Epimeria (Laevepimeria), d’Acoz & Verheye, 2017

d’Acoz, Cédric d’Udekem & Verheye, Marie L., 2017, Epimeria of the Southern Ocean with notes on their relatives (Crustacea, Amphipoda, Eusiroidea), European Journal of Taxonomy 359, pp. 1-553 : 106-107

Subgenus Laevepimeria subgen. nov.

urn:lsid:zoobank.org:act:D1B62023-FFE4-4AEB-A345-89459C1063AC

Epimeriella Walker, 1906: 17 (in part).

Epimeriella – Gurjanova 1955: 189, 206 (in part). — J.L. Barnard 1961: 102 (in part); 1969: 161, 395 (in part). — McCain 1971: 160 (in part). — Karaman & J.L. Barnard 1979: 109 –110 (in part). — Holman & Watling 1983: 31 (in part, discussion). — Andres & Lott 1986: 131–136 (in part). — J.L. Barnard & Karaman 1991: 380, 394, 702 (in part). — Coleman 1998b: 215; 2007: 56 (in part). — Lörz & Brandt 2004: 179, 184, 188, 189 (in part).

Etymology

Combination of laevis, smooth in Latin, and Epimeria . That name, which is feminine, alludes to the absence of ornamentation in the species of that subgenus.

Type species

Epimeria walkeri (K.H. Barnard, 1930) .

Description

Body opaque, with teguments moderately calcified. Rostrum small but not minute (reaching about mid of article 1 of antenna 1). Eyes not conical. Pereionites and pleonites completely smooth (only pleonite 3 can be posterodorsally produced into a low bump). Coxae 1–4 with sharp or blunt tip. Coxae 1–3 not keeled along their axis. Coxa 1 with anterior margin proximally concave and with subdistal dilatation. Coxa 4 without carina or groove; posteroventral border straight or nearly so. Coxae 5–6 toothless. Mid of posterior border of epimeral plates 1–3 not produced into a tooth. Posteroventral tooth of epimeral plate 3 small. Dorsal process of urosomite 1 produced into a large blunt tooth, of which the anterior border is shorter than the posterior border (the posterior border of the tooth extend to the posterior border of urosomite 1). Urosomite 2 without pair of small teeth pointing upwards. Lateral borders of urosomite 3 posteriorly terminated into a blunt angle. Peduncle of antenna 1 without teeth. Mandible with molar process drawn out, without triturative surface. Lower lip with wide hypopharyngeal gap. Palp of maxilliped with 4 articles. Gnathopods of normal size, with carpus and propodus very stout, with palm reduced or normal; propodus not expanded distally; dactylus very stout, with long slender posterior teeth perpendicular (or nearly perpendicular) to axis of dactylus (as in a comb). Basis of pereiopods 5–6 fairly broad, with indistinct trace of posteroproximal process, with or without trace posterodistal blunt process projecting posteriorly. Basis of pereiopod 7 with posterior border convex along all its length or with slight distal concavity, with large distal lobe reaching 0.3 of merus. Merus of pereiopod 7 broad. In pereiopod 7, the sum of the merus, carpus and propodus is short: only about as long as basis or a little bit more. Dactylus of pereiopods 5–7 short.

Body length

The maximum body length recorded in Laevepimeria species ranges between 15 and 32 mm.

Ecology

Benthic, 170– 889 m.

Distribution

Circum-Antarctic, as far north as Elephant Island.

Remarks

Laevepimeria subgen. nov. and Epimeriella form a large clade together. These subgenera share synapomorphies in the morphology of the mandible (molar process non triturative) and the lower lip (wide hypopharyngeal gap), and were formerly grouped into the genus Epimeriella s. lat. However, Laevepimeria subgen. nov. and Epimeriella s. str. exhibit striking differences in the morphology of the body, gnathopods and pereiopods. These differences are presumably related to their benthic lifestyle ( Laevepimeria subgen. nov.) versus a pelagic or semi-pelagic lifestyle ( Epimeriella ). These subgenera can be identified without dissection, which was not possible with the former concept of Epimeriella .

Key to the species of Laevepimeria

1. Coxa 4 narrow; palm of gnathopods not reduced (gnathopods subcheliform); posterior border of basis of pereiopod 7 regularly rounded …………………………………………………………………2

– Coxa 4 broad; palm of gnathopods reduced (gnathopods nearly achelate); posterior border of basis of pereiopod 7 sinuate ……………………………………………………………………………3

2. Tip of coxae 1–2 subacute …………………………………………………… E. (Laevepimeria) cinderella subgen. et sp. nov. [Elephant Island and tip of Antarctic Peninsula]

– Tip of coxae 1–2 very broadly rounded ………………………………………………………… …………………………………………… E. ( Laevepimeria ) sp. subgen. nov. [Bransfield Strait]

3. Rostrum narrow in frontal view; eyes huge (interocular distance about 1.3 × as wide as eye size when seen in frontal view) and oriented forward (in frontal view the eyes appears about as high as wide); in lateral view the eyes almost reach the tip of head and the head appears as very strongly curved; posterodistal corner of basis of pereiopod 5 produced into a blunt angle, posterodistal corner of basis of pereiopod 6 forming a well defined squared angle; posterodistal corner of basis of pereiopod 7 forming a triangular tooth; pleonites 1–3 not carinate and not posteriorly produced..……..... E. (Laevepimeria) walkeri subgen. nov. (K.H. Barnard, 1930). [Elephant Island, tip of Antarctic Peninsula, Weddell Sea, Adélie Coast, Ross Sea]

– Rostrum broad in frontal view; eyes medium-sized (interocular distance about 3 × as wide as eye size when seen in frontal view) and their orientation is no more lateral than frontal (in frontal view the eyes appears as higher than wide); in lateral view the eyes are far from reaching the tip of head and the head appears as moderately curved; posteroventral corner of basis of pereiopod 5 and pereiopod 6 rounded; posterodistal corner of basis of pereiopod 7 forming a tiny rounded lobe; pleonites 1–3 weakly carinate and posterodorsally weakly produced ..…………………... E. (Laevepimeria) anodon subgen. et sp. nov. [Adélie Coast]