Litarachna samudra Pesic & Zawal 2026, sp. nov.

Litarachna samudra Pešić & Zawal sp. nov. urn:lsid:zoobank.org:act: 21888B63-41C7-4AB0-BD43-1EA2BAE5748A Figure 1 Material examined— Holotype ♀, dissected and slide mounted (RMNH), Thailand, TAJ23 Andaman See, Ko Muk Island, 7.358088° N, 99.294414° E, collected from rocks covered with Balanus growth and very short algae, 29 February 2024 leg. Zawal, sequenced (Voucher IdD: K84_12, Bold Id: HYDPT204-24). Diagnosis (Female; male unknown). Morphological —Ventral glandularium 3 (V3 gland) not fused with CxIV; P-2 with a ventral extension; P-4 with setal tubercles, a peg-like seta near the setal tubercles, and an additional peg-like medial seta located in the dorsal third of the segment. Molecular —this lineage is represented by a unique Barcode Index Number (BIN: BOLD:AHO5269). It differs from its closest congeneric species, Litarachna smiti, by a 16.9% K2P genetic distance in the COI barcode region. Description. Female—Idiosoma L 391, W 341; coxal field L 131, W 267; Cx-I separated medially; suture lines Cx-I/II and Cx-III/IV complete, suture line Cx-II/III incomplete; posterior margin of Cx-IV with two pairs of apodemes, the medial apodemes much longer than the lateral ones, strongly exceeding the posterior margin of genital field. Genital field L 71, W 45, pre- and post-genital sclerites bowed. The large glandularia-like structure (V3 gland according to Wiles et al. 2002) and a pair of small platelets with Cxgl-4 (E4 according to Wiles et al. 2002) and associated setae placed between the posterior lateral and medial apodemes of Cx-IV. Posterior to the genital field a pair of platelets with three pores and three pairs of large wheel-like acetabula, with relatively few radiating spokes. Excretory pore unsclerotized, near the posterior idiosoma margin. Palp: dL/H: P-1, 16/19; P-2, 88/50; P-3, 26/39; P-4, 91/23; P-5, 31/13; dL P-4/P-5 ratio 0.96; ventral extension of P-2 relatively longer and triangular extension, P-4 with setal tubercles, a peg-like seta near the setal tubercles, and an additional peg-like medial seta located in the dorsal third of the segment (Figures 1 B-C). Chelicera total L 191, basal segment L 142, claw L 50, L basal segment/claw ratio 2.8; gnathosoma L 138. dL of I-leg-1 to -6: 44, 40, 47, 52, 75, 92; IV-leg-4 with one swimming seta, IV-leg-4 and -5 lost during dissection. Male—Unknown. Etymology— The specific epithet is derived from the Thai word Samut (สมุทร), which originates from the Sanskrit Samudra (meaning ‘ocean’ or ‘sea’), referring to the marine habitat from which the species was collected. The specific epithet is a noun in apposition. Species delimitation using DNA barcodes —The final alignment for species delimitation utilizing COI sequence data comprised 674 nucleotide positions (nps) from 78 Litarachna specimens and one outgroup, Pontarachna punctulum Philippi, 1840 (NLACA1001-17) from France, used to root the tree. The Neighbour-Joining (NJ) tree is presented in Figure 3. The COI sequence retrieved from the single specimen described herein as Litarachna samudra sp. nov. appeared as a sister taxon to L. smiti Pešić, Chatterjee & Ahmed Abada, 2008, a species known from the Red Sea (Pešić et al. 2008a, b). The mean genetic distance between the COI sequences of these two species was estimated at 16.9% (K2P), indicating long-standing isolation between the two lineages. Remarks. The new species from the Andaman Sea closely resembles L. smiti, a species known from the Red Sea coast of Saudi Arabia (Pešić et al. 2008a, b) and Egypt (Pešić et al. 2026b). Among the species having a ventral extension on P-2 and setal tubercles on P-4, both abovementioned species possess a peg-like seta near the setal tubercles on P-4 and a V3 gland that is not fused with Cx-IV. However, the new species can be easily separated by the presence of a peg-like medial seta in the dorsal third of P-4, which is absent in L. smiti (see Pešić et al. 2008a, b). Distribution— Thailand.