Liberonautes njala, Mvogo Ndongo & von Rintelen & Clark & Cumberlidge, 2024

Liberonautes njala sp. nov.

(figs. 2B, 3B View Fig , 4B, 5B, 6 View Fig F-J, 7D-F)

Material examined.— Sierra Leone. Holotype: adult ♂ (CW 66.3, CL 44.2, CH 30.0, FW 20.1 mm), Tai River , near Njala Campus (08°06ļ14.9ļļN 12°05ļ00.9ļļW), Southern Province , 65 m asl, coll. P. A. Mvogo Ndongo, 19 January 2021 (ZMB Crust. 33102). Paratype: adult ♂ (CW 52.3, CL 35.6, CH 23.1, FW 16.5 mm) (ZMB Crust. 33103), all same data as holotype. Non-types: 3 subadult ♂♂ (CW 28.4, 32.3, 37.1, CL 21.2, 23.5, 26.9, CH 13.3, 14.0, 15.9, FW 9.6, 10.5, 12.6 mm, respectively) bridge at Taiama (08°12ļ13ļļN 12°3ļ58.3ļļW), River Tai , Southern Province , 61 m asl, coll. P.A. Mvogo Ndongo, 19 January 2021 (CARC-03).

Diagnosis.— Large species, adult between CW 52-66 mm; postfrontal crest incomplete, not traversing carapace, ends not encountering carapace margins; anterolateral, posterolateral carapace surfaces smooth (figs. 2B, 3B View Fig , 5B); semicircular, urogastric, cardiac, cervical, transverse branchial carapace grooves all deep, distinct (figs. 2B, 3B View Fig ); exorbital tooth low, blunt ( figs. 3B View Fig , 5B); intermediate tooth medium-sized, epibranchial tooth granular ( figs. 3B View Fig , 4B, 5B); surface texture of branchiostegite subhepatic region smooth; major cheliped dactylus highly curved leaving broad oval interspace when closed ( fig. 6F View Fig ); G1TA length long, ca. half as long as G1SA (G1TA/G1SA = 0.5), G1SA lateral margin distinctly curved inward (fig. 7D, E).

Description of holotype.— Carapace transversely oval, wide (CW/FW = 3.3), moderately high (CH/FW l.4), front gently indented medially, wide (FW/CW = 0.3). Entire carapace surface generally smooth. Cervical grooves deep, long, ending just before encountering postfrontal crest; semicircular, urogastric, cardiac, cervical, transverse branchial grooves all deep (figs. 2B, 3B View Fig , 5B). Postfrontal crest distinct, consisting of fused epigastric crest, incomplete, not traversing entire carapace, lateral ends not meeting carapace margins; mid-groove on postfrontal crest short, forked. Exorbital tooth small, blunt, intermediate tooth triangular, medium-sized, epibranchial tooth small, low, granular (figs. 2B, 3B View Fig , 4B, 5B). Carapace lateral margin posterior to epibranchial tooth raised, marked by row of small granules, continuous with carapace posterolateral margin. Carapace posterior margin rounded, width subequal to FW (figs. 2B, 3B View Fig ). Carapace branchiostegite divided by transverse, vertical grooves into three regions (figs. 4B, 5B). Transverse suture beginning at respiratory opening, curving backward, dividing suborbital, subhepatic regions from pterygostomial region (figs. 4B, 5B); vertical sulcus curving backward to meet epibranchial tooth, dividing suborbital from subhepatic regions (figs. 4B, 5B). Suborbital, subhepatic, pterygostomial regions all smooth (figs. 4B, 5B).

Mandibular palp comprising basis plus two endopod articles; terminal article with small hardened ridge on superior margin near article junction ( fig. 6I View Fig ). Third maxillipeds filling entire buccal cavern except for transversely oval efferent respiratory openings visible at superior lateral corners; exopod with well-developed slender flagellum; ischium with distinct vertical sulcus (figs. 4B, 5B, 6J View Fig ).

Thoracic sternal sulcus S2/3, deep, horizontal, ends not meeting side margins, S3/4 reduced to 2 short notches on margins, obscure in middle; episternal sulci S4/E4-S6/E6 visible, S7/E7 obscure (fig. 4B).

Chelipeds unequal ( fig. 6F, G View Fig ), right higher, longer than left ( fig. 6F View Fig ). Right chela movable finger (dactylus) highly arched, cutting edge lacking teeth, enclosing wide interspace; dactylus tip overlapping fixed finger (propodus pollex) tip when closed; fixed finger cutting edge with 4 small teeth proximally, otherwise lacking teeth ( fig. 6F View Fig ). Cheliped merus inferior margins smooth; distal meral tooth small, distinct; superior surface of merus with rows of carinae ( fig. 6H View Fig ). Cheliped carpus inner margin distal tooth large, pointed, proximal tooth small, pointed, followed by granules ( fig. 6H View Fig ). Walking legs P2-5 robust, P3 longest, P5 shortest; dactyli of P2-5 with short downward-pointing sharp bristles, P5 dactylus shortened (fig. 2B).

Pleomeres (PL1-6) and telson triangular with sinuous lateral margins ( Fig. 4B View Fig ). PL3 trapezoidal, broadest; PL4, PL5 trapezoidal. PL6 broader than long, rectangular ( Fig. 4A View Fig ). Telson triangular, with almost straight lateral margins Fig. 4B View Fig ).

G1TA slim, curved, needle-like, long, ca. half as long as G1SA (G1TA/G1SA = 0.5); G1SA proximal half conspicuously broad, distal half abruptly narrow, columnar, lateral margin distinctly curved inward (fig. 7D, E); G2TA long, more than half length of G2SA (G2TA/G2SA = 0.6), flagellum-like ( Fig. 7F View Fig ).

Colour in life.— Dorsal carapace, pereiopods P1-5 dark violet (fig. 2B).

Etymology.— The new species is named for Njala, the type locality in the Southern Province, Sierra Leone. The species name njala is used as a noun in apposition.

Habitat.— Liberonautes njala sp. nov. is an aquatic species that was collected either in nets set in the river, or by hand, from under large rocks on the riverbed.

Distribution.— Known only from the River Tai, near the small town of Njala and Taiama, Southern Province, Sierra Leone (fig. 1).