Nanogalathea psecas, Macpherson & Rodríguez-Flores & Machordom, 2025

Nanogalathea psecas sp. nov.

( Fig. 13 View FIGURE 13 )

Type material. Holotype: Philippines, MUSORSTOM 3, Stn DR 117, 12°31’N, 120°39’E, 3 June 1985, 92–97 m: M 1.8 mm (MNHN-IU-2016-502). GoogleMaps

Paratypes: same data than holotype: 1 M 1.7 mm, 2 F 1.6–1.7 mm (MNHN-IU-2014-13802).

Etymology. From the Greek, psekas, small drop, in reference to the small size of the species.

De s cription. Carapace: Length 0.9 × width; transverse ridges granulated. Gastric region with numerous short or scale-like ridges; epigastric region with 2-3 pairs of minute submedian spines or acute granules; anterior protogastric ridge medially interrupted, not extending laterally to carapace margin; anterior mesogastric ridge scale-like; metagastric ridge laterally interrupted by cervical groove, laterally scale-like. Mid-transverse ridge laterally interrupted, preceded by shallow cervical groove, followed by 2 laterally interrupted ridges, and some short or scale-like ridges on branchial and intestinal areas. Lateral margins medially convex, with 7–8 spines: 2 spines (anterolateral, hepatic) in front and 5–6 spines (3 anterior branchial spines, 2–3 posterior branchial spines) behind distinct anterior cervical groove. Anterolateral spine well-developed, not reaching anteriorly to level of lateral orbital spine. Hepatic spine small, set slightly dorsomesial from lateral margin. First anterior branchial spine slightly longer than second and third spines. Posterior branchial spines progressively smaller posteriorly, first spine subequal to anterior branchial spines. Rostrum widely triangular, downwards directed, 0.5 × pcl; length-width ratio 0.9; lateral margins unarmed, slightly convex, with distinct pair of sub-apical spines; dorsally concave. Pterygostomian flap with sharp anterior spine, upper margin with minute spines or granules; entire surface with series of scale-like ridges.

Thoracic sternum: Sternal plastron slightly wider than long (length-width ratio 0.9), lateral margins divergent posteriorly. Sternite 3 about twice as wide as long; anterior margin slightly convex, with median notch.

Pleon: Tergites 2 and 3 with anterior and posterior transverse ridges; tergite 4 with anterior ridge only; tergites 5 and 6 smooth, without elevated ridges. Males with G1 absent.

Eye: Eye stalk a little wider than long, peduncle mesially with minute spines and plumose setae; cornea narrower than peduncle.

Antennule: Article 1 with 3 distal spines, distomesial spine distinct; 2 distolateral spines, and 2 lateral spines, proximal as long as distomesial spine.

Antenna: Article 1 with prominent mesial process, distally reaching end of peduncle. Article 2 with distinct mesial and lateral spines. Article 3 usually unarmed or with minute distomesial spine. Article 4 unarmed.

Mxp3: Ischium with pronounced distal spines on flexor and extensor margins; crista dentata with regular row of 18–19 spines along entire margin. Merus slightly shorter than ischium at midlength, with strong distal spines on extensor margins, smaller than spine at midlength on flexor margin, otherwise unarmed.

Cheliped (P1): missing.

Walking legs (only P3; P2 and P4 missing in all specimens): Merus length 0.5 × pcl; extensor margin with row of 5 spines, proximally diminishing, with prominent distal spine; flexor margin with distal spine. Carpus with 2 spines on extensor margin, distal spine prominent; flexor margin unarmed. Propodus slightly shorter than menus, length 6 × height; extensor margin unarmed; flexor margin with 3 slender movable spines in addition to distal pair. Dactyli 0.8 × propodus length, ending in incurved, strong, sharp spine; flexor margin with 6 movable spines, otherwise unarmed.

Setae: Unfortunately, most setae are lost in all specimens. 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; (2) long thick plumose setae, with long setules along one side of shaft, sparsely located on carapace and pleon.

Genetic data. No data

Remarks. The genus Nanogalathea was described by Tirmizi & Javed (1980) to include a small species of squat lobster ( N. raymondi ) collected during the International Indian Ocean Expedition in the Andaman Sea, at 77 m. Recently, a second species ( N. longispina ) was described by Tiwari et al. (2024) from Kerala, Arabian Sea. The genus is characterized by its small size, a leaf-like rostrum, without supraocular spines, and carapace with weak ridges.

The new species is clearly different from N. raymondi by the following aspects:

—The lateral margins of the rostrum are straight in N. raymondi , whereas these margins are convex in the new species. Furthermore, the distal spines of the rostrum seem more distinct in the new species than in N. raymondi and N. longispina .

—The epigastric region is armed with 2–3 pairs of spines in the new species, whereas this region is unarmed in N. raymondi and N. longispina .

—The hepatic margin of the carapace is unarmed in N. longispina , whereas there is a marginal spine in the new species.

Distribution. The Philippines, between 92 and 97 m.