Neoleptastacus Nicholls, 1945

Sak, Serdar, Karaytuğ, Süphan & Huys, Rony, 2024, Review of Neoleptastacus Nicholls, 1945 (Harpacticoida, Arenopontiidae), including an updated key to species and proposal of Phreatipontia gen. nov., Zootaxa 5525 (1), pp. 1-66 : 6

Genus Neoleptastacus Nicholls, 1945

Pararenopontia Bodiou & Colomines, 1986 (type species by original designation: Arenopontia breviarticulata Mielke, 1975 )

Diagnosis (adapted from Sak et al. 2008). Arenopontiidae . Urosomites occasionally with conspicuous surface ornamentation ( N. clasingi , ornamentus , reductaspina ). Anal somite with ( acanthus -group) or without (all other species groups) paired dorsolateral spinous processes. Anal operculum sometimes with median extension. Hyaline frills of abdominal somites with rectangular digitate or non-digitate lappets. Caudal ramus usually with dorsolateral spur near medial margin. P1 exopod 2- or 3-segmented; exp-1 with/without outer spine; exp-3 (or exp-2 when exopod 2-segmented) with one–two spine(s) and two geniculate setae. P1 endopod not prehensile, at least as long as exopod; enp-2 with outer spine and inner geniculate seta at distal margin. P2–P3 endopods 1- or 2-segmented. P3 endopod with outer distal element (when present) usually fused at base. P4 enp-2 with well developed outer distal element (except in trisetosus -group). Armature formula as follows:

	Exopod	Endopod
P1	0.0.02(1–2) or 0.021	1.011
P2	0.0.021	0.(0–1)(1–2)0 or 110
P3	0.0.021	0.0(1–2)0 or 010
P4	0.0.(0–1)21	0.020

P3 endopod ♂ not sexually dimorphic. P5 with outer basal seta and one–four discrete elements; innermost element fused to segment forming spinous process (weakly delimited in N. trisetosus and N. panamensis sp. nov.); length of process sometimes sexually dimorphic. P 6 ♂ with one–two elements.

Type species. Neoleptastacus spinicaudatus Nicholls, 1945 [by monotypy].

Other species. Twenty-three. See Table 1 .

Species inquirenda. Neoleptastacus secundus Krishnaswamy, 1957 ; N. accraensis ( Lang, 1965) .

Taxa of doubtful identity. Arenopontia acantha Chappuis, 1954 sensu Božić (1967) ; Arenopontia? gussoae Cottarelli, 1973a sensu Mielke (1982b) [partim]; Arenopontia? gussoae Cottarelli, 1973a sensu Mielke (1987) [2nd form].

Gender. Masculine.

The genus shows considerable variation in swimming leg armature and segmentation, P5 morphology, abdominal ornamentation and caudal ramus structure. However, all species display a spinous apical process on the P5 which is derived from the fused innermost element (weakly delimited in N. trisetosus and N. panamensis sp. nov.). This apomorphic character state is unique in the Arenopontiidae and potentially serves as evidence in support of the monophyly of the genus. For practical reasons we have recognized several species groups within Neoleptastacus , some of which are monophyletic and may eventually be attributed separate generic status ( Table 2 ). The majority of these groups are characterized by one or several autapomorphic character states with the notable exception of the spinicaudatus -group which contains the type species. For this reason, we have refrained from proposing new genera (except for the speluncae -group) as this would render Neoleptastacus a paraphyletic taxon.