Galearctus sp.

Galearctus sp.

Stage IX (Final)

( Figs. 2–3 View FIGURE 2 View FIGURE 3 )

Material used for drawings: EL 021, reg. NHMUK 2024. 241; EL 080, reg. NHMUK 2024. 242; EL 085, reg. NHMUK 2024. 243; EL 086, reg. NHMUK 2024. 244; EL 087, reg. NHMUK 2024. 245.

Morphometry: N = 29, BL = 18.7–23.2 mm, CL = 11.0– 14.5 mm, CW = 11.8–16.6 mm, TL = 5.4–7.1 mm, TW = 7.0– 8.5 mm, PL = 3.9–5.0 mm, PW = 3.9–5.3 mm, EL/BL = 0.15–0.19, CL/CW = 0.84–0.97.

Cephalic shield ( Fig. 2A View FIGURE 2 ): Pear-shape, wider than long (CL/CW = 0.8–1.0).

Eyes ( Figs. 2A View FIGURE 2 , 3A View FIGURE 3 ): eyestalk long (EL/BL = 0.15–0.19).

Antennule ( Figs. 2A View FIGURE 2 , 3A View FIGURE 3 ): Longer than antenna, peduncle 3-articled; first and second article longer than third (1/0.8/0.5). Primary flagellum with 14–15 rows of aesthetascs (sensory setae). Accessory flagellum longer than primary, not articulated and lacking setae.

Antenna ( Figs. 2A View FIGURE 2 , 3A View FIGURE 3 ): Uniramous and not articulated; shorter than antennule. External lateral margin of endopod expanded medially. Exopod absent.

Paragnaths ( Fig. 3B View FIGURE 3 ): Inner margin with setae and small denticles.

Mandibles ( Fig. 3C, D View FIGURE 3 ): Asymmetrical dentition. Left mandible with 9–12 teeth and molar process crowned with abundant denticles; right mandible with ~19 elongated teeth curved towards the molar process. Palp absent.

Maxillule ( Fig. 3E View FIGURE 3 ): Coxal endite with 6 plumodenticulate setae; basial endite with 3 plumodenticulate spines and 6 simple setae. Endopod and exopod absent.

Maxilla ( Figs. 2A View FIGURE 2 , 3F View FIGURE 3 ): Uniramous. Coxal and basial endites, and endopod undifferentiated with 4 simple setae on superior margin of lateral process; exopod (scaphognathite) flattened and expanded, without marginal setae.

First maxilliped ( Figs. 2A View FIGURE 2 , 3F View FIGURE 3 ): Uniramous. Endopod elongated and not articulated, endite flattened and rounded. Exopod absent.

Second maxilliped ( Figs. 2A View FIGURE 2 , 3G View FIGURE 3 ): Biramous. Coxa without setae; basis delimited by 1 or 2 distal setae; endopod with 4 articles, ischium-merus (undifferentiated), carpus, propodus, dactylus with 1, 1, 7 (2 serrated setae) and 4 simple setae, respectively. Exopod present as small bud.

Third maxilliped ( Figs. 2A View FIGURE 2 , 3H View FIGURE 3 ): Biramous. Coxa with distal ventral spine present. Basis delimited by small exopod bud; 4-articled endopod, ischium-merus (undifferentiated), carpus, propodus, and dactylus with 4, 5, ~50 (2 distal serrated) and ~100 simple setae, respectively. Setae on inner margin of dactylus longer than outer margin.

Pereiopods ( Fig. 2A, C–F View FIGURE 2 ): P1–4 biramous. Coxa without setae, but small distal ventral spine present; basis delimited by distal spine with 5–7 medial setae; endopod with 4 articles, ischium-merus (undifferentiated) with 2 distal spines, carpus with 1 distal spine, P1–4 propodus with ~75, 65, 45 and 30 simple setae, P1–4 dactylus with 10, 9, 5 and 4 simple setae, respectively. Exopods of P1–4 with 26–28, 26–28, 25–26 and 25–26 pairs of setae, respectively. P5 uniramous and 3-articled. Coxa with ventral distal spine; basis-ischium-merus undifferentiated, without spines; carpus-propodus-dactylus undifferentiated, without spines.

Gills ( Fig. 2A, B View FIGURE 2 ): Present as buds. Mxp. 3 and P1 with 1 pleurobranch, 1 arthrobranch and 2 podobranchs; P2–4 with 2 pleurobranchs, 1 arthrobranch and 2 podobranchs; P5 with 1 pleurobranch.

Thorax ( Fig. 2A, B View FIGURE 2 ): Rounded, slightly wider than long. Sternites 1–5 without dorsal or ventral thoracic spines.

Pleon ( Fig. 2A View FIGURE 2 ): Pleopods and uropods well-developed and biramous. Pleopod 1 absent. Pleopods 2–5 flattened and elongated; endopod longer than exopod. Posterior margin of uropods pointed; exopods longer than endopods.

Telson ( Fig. 2A View FIGURE 2 ): Distal margin concave, with 8–9 paired dorsal small setae and 2 terminal processes without setae and not exceeding uropods.