Ngankeecaris, Okuno & Yoshida, 2024

Okuno, Junji & Yoshida, Ryuta, 2024, A new genus, Ngankeecaris (Decapoda, Palaemonidae), with supplementary records of its type species, N. dardanicola (Bruce & Okuno, 2006) from the Ryukyu Islands, Japan, Zootaxa 5476 (1), pp. 342-346 : 343

Genus Ngankeecaris gen. nov.

Type species. Periclimenes dardanicola Bruce & Okuno, 2006 , by present designation.

Diagnosis. Small sized palaemonid shrimp with feebly depressed subcylindrical body form. Carapace smooth, antennal and fixed hepatic spines present, inferior orbital angle produced, without reflected inner ventral flange, pterygostomial margin subquadrate, not produced. Rostrum well developed, directed ventrally, lamina moderately deep, with 5–7 dorsal teeth and a single ventral tooth, lateral carina distinct. Ophthalmic somite without interocular process. Fourth thoracic sternite without median process, fourth and fifth sternites anteriorly each with transverse ridge with small median notch. Abdomen smooth, third tergite not posterodorsally produced, fourth and fifth pleura bluntly angular posteroventrally. Telson slightly tapering distally, dorsal surface armed with two pairs of spines in posterior half, posterior margin with three pairs of spines. Eye with developed globular cornea. Epistome unarmed. Antennule normally developed. Antenna with basicerite. Mandible without palp. Maxillipeds with exopods. Third maxilliped with a single arthrobranch. First pereiopod with movable finger not subspatulate, distal part armed or unarmed with fine denticulations. Second pereiopod with ischium, merus, carpus and palm armed ventrally with short transvers rows of spinulate tubercles. Third to fifth pereiopods with dactyli biunguiculate, propodi without distoventral tufts of setae. Endopod of first pleopod in males with median protuberance on inner margin.

Etymology. Combination of the Greek word karis meaning of shrimp, and the name of our friend, the late Dr. Ngan Kee Ng (1966–2022), who made numerous contributions on decapod crustacean taxonomy and gave us her warmest hospitality during our stay in Singapore. Gender: feminine.

Species included. In addition to the type species, Ngankeecaris acanthimera (Bruce, 2006) comb. nov., known only from the holotype captured at New Caledonia, belongs to the present new genus .

Common name. Gouzanze-kakure-ebi zoku (new standard Japanese name).

Remarks. As in the case of Periclimenes granuloides Hayashi, 1986 , P. tonga Bruce, 1988 , and Rapimenes granulimanus (Bruce, 1978) , some species included in Periclimenes sensu stricto and its closely related genera have the second pereiopod covered with granulations ( Li 2000). However, the presence of the short transvers rows of spinulate tubercles on the ventral surface of the second pereiopod ( Fig. 1C ) is an unusual morphological feature that only two species, N. dardanicola and N. acanthimera possess. Bruce (2006: fig. 6) represented the details of this feature by SEM images.

The structure of the thoracic sternites has not been previously described in N. dardanicola comb. nov. (see Bruce & Okuno 2006). In the holotype and paratype from Suruga Bay and an additional specimen from the Ryukyu Island, we can observe the presence of anterior transverse ridge with median notch on the fourth and fifth sternites. The ridges of the fifth sternite are higher than those of the fourth, and the notch is more distinct in the fifth than in the fourth ( Fig. 1B ). These morphological features in N. dardanicola comb. nov. are similar as those reported for N. acanthimera comb. nov. by Bruce (2006).

The general body form of Ngankeecaris gen. nov. resembles some of the Periclimenes members, P. paraparvus Bruce, 1969 , P. parvispinatus Bruce, 1990 , and P. parvus Borradaile, 1898 . These three species have been known only by their type specimens. Ngankeecaris gen. nov. shares with them the following morphological features: 1) the rostrum directed downwards, with deep lamina dorsally and ventrally dentate ( Fig. 1A ); 2) the supraorbital spine and eave being absent ( Fig. 1A ); 3) the dactylus of the first pereiopod not being subspatulate; and 4) the ambulatory pereiopods having biunguiculate dactyli. However, the feebly developed pterygostomial margin of the carapace ( Fig. 1A ) distinguishes Ngankeecaris gen. nov. from these Periclimenes species having a markedly produced subrectangular pterygostomial margin in addition to the row of tubercles on the ventral surface of the second pereiopods in Ngankeecaris gen. nov. that are absent in these Periclimenes species ( Bruce 1969, 1990; Bruce & Okuno 2006). Bruce (1969) indicated that P. paraparvus is distinguished from P. parvus by the lack of the short transverse rows of tubercles on the palm of the second pereiopod. Periclimenes parvus compared here is regarded to refer to the specimen from Indonesia reported by Holthuis (1952), and subsequently this specimen was designated as one of the paratypes of N. dardanicola by Bruce & Okuno (2006). The re-examination of the syntype of P. parvus showed that its second pereiopod is unarmed ( Bruce & Okuno 2006).

Figures

FIGURE 1. Ngankeecaris dardanicola (Bruce & Okuno, 2006) comb. nov. A, C, CMNH-ZC 2856, ♀, CL 4.3 mm; B, CMNH- ZC 1895, female (paratype of Periclimenes dardanicola), CL 3.6 mm. A, anterior part of carapace with rostrum, lateral; B, fourth and fifth thoracic sternites, ventral; C, right second pereiopod, distal part of merus, carpus and proximal part of palm, ventral.