Lacunipotamon globus, Ng & Tan & Ngo, 2023

Ng, Peter K. L., Tan, Zhi Wan & Ngo, Van Tri, 2023, Fig. 20 in Lanternflies (Hemiptera: Fulgoridae) of Taiwan., Zoological Studies 62 (20), pp. 1-58 : 5-51

Lacunipotamon cymatile Huang, Shih & Ahyong, 2020 ( Figs. 7–10 )

Lacunipotamon cymatile Huang, Shih & Ahyong, 2020: 1369 , figs. 4–6, 7C, D, 9B.

Material examined: Paratypes: 1 male (42.6 × 32.0 mm), 1 female (40.5 × 30.9 mm) ( ZRC 2018.1182), small hillstream, forest floor, Leiping Town Daxin County, Chongzuo City, Guangxi Province, 22.65°N 107.10°E, China, 300 m asl, coll. C. Huang with locals, August 2018.

Diagnosis: Carapace transversely ovate, wider than long; dorsal surface gently convex with median part appearing almost flat in frontal view; lateral part of postorbital crista distinct but more rounded, epibranchial tooth very low; epistomal median lobe well-developed, extending beyond lateral margins; suborbital and subhepatic regions with distinct low rugae, pterygostomial region distinctly rugose, with low granules; large adult major chela with strongly curved fingers that form almost circular gape when closed; groove between male thoracic sternites 3 and 4 very shallow, barely visible; anterior male thoracic sternites relatively flat, sternite 4 forming gently curved structure with sternite 5; male pleon broadly triangular; G1 relatively long, slender, proximal part of outer margin of subterminal segment sinuous, terminal segment with almost symmetrical, hemispherical dorsal flap, distal part straight, appears partially folded; vulva very large, occupying about three-quarters space of sternite 6, no visible vulvar cover on outer margin.

Colour: In adults, the carapace surface and meri of the third maxillipeds are sky blue; the orbits, epistome and chelipeds are ivory white with the ambulatory legs light olive-brown (cf. Huang et al. 2020: fig. 9B).

Remarks: Lacunipotamon cymatile has the most rugose suborbital, subhepatic and pterygostomial regions compared to congeners, the surfaces being lined with distinct striae and flattened granules ( Fig. 7D, E ). Other species of Lacunipotamon have these surfaces smooth or almost smooth (e.g., Fig. 3D, E ). The same is true for the surface of the chelipeds, being gently rugose in L. cymatile ( Fig. 7A, F ); in other Lacunipotamon species, the surface is almost smooth (e.g., Fig. 3A, F ).

Lacunipotamon globus n. sp. ( Figs. 11–16 ) urn:lsid:zoobank.org:act:73D38914-14B5-4AAD-92AA-CADDE9BD425C

Material examined: Holotype: male (37.5 × 28.2 mm) ( ZRC 2022.0805 ), foot of karst forest hill, Bắc Ngầm Commune , Bảo Th ắng District, Lào Cai Province, northern Vietnam, ca. 22.39°N 104.21°E, coll. local people, 10 July 2022 . Paratypes: 2 males (32.8 × 25.0 mm, 33.9 × 26.3 mm), 1 female (39.5 × 29.5 mm) ( ZRC 2022.0805), same data as holotype.

Diagnosis: Carapace almost round, slightly wider than long; dorsal surface gently convex with median part appearing almost flat in frontal view; lateral part of postorbital crista low, not pronounced, epibranchial tooth low but distinct; epistomal median lobe well-developed, extending beyond lateral margins; suborbital, subhepatic and pterygostomial regions smooth or almost so; adult major chela with gently curved fingers that do not form wide gape when closed; groove between male thoracic sternites 3 and 4 distinct; anterior male thoracic sternites relatively flat, sternite 4 forming gently curved structure with sternite 5; male pleon broadly triangular; G1 relatively long, proximal part of outer margin of subterminal segment gently sinuous, terminal segment with almost asymmetrical, triangular dorsal flap, higher on proximal section, distal part strongly recurved posteriorly, surface gently wrinkled; vulva large, occupying about two-thirds space of sternite 6, low, barely visible vulvar cover on outer margin.

Variation and females: While the form of the male pleon is always wide in L. globus n. sp., the lateral margins of smaller males tend to be more concave ( Fig. 14G ) than those of large ones ( Fig. 14F ). Female specimens are similar to males in most key non-sexual characters except the chelae are less asymmetrical although one chela is always larger in adults ( Fig. 16A ). In the female, the epibranchial tooth is lower and less distinct compared to the males ( Fig. 16B ).

Colour: There seems to be substantial colour variation in this species. The holotype male is bright yellow overall ( Fig. 11 ) but another paratype male is orange and red ( Fig. 12 ), as is the paratype female. Another paratype male is dark brown overall.

Etymology: The name is derived from the Latin “globus ” for globe, alluding to the shape of the carapace. The name is used as a noun in apposition.

Remarks: Although L. globus n. sp. and L. albusorbitum closely resemble each other in external morphology, one obvious difference is in the form of the epistomal median lobe. In L. globus , the median lobe is subtriangular in shape and projects well beyond the lateral margins ( Fig. 13D, E ) (versus median lobe very low and almost level with the lateral margins in L. albusorbitum ; Fig. 1D ). Although the G1 of L. globus is superficially similar to that of L. albusorbitum , the overall structure is proportionately more elongate ( Fig. 15A–C ) (versus G1 relatively shorter in L. albusorbitum ; Fig. 2 ); the outer margin of the proximal part of the subterminal segment is gently convex ( Fig. 15A ) (versus outer margin distinctly convex in L. albusorbitum ; Fig. 2A, B ); the terminal segment is more prominently bent upwards ( Fig. 15A– C ) (versus G1 terminal segment more confluent with subterminal segment in L. albusorbitum ; Fig. 2 ); and the dorsal flap on the G1 terminal segment is distinctly triangular in shape ( Fig. 15A–C ) (versus dorsal fold more semicircular and almost symmetrical in shape in L. albusorbitum ; Fig. 2 ). The groove between male thoracic sternites 3 and 4 is also distinctly deeper in L. globus ( Fig. 14A, B ) compared to the condition in L. albusorbitum , which is markedly shallower ( Fig. 1B ). The form of the external orbital tooth is different in form, with that of L. globus wider, with the outer margin almost twice the length of the inner margin, and there is a low epibranchial tooth visible ( Fig. 13A, B ) (versus tooth relatively shorter and more acute, without any trace of an epibranchial tooth in L. albusorbitum ; Fig. 1A ). Although the three male specimens of L. globus have the same external orbital tooth structure, that of the female, however, more closely resembles that of L. albusorbitum (cf. Fig. 16A, B ), suggesting this character may not be reliable, at least between sexes.

The type locality of L. globus is not far from the type locality of L. albusorbitum , being only about 50 km southeast of that for L. albusorbitum in Basa, Hekou, in southern Yunnan ( Fig. 55 ).

Lacunipotamon panda n. sp. ( Figs. 17–21 ) urn:lsid:zoobank.org:act:3D678813-EBA0-48C8-B99D-78D2027AF14C

Material examined: Holotype: male (38.3 × 27.4 mm) ( ZRC 2022.0706 ), after heavy rain, isolated karst forest with planted bamboo and small trees and liana, Thien Ke Commune , Son Duong District, Tuyen Quang Province, site adjacent to Tam Dao Mountain Range, northern Vietnam, 21.58°N 105.48°E, 74 m asl, coll. local people, 12 May 2022 . Paratypes: 1 male (38.6 × 27.3 mm), 2 females (34.7 × 25.1 mm, 36.8 × 25.6 mm) ( ZRC 2022.0707), same data as holotype.

Diagnosis: Carapace transversely ovate, wider than long; dorsal surface gently convex in frontal view; lateral part of postorbital crista distinct, sharp, epibranchial tooth low but distinct; epistomal median lobe low, tip almost level with lateral margins; suborbital, subhepatic and pterygostomial regions smooth or almost so; adult major chela with strongly curved fingers that form almost circular gape when closed; groove between male thoracic sternites 3 and 4 distinct; anterior male thoracic sternites relatively flat, sternite 4 forming gently curved structure with sternite 5; male pleon triangular; G1 slightly longer, relatively slenderer, proximal part of outer margin of subterminal segment gently sinuous, terminal segment with almost symmetrical, subovate flap, distal part gently upcurved, tip subtruncate; vulva large, occupying about two-thirds space of sternite 6, with prominent longitudinally ovate vulvar cover on outer margin.

Variation and females: The male holotype is atypical in that the pleon has been damaged before and subsequent moults have resulted in some teratological features. The structure is asymmetrical, suggesting the injury was on the right side of somites 4–6 and somites 4 and 5 have become fused as well ( Fig. 19E ). Other male specimens have a normal pleon ( Fig. 19F ). While the fingers of the normal adult male chela are slender and strongly curved, forming a round gape when closed ( Fig. 18F ), one of the paratype males has a somewhat atypical structure, with the fingers stout and more laterally flattened, with a large median tooth present on the cutting edge of the pollex and the gape is much less pronounced ( Fig. 19F ). Female specimens are similar to males in all key non-sexual characters except the chelae are less asymmetrical, although one chela is always larger in adults ( Fig. 21A ).

Colour: The colour of adult males and females is relatively constant. The overall carapace and chelipeds are white to greyish- or yellowish-white, and the ambulatory legs brownish-purple to almost black, with the joints bright orange; the ocular peduncles are pale orange ( Fig. 17 ).

Etymology: The species is named after the Chinese Giant Panda, Ailuropoda melanoleuca David, 1869 ; alluding to the distinctive colour pattern. The name “panda ” is used as a noun in apposition.

Remarks: The low epistomal median lobe of L. panda n. sp. ( Fig. 18D, E ) is a character shared with L. albusorbitum . The two species, however, differ markedly in other characters; the adult male carapace is proportionately wider with the lateral part of the postorbital crista relatively sharp as it joins low epibranchial tooth ( Fig. 18A, B ) (versus adult male carapace more globose, with the postorbital crista very low and rounded, and there is no epibranchial tooth visible in L. albusorbitum ; Fig. 1A ); the grooves between male thoracic sternites 3 and 4 are distinct ( Fig. 19A ) (versus grooves shallow in L. albusorbitum ; Fig.

1B); the male pleon is proportionately less wide ( Fig. 19F, G ) (versus distinctly wider in L. albusorbitum ; Fig. 1B ); the fingers of the major adult male chela are prominently gaping ( Fig. 18F ) (versus fingers not gaping in L. albusorbitum ; Fig. 1C ); the overall G1 is proportionately more elongate ( Fig. 20A ) (versus G1 proportionately shorter in L. albusorbitum ; Fig. 2A, B ); the distal part of the G1 terminal segment is gently curved ( Fig. 20A–C ) (versus distal part of the G1 is more distinctly bent in L. albusorbitum ; Fig. 2 ); the dorsal fold of the G1 terminal segment is wider with the distal part conical and gently curved upwards ( Fig.

20A–C) (versus dorsal fold of the G1 terminal segment more semicircular with the distal part strongly recurved in L. albusorbitum ; Fig. 2 ). The colour in life of the two species are also quite different; in L. panda , the carapace and chelipeds are white with the legs dark purple and the joints orange ( Fig. 17 ) but in L. albusorbitum , the carapace and chelipeds are believed to be red (cf. Huang et al. 2020: fig. 8A).

Lacunipotamon contrastum n. sp. ( Figs. 22–27 ) urn:lsid:zoobank.org:act:A6185C79-1608-493B-9E89-D863D5BAC56B

Material examined: Holotype: male (38.4 × 27.2 mm) ( ZRC 2022.0786 ), small intermittent stream bank, covered with shrubs and lianas, close to foot of karst forest hill, Yên L ạc Commune, Phú LƯƠng District, Thái Nguyên Province, northern Vietnam, ca. 21.75°N 105.74°E, coll. local people, ca. 2200 hours, 24 June 2022 . Paratypes: 1 male (39.1 × 29.7 mm), 2 females (40.9 × 30.1 mm, 39.6 × 29.3 mm) ( ZRC 2022.0787), same data as holotype.

Diagnosis: Carapace transversely ovate, wider than long; dorsal surface gently convex with median part appearing almost flat in frontal view; lateral part of postorbital crista distinct but more rounded, epibranchial tooth low but distinct; epistomal median lobe well-developed, extending beyond lateral margins; suborbital, subhepatic and pterygostomial regions smooth or almost so; adult major chela with strongly curved fingers that form almost circular gape when closed; groove between male thoracic sternites 3 and 4 distinct; anterior male thoracic sternites relatively flat, sternite 4 forming gently curved structure with sternite 5; male pleon triangular; G1 relatively shorter, stockier, proximal part of outer margin of subterminal segment with convex margin, terminal segment with almost symmetrical, subovate flap, distal part short, gently upcurved, tip truncate; vulva large, occupying about two-thirds space of sternite 6, with prominent longitudinally ovate vulvar cover on outer margin.

Variation and females: The gape of the fingers in the major male chela can be very large in some specimens ( Fig. 25 ) even though their carapace sizes are similar to the holotype ( Fig. 23F ), suggesting that this may be associated to male-dominance. Female specimens are similar to males in all key non-sexual characters except the chelae are less asymmetrical although one chela is always larger in adults ( Fig. 27A ).

Colour: The overall carapace and chelipeds of adult males and females are white to greyish-white, and the ambulatory legs purple with the joints yellow; the ocular peduncles are light purple ( Fig. 22 ).

Etymology: The name is derived from the Latin “contrasta”, alluding to the marked colour difference between the white carapace and the purple ambulatory legs.

Remarks: The life colours and the contrasting pattern of L. contrastum n. sp. is most like L. panda n. sp. Lacunipotamon contrastum can easily be distinguished in having the epistomal median lobe subtriangular in shape and projecting well beyond the lateral margins ( Fig. 23D, E ) (versus median lobe low and almost level with the lateral margins in L. panda ; Fig. 18D, E ); possessing a relatively shorter and stockier G1 ( Fig. 26A ) (versus G1 slightly longer and slenderer in L. panda ; Fig. 20A ); and the tip of the G1 is distinctly truncate ( Fig. 26A–C ) (versus tip more conical in L. panda ; Fig. 20A–C ). The adult major male chela of L. contrastum also appears to have more pronounced gaping fingers ( Figs. 23F , 25 ) than L. panda ( Fig. 18F ), even though specimens are of comparable sizes.

Lacunipotamon sublividum n. sp. ( Figs. 28– 32 , 38E–H ) urn:lsid:zoobank.org:act:3D8841E9-9072-451B-9A46-D9868035FCE0

Material examined: Holotype male (30.5 × 22.9 mm) ( ZRC 2022.0807 ), in stream bank close to karst forest, Phìn H ồ Village, Ma Quai Commune, Sìn H ồ District, Lai Chau Province, northern Vietnam, ca. 22.26°N 103.15°E, coll. local people, 27 July 2022 . Paratypes: 2 males (25.6 × 18.8 mm, 26.6 × 19.6 mm), 2 females (24.3 × 18.2 mm, 32.1 × 23.5 mm) ( ZRC 2022.0803), same data as holotype.

Diagnosis: Carapace transversely ovate, wider than long; dorsal surface with branchial regions distinctly inflated, median part appearing concave in frontal view; lateral part of postorbital crista low, not pronounced, no epibranchial tooth visible, anterolateral margin appears entire; epistomal median lobe well-developed, extending well beyond lateral margins; suborbital, subhepatic and pterygostomial regions smooth or almost so; adult major chela with distinctly curved fingers that form wide gape when closed; groove between male thoracic sternites 3 and 4 distinct; anterior male thoracic sternites relatively flat, sternite 4 forming gently curved structure with sternite 5; male pleon triangular; G1 relatively short, proximal part of outer margin of subterminal segment gently sinuous to almost straight, terminal segment with almost symmetrical, subovate flap, distal part short, gently upcurved, tip very wide, appears dilated; vulva large, occupying about two-thirds space of sternite 6, low vulvar cover on outer margin.

Variation and females: Female specimens are similar to males in all key non-sexual characters except the chelae are less asymmetrical, although one chela is always larger in adults ( Fig. 32A ). The absence of an epibranchial tooth is evident even in subadults and females ( Figs. 28G , 32A ).

Colour: In adult males, the overall carapace is blue under bright light but a duller in the shade; the chelipeds have the dorsal surfaces light blue with the outer and inner surfaces more white; the ambulatory legs are brownish-purple to almost black, with the ambulatory legs olive brown to grey; the ocular peduncles are grey; and the ventral surfaces are yellowish-white ( Fig. 28A– F ). Females and subadults have more olive-coloured carapaces ( Fig. 28G, H ).

Etymology: The name is derived from the Latin word for bluish, “sublividus”, alluding to the colour of the carapace in fresh specimens.

Remarks: Lacunipotamon sublividum n. sp. most closely resembles L. mimicum n. sp. in terms of external carapace and gonopod morphology. Differences between the two species are elaborated in the remarks for L. mimicum (see later). With regards to the anterolateral margin being entire with no epibranchial tooth visible, L. sublividum resembles L. albusorbitum . The carapace of L. sublividum , however, is distinctly wider than that of L. albusorbitum ( Fig. 29A, B versus Fig. 1A ), and the epistomal median lobe is also well developed and projects beyond the lateral margins ( Fig. 29D, E versus Fig. 1D ). The carapace shape and well developed epistomal median lobe allies L. sublividum with L. thuanchau n. sp. and L. pectum n. sp. Lacunipotamon sublividum can easily be separated from L. pectum in its flatter and less prominent male anterior thoracic sternum ( Fig. 30A, B ), which in the latter species is swollen and forms a sharp angle with the remaining sternites ( Fig. 46A–D ). Their colours are also quite different, bluish in L. sublividum ( Fig. 28A–E ) but evenly white to pale grey in L. pectum ( Fig. 44 ). Lacunipotamon sublividum can easily be separated from L. thuanchau by their different G1 structures; the dorsal lobe on the terminal segment is evenly subovate with the tip broad and subtruncate in L. sublividum ( Fig. 31A–C ) but in L. thuanchau , the dorsal lobe is higher on the proximal part with the margin sinuous and the distal part is conical and gently upcurved ( Fig. 42A–C ).

Lacunipotamon mimicum n. sp. ( Figs. 33–37 , 38A–D ) urn:lsid:zoobank.org:act:1FEA01F2-BBE6-4112-913F-0017BBD66A88

Material examined: Holotype male (31.3 × 23.0 mm) ( ZRC 2022.1024 ), in heavy rain, at foot of karst hill, Nậm Tăm Village , N ậm Tăm Commune, Sin H ồ District, Lai Châu Province, northern Vietnam, ca. 22.17°N 103.26°E, coll. Ngo Van Tri, 3 July 2022 . Paratypes: 1 male (30.3 × 22.6 mm), 2 females (30.1 × 23.2 mm, 28.8 × 22.0 mm) ( ZRC 2022.1025), same data as holotype.

Diagnosis: Carapace transversely ovate, wider than long; dorsal surface gently convex in frontal view; lateral part of postorbital crista low, not pronounced, no epibranchial tooth visible, anterolateral margin appears entire; epistomal median lobe low, rounded, almost level with lateral margins; suborbital, subhepatic and pterygostomial regions smooth; adult major chela with distinctly curved fingers that form wide gape when closed; groove between male thoracic sternites 3 and 4 distinct; anterior male thoracic sternites relatively flat, sternite 4 forming curved structure with sternite 5 in large males; male pleon triangular; G1 relatively short, proximal part of outer margin of subterminal segment gently sinuous to almost straight, terminal segment with almost symmetrical, subovate flap, distal part short, gently upcurved, tip wide, appears dilated; vulva large, occupying about two-thirds space of sternite 6, no vulvar cover on outer margin.

Variation and females: The G1 of the paratype male (30.3 × 22.6 mm, ZRC 2022.1025) differs from the holotype male in that the distal part of the terminal segment is slightly shorter and the dorsal flap is slightly more symmetrical in shape; and the distal part of the subterminal segment is slightly wider as well ( Fig. 36A versus Fig. 36E ). Female specimens are similar to males in all key non-sexual characters except the chelae are less asymmetrical although one chela is always larger in adults ( Fig. 37A ).

Colour: This species is similar to L. sublividum n. sp. in its bluish colouration in life. The overall carapace varies from greenish steel blue to steel blue; the chelipeds have the dorsal surfaces similar to carapace colouration with the fingers, outer, inner and ventral surfaces more dirty pale yellow; the ambulatory legs are dirty pale yellow, with bluish streaks interspersed throughout; the ocular peduncles are light brown; and the ventral surfaces are yellowish-white ( Fig. 33 ).

Etymology: The Latin name is derived from the Greek word for mimic, “mīmikós”, for its close resemblance to L. sublividum .

Remarks: Like L. sublividum n. sp., the anterolateral margin of L. mimicum n. sp. ( Fig. 34B ) is also entire with no epibranchial tooth, a condition also similar to L. albusorbitum ( Fig. 1A ). Moreover, the epistomal median lobe is also low as in L. albusorbitum ( Figs. 1D , 34E ). Lacunipotamon mimicum , however, can be easily distinguished from L. albusorbitum by its more transverse carapace and G1 terminal segment being very gently upcurved with a dilated tip ( Figs. 34A , 36A–C, E ) (versus a less transverse carapace and a G1 terminal segment that is strongly recurved posteriorly at the distal end in L. albusorbitum ; Figs. 1A , 2 ).

Overall, L. mimicum most closely resembles L. sublividum with regards to its overall colouration, carapace and G1 morphology. The G1 morphology of L. mimicum is very similar to that of L. sublividum , with the distal end of the terminal segment of the holotype of L. mimicum being relatively longer and slenderer in L. mimicum ( Fig. 36A–C ), which in L. sublividum , appears to be shorter and more strongly dilated ( Fig. 31A–C ). The G1 of the paratype male of L. mimicum , however, is much closer to that of L. sublividum , although the distal part of the terminal segment is still slightly longer ( Fig. 36E ). With a larger series of specimens, these small differences may not be reliable. In any case, the two species have obvious and consistent differences in its external morphology that easily allow their separation. All specimens of L. mimicum possess a carapace that is proportionately more transverse, that is transversely convex when seen from the front and an epistomal median lobe that is low ( Figs. 34A, D, E , 38A–D ). This contrasts with all specimens of L. sublividum possessing a carapace that is less transverse, with a more strongly inflated branchial regions, making the median part of the carapace appearing weakly concave when viewed from the front with a well-developed epistomal median lobe ( Figs. 29A, D, E , 32E , 38E–H ).

Although both L. mimicum and L. sublividum are distributed in the same district and province (Sin Hồ District, Lai Châu Province), they actually occur on two distinct and isolated mountain ranges and watersheds ( Fig. 55 ). Given that freshwater crabs are characterised by their low dispersal capabilities ( Cumberlidge et al. 2009), the physical obstacles between their localities and the observed morphological differences support recognising them as two distinct species for now.

Lacunipotamon thuanchau n. sp. ( Figs. 39–43 ) urn:lsid:zoobank.org:act:3685138C-8FA3-4FC2-878C-DAD2A0D3B947

Material examined: Holotype: male (29.6 × 20.8 mm) ( ZRC 2022.0808 ), stream bank close to karst forest hill, Chi ềng Pha Commune, Thuan Chau District, Son La Province, northern Vietnam, ca. 21.51°N 103.64°E, coll. local people, 6 July 2022 . Paratypes: 2 males (25.8 × 18.2 mm, 29.0 × 21.0 mm), 1 female (27.8 × 19.7 mm) ( ZRC 2022.0804), same data as holotype.

Diagnosis: Carapace transversely ovate, wider than long; dorsal surface gently convex with median part appearing almost flat in frontal view; lateral part of postorbital crista low but pronounced, forming rounded angle with lateral margin but no epibranchial tooth visible, anterolateral margin appears entire; epistomal median lobe well-developed, extending well beyond lateral margins; suborbital, subhepatic and pterygostomial regions smooth or almost so; adult major chela with distinctly curved fingers that form wide gape when closed; groove between male thoracic sternites 3 and 4 distinct; anterior male thoracic sternites relatively flat, sternite 4 forming gently curved structure with sternite 5; male pleon triangular; G1 relatively short, proximal part of outer margin of subterminal segment gently convex with basal cleft, terminal segment with asymmetrical lobe, proximal section higher than distal section, distal part conical, gently upcurved, tip relatively sharp; vulva large, occupying about two-thirds space of sternite 6, low vulvar cover on outer margin.

Variation and females: Female specimens are similar to males in all key non-sexual characters except the chelae are less asymmetrical, although one chela is always larger in adults ( Fig. 43A ).

Colour: In life, the colour varies from a dirty green carapace, ambulatory legs and chelipeds with white fingers, to bright orange overall with white fingers, to colours intermediate between the two ( Fig. 39 ). The holotype male has an intermediate colour.

Etymology: The species is named after its type locality in Thuan Chau District. The name is used as a noun in apposition.

R e m a r k s: The external morphology of L. thuanchau n. sp. is closest to L. sublividum n. sp., but the G1 structure is most similar to that of L. pectum n. sp. (see remarks for these species for detailed comparisons).

Lacunipotamon pectum n. sp. ( Figs. 44–48 ) urn:lsid:zoobank.org:act:9C9EC5AE-B275-420D-B953-F6E277D7E0F3

Material examined: Holotype: male (38.3 × 26.4 mm) ( ZRC 2022.0788 ), small stream banks close to karst forest, Na Sy Village , Hát L ốt Commune, Mai Son District, Son La Province, northern Vietnam, ca. 21.18°N 104.09°E, coll. local people, ca. 2100 hours, 6 July 2022 . Paratypes: 1 male (39.2 × 27.1 mm), 3 females (22.2 × 16.3 mm, 30.1 × 21.5 mm, 31.0 × 22.2 mm) ( ZRC 2022.0789), same data as holotype.

Diagnosis: Carapace transversely ovate, wider than long; dorsal surface gently convex with median part appearing almost flat in frontal view; lateral part of postorbital crista low but pronounced, forming rounded angle with lateral margin but no epibranchial tooth visible, anterolateral margin appears almost entire; epistomal median lobe well-developed, extending well beyond lateral margins; suborbital, subhepatic and pterygostomial regions smooth or almost so; adult major chela with strongly curved fingers that form almost circular gape when closed; groove between male thoracic sternites 3 and 4 distinct; anterior male thoracic sternites projecting anteriorly, appears inflated, sternite 4 forming prominent angular structure with sternite 5; male pleon more acutely triangular; G1 relatively long, slender, proximal part of outer margin of subterminal segment sinuous, terminal segment with asymmetrical lobe, proximal section higher than distal section, distal part conical, gently upcurved, tip relatively sharp; vulva very large, occupying about three-quarters space of sternite 6, no visible vulvar cover on outer margin.

Variation and females: Female specimens do not have the anterior thoracic sternum swollen and projected anteriorly; with sternite 4 joining sternite 5 smoothly and gently ( Figs. 44F , 48C ). They are otherwise similar to males in all key non-sexual characters except the chelae are less asymmetrical, although one chela is always larger in adults ( Fig. 48A ).

Colour: The colour of adult and subadult specimens are relatively consistent, with the carapace white to pale greyish-white; the chelipeds and ambulatory legs are white to yellowish-white, the ocular peduncles are grey and the ventral surfaces are yellowish-white ( Fig. 44 ).

Etymology: The name is derived from the Latin “pectus” for chest, alluding to the prominent dilated male anterior thoracic sternites of the species.

Remarks: In the general features of the carapace, L. pectum n. sp. most closely resembles L. sublividum n. sp. and L. thuanchau n. sp. While the anterolateral margin of L. pectum is unarmed, the external orbital tooth forms a rounded angle with the swollen anterolateral margin ( Fig. 45A, B ); this is unlike the more confluent condition observed in the other two species in which there is no obvious angle ( Figs. 29A, B , 40A, B ). The most obvious difference is the unique inflated male anterior thoracic sternum in L. pectum , so much so that sternite 4 forms a sharp angle with sternite 5 ( Fig. 46A–D ). In addition, for L. pectum , the male pleon is proportionately narrower ( Fig. 46G ) (versus distinctly wider in the other two species; Figs. 30A, B , 41A, B ). The G1 of L. pectum closely resembles that of L. thuanchau , with the dorsal fold of the terminal segment and the distal part similar in form ( Figs. 42A– C , 47A–C ). The overall G1 of L. pectum , however, is distinctly longer and slenderer in proportions ( Fig. 47A–C versus Fig. 42A–C ).

It is noteworthy that L. pectum was collected from the same area as L. thuanchau , the two locations only about 50–70 km from each other, along the Đà River ( Fig. 55 ). The two species, however, are quite different even in colour; with L. pectum an evenly pale grey to white ( Fig. 44 ) while L. thuanchau has an orange to greenish carapace ( Fig. 39 ). More importantly, the carapace of L. pectum has the anterior male thoracic sternum prominently inflated and projects outwards ( Fig. 46A–D ) and the male pleon is proportionately narrower ( Fig. 46C, G ). As discussed earlier, the G1 of L. pectum is similar to that of L. thuanchau , but is overall longer and slenderer in proportions.

Lacunipotamon purpureum n. sp. ( Figs. 49–53 ) urn:lsid:zoobank.org:act:AED54A01-773A-4699-9C11-A8062752652B

Material examined: Holotype: male (28.8 × 21.2 mm) ( ZRC 2022.1026 ), burrow along stream bank, Xuân SƠn National Park , Tân SƠn District , Phú Th ọ Province, Vietnam, coll. V. T. Ngo, 7 June 2011 . Paratypes: 4 females (26.3 × 18.9 mm, 23.5 × 17.2 mm, 18.9 × 14.4 mm, 18.3 × 13.6 mm) ( ZRC 2022.1027), same data as holotype.

Diagnosis: Carapace transversely ovate, wider than long; dorsal surface gently convex with median part appearing almost flat in frontal view; lateral part of postorbital crista low but pronounced, forming well defined broad angle with lateral margin; epistomal median lobe well-developed, broadly triangular, extending well beyond lateral margins; suborbital, subhepatic, pterygostomial regions smooth; adult major chela with distinctly curved fingers that form wide gape when closed; groove between male thoracic sternites 3 and 4 deep, distinct; anterior male thoracic sternites flat, smooth; male pleon triangular; G1 relatively long, slender, subterminal segment gently sinuous, terminal segment slender, subconical, very gently curved upwards distally, with well-produced basal dorsal flap, with apex near base of segment, only tapering strongly past proximal third to just past median of terminal segment, then tapering very gently to distal end; terminal segment tip blunt; vulva large, occupying about two-thirds space of sternite 6, no visible vulvar cover on outer margin.

Variation and females: Female specimens are similar to males in all key non-sexual characters except the chelae are less asymmetrical, although one chela is always larger in adults ( Fig. 53A ).

Colour: The colour of adult and subadult specimens are relatively consistent, with the carapace purple; chelipeds cutting edge ivory white, and the ventral surfaces are yellowish-white ( Fig. 49 ).

Etymology: The species name, derived from the Latin “purpureus” for purple, alluding to the life colouration.

Remarks: Lacunipotamon purpureum n. sp. most closely resembles L. yuanshi Huang, Shih & Ahyong, 2020 , in its external morphology, especially in terms of the presence of a well-developed and complete suture between sternites 3 and 4, which immediately separates them from L. albusorbitum Dai, Song, He, Cao, Xu & Zhong, 1975 which possess an almost indiscernible demarcating suture between sternites 3 and 4 ( Fig. 1B ), and L. cymatile Huang, Shih & Ahyong, 2020 , L. globus n. sp., L. panda n. sp., L. contrastum n. sp., L. sublividum n. sp., L. mimicum n. sp., L. thuanchau n. sp. and L. pectum n. sp., with their weak and/or incomplete demarcating suture between sternites 3 and 4 ( Figs. 8A , 14B , 19A , 24A , 30A , 35A , 41B , 46A ). Lacunipotamon purpureum , however, can be easily distinguished from L. yuanshi by the following differences: external orbital tooth being less strongly produced, broadly triangular ( Figs. 50A, B , 53B ) (versus external orbital tooth more strongly produced, narrowly triangular in L. yuanshi ; Figs. 3A, B , 6B ); the lateral margins of the epistomal median lobe are almost straight ( Fig. 50E ) (versus margins weakly convex in L. yuanshi ; Fig. 3E ); the groove demarcating suture between sternites 3 and 4 is distinctly anterior to the sternopleonal cavity ( Fig. 51B ) (versus groove is almost confluent with edge of sternopleonal cavity in L. yuanshi ; Fig. 4A, B ); and the G1 terminal segment is elongate, gently tapering distally with a large trapezoidal basal flap, with an almost perpendicular edge near the base before becoming parallel to the terminal segment, continuing to the posterior third portion of terminal segment where it tapers distally with a gently concave edge ( Fig. 52C, D ) (versus G1 terminal segment distinctly shorter, not visibly tapering distally, with large rounded basal flap with apex at posterior third of terminal segment and subquadrate dorsal projection, directed obliquely anteriorly in L. yuanshi ; Fig. 5B, C ).

Figures

Fig. 7. Lacunipotamon cymatile Huang, Shih & Ahyong, 2020, paratype male (42.6 × 32.0 mm) (ZRC 2018.1182), China. A, overall dorsal habitus; B, dorsal view of carapace; C, left third maxilliped; D, frontal view of cephalothorax; E, antennules, antennae and epistome; F, chelae.

Fig. 8. Lacunipotamon cymatile Huang, Shih & Ahyong, 2020, paratype male (42.6 × 32.0 mm) (ZRC 2018.1182), China. A, anterior half of thoracic sternum and buccal cavity; B, median part of thoracic sternum and pleon; C, sternopleonal cavity; D, left fourth ambulatory leg; E, posterior half of thoracic sternum and pleon; F, pleon.

Fig. 9. Lacunipotamon cymatile Huang, Shih & Ahyong, 2020, paratype male (42.6 × 32.0 mm) (ZRC 2018.1182), China. A, left G1 (ventral view); B, distal part of left G1 (ventral view); C, distal part of left G1 (dorsal view); D, left G2. Scale bars: A, D = 1.0 mm; B, C = 0.5 mm.

Fig. 10. Lacunipotamon cymatile Huang, Shih & Ahyong, 2020, paratype female (40.5 × 30.9 mm) (ZRC 2018.1182), China. A, overall dorsal habitus; B, dorsal view of carapace; C, pleon; D, sternopleonal cavity showing vulvae.

Fig. 3. Lacunipotamon yuanshi Huang, Shih & Ahyong, 2020, paratype male (27.6 × 21.4 mm) (ZRC 2018.1185), China.A, overall dorsal habitus; B, dorsal view of carapace; C, left third maxilliped; D, frontal view of cephalothorax; E, antennules, antennae and epistome; F, chelae.

Fig. 11. Lacunipotamon globus n. sp., colour in life, holotype male (37.5 × 28.2 mm) (ZRC 2022.0805), Vietnam.

Fig. 12. Lacunipotamon globus n. sp., colour in life. A–D, paratype male (32.8 × 25.0 mm) (ZRC 2022.0805), Vietnam; E, F, paratype female (39.5 × 29.5 mm) (ZRC 2022.0805), Vietnam.

Fig. 13. Lacunipotamon globus n. sp., holotype male (37.5 × 28.2 mm) (ZRC 2022.0805), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, left third maxilliped; D, frontal view of cephalothorax; E, antennules, antennae and epistome; F, chelae.

Fig. 14. Lacunipotamon globus n. sp. A–F, holotype male (37.5 × 28.2 mm) (ZRC 2022.0805), Vietnam; G, paratype male (32.8 × 25.0 mm) (ZRC 2022.0805), Vietnam. A, anterior half of thoracic sternum and buccal cavity; B, median part of thoracic sternum and pleon; C, sternopleonal cavity; D, left fourth ambulatory leg; E, posterior half of thoracic sternum and pleon; F, G, pleon.

Fig. 15. Lacunipotamon globus n. sp., holotype male (37.5 × 28.2 mm) (ZRC 2022.0805), Vietnam. A, left G1 (ventral view); B, distal part of left G1 (ventral view); C, distal part of left G1 (dorsal view); D, left G2. Scale bars:A, D = 1.0 mm; B, C = 0.5 mm.

Fig. 16. Lacunipotamon globus n. sp., paratype female (39.5 × 29.5 mm) (ZRC 2022.0805), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, pleon; D, sternopleonal cavity showing vulvae.

Fig. 1. Lacunipotamon albusorbitum Dai, Song, He, Cao, Xu & Zhong, 1975, holotype male (34.6 × 27.0 mm) (CAS CB 05108), China. A, overall dorsal habitus; B, ventral view of cephalothorax; C, D, frontal view of cephalothorax.

Fig. 2. Lacunipotamon albusorbitum Dai, Song, He, Cao, Xu & Zhong, 1975, holotype male (34.6 × 27.0 mm) (CAS CB 05108), China. A, left G1 (ventral view); B, left G1 (dorsal view); C, distal part of left G1 (ventral view); D, distal part of left G1 (dorsal view).

Fig. 55. Distribution map of known Lacunipotamon species: numbered and coloured circles denote type locality of species: (1) L. albusorbitum Dai, Song, He, Cao, Xu & Zhong, 1975; (2) L. yuanshi Huang, Shih & Ahyong, 2020; (3) L. cymatile Huang, Shih & Ahyong, 2020; (4) L. globus n. sp.; (5) L. panda n. sp.; (6) L. contrastum n. sp.; (7) L. sublividum n. sp.; (8) L. mimicum n. sp.; (9) L. thuanchau n. sp.; (10) L. pectum n. sp.; (11) L. purpureum n. sp.

Fig. 17. Lacunipotamon panda n. sp., colour in life. A, paratype female (34.7 × 25.1 mm) (ZRC 2022.0707), Vietnam; B, paratype male (38.6 × 27.3 mm) (ZRC 2022.0707), Vietnam; C–F, holotype male (38.3 × 27.4 mm) (ZRC 2022.0706), Vietnam.

Fig. 18. Lacunipotamon panda n. sp., holotype male (38.3 × 27.4 mm) (ZRC 2022.0706), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, right third maxilliped; D, frontal view of cephalothorax; E, antennules, antennae and epistome; F, right major chela; G, left minor chela.

Fig. 19. Lacunipotamon panda n. sp. A–E, holotype male (38.3 × 27.4 mm) (ZRC 2022.0706), Vietnam; F, G, paratype male (38.6 × 27.3 mm) (ZRC 2022.0707), Vietnam. A, anterior half of thoracic sternum and pleon; B, sternopleonal cavity; C, left fourth ambulatory leg; D, pleonal somites 1–4; E, G, pleon; F, right major chela.

Fig. 20. Lacunipotamon panda n. sp., holotype male (38.3 × 27.4 mm) (ZRC 2022.0706), Vietnam. A, left G1 (ventral view); B, distal part of left G1 (ventral view); C, distal part of left G1 (dorsal view); D, left G2; E, distal part of distal segment of left G2. Scale bars: A, D = 1.0 mm; B, C = 0.5 mm.

Fig. 21. Lacunipotamon panda n. sp., paratype female (36.8 × 25.6 mm) (ZRC 2022.0707), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, pleon; D, sternopleonal cavity showing vulvae.

Fig. 22. Lacunipotamon contrastum n. sp., colour in life. A–F, paratype male (39.1 × 29.7 mm) (ZRC 2022.0787), Vietnam; G, paratype female (40.9 × 30.1 mm) (ZRC 2022.0787), Vietnam.

Fig. 23. Lacunipotamon contrastum n. sp., holotype male (38.4 × 27. 2mm) (ZRC 2022.0786), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, right third maxilliped; D, frontal view of cephalothorax; E, antennules, antennae and epistome; F, chelae.

Fig. 24. Lacunipotamon contrastum n. sp., holotype male (38.4 × 27. 2mm) (ZRC 2022.0786), Vietnam. A, anterior half of thoracic sternum; B, median part of thoracic sternum and pleon; C, posterior half of thoracic sternum and pleon; D, sternopleonal cavity; E, left fourth ambulatory leg; F, pleonal somites 1–4; G, pleon.

Fig. 25. Lacunipotamon contrastum n. sp., paratype male (39.1 × 29.7 mm) (ZRC 2022.0787), Vietnam.A, overall dorsal habitus; B, chelae.

Fig. 26. Lacunipotamon contrastum n. sp., holotype male (38.4 × 27. 2mm) (ZRC 2022.0786), Vietnam. A, left G1 (ventral view); B, distal part of left G1 (ventral view); C, distal part of left G1 (dorsal view); D, left G2. Scale bars: A, D = 1.0 mm; B, C = 0.5 mm.

Fig. 27. Lacunipotamon contrastum n. sp., paratype female (40.9 × 30.1 mm) (ZRC 2022.0787), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, pleon; D, sternopleonal cavity showing vulvae.

Fig. 28. Lacunipotamon sublividum n. sp., colour in life. A–F, holotype male (30.5 × 22.9 mm) (ZRC 2022.0807), Vietnam; G, H, paratype female (32.1 × 23.5 mm) (ZRC 2022.0803), Vietnam.

Fig. 29. Lacunipotamon sublividum n. sp., holotype male (30.5 × 22.9 mm) (ZRC 2022.0807), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, left third maxilliped; D, frontal view of cephalothorax; E, antennules, antennae and epistome; F, chelae.

Fig. 30. Lacunipotamon sublividum n. sp., A–F, holotype male (30.5 × 22.9 mm) (ZRC 2022.0807), Vietnam; G, paratype male (25.6 × 18.8 mm) (ZRC 2022.0803), Vietnam. A, anterior half of thoracic sternum and buccal cavity; B, median part of thoracic sternum and pleon; C, sternopleonal cavity; D, left fourth ambulatory leg; E, posterior half of thoracic sternum and pleon; F, G, pleon.

Fig. 31. Lacunipotamon sublividum n. sp., holotype male (30.5 × 22.9 mm) (ZRC 2022.0807), Vietnam. A, left G1 (ventral view); B, distal part of left G1 (ventral view); C, distal part of left G1 (dorsal view); D, left G2. Scale bars: A, D = 1.0 mm; B, C = 0.5 mm.

Fig. 32. Lacunipotamon sublividum n. sp., paratype female (32.1 × 23.5 mm) (ZRC 2022.0803), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, pleon; D, sternopleonal cavity showing vulvae; E, frontal view showing inflated branchial regions.

Fig. 38. Epistomal median lobes of Lacunipotamon. A–D, L. mimicum n. sp.; E–H, L. sublividum n. sp., A, holotype male (31.3 × 23.0 mm) (ZRC 2022.1024); B, paratype male (30.3 × 22.6 mm) (ZRC 2022.1025); C, paratype female (30.1 × 23.2 mm) (ZRC 2022.1025); D, paratype female (28.8 × 22.0 mm) (ZRC 2022.1025); E, holotype male (30.5 × 22.9 mm) (ZRC 2022.0807); F, paratype male (26.6 × 19.6 mm) (ZRC 2022.0803); G, paratype male (25.6 × 18.8 mm) (ZRC 2022.0803); H, paratype female (32.1 × 23.5 mm) (ZRC 2022.0803). All specimens from Vietnam.

Fig. 46. Lacunipotamon pectum n. sp., holotype male (38.3 × 26.4 mm) (ZRC 2022.0788), Vietnam. A, anterior half of thoracic sternum; B, median part of thoracic sternum and pleon; C, posterior half of thoracic sternum and pleon; D, sternopleonal cavity; E, left fourth ambulatory leg; F, pleonal somites 1–4; G, pleon.

Fig. 44. Lacunipotamon pectum n. sp., colour in life. A–C, holotype male (38.3 × 26.4 mm) (ZRC 2022.0788), Vietnam; D, paratype male (39.2 × 27.1 mm) (ZRC 2022.0789), Vietnam; E, F, paratype female (30.1 × 21.5 mm) (ZRC 2022.0789), Vietnam; G, paratype female (31.0 × 22.2 mm) (ZRC 2022.0789), Vietnam.

Fig. 42. Lacunipotamon thuanchau n. sp., holotype male (29.6 × 20.8 mm) (ZRC 2022.0808), Vietnam. A, left G1 (ventral view); B, distal part of left G1 (ventral view); C, distal part of left G1 (dorsal view); D, left G2. Scale bars: A, D = 1.0 mm; B, C = 0.5 mm.

Fig. 33. Lacunipotamon mimicum n. sp., colour in life. A–E, holotype male (31.3 × 23.0 mm) (ZRC 2022.1024), Vietnam; F–H, paratype female (28.8 × 22.0 mm) (ZRC 2022.1025), Vietnam.

Fig. 34. Lacunipotamon mimicum n. sp., holotype male (31.3 × 23.0 mm) (ZRC 2022.1024), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, left third maxilliped; D, frontal view of cephalothorax; E, antennules, antennae and epistome; F, chelae.

Fig. 35. Lacunipotamon mimicum n. sp. A–F, holotype male (31.3 × 23.0 mm) (ZRC 2022.1024), Vietnam; G, paratype male (30.3 × 22.6 mm) (ZRC 2022.1025), Vietnam. A, anterior half of thoracic sternum and buccal cavity; B, median part of thoracic sternum and pleon; C, sternopleonal cavity; D, left fourth ambulatory leg; E, posterior half of thoracic sternum and pleon; F, G, pleon.

Fig. 36. Lacunipotamon mimicum n. sp. A–D, holotype male (31.3 × 23.0 mm) (ZRC 2022.1024) E, paratype male (30.3 × 22.6 mm) (ZRC 2022.1025), Vietnam. A, E, left G1 (ventral view); B, distal part of left G1 (ventral view); C, distal part of left G1 (dorsal view); D, left G2. Scale bars: A, D, E = 1.0 mm; B, C = 0.5 mm.

Fig. 37. Lacunipotamon mimicum n. sp., paratype female (30.1 × 23.2 mm) (ZRC 2022.1025), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, pleon; D, sternopleonal cavity showing vulvae.

Fig. 39. Lacunipotamon thuanchau n. sp., colour in life.A, B, H, paratype male (25.8 × 18.2 mm) (ZRC 2022.0804), Vietnam; C, D, paratype female (27.8 × 19.7 mm) (ZRC 2022.0804), Vietnam; E–G, paratype male (29.0 × 21.0 mm) (ZRC 2022.0804), Vietnam.

Fig. 40. Lacunipotamon thuanchau n. sp., holotype male (29.6 × 20.8 mm) (ZRC 2022.0808), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, left third maxilliped; D, frontal view of cephalothorax; E, antennules, antennae and epistome; F, chelae.

Fig. 41. Lacunipotamon thuanchau n. sp. A–F, holotype male (29.6 × 20.8 mm) (ZRC 2022.0808), Vietnam; G, paratype male (25.8 × 18.2 mm) (ZRC 2022.0804), Vietnam. A, anterior half of thoracic sternum and buccal cavity; B, median part of thoracic sternum and pleon; C, sternopleonal cavity; D, left fourth ambulatory leg; E, posterior half of thoracic sternum and pleon; F, G, pleon.

Fig. 43. Lacunipotamon thuanchau n. sp., paratype female (27.8 × 19.7 mm) (ZRC 2022.0804), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, pleon; D, sternopleonal cavity showing vulvae.

Fig. 48. Lacunipotamon pectum n. sp., paratype female (31.0 × 22.2 mm) (ZRC 2022.0789), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, pleon; D, sternopleonal cavity showing vulvae.

Fig. 45. Lacunipotamon pectum n. sp., holotype male (38.3 × 26.4 mm) (ZRC 2022.0788), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, left third maxilliped; D, frontal view of cephalothorax; E, antennules, antennae and epistome; F, chelae

Fig. 47. Lacunipotamon pectum n. sp., holotype male (38.3 × 26.4 mm) (ZRC 2022.0788), Vietnam. A, left G1 (ventral view); B, distal part of left G1 (ventral view); C, distal part of left G1 (dorsal view); D, left G2. Scale bars:A, D = 1.0 mm; B, C = 0.5 mm.

Fig. 49. Lacunipotamon purpureum n. sp., colour in life. A–F, holotype male (28.8 × 21.2 mm) (ZRC 2022.1026), Vietnam.

Fig. 50. Lacunipotamon purpureum n. sp., holotype male (28.8 × 21.2 mm) (ZRC 2022.1026), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, left third maxilliped; D, frontal view of cephalothorax; E, antennules, antennae and epistome; F, chelae.

Fig. 51. Lacunipotamon purpureum n. sp., holotype male (28.8 × 21.2 mm) (ZRC 2022.1026), Vietnam. A, anterior thoracic sternum; B, anterior half of thoracic sternum; C, posterior half of thoracic sternum and pleon; D, sternopleonal cavity; E, left fourth ambulatory leg; F, pleonal somites 1–4; G, pleon.

Fig. 52. Lacunipotamon purpureum n. sp., holotype male (28.8 × 21.2 mm) (ZRC 2022.1026), Vietnam. A, right G1 (ventral view); B, distal part of right G1 (ventral view); C, distal part of right G1 (dorsal view); D, right G2. Scale bars: A, D = 1.0 mm; B, C = 0.5 mm.

Fig. 53. Lacunipotamon purpureum n. sp., paratype female (26.3 × 18.9 mm) (ZRC 2022.1027), Vietnam. A, overall dorsal habitus; B, dorsal view of carapace; C, pleon; D, sternopleonal cavity showing vulvae.

Fig. 6. Lacunipotamon yuanshi Huang, Shih & Ahyong, 2020, paratype female (24.4 × 19.5 mm) (ZRC 2018.1185), China.A, overall dorsal habitus; B, dorsal view of carapace; C, pleon; D, sternopleonal cavity showing vulvae.

Fig. 4. Lacunipotamon yuanshi Huang, Shih & Ahyong, 2020, paratype male (27.6 × 21.4 mm) (ZRC 2018.1185), China. A, anterior half of thoracic sternum and buccal cavity; B, median part of thoracic sternum and pleon; C, sternopleonal cavity; D, left fourth ambulatory leg; E, posterior half of thoracic sternum and pleon; F, pleon.

Fig. 5. Lacunipotamon yuanshi Huang, Shih & Ahyong, 2020, paratype male (27.6 × 21.4 mm) (ZRC 2018.1185), China. A, left G1 (ventral view); B, distal part of left G1 (ventral view); C, distal part of left G1 (dorsal view); D, left G2. Scale bars:A, D = 1.0 mm; B, C = 0.5 mm.