Orthomanus, 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 : 2351-2353

Orthomanus gen. nov.

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

Diagnosis

Head galeate; rostrum moderately deflexed; lateral cephalic lobe rounded; lower lip, inner lobes coalescent basally; maxilla 1, first distolateral spine-tooth of outer plate massively enlarged; maxilla 2, plates setose, short; mandibular molar a conical hump, with two spine-teeth apically, situated very close to spine row, palp triarticulate and setose; antenna 1, peduncular article 2 subequal to article 3; gnathopods 1 and 2 subchelate, similar in shape, anterior margin of carpi obsolescent, carpal lobes slender and elongate, appressed to propodi, propodi elongate, palms transverse; pereopods 3 and 4, dactyli vestigial; pereopods 5 and 6, dactyli short; pereopod 7, basis subovate, posteroventral lobe produced rounded; epimeral plates 1–3 subquadrate posteroventrally.

Type species

Orthomanus koreanus sp. nov. by monotypy.

Etymology

The genus name is from the Greek orthos (straight) and Latin manus (hand), referring to the transverse palms of gnathopods 1 and 2.

Remarks

The new genus Orthomanus has close affinities with Perioculodes Sars, 1895 in possessing the following characters; 1) incisor of mandible toothed; 2) gnathopods 1 and 2 carpi rather short; 3) pereopods 3 and 4 dactyli short; 4) pereopod 7 basis with rounded posteroventral lobe; 5) epimeral plate 3 subquadrate. As shown in Table 1, Orthomanus is readily distinguished from Perioculodes and the other three genera by the following characters; 1) outer plate of maxilla 1 with massive apical spine-tooth; 2) maxilla 2 strongly setose; 3) gnathopods 1 and 2 carpi reduced; 4) gnathopods 1 and 2 propodi with transverse palms; 5) pereopods 3 and 4 dactyli vestigial; and 6) pereopods 5 and 6 dactyli short. These combined characters are not found among any known oedicerotid genera.