lectotype of Raoulserenea ornata ( Miers, 1880) and holotype of Mesacturus furcicaudatus ( Miers, 1880) , the holotype of C. excavata was collected during the voyage of the HMS Herald from an unrecorded locality. The Herald collected in the southwestern Pacific Ocean between northern Australia, New Caledonia and particularly Fiji between 1853 and 1861 ( David 1995) and it a likely the holotype of C. excavata is from one of these localities.

Distribution. Southwestern Pacific from New Caledonia and Fiji to the Society Islands; now from the Austral Islands; shallow water to 90 m.

Figures

FIGURE 1. A, Bathysquilla microps (Manning, 1961), female, TL 86 mm, BENTHAUS stn CP 1891 (MNHN IU- 2016 - 9501). B, Odontodactylus hawaiiensis Manning, 1967, female, TL 80 mm, BENTHAUS stn CP 1922 (MNHN IU- 2016 - 9517). C, Chorisquilla excavata (Miers, 1880), female, TL 28 mm, BENTHAUS stn DW 1926 (MNHN IU- 2016 - 9518). (Photos: Laurent Albenga).