Toamasina Leever & Daniels & Soma & Cumberlidge 2022, gen. 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

description: Toamasina gen. nov.
(Figures 1 (b,d,f), 2(b,d,f), 3(b), 4(c,d,g,h), 5(d), 6; Tables 1–4)
Nomenclatural statement: A life science identifier (LSID) number was obtained for the new genus:
Foza Cumberlidge and Meyer, 2009: 81 (partim): (not F. ambohitra Cumberlidge and Meyer, 2009, figs 1–3, tab. 1).
Type species
Toamasina clarki sp. nov., by present designation.
Diagnosis
Entire carapace surface smooth except for faint carinae on anterolateral corners; front narrow (FW/CW = 0.27); epigastric crests, epibranchial teeth in advanced position in line with the postorbital margin; postorbital crests faint, ending before meeting epibranchial teeth; cardiac, urogastric sulci, semicircular sulcus, cervical sulci 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)). 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 with long flagellum (equal to merus length); ischium with deep vertical sulcus angled diagonally, located medially (Figure 2 (f)). Thoracic sternal suture S2/3 deep, completely traversing sternum, S3/4 broadly U-shaped, deep at edges, not meeting anterior margin of subpleonal cavity; anterior subpleonal cavity lacking setae; S4/5 meeting pleon at PL5/6 suture; S6/7 meeting submedial part of PL6 (Figure 1 (f)). Left chela larger, cutting edge of fixed finger (pollex) with four large molars on proximal third, followed by medium and small teeth distally, cutting edge of dactylus with four large teeth proximally followed by small teeth (Figure 4 (d)); dactylus of left chela distinctly arched (Figure 4 (d)); left chela propodus longer (29 mm vs 24 mm) and higher (16 mm vs 8 mm) (Figure 4 (d)) than right chela propodus (Figure 4 (c)); cutting edges of dactylus, pollex of right chela lined with small, even, sharp teeth (Figure 4 (c)); dactylus of right chela straight, not arched (Figure 4 (c)); lower margin of propodus of left chela strongly indented medially (Figure 4 (d)). Distal tooth on inner margin of cheliped carpus large, acute; proximal tooth smaller, pointed, followed by small granules (Figure 4 (g)). Inferior margins of cheliped merus lined with small, rounded teeth, distal tooth largest; inferior margins of cheliped ischium lined with small, rounded teeth (Figure 4 (h)). Ambulatory legs (P2–5) medium length (ΣP2–5/CW = 6.4) (Figure 3 (b); Table 3). Male pleon plus telson triangular, tapered distally, widest at PL3, narrowest at telson; PL6 relatively broad, with gently concave lateral margins; telson with straight lateral margins, apex rounded (Figure 1 (f)). G1 TA medium length (G1 TA/G1 SA = 0.3), slim, widened by distinct hump at midpoint, distal half straight, tip pointed; G1 SA with distinct raised rounded shoulder on external margin near G1 TA-SA junction (Figure 5 (d,e); Table 4). G2 TA long (G2 TA/SA = 0.62), flagellum-like, straight, not curved distally (Figure 5 (f)).
Distribution
Endemic to Madagascar; Toamasina gen. nov. is known only from a single locality, Akirindro Mountain, 7.6 km NNW of Ambinantelo (15.2883°S, 49.5483°E), 600 m ASL, in the Analanjirofo Region of northern Toamasina Province (Figure 6).
Etymology
The genus name refers to Toamasina Province where the crab was collected. The name is used as a Latin noun in nominative singular and treated as feminine.
Species included
Toamasina clarki sp. nov.
Remarks
The new genus is established based on morphological and phylogenetic evidence. The phylogeny in Cumberlidge et al. (2020, fig. 1) indicates that Toamasina clarki sp. nov. is genetically separate from V. ambohitra (Cumberlidge and Meyer, 2009) comb. nov. The morphological studies of Cumberlidge and Meyer (2009) and Cumberlidge et al. (2015) included the specimen of Toamasina clarki sp. nov. (NMU PN 17– 21.3.2003) from Toamasina Province in F. ambohitra; however, phylogenetically (Cumberlidge et al. 2020, fig. 1) this specimen is positioned on a related, but clearly separate, lineage from the types of both F. ambohitra (now Vahatra ambohitra (Cumberlidge and Meyer, 2009) comb. nov.) and F. raimundi. Distinguishing characters that separate Toamasina gen. nov. from Vahatra gen. nov., and both of these new genera from the other Malagasy genera are provided in the remarks for Vahatra gen. nov. above.
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 254-255, DOI: 10.1080/00222933.2022.2049389, http://zenodo.org/record/6758291