Imbachoculodes, 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 : 2360-2361

Imbachoculodes gen. nov.

(Korean name: Ga-neun-son-but-eun-nun-yeop-sae-u-sok, new)

Diagnosis

Rostrum slightly deflexed; eye obscure; lateral cephalic lobe subacute or rounded; lower lip, inner plate coalescent, broad; mandible, incisor rather smooth, with obsolescent teeth, mandibular molar small, positioned close to end of spine row; maxilliped outer plate broad, about as wide as article 2 of the maxilliped palp; gnathopods 1 and 2 subchelate, similar in shape, slender, anterior margin of carpi elongate, about half length of propodi, carpal lobes narrow and appressed to ventral margin of propodi, propodi elongate-rectangular with oblique palms; pereopods 3–6, dactyli elongate, subequal to propodi; pereopod 7, basis narrowing distally, lacking posteroventral lobe; epimeral plate 3 with rounded posteroventral margin.

Type species

Imbachoculodes namhaensis sp. nov.

Species

Imbachoculodes angustipes ( Ledoyer, 1983) comb. nov.; Imbachoculodes longirostratus ( Hirayama, 1987) comb. nov.; Imbachoculodes namhaensis sp. nov.; Imbachoculodes vietnamensis sp. nov.

Etymology

The genus name is a combined form honouring Marilyn Clark Imbach, who first recognized that the specimen should belong to a new genus, and the suffix - oculodes.

Remarks

The genus Imbachoculodes is similar to Perioculodes Sars, 1895 in having the coalesced inner lobes of the lower lip and the oblique palms of gnathopods 1 and 2. Species of Imbachoculodes however, are unique in the Synchelidium group (including Perioculodes ) as mentioned by Hirayama (1992), in having the following characteristics: 1) mandible, incisor teeth obsolescent; 2) gnathopods 1 and 2 feeble and slender; 3) gnathopods 1 and 2, carpus elongate, about 0.5 times propodus; 4) pereopods 3–6, dactyli elongate; 5) pereopod 7, basis narrowing distally, lacking posteroventral lobe; and 6) epimeral plate 3 rounded posteroventrally. Diagnostic characters of the new genus are the slender and weakly setose, elongated carpi on gnathopods 1 and 2, elongated dactyli on pereopods 3 and 4 and pereopod 7 basis without posteroventral lobe. These characteristics show a close affinity to Hongkongvena Hirayama, 1992 . This genus is differentiated from Imbachoculodes by the following characteristics ( Hongkongvena condition in parentheses): 1) rostrum elongate (vs. short); 2) gnathopods 1 and 2 propodal palms oblique (vs. parallel to anterior margin); 3) gnathopods 1 and 2 carpi half length of propodi (vs. subequal or longer than propodi); 4) gnathopods 1 and 2 carpal lobes appressed along the ventral margin of the propodi (vs. gradually extending away from the ventral margin of the propodi); 5) epimeral plate 3 posterior margin smooth (vs. with prominent posterior cusp); 6) uropods 1–3, inner rami with spines (vs. setae); and 7) telson, subrectangular with rounded apex (vs. truncate distally).

The new genus is composed of four species: Imbachoculodes angustipes ( Ledoyer, 1983) comb. nov.; Imbachoculodes longirostratus ( Hirayama, 1987) comb. nov.; Imbachoculodes namhaensis sp. nov.; and Imbachoculodes vietnamensis sp. nov.

Ledoyer (1983) placed Perioculodes longimanus angustipes as a subspecies of P. longimanus (Bate and Westwood, 1868) based on characteristics including a distally broadened coxa 1, slender gnathopods 1 and 2 propodi (5 times as long as broad), elongated dactyli on pereopods 3 and 4 (as long as propodi), posteroventral corner of coxa 4 lacking strong seta and basis of pereopod 7 lacking the posteroventral lobe. These characters are considered here to be of generic level value and are used to diagnose the new genus Imbachoculodes . Therefore we transfer Perioculodes angustipes to the new genus.