Bruceopsis, Anker, Arthur, 2010

Anker, Arthur, 2010, Description of a new genus and two new species of alpheid shrimps from Guam (Crustacea, Decapoda) *, Zootaxa 2372, pp. 389-404 : 390-391

Bruceopsis gen. nov.

Diagnosis. Body not particularly slender or compressed. Carapace smooth, without teeth, grooves or ridges; cardiac notch well developed. Frontal margin with acuminate rostrum and more or less developed orbital teeth. Pterygostomial angle slightly projecting anteriorly, rounded. Eyes completely or almost completely concealed in dorsal and lateral views; corneas well developed. Epistomial sclerites with sharp, ventrally projecting teeth. Abdomen with second pleomere conspicuously enlarged in female; sixth abdominal somite not elongate, with distinct, more or less projecting articulated plate at posteroventral angle. Telson with two pairs of dorsal spines and two pairs of posterolateral spines; posterior margin rounded; anal tubercles absent.

Antennular peduncle with elongate stout stylocerite; lateral antennular flagellum with well-developed secondary ramus. Antenna with robust basicerite and broadly ovate scaphocerite. Mouthparts typical for Alpheidae ; mandible with palp, molar and incisor processes well developed; maxillule with bilobed palp, both lobes furnished with setae; first maxilliped with segmented palp and moderately developed caridean lobe. Third maxilliped pediform, setose; lateral plate of coxa small; tip of ultimate segment with small subdistal spines. First to fourth pereiopods with small coxal lobes laterally (less pronounced on P2). First pereiopods (= chelipeds) moderately or not enlarged, equal or unequal in size, symmetrical or asymmetrical in shape, carried extended with dactylus in dorsolateral position; ischium unarmed, merus smooth, with one comb-like setal row distomesially; carpus cup-shaped, with comb-like setal rows mesially (carpo-meral brush); chela simple, with smooth palm; linea impressa and adhesive discs not distinct; cutting edges of fingers unarmed or armed with small, simple teeth, without snapping mechanism. Second pereiopod with five-segmented carpus, first segment longest. Third and fourth pereiopods slender; ischium with spines; merus and carpus unarmed; propodus with small ventral spines; dactylus simple, acute distally, notched on dorsal (extensor) margin. Fifth pereiopod with setal brush on propodus. Male second pleopod unknown; female second pleopod with appendix interna. Uropod with sinuous diaeresis on exopod. Gill/exopod formula: 5 pleurobranchs (above P1–5); 1 arthrobranch (at Mxp3); 0 podobranchs; 7 epipods (2 on coxae of Mxp1–2; 5 mastigobranchs on coxae of Mxp3, P1–4; 5 setobranchs on coxae of P1–5); 3 exopods (Mxp1–3).

Type species. Bruceopsis projectus sp. nov.

Other species included. Bruceopsis guamensis sp. nov.

Etymology. The new genus is named for Dr. Alexander J. (Sandy) Bruce (Queensland Museum, Brisbane), for his more than significant contribution to the taxonomic knowledge of caridean shrimps; the generic name derives from Sandy’s last name and the last five letters from Alpheopsis , a genus that superficially resembles Bruceopsis gen. nov.

Distribution. Bruceopsis gen. nov. is presently known only from Guam in the Mariana Islands in the western Pacific Ocean.

Remarks. Based on morphological criteria, Bruceopsis gen. nov. belongs to a small group of mostly monotypic genera characterised by the dorsally completely or almost completely concealed eyes and the presence of carpal brushes on the chelipeds. The other three genera in this group are Coutieralpheus , Leslibetaeus and Harperalpheus . Bruceopsis gen. nov. differs from all three genera by the distinctly notched dorsal margin of the dactyli of the third to fifth pereiopods; the presence of a blunt process on the coxae of the first to fourth pereiopods; and the presence of carpo-meral brushes on the chelipeds, as opposed to the carpal brushes in other genera. The new genus differs from Coutieralpheus by the generally weaker chelipeds, the presence of orbital teeth; the absence of stout setae on the tip of the rostrum; the absence of spines on the merus of the third and fourth pereiopods, and also the significantly longer stylocerite. It differs from both Leslibetaeus and Harperalpheus by the sixth pleonite bearing a distinct, more or less projecting, articulated triangular plate at posteroventral angle; and specifically from Leslibetaeus by the presence of orbital teeth and especially a well-developed rostrum; the much longer stylocerite and scaphocerite; the presence of a spine on the ischium of the third and fourth pereiopods; the general shape of the chelipeds, including a more slender chela and the absence of strong spines on the dorsal margin of the ischium. The new genus can be separated from Harperalpheus by the non-protruding pterygostomial angle of the carapace; the presence of orbital teeth; the distally rounded (not sharply produced) preanal plate on the sternal side of the sixth pleonite; and the absence of spine on the merus of the third to fifth pereiopods.

On the other hand, Bruceopsis gen. nov. superficially resembles and shares numerous features with genera characterised by dorsally covered eyes, a more or less developed rostrum, the presence of an articulated plate on the sixth pleonite and the symmetrical or subsymmetrical chelipeds. This group includes the fairly speciesrich, heterogeneous and possibly non-monophyletic genus Alpheopsis , the smaller and much more homogeneous genera, Prionalpheus Banner & Banner 1960 , Parabetaeus Coutière, 1896 and the recently described, monotypic genus, Pseudalpheopsis Anker, 2007 . Bruceopsis gen. nov. differs from all these genera by the presence of mero-carpal brushes on the chelipeds, but also by the notched dorsal margin of the dactyli of the third to fifth pereiopods and the presence of a blunt process on the coxae of the first to fourth pereiopods. The new genus can be distinguished from Alpheopsis s. lat. by the absence of strong spines on the cheliped ischia (these spines are typically present in Alpheopsis ); from Parabetaeus by the non-projecting posterior margin of the telson; from Prionalpheus by the non-specialised mouthparts and non-biunguiculate dactylus of the third to fifth pereiopods; and from Pseudalpheopsis by the absence of a tooth above the pterygostomial angle of the carapace, the cheliped fingers not conspicuously gaping distally and without an elevated toothed ridge on the cutting edges proximally. It is possible that Bruceopsis n. gen. represents a relatively basal lineage within a larger clade that contains Alpheopsis sensu lato, Pseudalpheopsis , Parabetaeus , Prionalpheus , possibly Coutieralpheus and Harperalpheus , and perhaps also Nennalpheus Banner & Banner, 1981 , Notalpheus Méndez & Wicksten, 1981 , and Orygmalpheus De Grave & Anker, 2000 .