Epimeria (Drakepimeria) macrodonta, 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 : 47-49

Epimeria (Drakepimeria) macrodonta subgen. nov. Walker, 1906

Figs 72–76

Epimeria macrodonta Walker, 1906: 16 (in part).

Epimeria macrodonta – Walker 1907: 24 (in part), pl. 8 fig. 14. — Lockyer 1907: 35. — J.L. Barnard 1961: 103 (key, in part). — McCain 1971: 161. — Dell 1972: 71, fig. 7a (after Walker). — De Broyer & Klages 1991: 165 (key, in part). — Wakabara & Serejo 1999: 642 (key, in part). — Lörz et al. 2007: 32, table 1 (lectotype designation).

Epimeria macrodonta macrodonta – Gurjanova 1955: 195.

Type material

Lectotype

National Antarctic Expedition 1901 – 1904, RV Discovery:

SOUTHERN OCEAN: 1 spec., sex undetermined, Ross Sea, W. Q. [Winter Quarters — hole 12] 2–4 Sep. 1903, “236”, “237” (these two enigmatic numbers are put in a circle), J.107, depth not stated, lectotype designated by Lörz et al. (2007), although no label by Lörz indicating its status as lectotype is present ( BMNH 1907.6.6.259-262) (in part).

Paralectotypes

National Antarctic Expedition 1901 – 1904, RV Discovery:

SOUTHERN OCEAN: 1 juv., mixed in the same tube with an adult ♀ of Epimeria colemani, Ross Sea , no locality but presumably McMurdo Sound, n° 13, 914 m (500 fathoms), 22 Jan. 1902, obviously 2 of the paralectotypes of Epimeria macrodonta designated by Lörz et al. (2007), albeit no label by Lörz indicating their status as paralectotypes ( BMNH 1907.6.6.259-262) (in part); 1 spec., sex undetermined, dissected by Walker, Ross Sea, no locality but presumably McMurdo Sound, 914 m (500 fathoms), 22 Jan. 1902, obviously 1 of the paralectotypes of Epimeria macrodonta designated by Lörz et al. (2007), albeit no label by Lörz indicating its status as paralectotype, 3 tubes ( BMNH 1907.6.6.259-262) (in part).

Description

Basis of description. Description based on lectotype.

ROSTRUM. Long, reaching base of article 2 of peduncle of antenna 1 (teeth excluded), strongly curved, sharp-tipped in lateral view.

EYE. Large, broadly elliptic.

PEREION–PLEOSOME TOOTH PATTERN. Pereionite 1 with small and blunt posterior mid-dorsal protrusion, with pair of low dorsolateral protrusions; pereionite 2 much narrower than pereionites 1 and 3, without mid-dorsal tooth and without pair of dorsolateral teeth; pereionite 3 with medium-sized fairly broad and fairly blunt mid-dorsal tooth pointing upwards and pair of low and blunt, conical, dorsolateral teeth; pereionite 4 to pleonite 2 with large, narrow to very narrow, acute mid-dorsal tooth, of which the anterior border is almost regularly curved, with inconspicuous trace of angular discontinuity (pereionites 4–6) or with weak but distinct angular discontinuity (pereionite 7 and pleonites 1–2), and the posterior border is slightly concave, with pair of conical dorsolateral teeth of which the size gradually increases posteriorly (these pairs of teeth are never duplicate); pleonite 3 with large narrowly triangular acute-tipped subsymmetrical mid-dorsal tooth, and pair of large narrowly conical dorsolateral teeth (size of mid-dorsal teeth weakly and gradually increasing from pereionite 4 to pleonite 2; mid-dorsal tooth of pleonite 3 distinctly shorter than tooth of pleonite 2).

COXAE 1–3. Strongly carinate and distally sharp; in dorsal view, the tip coxa 3 appears as projecting laterally.

COXA 4. Anterodorsal border straight, anteroventral border distally nearly straight, these two borders being joined by a long weak curve (anterior angle), this anterior angle is weakly projecting forward; ventral tooth extremely long, very narrow and acute, weakly arching backwards; lateral carina with well developed tooth pointing obliquely backwards (in dorsal view its anterior border strongly diverges from body axis; in dorsal view this tooth form a narrow U-shaped notch with the coxa); carina very distant from margin of coxa at its deepest point.

COXA 5. With long, sharp and narrowly triangular, carinate, lateral tooth pointing obliquely backwards (its anterior and posterior margins are distinctly oblique to body axis).

COXA 6. With mid-sized, sharp and narrowly triangular, carinate, lateral tooth pointing obliquely backwards; its anterior border is distinctly convex); posteroventral corner broadly rounded.

COXA 7. With ventral border distinctly curved, with posterior border nearly straight (inconspicuously convex), their convergence forming a curve (a very blunt squared angle).

EPIMERAL PLATES 1–3. Posteroventral angle produced into a very long and very sharp tooth.

UROSOME TOOTH PATTERN. Urosomite 1 with large and sharp narrow tooth pointing upwards; urosomite 2 with pair of mid-sized posterior dorsolateral teeth pointing upwards; urosomite 3 with pair of mid-sized posterior dorsolateral teeth pointing obliquely backwards.

TELSON. Cleft on 0.33; tips of lobes subacute, notch narrowly V-shaped.

PEDUNCLE OF ANTENNA 1. Article 1 with long lateral tooth and short medial tooth reaching respectively 0.9 and 0.33 of article 2 (teeth excluded) and long ventral tooth overreaching tip of article 2 (teeth excluded) by 0.4 of its length; article 2 with huge lateral tooth of which 0.6 is overreaching tip of article 3, and very huge medial teeth of which 0.7 is overreaching tip of article 3, without ventral tooth; article 3 with tiny ventral tooth, about 0.25 times as long as article itself.

GNATHOPODS 1–2. Carpus and propodus of normal slenderness; palm distinct.

PEREIOPODS 5–7. Merus, carpus and propodus slender; basis of pereiopods 5–6 of normal width, with posteroproximal process rounded and strongly protruding, with posterodistal tooth very strong (nearly as long as basis width); basis of pereiopod 7 broad with posterodistal tooth acute, triangular, mid-sized, followed more proximally by distinct concavity, directed posteriorly.

Body length

Up to 25 mm.

Variations

The juvenile specimen has no posterodorsal bump on pereionite 1.

Distribution

Ross Sea: Winter Quarters Bay [about 77°50ʹ S, 166°39ʹ E], no depth record [lectotype]; Ross Sea, no locality, 914 m [paralectotypes] ( Walker 1906, 1907). The paralectotypes were presumably collected in McMurdo Sound because Hodgson (1907) stated that “on the 20th of January 1902, the ‘Discovery’ passed across the mouth of the McMurdo Sound” and the specimens were collected shortly afterwards, on 22 Jan. 1902.

Remarks

Epimeria macrodonta is morphologically similar to E. anguloce sp. nov. (Antarctic Peninsula, eastern Weddell Sea and Prydz Bay) and E. corbariae sp. nov. (Adélie Coast). Epimeria macrodonta can be distinguished from its relatives by the length of the teeth on article 1 of antenna 1 peduncle. In E. macrodonta , the lateral tooth is indeed considerably longer than the medial tooth, whilst in other species the teeth are subequal. It also exhibits other distinctive characters: lateral and medial tooth of article 2 of peduncle of antenna 1 especially long; ornamentation of pereionite 1 weak or absent; middorsal tooth of pereionite 4 to pleonite 2 especially long and slender (those of pereionite 6 and pleonite 1–2 exhibiting a slight angular discontinuity on their anterior border); ventral tooth of coxa 4 especially long; lateral tooth of coxae 4 and 5 very oblique in dorsal view; coxa 7 with posterior border nearly straight (inconspicuously convex), with posteroventral angle rounded; posterodistal tooth of basis of pereiopod 7 not very strong.

The type locality of E. macrodonta is Ross Island (Ross Sea). Lörz et al. (2007) mistakenly reported Ross Island as being located off the Antarctic Peninsula. This lapsus might result from a confusion between Ross Island (Ross Sea) and James Ross Island (Antarctic Peninsula).

E. macrodonta s. lat. has previously been recorded throughout the Southern Ocean, south of the Polar Front at depths shallower than 1000 m. However, all specimens except the lectotype and two of the three paralectotypes of E. macrodonta belong to other species.

Figures

Fig. 72. Epimeria (Drakepimeria) macrodonta subgen. nov. Walker, 1906, sex undetermined, lectotype, RV Discovery, National Antarctic Expedition 1902–1904, Ross Sea, Winter Quarters — hole 12, 2 to 4.9.1903, J.107, BMNH 1907.6.6.259-262 (in part). A. Left habitus. B. Right habitus.

Fig. 73. Epimeria (Drakepimeria) macrodonta subgen. nov. Walker, 1906, sex undetermined, lectotype, RV Discovery, National Antarctic Expedition 1902–1904, Ross Sea, Winter Quarters — hole 12, 2 to 4.9.1903, J.107, BMNH 1907.6.6.259-262 (in part). A. Facial habitus. B. Head in frontal view.

Fig. 74. Epimeria (Drakepimeria) macrodonta subgen. nov. Walker, 1906, sex undetermined, lectotype, RV Discovery, National Antarctic Expedition 1902–1904, Ross Sea, Winter Quarters — hole 12, 2 to 4.9.1903, J.107, BMNH 1907.6.6.259-262 (in part). A. Coxae 1–7, basis of pereiopods 5–7. B. Pereiopod 7 and epimeral plates 1–3.

Fig. 75. Epimeria (Drakepimeria) macrodonta subgen. nov. Walker, 1906, sex undetermined, lectotype, RV Discovery, National Antarctic Expedition 1902–1904, Ross Sea, Winter Quarters — hole 12, 2 to 4.9.1903, J.107, BMNH 1907.6.6.259-262 (in part). A. Head in lateral view and coxae 1–3. B. Dorsal habitus. C. Coxa 7.

Fig. 76. Epimeria (Drakepimeria) macrodonta subgen. nov. Walker, 1906, sex undetermined, lectotype, RV Discovery, National Antarctic Expedition 1902–1904, Ross Sea, Winter Quarters — hole 12, 2 to 4.9.1903, J.107, BMNH 1907.6.6.259-262 (in part). A. Pleon in lateral view. B. Pleon in dorsal view.