Eurypylus koreanus Karanovic & Soh, 2015, sp. nov.

Eurypylus koreanus sp. nov.

(Figures 1 A, 2, 3)

Etymology. The species is named after Korea.

Material examined. Holotype female dissected on one slide, shell on SEM stub (NIBR IV 0000287229); paratype female dissected on one slide, shell on micropaleontological slide (NIBR IV 0000287230), three paratypes (one female and two juveniles) in ethyl alcohol (NIBR IV 0000287231), and two paratypes used for DNA sequencing from (type locality) South Korea, East China Sea, Jeju Strait, Chuja Island, 29 November 2012, 33°43’37.954”N 126°21’36.641”E, collector H. Y. Soh.

Description. Female. Shell (Figures 1 A, 2A) ornamented with several ridges and wide, shallow pits. Caudal process not very long and distally pointed. Postero-dorsal bulge appearing fairly flat in lateral view. Dorsal and ventral edges of bulge almost straight, giving bulge square-like appearance. Dorsal margin above bulge straight, than rounded towards anterior and sloping down towards posterior end. Ventral margin rounded. Minute spines present along shell edges. Long individual bristles very sparsely distributed on lateral surface of valves. Long pore canals lead from posterior process to inside of valves, shorter ones present along entire anterior and ventral margin (Fig. 2 A). Anterior infold without bristles. Infold of caudal process with numerous short bristles (Fig. 2 B). Shell L (including caudal process) = 1.13 mm.

A1 (Figure 2 C). First segment long and bare. Second segment with few dorsal spines and annulated, bare dorsal bristle not reaching distal margin of following segment. Third and fourth segment fused; third with annulated, bare dorsal bristle reaching 1/3 of following segment and one slightly shorter ventral bristle. Fourth segment with one short, bare, annulated bristle dorsally and two bare, annulated bristles ventrally (one only reaching distal margin of following segment, other almost three times longer). Fifth and sixth segments fused. Bristle of fifth segment long, annulated and bare; seta on sixth segment very short, also bare. Seventh segment: abristle short (about two times longer than sixth segment’s bristle); b-bristle slender, bare and about two times longer than a-bristle; c-bristle as long as bristle of fifth segment. Eight segment: d- and e-bristles equally long, bare and shorter than c-bristle, e-bristle with one small filament about at half length; f- and g-bristles slightly shorter than fifth segment bristle, both annulated and bare. All bristles except sixth segment’s, a-, and b- with blunt tips.

Bellonci Organ (Figure 2 C). Cylindrical, not segmented.

Eyes. Both medial and lateral eyes present. Lateral eyes with three ommatidia. Medial eye with scattered pigment.

A2 (Figure 2 D). Prp bare. Enp with two short basal bristles (both annulated and bare), and one long, annulated and bare bristle situated on terminal node. Exp: first segment with small terminal medial recurved tubular bristle; bristle on second segment with slender proximal ventral spines and distal swimming setae; bristles on segments 2– 8 with swimming setae, no spines; ninth segment with two bristles (one short, bare and other longer with swimming setae).

Md (Figure 2 E, F). Cx endite not observed, Cx with short slender spines near ventral margin. Bs: ventral margin with four short bristles, dorsal margin bare with exception of a short marginal slender bristle. First Enp segment with short spines and with one stout claw distally; second Enp segment with one minute spine on dorsal margin, and strong claw ventrally; third Enp segment with stout terminal claw and small ventral spine.

Mxl (Figure 3 A, B). Cx with long, bare dorsal bristle. Endite I with four pectinate ringed claws; endite II with two pectinate claws and one ringed bristle; endite III with four pectinate claws and three ringed bristles. Exp with three bristles: two short and one long. First Enp segment with spinous alpha- and beta-bristles. Second Enp segment with five pectinate claws, two a- and one c-bristle.

L5 (Figure 3 C). Lobe one with one short bristle; lobe two with two bristles (one two times longer than other; shorter armed with tiny spines); lobes 3–5 fused and with total of seven bristles, all annulated and with spines, except most dorsal short bristle. Entire appendage hirsute.

L6 (Figure 3 E). Single endite with two bristles. Terminal segment with nine annulated bristles, each with short setulae, and almost all subequally long (except seventh in the row, which much shorter). Nine bristles followed by space and two long plumose bristles. Entire appendage hirsute.

L7 (Figure 3 D). Proximal group with only two bristles (one on each side) each with two or three bells. Terminal group with three bristles on each side, each with two or five bells. Terminus with opposing combs, each with about five alate teeth.

UL (Figure 3 F). Each lamella with five claws; claws one and two non-articulated; claws with long and short teeth along posterior edge. Each lamella with few spines along margin following claws.

Remarks and affinities. According to Kornicker (1996) the genus can be divided into two groups: petrosus - group containing species with secondary claws following the two primary ones, and the rousei -group where the two primary claws are followed by another set of primary claws. Eurypylus koreanus, together with E. darwinensis Kornicker, 1996, E. eagari Kornicker & Iliffe, 2000, E. hapax Kornicker & Iliffe, 2000, E. petrosus Brady, 1869 and E. setiferus (Poulsen, 1965) belongs to the petrosus -group. Eurypylus darwinensis and E. eagari have six claws, while E. setiferus has seven claws on the UL and thus all three clearly differ from E. koreanus. Eurypylus petrosus was originally described after juvenile (Brady 1869), and later on redescribed based on the type material (Kornicker & McKenzie 1976). The species is known only from the Cape Verde Island and is characterized by having only four claws on the UL. Although the number of claws may increase with maturity, the species has a different carapace shape in comparison to E. koreanus, i.e. almost without any caudal extensions. Eurypylus harpax remains the only species in the group, which, like the new one, has five claws on the UL. However, it has a very short, distally flat and wide caudal process; it lacks ribs and wide fossae on the surface of the shell, and can be easily distinguished from E. koreanus.