Sundathelphusa quirino, Husana & Ng, 2019

Husana, Daniel Edison M. & Ng, Peter K. L., 2019, On the identity of Sundathelphusa philippina (von Martens, 1868) (Decapoda: Brachyura: Gecarcinucidae) from the Philippines, with descriptions of two new species, Zootaxa 4585 (2), pp. 315-331 : 326-329

Sundathelphusa quirino sp. nov.

( Figs. 7–8 ; 9E, F )

Material examined. Holotype: ♂ (49.3 × 37.5 mm), NMCR 50701, Aglipay Cave , Aglipay town , Quirino province, Luzon Island, 16˚28.439'N 121˚36.577'E, coll. D.E. Husana, 17 April 2009 . Paratypes: 1 ♂ (44.0 × 34.2 mm), 2 ♀♀ (45.3 × 35.4 mm, 52.8 × 41.0 mm), ZRC 2017.1063 , same data as holotype ; 1 ♀ (27.4 × 23.0 mm), ZRC 2017.1257 , Diduyan River , Sitio Tubo , Dingasan, Quirino Province, Luzon, coll. L. Liao, 3 February 1999 ; 1 ♂ (47.6 × 36.9 mm), 1 ♂ (33.1 × 26.1 mm) (only carapace intact), 1 ♀ (crushed), RMNH 32925 , Disiluat Cave , 8 km from San Leonardo, Quirino, Luzon, coll. F. Alanday, July 1979. All locations in the Philippines .

Description. Carapace trapezoidal in shape, widest at anterior quarter, dorsal surface distinctly convex longitudinally, dorsoventrally inflated, regions distinct ( Fig. 7A ). Frontal region sloping anteroventrally; anterolateral regions inflated dorsolaterally, smooth; cervical grooves deep; H-shaped gastric groove deep; epigastric cristae, distinct, edges rough, separated by distinct median furrow; postorbital cristae, sharp but low; epigastric and postorbital cristae confluent; epibranchial teeth and postorbital cristae not confluent, separated by gaps ( Fig. 7A ). Frontal margin broadly protruded, two lobes clearly separated with broad median concavity; external orbital tooth produced anteriorly, outer margin longer than inner margin; epibranchial tooth distinct, triangular, well separated from external orbital tooth, tapering anteriorly, surface and margin flat; anterolateral margin convex, with very low crest, not distinct from lateral view, not clearly demarcated from posterolateral margin; posterolateral margin gently concave, converging gradually towards posterior margin of carapace ( Fig. 7A ). Frontal median triangle complete; dorsal and lateral margins distinct, smooth, confluent; dorsal margin more produced anteriorly than lateral margins ( Fig. 8F ); orbit well demarcated; supraorbital margin smooth; infraorbital margin, smooth, sinuous, protruded anteriorly; outer edge reaching and fused with anterolateral margin; suborbital and subbranchial regions covered with scattered oblique long, short striae; pterygostomial region smooth with oblique ridges on upper outer part ( Fig. 7C ). Posterior margin of epistome with three lobes, median lobe large, subtriangular, notch absent; lateral lobes wider and protruded, placed more anteriorly than median lobe ( Figs. 7C ; 8G ).

Eyes well developed, occupying entire orbit ( Fig. 7A, C ). Ischium of third maxilliped rectangular, bearing distinct submedian sulcus closer to mesial margin; merus quadrate, anteroexternal angle convex, anterior margin slightly concave; tip of exopod reaches midpoint of outer margin of merus, with long flagellum reaching beyond mesial margin ( Fig. 7B, C ).

Adult chelipeds relatively stout, subequal, stronger in males; dorsal margin of merus serrated, dorsal margin with distinct subdistal tooth; carpus with strong distal inner angle, flattened dorsoventrally, laterally fringed with proximal teeth; palm with minutely granulated outer surface; ventral margin granulated; fingers robust, cutting edges with teeth of various sizes, largest medially, smaller on distal and proximal parts ( Fig. 7E, F ).

Ambulatory legs relatively longer ( Figs. 7A ; 9E, F ), second leg longest; anterior margin of merus serrated, without subdistal tooth or spine, posterior margins smooth on all legs; carpus short, with longitudinal submedian ridge on dorsal and ventral surfaces of all legs except on fourth leg that lacks ventral ridge, with barely visible dorsal ridge, widened distally, outer margins smooth; propodus with rows of spines on inner margins, outer margins smooth; dactylus with rows of short spines on all margins, spines of both outer and inner margins of dactylus almost equal in length ( Figs 7A ; 9F ).

Male sternopleonal cavity reaching to level of proximal quarter of coxae of chelipeds. Adult male pleon narrow, T-shaped; somite 1 very short, proximal and distal margins sinuous; somite 2 transversely subrectangular; somites 3–5 narrow gradually; lateral margins of somite 3 convex, lateral margins of somite 4 slightly convex with angle at distal end, lateral margins of somite 5 concave; somite 6 length equal to width at widest point, lateral margins concave; telson subtriangular, length equal at the broadest distal margin, lateral margin convex medially, rounded distally ( Figs. 7D ; 8H, M ).

G1 relatively slender, almost straight but slightly bended outward; outer margin of subterminal segment slightly concave; terminal segment slightly curved outward, tapering, cylindrical, slightly setose ( Fig. 8 A–D, I–L). G2 longer than G1, distal segment long, about half length of basal segment ( Fig. 8E ).

Etymology. The species is named after the province of Quirino where all the materials were collected. The name is used as a noun in apposition.

Remarks. The Quirino specimens, while superficially resembling S. philippina sensu stricto, differ markedly in having proportionately more slender and longer ambulatory merus; more inflated anterolateral region, the proximal part of the telson and distal region of pleonal somite 6 are proportionately wider, and the G1 has a relatively straighter distal segment ( Figs. 8 A–D, I–L; 9E, F) (vs. relatively shorter and stouter ambulatory legs, less convex anterolateral region, less wide telson and somite 6, and a more curved G1; Figs. 2 A–D, F–S; 9A, B). As such, they are here referred to a new species, S. quirino sp. nov.

The type locality of S. quirino sp. nov. is quite far from the known distribution range of S. philippina sensu stricto and are separated by at least two geographic barriers. The Sierra Madre-Caraballo-Cordillera mountain ranges separates the type locality of S. quirino sp. nov. in the far north of Luzon Island while the San Bernardino Strait in the south separates the big islands of Luzon and Samar.

While some of the specimens of S. quirino sp. nov. were collected from caves, none of the material has the typical characters associated with stygobionts (see discussion for S. philippina ) and the species is probably at most a facultative cavernicole (see Ng 2013; Husana et al. 2014).

Figures

FIGURE 2. Sundathelphusa philippina (von Martens, 1868). A–G, paralectotype ♂ (51.4 × 42.8 mm), ZMB 1050, Samar; H– K, lectotype ♂ (42.8 × 34.8 mm), ZMB 1055, Samar; L–O, U, ♂ (33.8 × 27.2 mm), ZRC 2017.1059, Leyte; P–T, V, ♂ (51.3 × 40.2 mm), ZRC 2009.409, Luzon; W, ♂ (33.7 × 26.8 mm), ZRC 2009.409, Luzon. A, H, dorsal view of right G1; B, I, ventral view of right G1; C, J, dorsal view of terminal segment of right G1; D, K, ventral view of terminal segment of right G1; L, P, ventral view of left G1; M, Q, dorsal view of left G1; N, R, ventral view of terminal segment of left G1; O, S, dorsal view of terminal segment of left G1; E, male pleonal somites 3–6 and telson; F, frontal median triangle; G, posterior margin of epistome; T, right G2; U–W, male pleonal somites 4–6 and telson. Scales: A, B, H, I, L, M, P, Q = 1.0 mm; U, W = 2.0 mm; E = 5.0 mm; F, G, V = 3.0 mm; C, D, J, K, N, O, R, S = 0.5 mm.

FIGURE 7. Sundathelphusa quirino sp. nov., holotype ♂ (49.3 × 37.5 mm), NMCR 50701, Quirino. A, overall habitus; B, left third maxilliped; C, frontal view of cephalothorax; D, ventral view cephalothorax; E, outer view of right chela; F, outer view of left chela.

FIGURE 8. Sundathelphusa quirino sp. nov. A–H, holotype ♂ (49.3 × 37.5 mm), NMCR 50701, Quirino; I–M, paratype ♂ (47.6 × 36.9 mm), ZRC 2017.1063, Quirino. A, I, ventral view of left G1; B, J, dorsal view of left G1; C, K, ventral view of terminal segment of left G1; D, L, dorsal view of terminal segment of left G1; E, left G2; F, frontal median triangle; G, posterior margin of epistome; H, male pleonal somites 3–6 and telson; M, pleonal somites 4–6 and telson. Scales: A, B, E, F, G, I, J = 1.0 mm; C, D, K, L = 0.5 mm; H, M = 3.0 mm.

FIGURE 9. Right third and fourth ambulatory legs. A, B, Sundathelphusa philippina (von Martens, 1868), ♂ (51.3 × 40.4 mm), ZRC 2009.0409, Luzon; C, D, S. cebu sp. nov., holotype ♂ (38.1 × 31.2 mm), ZRC 2017.1254, Cebu; E, F, S. quirino sp. nov., holotype ♂ (49.3 × 37.5 mm), NMCR 50701, Quirino. A, C, E, third ambulatory leg; B, D, F, fourth ambulatory leg. Scales: A–F = 5.0 mm.