Galathea pennata, Macpherson & Rodríguez-Flores & Machordom, 2025

Galathea pennata sp. nov.

( Fig. 9 View FIGURE 9 )

Material examined. Holotype: Papua New Guinea. BIOPAPUA, Stn CP 3659, 04°14’S, 152°17’E, 22 September 2010, 508 m: F 4.0 mm (MNHN-IU-2011-1940). GoogleMaps

Etymology. From the Latin, penna, in reference to the presence of some tuft of plumose setae on the carapace.

Description. Carapace: As long as broad; cervical groove distinct, laterally bifurcated. Gastric region with some transverse ridges: 2 epigastric ridges, anterior ridge medially interrupted, with 2 median spines, posterior ridge short, scale-like; 2 protogastric ridges, anterior ridge medially interrupted, without parahepatic spine, posterior ridge long, with some median long and thick plumose setae, short median ridge behind this ridge; 2 mesogastric ridges, anterior ridge medially uninterrupted, not extending laterally to anteriormost of branchial marginal spines, posterior ridge short; 2 metagastric ridges, anterior one uninterrupted, not extending laterally to anterior branchial ridges and with some median long thick plumose setae, posterior ridge scale-like. Hepatic region unarmed. Anterior branchial region with distinct ridges. Mid-transverse ridge uninterrupted, preceded by shallow cervical groove. Posterior branchial region with 6 transverse ridges, 2 ridges uninterrupted. Lateral margins convex medially, with 6 spines: 2 spines in front of and 4 spines behind anterior cervical groove; first anterolateral, well-developed, at level of lateral limit of orbit; second, small, at midlength between anterolateral spine and anteriormost spine of branchial margin, with small accompanying spine ventral to between first and second; 2 spines on anterior branchial region, last small, and 2 spines on posterior branchial margin, last small. Lateral limit of orbit unarmed; infraorbital margin with strong spine. Rostrum 1.8 times as long as broad, length 0.6 postorbital carapace length and breadth 0.3 that of carapace; distance between distalmost lateral incisions 0.25 distance between proximalmost lateral incisions; dorsal surface nearly horizontal in lateral view, with numerous setae; lateral margin with 4 deeply incised sharp teeth.

Pterygostomian flap rugose, unarmed, ridges with short setae, anterior margin bluntly angular.

Thoracic sternum: As long as broad, lateral extremities gently divergent posteriorly. Sternite III with median shallow notch. Sternite IV with anterior part as wide as sternite III, with some minute striae. Sternites IV–VI with a few striae on lateral sides. Sternite III ~ 2.1 × as wide as long; sternite IV nearly 2.0 × as wide as long, and 3.5 × as wide as sternite III.

Pleon: Tergites II and III each with 2 transverse uninterrupted ridges on tergite, anterior ridge more distinctly elevated than posterior ridge; tergite of somite IV with posterior ridge medially interrupted; tergite of somites V and VI with 2 ridges.

Eye: Ocular peduncles 1.5 times longer than broad, maximum corneal diameter 0.7 rostrum width.

Antennule: Article 1 with 2 spines; well-developed distodorsal and distolateral spines, distodorsal larger; distomesial spine distinct, clearly not reaching midlength of distolateral spine. Ultimate article with tuft of long setae on distodorsal margin.

Antenna: Article 1 with ventral distomesial spine reaching distal margin of article 2. Article 2 with 2 well-developed distal spines, lateral spine longer than mesial and reaching midlength of article 3. Articles 3 and 4 unarmed.

Mxp3: Ischium with well-developed spine on flexor distal margin; extensor margin ending in acute angle; crista dentata with 21 denticles. Merus shorter than ischium; flexor margin with 3 spines, decreasing in size distally; extensor margin with distal spine. Carpus unarmed.

P1: 3.5 times carapace length. Merus 1.2 times length of carapace, 1.6 times as long as carpus, with spines arranged roughly in rows, dorsomesial spines stronger; distal spines prominent. Carpus 0.9 length of palm, twice longer than broad; dorsal surface with some small spines; mesial margin with well-developed spines. Palm 2.1 times longer than broad, lateral and mesial margins subparallel; some spines arranged roughly in dorsolateral and dorsomesial rows, some small spines scattered on dorsal side. Fingers 0.8 times palm length, each finger distally with two rows of teeth, spooned; fixed finger with some small proximal spines.

P2–4: Moderately slender. P2 2.1 times carapace length. Meri successively shorter posteriorly (P3 merus 0.8 length of P2 merus, P4 merus 0.8 length of P3 merus); P2 merus 0.8 carapace length, 4.7 times as long as broad, 1.2 times longer than P2 propodus. Extensor margin with row of 6–8 proximally diminishing spines on P2–3, 1 distal spine on P4; ventral margins distally ending in strong spine, lateral sides unarmed. Carpi with 3–5 spines on extensor margin on P2–4, distalmost smaller than distal second, sometimes absent; lateral surface with several acute granules sub-paralleling extensor margin; flexor distal margin acute. Propodi 4.3–5.0 times as long as broad; extensor margin with 0–2 small proximal spines; flexor margin with 5–7 slender movable spines, terminal spines paired. Dactyli distally ending in well-curved strong spine, length 0.6–0.8 that of propodi; flexor margin with 6–7 proximally diminishing teeth, terminal tooth moderately prominent.

Epipods absent on pereiopods.

Setae: Two types of setae were observed, (1) short plumose setae, with setules along both sides of shaft, densely located on ridges of carapace and pleon, and scales of P1–4; (2) long thick plumose setae, with setules along both sides of shaft, sparsely located on carapace, pleon, and P1–4.

Genetic data. COI.

Remarks. The new species is referred to the group of species characterized by the presence of one small but distinct spine between the anterolateral spine and the anteriormost branchial marginal spine, two well-developed distal spines on the antennular basal article, the possession of two epigastric spines and the absence of hepatic and parahepatic spines, and epipods. It resembles Galathea yamashitai Miyake & Baba, 1967 from East China Sea, although both species can be distinguished by the following characters:

—The antennal article 3 has a distomesial spine in G. yamashitai , whereas this spine is absent in the new species.

—The second lateral spine of the carapace is present in the new species, instead of absent in G. yamashitai .

—Pleonal tergites 2–3 with 2 ridges in the new species, whereas there are 4–5 ridges in G. yamashitai .

Unfortunately, genetic data for G. yamashitai are not available. The closest species are G. lopisma Macpherson, Rodríguez-Flores & Machordom, 2023 , from the Mozambique Channel, and G. setigera Macpherson & Robainas-Barcia, 2015 , from the Kei Islands. The divergences for COI are 15.06% with G. setigera and 17.63% with G. lopisma ; there are no data for 16S.

Distribution. Papua New Guinea, 508 m.