Exalloniscus siamensis, Taiti & Cardoso, 2020

Exalloniscus siamensis View in CoL n. sp.

Figures 7, 8, 22B

urn:lsid:zoobank.org:act:

Material examined

THAILAND: Holotype: ♂ ( MNHN), Phangnga Province, Phangnga, near Tham Poung Chang sink, 8°26’34.3”N 98°30’54.6”E, 10 m a.s.l., forest litter and soil, 19.VII.1987, leg. L. Deharveng and A. Bedos. GoogleMaps Paratypes: 3 ♀♀ ( MNHN) , 2 ♂♂, 3 ♀♀ ( MZUF), same data as holotype GoogleMaps .

Description

Maximum length: ♂ 4.5 mm; ♀ 6 mm. Body oval, flattened ( Figure 7A); cephalon, pereon and pleonites 1, 2 brown with yellowish muscles spots, antennae, pleonites 3-5, telson and uropods colourless ( Figure 22B). Dorsum covered with large triangular scale-setae ( Figure 7B). Cephalon ( Figure 7C,D) with lateral lobes triangular, slightly protruding laterally; frontal line sinuous, suprantennal line straight in middle part; eyes with five ommatidia. Pereonites with postero-lateral corners acute, directed backwards ( Figure 7A,E). Pleonites 3-5 with epimera falciform, directed backwards. Telson wider than long, triangular with slightly concave sides and rounded apex reaching posterior margin of pleonite 5 epimera ( Figure 7F). Antennula ( Figure 7G) third article with many superimposed aesthetascs. Antenna ( Figure 7H) fifth article of peduncle as long as flagellum; ratio of flagellum joints 2:1:1; one aesthetasc on second and two aesthetascs on third article. Buccal pieces as in E. schmalfussi n. sp. Pereopods with dactylar seta flagelliform. Pereopod 1 carpus with transversal antennal grooming brush ( Figure 8B). Pereopod 7 ( Figure 8C) basis with distinct water conducting system. Uropod ( Figures 7F, 8A) protopod slightly surpassing tip of telson; exopod slightly longer than endopod and twice as long as protopod.

Male: Pereopods 1-3 carpus and merus with long strong setae on sternal margin ( Figure 8B). Pereopod 7 ( Figure 8C) sternal margin of merus, carpus and propodus with some strong setae, ischium sternal margin straight. Pleopod 1 ( Figure 8D) exopod triangular, longer than wide, outer margin slightly sinuous, posterior point rounded; endopod distal part bent outward, with subapical flat triangular lobe directed inward. Pleopod 2 ( Figure 8E) exopod triangular with outer margin almost straight bearing few setae; endopod flagelliform, distinctly longer than exopod. Pleopod 3-5 exopods ( Figure 8 F-H) triangular with few setae on outer margin.

Etymology The new species is named for Siam, the former name of Thailand.

Remarks

The new species is characterized by the colour pattern (brown with pale antennae, pleonites 3-5, telson and uropods) and by the shape of the male pleopod 1 endopod with distal part bent outward and bearing a subapical flat triangular lobe directed inwards. A similar colour pattern is also present in E. bicoloratus Taiti & Ferrara, 1988 , but in the latter the cephalon and first pereonite are colourless. In having the male pleopod 1 exopod with a long and rounded posterior point, the new species resembles E. maschwitzi and E. sumatranus but it is readily distinguishable from both in the shape of the distal part of the male pleopod 1 endopod.