Lacunipotamon Dai, Song, He, Cao, Xu & Zhong, 1975

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 : 2-4

Lacunipotamon Dai, Song, He, Cao, Xu & Zhong, 1975

Lacunipotamon Dai, Song, He, Cao, Xu & Zhong, 1975: 263 ; Dai 1999: 143; Ng et al. 2008: 164; Chu et al. 2018: 5; Huang et al. 2020: 1363.

Type species: Lacunipotamon albusorbitum Dai, Song, He, Cao, Xu & Zhong, 1975 , by original designation.

Diagnosis: Carapace almost round to transversely ovate, wider than long, prominently inflated, high; epigastric cristae very low to almost not visible; postorbital cristae poorly developed, only visible along outer part, not sharp, sometimes not easily visible, reaches anterolateral margin; epibranchial tooth or tubercle may be present at junction with postorbital angle; anterolateral margin not cristate, rounded; epistomal median lobe low or well developed, tip almost level with or extending well beyond lateral parts, lateral margins gently sinuous; third maxilliped with slender exopod that reaches beyond distal edge of ischium, with distinct flagellum that is as long as width of merus; adult males prominently heterochelous, major chela sometimes with long curved fingers that form very wide gape when closed; ambulatory legs with long, slender dactylus; anterior male thoracic sternum relatively narrow transversely, suture between sternites 2 and 3 deep, sternites 3 and 4 fused but demarcated by grooves of varying depths; sternopleonal cavity usually reaching to imaginary line connecting median part or distal third of coxae of chelipeds; press-button tubercle of male sternopleonal locking mechanism relatively low, on distal of third sternite 5; male thoracic sternite 8 not visible when pleon closed; male pleon broadly triangular to triangular, somites 1 and 2 wide; G1 with subterminal segment gradually tapering towards terminal segment, gently curved outwards distally, groove for G2 ventral; subterminal segment distinctly separated from terminal segment by deep grooves; terminal segment relatively short, subcylindrical, with large dorsal lobe on proximal part, distal part conical to tapering, almost straight to strongly recurved; G2 elongate, slightly longer than G1; basal segment longer than distal segment; vulva large, on proximal part of sternite 6, occupying more than half width of sternite, proximal part adjacent to suture with sternite 5, lateral vulvar cover may be present, no visible operculum.

Remarks: Four genera of potamids with very high and swollen carapaces and relatively short ambulatory legs are present in southernmost China and northern Vietnam: Lacunipotamon Dai, Song, He, Cao, Xu & Zhong, 1975 , Hainanpotamon Dai, 1995 , Laevimon Yeo & Ng, 2005 , and Vietorientalia Đăng, 2012 . All have their dorsal carapace surfaces relatively smooth with the epigastric and postorbital cristae weak or indiscernible. They are most easily distinguished by their G1 structures. Lacunipotamon has a prominent long dorsal fold on the G1 terminal segment that stretches more than half its length; that of Hainanpotamon is slenderer, more elongate and tapering with the dorsal fold low and only distinct on the proximal part (e.g., see Yeo and Naruse 2008: fig. 3A–D); and in Laevimon , the G1 terminal segment is subcylindrical in shape with a small dorsal fold on the proximal part and the inner distal part is produced into a sharp projection (cf. Yeo and Ng 2005: fig. 3B–E). Laevimon is also distinct in that male thoracic sternites 3 and 4 are separated by a prominent ridge which joins the distal edge of the sternopleonal cavity ( Yeo and Ng 2005: fig. 2C); in the other genera, sternites 3 and 4 are completely fused or there is a visible groove (very shallow or deep) between them.

The situation with Vietorientalia needs elaboration. Yeo and Ng (1998) noted that the potamid name Orientalia Đăng, 1975 , was preoccupied by an earlier name for a mollusc, but decided against establishing a replacement name as they believed it was synonymous with Hainapotamon Dai, 1995. This was discussed by Yeo and Naruse (2008) who examined the two species Đăng (1975) had described under Orientalia , noting that there were no major morphological differences. Đăng (2012), however, disagreed, arguing that there remained some differences in the G1 structure and also in their biogeography, and established a replacement name, Vietorientalia , for his two species. Unpublished genetic data by H.- T. Shih (National Chung Hsing University, Taichung) of the various species suggests that there are several groups in what is now called Hainanpotamon , with one species from central Vietnamese, H. auriculatum Yeo & Naruse, 2008 , belonging to a separate clade from the Chinese ones (pers. comm. to first author). Unfortunately, the genetic characteristics of the two species described by Đăng (1975) are not yet known. As such, it seems best to provisionally recognise a Vietnamese genus-level group, Vietorientalia , as suggested by Đăng (2012). Hainanpotamon auriculatum is provisionally retained in Hainanpotamon as well until the broader studies can be done to revise the affected taxa. For the characters discussed above at least, they are the same for both Vietorientalia and Hainanpotamon .

In addition, the suborbital, subhepatic and pterygostomial regions of the six known species of Hainanpotamon and two of Laevimon are distinctly rugose and tuberculate (e.g., Yeo and Naruse 2008: fig. 4B; Yeo and Ng 2005: fig. 2B). In Lacunipotamon , these surfaces are usually smooth to almost smooth (e.g., Fig. 3D, E ), except in L. cymatile which has these surfaces rugose ( Fig. 7D, E ). The original description of Laevimon tankiense ( Đăng & Trần, 1992) (as a species of Orientalia ) is not very informative but Yeo and Ng (2005) managed to examine the types and they refigured the species, clearly showing the rugose frontal surfaces ( Yeo and Ng 2005: fig. 4B).

Ng et al. (2008: 164) listed Potamon klossianum Kemp 1923 as a species of Lacunipotamon but this is in error. Yeo and Ng (2008: 298) had transferred the species to Villopotamon Đăng & Hồ, 2003.

Lacunipotamon albusorbitum Dai, Song, He, Cao, Xu & Zhong, 1975 ( Figs. 1 , 2 )

Lacunipotamon albusorbitum Dai, Song, He, Cao, Xu & Zhong, 1975: 264 , pl. 3(8), text-fig. 8; Dai 1999: 143, pl. 9(1), text-fig. 74; Ng et al. 2008: 164; Cumberlidge et al. 2009: appendix 1; Chu et al. 2018: 5; Huang et al. 2020: 1364, fig. 8A–D.

Material examined: Holotype: male (34.6 × 27.0 mm) ( CAS CB 05108 ), field collection number YN6375513, Basa , Hekou County, Yunnan, China, ca. 22.67°N 103.82°E, coll. 9 December 1963 . Paratype: 1 female (31.8 × 25.3 mm) ( CAS CB 05108), 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, no epibranchial tooth visible, anterolateral margin appears entire; epistomal median lobe low, tip almost level with lateral margins; adult major chela with gently curved fingers that do not form wide 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 short, proximal part of outer margin of subterminal segment with convex margin, terminal segment almost symmetrical, hemispherical dorsal flap, distal part strongly recurved posteriorly, surface wrinkled; vulva large, occupying about two-thirds space of sternite 6, low, barely visible vulvar cover on outer margin.

Colour: Huang et al. (2020: fig. 8A) noted that they had photographs of a specimen from the type locality which they believed to be L. albusorbitum although it could not be examined. This specimen had a red carapace with yellow orbital margins, the legs being dark purplish brown with the joints and dactyli dull orange.

Remarks: The two type specimens are the only known specimens of this species. Although Huang et al. (2020: fig. 8A) provided a colour photograph of a supposed recent specimen from the area, they could not confirm it as they were unable to examine it.

Figures

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. 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. 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).