Urocaris Stimpson, 1860

Bruce, A. J., 2007, The resurrection of the pontoniine genus Urocaris Stimpson, 1860, (Crustacea: Decapoda: Palaemonidae), Zootaxa 1632 (1), pp. 61-67 : 61-62

Genus Urocaris Stimpson, 1860

Urocaris Stimpson, 1860: 39 .— Kingsley, 1880: 380. — Rathbun, 1902: 126. — Borradaile, 1917: 353. — Holthuis, 1993: 164.

Diagnosis. Small sized shrimps of subcylindrical body form. Carapace smooth; rostrum well developed, compressed, with well developed dorsal carina with numerous acute dorsal teeth, lateral carinae feebly developed, ventral carina obsolete, ventral margin feebly dentate distally: orbit feebly developed, inferior orbital angle produced, blunt, knob-like, without ventral flange; supraorbital teeth and spines, epigastric and hepatic spines present, antennal spine absent:; antennule normally developed: antenna with basicerite with lateral tooth, scaphocerite well developed; eye with globular cornea, stalk elongate; epistome with short slender acute median process, hemispherical lateral bosses; mandible without palp, molar process robust, dentate, incisor processes normal; maxillula with bilobed palp, laciniae moderately slender; maxilla with simple palp, basal endite deeply bilobed, coxal endite obsolete, scaphognathite normal; first maxilliped with simple palp, basal endite broad, coxal endite feebly separated, exopod with well developed flagellum with broad caridean lobe, epipod large, triangular, feebly bilobed; second maxilliped with normal endopod, exopod similar to first maxilliped, without accessory lobe, coxa with subrectangular epipod, without podobranch; third maxilliped with slender endopod, ischiomerus fused with basis, exopod as in second maxilliped, coxa with well developed oval lateral plate, with single small multi-lamellar arthrobranch; fourth thoracic sternite without median process, with two transverse ridges, posterior ridge with paired submedian knobs; first pereiopods slender, chela with simple fingers with entire cutting edges; second pereiopods well developed, unequal, palm smooth, fingers without molar process or fossa, without dactylar flanges, merus and carpus unarmed; ambulatory pereiopods slender, dactyls biunguiculate; abdomen smooth, elongate, third segment slightly posterodorsally produced, sixth segment length subequal to CL, pleura rounded; telson with two pairs of dorsal spines and three pairs of posterior spines; uropod with protopodite posterolaterally unarmed, exopod with small distolateral tooth, small mobile spine.

Etymology. From “ουρα, cauda, καριζ, squilla”; probably in reference to the long abdomen of the type species ( Holthuis, 1993). Gender, feminine.

Systematic Position. Urocaris Stimpson is naturally particularly closely related to the genus Periclimenes Costa, 1844 , in which it has long been included. It is particularly closely related to the species of Periclimenes in the restricted genus, senso Bruce (2004). The genus Urocaris is distinguished from Periclimenes primarily by the absence of an antennal spine, a character, not found in the majority of pontoniine shrimp genera, that is shared by the species referred to Paraclimenes Bruce, 1994 . The latter is an Indo-West Pacific genus found in deep water conditions. Urocaris is easily distinguished from Paraclimenes by the rostrum, lacking a ventral carina, with few small acute distal teeth only in the former genus, and with a well developed ventral carina with 3–4 well developed, more centrally placed, acute teeth in the latter.

Urocaris is particularly similar to the Periclimenes species of the aesopius -species group, most noticeably in the form of the rostrum, slender, with a low dentate dorsal carina and obsolete ventral carina, with few small acute distal teeth only. The absence of the antennal spine in Urocaris immediately distinguishes it from all species of the Periclimenes aesopius species group. The knob-like inferior orbital angle in Urocaris , without a ventral flange, further separates these genera. As noted in the Etymology above, the reference of the generic name to the long abdomen of the type species ( Holthuis, 1993) indicates a further similarity to species of the aesopius group, in which the abdomen is also particularly well developed in comparison to the cephalothorax: it is further echoed in the specific name of the type species. The relative size of the abdomen compared with the carapace contrasts strongly with the genus Periclimenes ( Fig. 4 ).

The anteriorly directed median process and the hemispherical lateral bosses of the epistome ( Fig. 3A ) are unusual features without parallel in any other pontoniine genus so far reported. It is not present in aesopius species group, e.g. Periclimenes holthuisi (pers. obs.). A median process, however, has been reported in the un-related genera Bresilia spp. and Encantada ( Bruce, 2004) . Its functional importance is unknown..

Figures

FIGURE. 4. Comparison of abdominal size and postorbital carapace length between A, Urocaris longicaudata Stimpson, and B, Periclimenes amethysteus (Risso), adapted from Holthuis, 1993, fig. 155.

FIGURE. 3. Urocaris longicaudata Stimpson, male, Tobago, CL 1.9mm, OUMNH-ZC 2004-19-003. A, epistome. B, right inferior orbital region, lateral. C, same, dorsal. D, thoracic sternites. E, mandible, incisor process. F, left antennal peduncles and epistome, medial aspect.