Terrapotamon thungwa, Promdam & Yeesin & Ng, 2017

Promdam, Rueangrit, Yeesin, Pun & Ng, Peter K. L., 2017, A second new species of terrestrial long-legged Terrapotamon Ng, 1986 (Crustacea: Brachyura: Potamidae) from karst forests in Peninsular Thailand, Raffles Bulletin of Zoology 65, pp. 404-415 : 404-414

publication ID	https://doi.org/ 10.5281/zenodo.5357298
publication LSID	lsid:zoobank.org:pub:9726E37D-D2F9-4CC7-B784-C348755E6288
persistent identifier	https://treatment.plazi.org/id/7C311A26-3C1E-FFE8-FC77-F203FB5DFA3A
treatment provided by	Valdenar
scientific name	Terrapotamon thungwa
status	sp. nov.

Treatment

Terrapotamon thungwa View in CoL n. sp.

( Figs. 1–5 View Fig View Fig View Fig View Fig View Fig , 7A, C, E View Fig )

Material examined. Holotype: adult male (44.6 × 35.0 mm) ( ZRC 2016.0595 View Materials ), limestone bedrock, ca. 350 m asl, Ban Rao Pla, Tambon Thung Wa, Amphoe Thung Wa, Changwat Satun, coll. Y. Pun et al., 12 June 2016 . Paratypes: 2 adult females (41.4 × 32.9, 40.0 × 32.8 mm) (PSUNHM-2016.0001), same data as holotype ; 1 adult female (46.1 × 37.2 mm) ( ZRC 2016.0596 View Materials ), limestone bedrock at Khao Wang Phak Kud , Tambon Pa Kae Bo Hin , Amphoe Thung Wa, Changwat Satun, Peninsular Thailand, coll. R. Promdam & S. Promwichit, 10 September 2015 ; 1 adult male (41.1 × 33.3 mm), 1 adult female (31.1 × 25.5 mm) (PSUZC-CRU-0072), Ban Namtok Than Plio , Amphoe Thung Wa, Changwat Satun, Peninsular Thailand, coll. R. Promdam & S. Jantarit, 23 April 2016 ; 3 adult males (45.9 × 37.4 mm, 43.1 × 33.4 mm, 40.5 × 32.2 mm), 1 young female (29.4 × 23.8 mm) (PSUZC-CRU-0073), 1 young male (28.8 × 23.8) ( ZRC 2016.0597 View Materials ) Ban Namtok Than Plio , Amphoe Thung Wa, Changwat Satun, Peninsular Thailand, coll. R. Promdam & S. Jantarit, 27 April 2016 .

Comparative material. Terrapotamon longitarsus Lheknim & Ng, 2016 – Holotype: male (47.4 × 38.6 mm) ( ZRC 2016.0161 View Materials ), on limestone bedrock at Khao Raya Bung Sa, southernmost of Nakhon Si Thammarat mountain range, 30 m above mean sea level, Tambon Khuan Po, Muang Satun District, Changwat Satun, coll. V. Lheknim & P. Leelawathanagoon, 9 September 1999. Paratypes: 1 male (40.8 × 32.5 mm) ( PSUZC 20150726 View Materials - 01.01 View Materials ), limestone rock crevice, near locality of holotype, coll. R. Promdam & R. Engchoun, 26 July 2015 ; 1 male (28.4 × 23.8 mm) ( PSUZC 20150611 View Materials - 01.01 View Materials ), limestone rock crevice, near locality of holotype, coll. R. Promdam & R. Engchoun, 11 June 2015 . Others : 1 male (35.0 × 29.5 mm), 1 female (23.8 × 20.2 mm) ( ZRC 2016.0162 View Materials ), Changwat Satun, coll. Y. Pun & S. Buatip, 20 May 2016 ; 1 male (33.2 × 28.1 mm) (PSUZC- CRU-0071), Ban Namtok Than Plio, Amphoe Thung Wa , Changwat Satun, coll. R. Promdam & S. Jantarit, 23 April 2016 . All locations in southernmost part of Nakhon Si Thammarat mountain range, Peninsular Thailand .

Diagnosis. Carapace, chelipeds and ambulatory legs bright red in life ( Fig. 1 View Fig ); carapace transversely ovate, distinctly broader than long; dorsal surfaces almost smooth, gently convex, regions poorly demarcated ( Figs. 1A, D View Fig , 2A View Fig , 5A View Fig , 7A View Fig ); lateral regions with low, short, oblique striae ( Figs. 1A, D View Fig , 2A View Fig , 5A View Fig , 7A View Fig ); external orbital tooth triangular ( Figs. 1A, D View Fig , 2A View Fig , 5A View Fig , 7A View Fig ); anterolateral margin distinctly cristate ( Figs. 1A, D View Fig , 2A View Fig , 5A View Fig , 7A View Fig ); posterolateral margin gently converging to posterior carapace margin ( Figs. 1A, D View Fig , 2A View Fig , 5A View Fig , 7A View Fig ); epigastric and postorbital cristae distinct, rugose, not sharp, epigastric cristae distinctly anterior of postorbital cristae ( Figs. 1A, D View Fig , 2A View Fig , 5A View Fig , 7A View Fig ); sub-orbital, sub-branchial, pterygostomial regions covered with numerous well-spaced small sharp granules ( Figs. 1B View Fig , 2B View Fig , 7C View Fig ); posterior margin of epistome with relatively broad median triangular tooth ( Figs 1B View Fig , 2B View Fig , 7C View Fig ); ambulatory legs very long, slender ( Figs. 1A, D View Fig , 2A View Fig , 3E View Fig , 5A View Fig ); anterior thoracic sternum relatively broad ( Fig. 3B View Fig ); outer surface of major chela prominently granulated ( Figs. 2D View Fig , 7E View Fig ); last ambulatory propodus relatively long, 3.5–3.8 times longer than broad ( Fig. 3E View Fig ); G1 with strongly developed swelling on outer margin between terminal and subterminal segments, terminal segment relatively long, about 0.2 times length of subterminal segment, with distal part slender, elongated, tip bifurcated ( Fig. 4A–D View Fig ).

Description of male holotype. Carapace ( Figs. 1A View Fig , 2A View Fig , 7A View Fig ) transversely ovate, distinctly broader than long, relatively flat; dorsal surface almost smooth, glabrous, regions poorly demarcated, lateral regions with distinct oblique striae, cervical grooves faint, H-shaped median groove distinct. Anterolateral margins ( Figs. 1A View Fig , 2A View Fig , 7A View Fig ) arcuate, distinctly cristate, lined with blunt granules, appearing gently serrated, distinctly separated from gently converging posterolateral margins. Frontal margin ( Figs. 1A, B View Fig , 2A, B View Fig , 7A, C View Fig ) gently deflexed, sinuous, 2 lobes separated by broad, shallow sinus; epibranchial tooth distinct, clearly separated from external orbital angle margin by deep, V-shaped cleft; external orbital angle triangular, outer margin straight, gently serrated, subequal to inner margin. Epigastric and postorbital cristae ( Figs. 1A View Fig , 2A View Fig , 7A View Fig ) distinct, rugose, not sharp; epigastric cristae distinctly anterior of postorbital cristae, separated by distinct oblique groove. Orbits large ( Figs. 1A, B View Fig , 2A, B View Fig , 7A, C View Fig ); eyes well developed, cornea large, pigmentation well developed. Sub-orbital, sub-branchial, pterygostomial regions ( Figs. 1B View Fig , 2B View Fig , 7C View Fig ) covered with numerous wellspaced small sharp granules. Lateral part of epistome, outer surfaces (between anterior, posterior margins), inner part of pterygostomial regions hirsute ( Figs. 1B View Fig , 2B View Fig , 7C View Fig ). Anterior margin of epistome ( Figs. 1B View Fig , 2B View Fig , 7C View Fig ) straight, parallel with frontal margin; posterior margin with relatively broad median triangular tooth, lateral margins gently concave.

Exopod of third maxilliped ( Fig. 2C View Fig ) extending beyond distal margin of ischium, just reaching midway of merus; with distinct flagellum reaching about half width of merus. Ischium ( Fig. 2C View Fig ) subrectangular, relatively short, with deep median groove; merus squarish, cristate along margins.

Chelipeds ( Figs. 1A View Fig , 2A, D View Fig , 7E View Fig ) elongate, unequal, fingers of both chelae nearly as long as palm; outer surfaces of all articles distinctly granulated. Carpus ( Figs. 1A View Fig , 2A View Fig , 3F View Fig ) with long sharp, obliquely directed subdistal spine on inner angle; merus with subterminal spine behind inner part.

Ambulatory legs ( Figs. 1A View Fig , 2A View Fig , 3E View Fig ) very long, slender, last pair shortest, second pair longest; surfaces of all articles rugose, dorsal margin gently serrated; lower margin of merus, propodus and dactylus with scattered short stiff setae. Merus ( Figs. 1A View Fig , 2A View Fig , 3E View Fig ) without distinct subdistal spine; propodus relatively broad, distinctly longer than carpus, that of last leg 3.5–3.8 times longer than broad; dactylus of fourth pair about 10 times longer than proximal width; as long as propodus.

Anterior thoracic sternum (sternites 1–4) transversely broad ( Fig. 3B View Fig ). Suture between thoracic sternites 2, 3 ( Figs. 1C View Fig , 3A, B View Fig ) distinct, nearly straight. Thoracic sternites 3, 4 ( Figs. 1C View Fig , 3A, B View Fig ) separated by faintly discernible groove, extending from base of chelipeds to tip margin of sternopleonal cavity. Thoracic sternite 8 ( Fig. 3A View Fig ) completely separated by longitudinal median line, lacking transverse ridge. Press button pleonal locking mechanism on sternite 5 ( Fig. 3A View Fig ), knob-like, small. Male gonopore on coxa of fifth ambulatory leg.

Pleon ( Figs. 1C View Fig , 3B–D View Fig ) triangular; telson subequal in length to somite 6, lateral margins nearly straight, tip rounded; somite

1 reaches base of last pair of legs; somites 2–6 progressively broader, longer anteriorly.

G1 ( Fig. 4A–D View Fig ) stout; terminal segment clearly separated from subterminal segment, with strongly developed swelling on outer margin between terminal and subterminal segments; terminal segment relatively long, about 0.2 times length of subterminal segment, tapered, cone-shaped, with distal part slender, elongated, tip bifurcated, dorsal and ventral folds appressed. G2 ( Fig. 4E View Fig ) gently sinuous; with long flagellum, as long as basal segment.

Female characters. Non-sexual characters similar to the male holotype in nearly all respects ( Figs. 1D View Fig , 5A View Fig ). Chelipeds of females relatively smaller and less stout ( Fig. 5A View Fig ) compared to males. Female pleon almost round, covering almost whole of thoracic sternum. Vulvae ( Fig. 5B View Fig ) large, each without operculum; occupying almost entire width of sternite 6 along inner portion; openings covered by chitinised membranes.

Colour. In life, adult males and females of T. thungwa are similarly coloured ( Fig. 1 View Fig ). The dorsal surface of the carapace is almost bright red, with outer parts of the branchial to cardiac and intestinal regions, as well as the sub-orbital, sub-branchial and pterygostomial regions reddish-brown. The anterolateral and most of the orbital margins, rugosities on the hepatic region, outer part of the postorbital cristae, sub-orbital, sub-branchial and pterygostomial regions and posterior margin of the epistome are white. The cheliped colour varies with different localities; the chelipeds of the male holotype and female paratype (46.1 × 37.2 mm, ZRC 2016.0596) from the outside of the cave are bright red, while those of other paratypes from inside the cave have bright red palms and fingers but the carpus to basis-ischium is reddishbrown. The tips of fingers are always beige to bright yellow. The integument at the articulations between the carpus and merus of the cheliped is bright red. The ambulatory legs are bright red to dark brown ( Figs. 1 View Fig , 8A, B View Fig ). The small crab from inside the cave had a dirty brown dorsal carapace surface, and orange chelipeds and ambulatory legs ( Fig. 9B View Fig ).

Etymology. The name is derived from the type locality at Amphoe Thung Wa. The name is used as a noun in apposition.

Remarks. The long ambulatory legs of T. thungwa n. sp. is a character shared only by one other species of Terrapotamon , T. longitarsus Lheknim & Ng, 2016 , also from the Satun area in Peninsular Thailand. It is surprising to find two similar species occurring in the same area, but the differences between the two species are very marked and leave no doubt they are separate taxa. Terrapotamon thungwa can most easily be separated in its bright red overall coloration in life ( Figs. 1 View Fig , 8A View Fig ) (purple in T. longitarsus ; Fig. 6 View Fig ); the carapace appears proportionately broader, with the posterolateral margins gently converging towards the posterior carapace margin ( Figs. 1A, D View Fig , 2A View Fig , 7A View Fig ) (carapace appears longer, with the posterolateral margins prominently converging towards the posterior carapace margin in T. longitarsus ; Figs. 6A View Fig , 7B View Fig ); the external orbital tooth is relatively broader ( Figs. 1A, D View Fig , 2A View Fig , 7A View Fig ) (acutely triangular in T. longitarsus ; Figs. 6A View Fig , 7B View Fig ); the anterolateral crista is relatively stronger and more prominent ( Figs. 1A, D View Fig , 2A View Fig , 7A View Fig ) (weaker and less pronounced in T. longitarsus ; Figs. 6B View Fig , 7B View Fig ); the upper part of the branchiostegal region has several groups of small sharp granules ( Figs. 1B View Fig , 2B View Fig , 7A, C View Fig ) (absent or with only scattered granules in T. longitarsus ; Figs. 6B View Fig , 7B, D View Fig ); the suborbital region has prominent small sharp granules ( Figs. 1B View Fig , 2B View Fig , 7A, C View Fig ) (surface almost smooth in T. longitarsus ; Figs. 6B View Fig , 7B, D View Fig ); the pterygostomial region has numerous small sharp granules ( Figs. 1B View Fig , 2B View Fig , 7A, C View Fig ) (surface almost smooth or with very low rounded granules on outer part in T. longitarsus ; Figs. 6B View Fig , 7B, D View Fig ); the triangular median projection on the posterior margin of the epistome is relatively broader ( Figs. 1B View Fig , 2B View Fig , 7B View Fig ) (more acute in T. longitarsus ; Figs. 6B View Fig , 7D View Fig ); the male anterior thoracic sternum (sternites 1–4) is proportionately transversely broader ( Fig. 3B View Fig ) (transversely narrower in T. longitarsus ; Fig. 6C View Fig , cf. Lheknim & Ng, 2016: figs. 1D, 4D); the outer surface of the major chela is prominently granulated ( Figs. 2D View Fig , 7E View Fig ) (rugose or with scattered low granules in T. longitarsus ; Fig. 7F View Fig ); the last ambulatory propodus is relatively broader, being 3.5–3.8 times longer than broad ( Fig. 3E View Fig ) (about 4.5–5.5 times in T. longitarsus ); and the distal part of the G1 terminal segment is relatively more elongate, with the distal part tapering to a long slender tip ( Fig. 4A–D View Fig ) (relatively shorter, gradually tapering in T. longitarsus ; cf. Lheknim & Ng, 2016: Fig. 5A–D View Fig ).

Habitat. All the specimens of Terrapotamon thungwa were obtained from the karst landscape of Satun. From the material collected, it would appear that the area and habitat where T. thungwa occurs overlaps with T. longitarsus . Both species were found inside and outside the caves as well as in the karst forest. In the dark zone inside the cave, adults of T. thungwa were observed climbing on the cave walls ( Fig. 8B, C View Fig ), with a small specimen observed in a pool on the cave floor ( Fig. 9A, B View Fig ). Up to five specimens have been observed on the cave floor. Adult males of both two species were observed in rock pools at the bottom of deep crevices in the karst forest, while a small specimen of T. longitarsus were seen at a sheltered rock pool near the cave entrance ( Fig. 9C, D View Fig ). The crabs use these collected pools to replenish their gill chambers.

Conservation. There is a growing trade in aquarium crabs in Thailand, both for the local market as well as the international market. There seems to be growing interest in keeping colourful and exotic Chinese and Indo-Chinese freshwater crabs, with increasing varieties and quantities exported to first-world countries. As such, we have opted not to divulge precise location data with the type series for the present new species. Its relatively large size, rich colours and semiterrestrial habits would make it a prime candidate to be hunted down by unscrupulous collectors, even if the areas they occur in may be protected. The karst forest of Thung Wa is generally protected and there no concessions for mining or logging as yet. There are no immediate development threats, and as such, the species faces no obvious threats to their survival.