Flabellamon mulayit, Tan & Yeo, 2024

Tan, Zhi Wan & Yeo, Darren C. J., 2024, On the genus Flabellamon Ng, 1996, with descriptions of two new species (Crustacea: Brachyura: Potamidae), Zootaxa 5476 (1), pp. 434-446 : 442-444

publication ID	https://doi.org/ 10.11646/zootaxa.5476.1.32
publication LSID	lsid:zoobank.org:pub:078CE548-C895-4F3F-8965-66AB38C7388E
DOI	https://doi.org/10.5281/zenodo.12746922
persistent identifier	https://treatment.plazi.org/id/03B48782-FFD0-B86B-0186-F86C158AFD4B
treatment provided by	Plazi
scientific name	Flabellamon mulayit
status	sp. nov.

Treatment

Flabellamon mulayit sp. nov.

( Figs. 4A–C View FIGURE 4 , 5A–D View FIGURE 5 )

Potamon atkinsonianum View in CoL .— De Man 1898: 407 (part), pls. 4–5 fig. 6 (not Telphusa atkinsoniana Wood-Mason, 1871 View in CoL ).

Potamon (Potamon) atkinsonianus . — Rathbun 1904: 271 (part) (not Telphusa atkinsoniana Wood-Mason, 1871 View in CoL ).

Ranguna (Ranguna) turgidula .— Bott 1970: 164 (part) (not Potamon (Potamon) turgidulum Alcock, 1909 View in CoL ).

Potamon “atkinsonianum View in CoL ”.— Yeo & Ng 1999: 639 (part) (not Telphusa atkinsoniana Wood-Mason, 1871 View in CoL ).

Type material. Holotype: male (31.3 × 24.3 mm), MSNG III 214 , Thagata, sul Monte Mooleyit [= Mount Mulayit ], Myanmar, coll. L. Fea, 1887 . Paratype: 1 female (25.4 × 18.8 mm), MSNG III 214 , same data as holotype .

Diagnosis. Carapace ( Fig. 4A View FIGURE 4 ) transversely sub-ovate, low, broader than long (CW/CL ratio: 1.29); epigastric cristae well developed, not sharp, rugose, slightly anterior to postorbital cristae; postorbital cristae well developed, relatively sharp, rugose, confluent with epibranchial teeth epibranchial tooth blunt, broad, separated from external orbital tooth by deep broad V-shaped cleft; external orbital tooth lateral margin much longer than mesial margin. Third maxilliped exopod flagellum length subequal to width of merus. Male pleon ( Fig. 4B View FIGURE 4 ) with sixth somite lateral margins gently convex. G1 ( Fig. 5C, D View FIGURE 5 ) terminal segment appearing almost twisted longitudinally, with subdistal part of lateral margin truncate, dorsal flap high, subconical in appearance, narrow, with bluntly angular apex skewed towards proximal portion, gradually tapered distally, abruptly (almost perpendicularly) tapered proximally.

Etymology. The species is named after the type locality, Mount Mulayit. Used as noun in apposition.

Remarks. The present specimens were part of a mixed series of material identified by J. G. De Man as Potamon atkinsonianum ( Wood-Mason, 1871) ( De Man 1898; Rathbun 1904), a species now recognised as a member of the potamine genus Himalayapotamon ( Brandis 2001; Yeo & Ng 2004; Ng et al. 2008). De Man’s specimens differ from Himalayapotamon atkinsonianum ( Wood-Mason, 1871) sensu stricto in several external aspects including having broad, shallow cervical grooves with weakly rugose regions behind epigastric and postorbital cristae ( Figs. 1A View FIGURE 1 , 4A View FIGURE 4 ; cf. Pretzmann 1963: pl. 2 fig. 5; Ng 1996: figs. 1, 2A) (vs. deep, well developed cervical grooves and distinctly rugose regions behind epigastric and postorbital cristae; cf. Wood-Mason, 1871: 205, pl. 14 figs. 12–16; Alcock 1910: pl. 10, fig. 39; Brandis, 2001: fig. 3a). Bott (1970) later erroneously reassigned these specimens to Ranguna (Ranguna) turgidula (see earlier remarks for genus Flabellamon ). In fact, De Man’s material contains three taxa, viz., F. kuehnelti ( Pretzmann, 1963) , F. ngankee sp. nov. (see earlier) and the present undescribed taxon, herein named Flabellamon mulayit sp. nov. Flabellamon mulayit sp. nov. resembles F. kuehnelti in the large external orbital tooth with lateral margins much longer than mesial margins and G1 terminal segments with the subdistal part of the lateral margin appearing truncate ( Fig. 4A View FIGURE 4 , 5A–D View FIGURE 5 ; cf. Pretzmann 1963: pl. 2 fig. 5, 6; Ng 1996: figs. 1, 2A, 3A–D). Flabellamon mulayit , however, can be distinguished from F. kuehnelti by the following differences: blunt epibranchial tooth ( Fig. 4A View FIGURE 4 ) (vs. sharp epibranchial tooth; cf. Pretzmann 1963: pl. 2 fig. 5; Ng 1996: 1, 2A); and G1 terminal segment appearing almost twisted longitudinally with dorsal flap being relatively higher and narrower, with a bluntly angular apex skewed towards the proximal portion ( Fig. 5A–D View FIGURE 5 ) (versus G1 terminal segment not twisted longitudinally, with dorsal flap relatively lower and broader, with a broadly convex apex in the median portion; Fig. 5E View FIGURE 5 ; cf. Pretzmann 1963: pl. 2 fig. 6; Ng 1996: fig. 3C, D).

Flabellamon mulayit sp. nov. shares the same type locality data (Monte Mooleyit = Mount Mulayit, Myanmar) as the poorly known species, Quadramon mooleyitense ( Rathbun, 1904) , which is represented by only one juvenile female holotype specimen (14.6 × 11.8 mm). Yeo & Ng (2007) had earlier recognised the distinctiveness of Potamon (Potamon) mooleyitense Rathbun, 1904 , and established Quadramon Yeo & Ng, 2007 , [type species: Quadramon aborense (Kemp, 1913) ], as a separate genus for it. Quadramon mooleyitense can be easily separated from Flabellamon mulayit sp. nov. by the following characters it possesses: very small, low, external orbital tooth ( Fig. 4D View FIGURE 4 ) (vs. large, well developed external orbital tooth, Fig. 4A View FIGURE 4 ); small, sharp epibranchial tooth, separated from external orbital tooth by shallow, narrow, cleft ( Fig. 4D View FIGURE 4 ) (versus large, blunt epibranchial tooth, separated from external orbital tooth by deep, broad, cleft; Fig. 4A View FIGURE 4 ); and postorbital cristae not sharp, broken up into rugae, not confluent with epibranchial teeth ( Fig. 4D View FIGURE 4 ) (versus postorbital cristae sharp, entire, confluent with epibranchial teeth; Fig. 4A View FIGURE 4 ). These characters are not known to vary greatly with size or age related, within a species.