Toamasina clarki Leever & Daniels & Soma & Cumberlidge 2022, sp. nov.
Creators: name: Leever, Ellen M.
name: Daniels, Savel R.
name: Soma, Julia B.
name: Cumberlidge, Neil
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Potamonautidae
Toamasina
Toamasina clarki

description: Toamasina clarki sp. nov.
(Figures 1 (b,d,f), 2(b,d,f), 3(b), 4(c,d,g,h), 5(d,e,f), 6; Tables 1–4)
Foza ambohitra – Cumberlidge and Meyer 2009: 81 (only NMU PN 17– 21.3.2003)
Material examined
Type material. Holotype (formerly paratype of Foza ambohitra): Madagascar: adult ♂ (CW 43.0, CL 31.6, CH 17.7, FW 11.6 mm), Toamasina Province, Analanjirofo Region, Akirindro Mountain, 7.6 km NNW of Ambinantelo, (15.2883°S, 49.5483°E) 600 m ASL, coll. P. Naskrecki, 17–21 March 2003 (NMU PN 17– 21.3.2003) (GenBank MT749730).
Diagnosis
As for genus.
Description
Based on holotype, adult ♂. Carapace outline transversely oval, medium height (CH / CW = 0.41); entire carapace surface smooth except for faint carinae in anterolateral corners; front narrow (FW/CW = 0.27), deflexed; epibranchial tooth small, acute; epigastric crests, epibranchial teeth advanced in position, aligned with posterior margin of orbit; lateral margins evenly curved outward, raised rim lined with small granules; postorbital crests faint, ending before meeting epigastric teeth; mid-sulcus between epigastric crests forked posteriorly; cardiac, urogastric sulci, semicircular sulci, cervical sulci all faint (Figure 1 (b)). Branchiostegite suborbital region smooth except for horizontal line of granules across middle, subhepatic region smooth, pterygostomial region smooth except for small field of granules near third maxilliped (Figure 1 (d)). Epistomial tooth triangular, deflexed, edges smooth. Mandibular palp terminal article bilobed, anterior lobe on terminal article conspicuous, medium-sized (MPAL/MPTA = 0.5) (Figure 2 (b,d); Table 2). Exopod of third maxilliped reaching to lower half of merus, exopod with long flagellum (longer than merus width), ischium with deep vertical sulcus located medially, angled diagonally (Figure 2 (f)). Thoracic sternal suture S1/2 short, raised; S2/3 horizontal, completely traversing sternum; S3/4 broad, U-shaped, deepest at edges, not meeting anterior margin of subpleonal cavity (Figure 1 (d)); S4/5, S5/6, S6/7 medially interrupted, separated by narrow space; S7/8 complete, with longitudinal sulcus on S7, S8; S8 not visible when pleon closed; male subpleonal cavity deep, narrow, reaching to imaginary line joining posteriormost points of cheliped coxae; male pleonal locking tubercle low, round, positioned on distal third of S5; S4/5 meeting pleon at PL5/6 sulcus; S6/7 meeting PL6 midway from PL5/6 sulcus; episternal sulci S4/E4, S5/E5, S6/E6, S7/E7 obscure (Figure 1 (f)). Right chela largest, cutting edge of fixed finger (pollex of propodus) with four large molars on proximal half, followed by medium, small teeth distally; cutting edge of movable finger (dactylus) with four large teeth proximally followed by row of small teeth; right dactylus distinctly arched (Figure 4 (c)); right chela propodus longer (29 mm vs 24 mm) and higher (16 mm vs 8 mm) than left chela propodus; cutting edges of dactylus, pollex of left chela lined with small, even, sharp teeth; dactylus of left chela straight, not arched (Figure 4 (c)); lower margin of propodus of right chela strongly indented medially (Figure 4 (g,h)). Distal tooth on inner margin of cheliped carpus large, acute; proximal tooth smaller, pointed, followed by small granule. Inferior margins of cheliped merus lined with small, rounded teeth, distal tooth largest; inferior margins of cheliped ischium lined with small, rounded teeth. Ambulatory legs (P2–5) short (ΣP2–5/CW = 5.7) (Figure 3 (b); Table 3). Male pleon plus telson triangular, tapered distally, widest at PL3, narrowest at junction with telson; telson triangular with broad base, rounded apex. G1 TA medium length (G1 TA/G1 SA 0.3; Table 4), slim, widest at midpoint, tip pointed; G1 TA-SA sulcus faint on ventral side, distinct on dorsal side; DM at G1 TA-SA junction broad, trapezoid; DM superior margin diagonal, inferior margin J-shaped, lateral margin broad, medial margin narrow; G1 SA with distinct raised, rounded shoulder on external margin near G1 TA-SA junction (Figure 5 (g,e)). G2 TA long (G2 TA/SA = 0.62), flagellum-like, straight, not curved distally (Figure 5 (f)).
Size
Medium-sized species, the only known specimen is an adult male (CW 43 mm).
Colour
Unknown in life. The preserved specimen is uniformly pale brown.
Distribution
Akirindro Mountain, in the Analanjirofo Region of Toamasina Province, northern Madagascar, 600 m ASL (Figure 6).
Type locality
Madagascar: Akirindro Mountain, 7.6 km NNW of Ambinantelo, in the Analanjirofo Region of Toamasina Province (15.2883°S, 49.5483°E) 600 m ASL.
Habitat
Toamasina clarki sp. nov. is associated with the streams and rivers flowing from the humid lowland rainforests (below 900 m ASL) in the Madagascar Eastern Highlands freshwater ecoregion (FEOW 581; Abell et al. 2008).
Etymology
The species is named in honour of Dr Paul F. Clark of the Natural History Museum, London, UK, in recognition of his numerous significant contributions to crustacean biology over a long and illustrious career. The specific epithet is used as a Latin noun in genitive singular and treated as masculine.
Remarks
The specimen from Akirindro Mountain previously assigned to F. ambohitra is now recognised as Toamasina clarki gen. et sp. nov. based on morphological and molecular evidence. The differences among Toamasina gen. nov. representing T. clarki sp. nov. and the other genera of Malagasy freshwater crabs, including Vahatra gen. nov., are already provided (see remarks section for Vahatra gen. nov.).
description: Published as part of Leever, Ellen M., Daniels, Savel R., Soma, Julia B. & Cumberlidge, Neil, 2022, Two new genera and a new species of freshwater crabs from northern Madagascar: Vahatra gen. nov. for Foza ambohitra Cumberlidge and Meyer, 2009, and Toamasina gen. nov. for Toamasina clarki sp. nov. (Brachyura: Potamoidea: Deckeniidae), pp. 241-263 in Journal of Natural History 56 (1 - 4) on pages 255-258, DOI: 10.1080/00222933.2022.2049389, http://zenodo.org/record/6758291