Oxyurostylis, Corbera, Jordi, 2008

Corbera, Jordi, 2008, New cumacean species (Crustacea: Peracarida) from Salomon Islands, Zootaxa 1743, pp. 17-33 : 28-32

Oxyurostylis ? salomonensis sp. nov.

( Figs. 10–12 )

Type material. Salomon Islands, cruise SALOMON I, V/ O “Alis” stn CP1783, 8°32.8’S 160°41.7’E, 399– 700 m, 29.09.2001: 1 adult female partially dissected in two slides, holotype (MNHN-Cu1135)

Description. Adult female 15.05 mm total length. Carapace ( Fig. 10 A, B) a fourth of total length, with a pair of lateral serrate carinae that meet dorsally near the middorsal line and ventrally with a short row of spines that runs parallel to the lateral margin, a pair of spines near the frontal lobe; pseudorostral lobes acute covered by small spines; eyelobe flattened without lenses; antennal notch well marked, lateral margin serrate. All 5 pereonites visible, being the fifth the wider.

Antennule ( Fig. 10 C) peduncle 3-articulate, article 1 with a long pappose seta on distal corner and a row of spines on distal margin; article 2 the shortest, with a group of simple setae proximally; article 3 as long as article 1. Mandible navicular ( Fig. 10 D, E), with 13 setae between pars molaris and pars incisiva, being three of them bifid; lacinia mobilis on left mandible tridentate. Maxillule with two lobes, palp with two filaments. Maxilla ( Fig. 10 F) with two endites bearing serrate setae. Maxilliped 1 ( Fig. 10 G) basis with seven plumodenticulate setae; merus with a long pappose seta on distal outer corner; carpus with four comb-like setae on inner margin and a long papose seta on distal outer corner. Maxilliped 2 ( Fig. 11 A) basis as long as the rest of appendage with three pappose setae distally; ischium broader than long with a pappose seta on inner margin; merus with two pappose setae medially; carpus half length of basis, with more than ten pappose setae on inner margin and a long pappose seta on distal outer corner; propodus half length of carpus with a long pappose seta proximally and simple setae on inner margin. Maxilliped 3 ( Fig. 11 B) with a well developed exopod, basis almost twice as long as the rest of appendage, wider distally and slightly produced, with many pappose setae on inner margin and six long plumose setae distally; ischium very short and expanded laterally; merus with a long pappose seta on distal outer corner; carpus as long as propodus with three pappose setae on inner margin and a longer one on distal outer corner; propodus with forked setae on inner margin.

Pereopod 1 ( Fig. 11 C), basis with a well developed exopod; shorter than rest of appendage with pappose setae on the both margins; ischium with a long pappose seta on distal margin; merus half length of carpus with pappose setae distally, distal outer corner with a tooth; carpus shorter than propodus; propodus with simple setae on margin; dactylus as long as carpus, with simple setae on ventral margin and terminally. Pereopod 2 ( Fig. 11 D) with a well developed exopod; basis as long as next four articles together, with long pappose setae and serrations on both margins and a cuspidate and three simple setae on distal ventral corner; ischium very short; merus with long pappose setae on ventral and distal margins; carpus twice as long as merus; propodus a third of carpus with simple setae on margin; dactylus slightly longer than propodus with six simple setae on ventral margin and three terminally. Pereopod 3 ( Fig. 12 A) with a small rudimentary 2-articulate exopod; basis longer than the rest of appendage, with a row of long pappose and simple setae on anterior margin, four pappose and some small simple setae on posterior margin and a row of spines on outer face; ischium short with a long simple setae distally; merus as long as carpus, with three long simple setae; carpus with long simple setae increasing in length and thickness towards distal end of article; propodus with a long simple seta on distal corner. Pereopod 4 ( Fig. 12 B) with a small rudimentary 2-articulate exopod, basis as long as rest of appendage, with ten pappose setae on anterior margin and a pappose and several simple setae on posterior margin; merus shorter than carpus, with three simple setae on the margin and three distally; carpus with long simple setae increasing in length and thickness towards distal end of article; propodus with a long simple seta on distal corner. Pereopod 5 ( Fig. 12 C) basis shorter than rest of appendage, with pappose and simple setae on both margins; ischium with long simple setae on distal margin; merus nearly half length of carpus with simple setae on distal margin; carpus with long simple setae increasing in length and thickness towards distal end of article; propodus with a simple seta distally.

Telson ( Fig. 12 C) longer than last pleon segment, postanal part longer than preanal part and with 16–18 pairs of lateral cuspidate setae; tip broken. Uropod peduncle ( Fig. 12 D) 1.5 times as long as telson, nearly three times as long as endopod with 30–32 small cuspidate setae on inner margin. Endopod 3-articulate with cuspidate setae on inner margin and three cuspidate setae terminally. Exopod longer than endopod, with three simple setae terminally.

Etymology. The new species is named after the Salomon Islands where the holotype was collected.

Remarks. The new species is difficult to assign to any genus due to the broken telson. It could be included in the genus Diastylis Say, 1818 but apparently it did not have a pair of terminal setae on the tip of the telson. It is provisionally included in the genus Oxyurostylis Calman, 1912 because more probably its telson tapers in an acute point. However, in genus Oxyurostylis setae of telson are few and weak while in the new species described herein setae are abundant and robust. Furthermore, the eight currently known species of this genus are all living in shallow waters and have a developed eyelobe, while in Oxyurostylis ? salomonensis sp. nov. it is flattened and lacking visual organs. So the new species could represent a new genus, but it could be described after the finding of some more whole specimens.

Figures

FIGURE 10. Oxyurostylis? salomonensis sp. nov. adult female holotype (MNHN Cu 1135): A, whole animal in lateral view; B, cefalotorax in dorsal view; C, antennule; D, right mandible; E, left mandible; F, maxilla 2; G, maxilliped 1.

FIGURE 11. Oxyurostylis? salomonensis sp. nov. adult female holotype (MNHN Cu 1135): A, maxilliped 2; B, maxilliped 3; C, pereiopod 1; D, pereiopod 2.

FIGURE 12. Oxyurostylis? salomonensis sp. nov. adult female holotype (MNHN Cu 1135): A, pereiopod 3; B, pereiopod 4; C, pereiopod 5; D, last pleonite, uropod and telson.