Pavizham, Raj & Kumar & Ng, 2022

Raj, Smrithy, Kumar, Appukuttannair Biju & Ng, Peter K. L., 2022, Fig. 13. A in New Genus and Two New Species of Semiterrestrial Crabs (Decapoda: Brachyura: Gecarcinucidae) from the Southern Western Ghats, India., Zoological Studies 61 (49), pp. 1-16 : 2-6

Superfamily Gecarcinucoidea, Rathbun, 1904 Family Gecarcinucidae Rathbun, 1904

Pavizham gen. nov. urn:lsid:zoobank.org:act:D0B2BC35-73B2-41AF-8C5D-5C94D6080CA4

Diagnosis: Carapace deep, dorsal surface ovate, high, swollen, smooth ( Figs. 2 , 3A–C,); epigastric cristae faintly discernible; postorbital cristae not visible ( Figs. 2 , 3A–C); external orbital tooth very broad, low ( Fig. 3A, B); epibranchial tooth very small, low, just visible ( Figs. 2 , 3A, B). posterolateral margins distinctly converging towards posterior carapace margin ( Fig. 3A, B); third maxilliped ischium relatively long, exopod with distinct flagellum extending across width of merus ( Fig. 5A ); inner angle of carpus of adult male cheliped with distinct curved tooth ( Figs. 2 , 3A); base of closed fingers of major adult male chela with small gape ( Fig. 4D); ambulatory legs slender, not elongate ( Figs. 2 , 3A); anterior male thoracic sternum transversely broader, sternites 1 and 2 completely fused to form triangular plate, separated from sternite 3 by complete, shallow groove; sternites 3 and 4 fused, demarcated by shallow groove ( Figs. 3D, 4B, 5B ); male sternopleonal cavity deep, broad, reaching to imaginary line joining anterior points of cheliped coxae ( Figs. 3D, 4B); male pleonal locking tubercle low, round ( Fig. 4B); male pleon distinctly triangular, somite 6 broader than long; telson triangular with almost straight lateral margins ( Figs. 3D, 4A); G1 almost straight, groove for G2 ventral in position; terminal and subterminal segments clearly demarcated; terminal segment relatively long, conical, gradually tapering to truncate tip ( Fig. 5C–E ); G2 long, with long slender distal segment, nearly half length of basal segment ( Fig. 5F ).

Type species: Pavizham gavi sp. nov. by present designation.

Etymology: The name is derived from the Malayalam name ‘Pavizham’, for a precious stone (red coral), alluding to the smooth and polished appearance of the type species and its red colouration. Gender of name neuter.

Remarks: The swollen and smooth carapace of Pavizham n. gen. closely resembles that of Baratha Bahir & Yeo, 2007 , and Snaha Bahir & Yeo, 2007 . Pavizham can be separated from Baratha in having no visible postorbital cristae with the surface there smooth ( Fig. 3A–C) (versus postorbital crista sharp, distinct, cf. Bahir & Yeo, 2007: figs. 19A, 21A); the external orbital tooth is very broad and low ( Fig. 3B) (versus tooth acutely triangular and less wide, cf. Bahir & Yeo, 2007: figs. 19A, B, 21A, B); the third maxilliped ischium is proportionately much longer ( Fig. 5A ) (versus subquadrate, cf. Bahir & Yeo, 2007: figs. 19B, 21B); the suture between male thoracic sternites 2 and 3 are complete ( Figs. 3D, 5B ) (versus only medially visible, being completely fused laterally, cf. Bahir & Yeo, 2007: figs. 18A, 19C, 21C); the distinctly triangular male pleon ( Fig. 4A) (versus T-shaped, cf. Bahir & Yeo, 2007: figs. 18B, 19C, 21C); and the G1 terminal segment is more elongate ( Fig. 5C–E ) (versus short, cf. Bahir & Yeo, 2007: figs. 18C–F, 20A–D). Pavizham can be separated from Snaha in having a very small and low epibranchial tooth, the anterolateral margin being almost entire except for a shallow cleft ( Fig. 3B) (versus with small but visible epibranchial tooth, cf. Bahir & Yeo, 2007: figs. 28A, 30A); the third maxilliped exopod has a long flagellum ( Fig. 5A ) (versus no flagellum present, cf. Bahir & Yeo, 2007: fig. 27A); the third maxilliped ischium is proportionately much longer ( Fig. 5A ) (versus subquadrate, cf. Bahir & Yeo, 2007: fig. 27A); the inner angle of the carpus of the male cheliped has a distinct curved tooth ( Figs. 2 , 3A) (versus with low tubercle, cf. Bahir & Yeo, 2007: fig. 28A); there is a small gape at the base of the closed fingers of the major adult male chela ( Fig. 4D) (versus fingers has a wide basal gape when the fingers are closed, cf. Bahir & Yeo, 2007: fig. 28A); the suture between male thoracic sternites 2 and 3 is complete ( Figs. 3D, 5B ) (versus only medially visible, being completely fused laterally, cf. Bahir & Yeo, 2007: figs. 28C, 29A, 30C); the male sternopleonal cavity reaches to an imaginary line connecting the anterior edges of the coxae of the chelipeds ( Figs. 3D, 4B) (versus cavity reaches to an imaginary line connecting the midpoints of the coxae of the chelipeds, cf. Bahir & Yeo, 2007: fig. 28C); and the triangular male pleon is distinctly triangular ( Fig. 4A) (versus T-shaped, cf. Bahir & Yeo, 2007: figs. 27B, 28C, 29B).

Pavizham is also morphologically similar to Indian genera like Ghatiana Pati & Sharma, 2014 , Gubernatoriana Bott, 1970 , Inglethelphusa Bott, 1970 , and Sahyadriana Pati & Thackeray, 2018 , but these differ in having no flagellum on the exopod of third maxilliped. Pavizham differs from Liotelphusa Alcock, 1909 in its carapace morphology, with its carapace distinctly more ovate in shape; from Arcithelphusa Pati & Sudha Devi, 2015 in having a prominently less arched carapace; and from Cylindrotelphusa Alcock,

1909 in having a much smoother one.

Distribution: The genus is known only from the southern Western Ghats Kerala ( Figs. 1 , 6 ).

Pavizham gavi sp. nov. ( Figs. 2–5 ) urn:lsid:zoobank.org:act:5B4074B1-DED9-4000-B9E0-AB2B3FF462AC

Material examined: Holotype: male (17.3 × 12.8 mm) (DABFUK/AR-BR-116), from a waterfall near Gavi, Pathanamthitta district Kerala, India, 9.421056°N, 77.162659°E, coll. S. Raj, coll. 17 September 2017.

Diagnosis: As for genus.

Description of male holotype: Carapace broader than long, width 1.3 times length; dorsal surface convex ( Figs. 2 , 3A, B). Frontal region relatively narrow, surface smooth ( Fig. 3C); lateral parts of anterolateral and posterolateral regions smooth ( Figs. 2 , 3A, B); suborbital region smooth; pterygostomial regions smooth, glabrous, separated from other regions by a groove; sub-branchial regions smooth ( Fig. 3C). Epigastric cristae are faintly visible, medially separated by a shallow groove; postorbital cristae not visible, surface smooth ( Figs. 2 , 3A–C). Cervical grooves distinct, not broad, shallow, joining prominent H-shaped grooves ( Figs. 2 , 3A, B). External orbital tooth, very broad and low, outer margin almost straight, ca. 10 times longer than inner margin ( Figs. 2 , 3A, B); epibranchial tooth very small ( Figs. 2 , 3A, B). Anterolateral margins distinctly convex, with small striae ( Figs. 2 , 3A, C). Posterior lateral margin gently concave, converging to almost straight or gently sinuous posterior carapace margin ( Figs. 2 , 3A, B). Orbits subovate, oblique in frontal view; eyes filling up most of orbital space, eye peduncle moderately long, stout, cornea moderately large ( Fig. 3C). Supraorbital margin sinuous, complete, suborbital margin concave ( Fig. 3C). Antennae short, not reaching cornea of eyes; antennules folding transversely in narrow fossa ( Fig. 3C). Posterior margin of epistome with distinct median triangular tooth ( Fig. 3C). Mandibular palp distinctly 2-segmented, terminal article bilobed.

Third maxilliped ischium rectangular, with distinct median sulcus; merus quadrate; exopod almost slender, not reaching midlength of merus, flagellum long, reaching about entire width of merus ( Figs. 3C, D, 5A ).

Chelipeds distinctly asymmetrical ( Figs. 2 , 3A, 4C, D). Dorsal margin of merus with small striae, appears unevenly serrated, ventral margin with low granules ( Figs. 2 , 3A, 4C, D). Outer surface of carpus rugose, distal angle with prominent sharp tooth ( Figs. 2 , 3A, 4C, D). Outer surface of chelae with small striae, fingers of major chelae curved, with median proximal gape when fingers closed, cutting margin with moderately large teeth and denticles; fingers of minor chelae curved, with small teeth and denticles ( Fig. 4C, D).

Ambulatory legs slender, not elongate; P3 longest, P5 shortest ( Figs. 2 , 3A). Merus with sharp dorsal and ventral margins, margins unevenly serrate but low; carpus with longitudinal median crest; propodus subrectangular, with low median longitudinal crest; dactylus elongate, gently curved, lined with small sharp spines ( Figs. 2 , 3A).

Anterior thoracic sternum transversely broad; sternites 1 and 2 completely fused to form triangular plate with convex lateral margins; separated from sternite 3 by a complete suture; sternite 3 and 4 fused, demarcated by shallow moderate oblique grooves; sutures between sternites 4/5, 5/6 and 6/7 medially interrupted, separated by narrow space; suture between sternites 7/8 complete, joining short longitudinal groove between sternites ( Figs. 3D, 4B, 5B ). Sternopleonal cavity deep, broad, reaching to imaginary line joining the anterior point of cheliped coxae ( Figs. 3D, 4B). Male pleonal-locking tubercle low, round, positioned on sternite 5 ( Fig. 4B). Penis on condyle of coxa of last ambulatory leg, visible as short papilla with subtruncate tip.

Pleon triangular, all somites and telson free; somites 1 and 2 longitudinally narrow, subequal in width, somite 3, 4 and 5 trapezoidal; somite 6 broader than long, with gently concave lateral margins; telson triangular with slightly concave lateral margins ( Figs. 3D, 4A).

G1 almost straight, groove for G2 ventral in position; terminal and subterminal segments clearly demarcated; terminal segment relatively long, conical, gradually tapering to truncate tip ( Fig. 5C–E ). G2 long, with long slender segment, nearly half the length of the basal segment ( Fig. 5F ).

Colour: In life most of the carapace and legs are red in colour ( Fig. 2 ). Chelipeds light red in colour ( Fig. 2 ).

Etymology: The species name is derived from the collection locality “gavi ” in the southern Western Ghats where the species was collected. The name is used as a noun in apposition.

Distribution: The species is known only from Gavi (9.421056°N, 77.162659°E) in the Pathanamthitta district of the southern Western Ghats, Kerala ( Fig. 1 ).

Remarks: While Pavizham gavi closely resembles Baratha peena Bahir & Yeo, 2007 and B. pushta Bahir & Yeo, 2007 , Snaha aruna Bahir & Yeo, 2007 and S. escheri ( Roux, 1931) ; the generic characters discussed above easily distinguish them.

Ecology: The species was collected from a waterfall ( Fig. 6 ) under stones and nothing more is known about its ecology. Despite several efforts, more specimens could not be collected. Its conservation status is indeterminate until more samples can be obtained and its actual range established.

Figures

Fig. 2. Pavizham gavi gen. nov., sp. nov., holotype male (17.3 × 12.8 mm) (DABFUK/AR-BR-116). Colour in life.

Fig. 5. Pavizham gavi gen. nov., sp. nov., holotype male (17.3 × 12.8 mm) (DABFUK/AR-BR-116). A, left third maxilliped (setae not drawn); B, thoracic sternites 1–4 and telson (setae on right side denuded); C, left G1 (ventral view); D, G1 terminal segment (ventral view); E, G1 terminal segment (dorsal view); F, left G2. Scale bars: A–C, F = 1.0 mm; D, E = 0.5 mm.

Fig. 1. Map of India showing type localities of Pavizham gavi gen. nov., sp. nov. and Rajathelphusa brunnea sp. nov.

Fig. 6. Habitat of Pavizham gavi gen. nov., sp. nov.: base of waterfall, Gavi, Pathanamthitta district, Kerala, India.