Imbachoculodes vietnamensis, Kim & Hendrycks & Lee, 2012

Kim, Young-Hyo, Hendrycks, Ed A. & Lee, Kyung-Sook, 2012, New genera and species of the Synchelidium group (Amphipoda: Oedicerotidae) from Asia-North Pacific, Journal of Natural History 46 (37 - 38), pp. 2349-2376 : 2367-2369

Imbachoculodes vietnamensis sp. nov.

(Korean name: Be-teu-nam-but-eun-nun-yeop-sae-u, new)

( Figure 9 )

Oedicerotidae genus sp. Imbach, 1967: 83, fig. 27.

Perioculopsis sp. Barnard and Karaman, 1991: 565.

Material

Holotype. Female. Body 3.0 mm, Bay of Nha-Trang , South Vietnam, station 267, 21 March 1960, collected with van Veen grab on coarse brown sand bottom, depth 15 m.

Etymology

The new species is named for its occurrence in Vietnam.

Description

Body ( Figure 9A ) 3.0 mm long. Head galeate, deeper than long, slightly longer than pereonites 1–3 combined. Rostrum short, deflexed, subacute distally. Lateral cephalic lobe rounded. Eye present. Mandible ( Figure 9B,C ) incisor smooth, triturative molar absent, palp triarticulate. Maxilla 1 ( Figure 9D ) inner plate subtriangular, outer plate with seven spine-teeth apically. Maxilliped ( Figure 9F ) outer plate not reaching end of article 2 of palp. Gnathopods 1 and 2 ( Figure 9G,H ) similar in shape, subchelate, slen- der, anterior margin of carpi elongate, carpal lobes narrow, elongate, slightly exceeding palmar corner, propodi subrectangular, palms oblique. Pereopod 7 ( Figure 9A ) basis subovate, lacking posteroventral lobe. Epimeral plate 3 ( Figure 9A ) posteroventral margin rounded. Uropod 1 ( Figure 9I ) peduncle longer than rami, outer ramus slightly shorter than inner. Uropod 2 ( Figure 9J ) peduncle subequal to inner ramus; inner ramus longer than outer ramus. Uropod 3 unknown. Telson ( Figure 9K ) subquadrate, broad, as wide as long.

Remarks

Imbach (1967) presented a single female specimen collected from Vietnam, South China Sea in which she states “... probably represents a new genus of the family Oedicerotidae ”. The specimen was partially figured, but some pereopods were not figured clearly enough for critical examination. It was left unnamed largely because only a single specimen was collected and several questionable points regarding the condition of the mouthparts could not be resolved. Barnard and Karaman (1991) transferred this unnamed species into Perioculopsis Schellenberg, 1925 because of the smooth incisors of the mandibles. We feel that the inclusion of this species into Perioculopsis is not satisfactory. It differs from Perioculopsis in several major characteristics: Perioculopsis has a posteroventrally bevelled coxa 6, a toothed peduncular article 1 of antenna 1, and an emarginate telson, whereas Imbach’s specimen does not have these features. This species has many characteristics in common with the new genus Imbachoculodes , such as slender gnathopods 1 and 2, the length ratio of carpi-propodi of gnathopods 1 and 2, elongated dactyli of pereopods 3 and 4, and posterodistally rounded epimeral plate 3, as well as a smooth incisor. Even though the specimen is unique and under normal conditions it is undesirable to describe new taxa from a single specimen, it does conform very well to our new genus. It is here described as a new species of the new genus Imbachoculodes .

For relationship to other species, see preceding remarks for I. namhaensis and the key.

Distribution

Vietnam (Bay of Nha-Trang).

Key to the species of Imbachoculodes gen. nov.

1. Lateral cephalic lobe acute or subacute.................................. 2 Lateral cephalic lobe rounded........................................... 3

2. Rostrum acute distally; antenna 1, peduncular article 2 shorter than article 3; outer plate of maxilliped extending beyond palp article 2............................................................ I. longirostratus ( Hirayama, 1987) Rostrum subacute distally; Antenna 1, peduncular article 2 longer than article 3; outer plate of maxilliped not reaching palp article 2.......................................................................... I. namhaensis sp. nov.

3. Telson broad, as wide as long; maxilla 2, both plates slender, about 0.2 times width.............................................. I. vietnamensis sp. nov. Telson longer than wide; maxilla 2, both plates broad, short, about 0.5 times width........................................ I. angustipes ( Ledoyer, 1983)

Figures

Figure 9. Imbachoculodes vietnamensis gen. et sp. nov., holotype, female, 3.0 mm: (A) habitus; (B) right mandible; (C) left mandible; (D) maxilla 1; (E) maxilla 2; (F) maxilliped; (G) carpusdactylus of gnathopod 1; (H) carpus-dactylus of gnathopod 2; (I) uropod 1; (J) uropod 2; (K) telson (after Imbach, 1967).