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IntroductionThe order Harpacticoida is one of the 10 orders of subclass Copepoda (Martin and Davis, 2001) and contains approximately 6000 species in 645 genera, which belong to 59 families (Ahyong et al., 2011). Marine harpacticoids are mostly benthic microcrustaceans, although a few are planktonic or are symbiotic with other animals. They are commonly the second most abundant taxon after nematodes in marine sediments (

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An attempt was made to test if Lourinia armata (Claus, 1866)—as it is currently diagnosed—represents a species complex. Detailed examination and comparisons of several specimens collected from different localities suggest that L. armata indeed represents a complex of four closely related morphospecies that can be differentiated from one another by only detailed observations. One of the four species is identified as Lourinia aff. armata and the other three species are described as new to science and named as Lourinia wellsi sp. nov., L. gocmeni sp. nov., and L. aldabraensis sp. nov. Detailed review of previous species records indicates that the genus Lourinia Wilson, 1924 is distributed worldwide. Ceyloniella nicobarica Sewell, 1940, originally described from Nicobar Island and previously considered a junior subjective synonym of L. armata is reinstated as Lourinia nicobarica (Sewell, 1940) comb. nov. on the basis of the unique paddle-shaped caudal ramus seta V. It is postulated that almost all of these records are unreliable in terms of representing true Lourinia aff. armata described herein. On the other hand, the comparative evaluation of the illustrations and descriptions in the published literature indicates the presence of several new species waiting to be discovered in the genus Lourinia.                 It has been determined that, according to updated modern keys, the recent inclusion of the monotypic genus Archeolourinia Corgosinho & Schizas, 2013 in the Louriniidae is not justified since Archeolourinia shermani Corgosinho & Schizas, 2013 does not belong to this family but should be assigned to the Canthocamptidae. On the other hand, it has been argued that the exact phylogenetic position of the Louriniidae still remains problematic since none of the diagnostic characters supports the monophyly of the family within the Oligoarthra. It has also been argued that the close relationship between Louriniidae and Canthocamptidae is supported since both families share the homologous sexual dimorphism (apophysis) on P3 endopod. The most important characteristic that can possibly be used to define Louriniidae is the reduction of maxilliped.

A new generic classification is proposed for the 32 valid species of the interstitial marine family Arenopontiidae (Copepoda, Harpacticoida), primarily based on new observations of type species and reliable descriptions from the literature. The subgeneric division of Arenopontia Kunz, 1937 is abolished, and both Arenopontia and Neoleptastacus Nicholls, 1945 are upgraded to full generic rank. Arenopontia is restricted to the subterranea group, comprising Arenopontia subterranea Kunz, 1937 (type), Arenopontia problematica Masry, 1970, Arenopontia nesaie Cottarelli, 1975, and Arenopontia riedli Lindgren, 1976. The doubtful status of both Arenopontia pontica Apostolov, 1969 and recent Egyptian records of A. nesaie is discussed, and the alleged cosmopolitanism of A. subterranea is reviewed. Arenopontia is characterized by the unique morphology of the P1 (prehensile endopod, armature of distal segments of exopod and endopod). The genus Psammoleptastacus Pennak, 1942 is reinstated to accommodate Psammoleptastacus arenaridus Pennak, 1942 (type), Arenopontia stygia Noodt, 1955 and Psammoleptastacus barani sp. nov. The latter is described from the Turkish Black Sea coast, and had previously been identified as A. stygia in Bulgarian waters. The species identified as A. subterranea by Rao & Ganapati in 1969 is considered species inquirenda in Psammoleptastacus. Neoleptastacus is resurrected to accommodate all arenopontiids that have an inner spinous process on the P5. The Chilean species Arenopontia clasingi Mielke, 1985, Arenopontia pacifica Mielke, 1985, and Arenopontia spicata Mielke, 1985 are transferred to Neoleptastacus. The genus Pararenopontia Bodiou & Colomines, 1986 is considered a junior synonym of Neoleptastacus, with its type species Pararenopontia breviarticulata (Mielke, 1975) being relegated to species incertae sedis in this genus. The monotypic genus Mesopontia gen. nov. is established to accommodate Arenopontia dillonbeachia Lang, 1965, which holds an intermediate position between Arenopontia and Neoleptastacus. Material from Puget Sound identified as Arenopontia spinicaudata (Nicholls, 1945) by Chappuis in 1958 is attributed to Mesopontia dillonbeachia comb. nov.Psammoleptastacus orientalis Krishnaswamy, 1957, Arenopontia intermedia Rouch, 1964, and Arenopontia peteraxi Mielke, 1982 are transferred to a new genus, Onychopontia gen. nov., together with Onychopontia nichollsi sp. nov. (type), which was discovered among type material of Neoleptastacus spinicaudatus Nicholls, 1945. Redescriptions are given for A. nesaie, P. arenaridus, N. spinicaudatus, and M. dillonbeachia. A key to the five arenopontiid genera as well as keys (or comparative tables) to the species of Arenopontia, Onychopontia, Mesopontia, and the spinicaudatus lineage of Neoleptastacus are provided. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 152, 409–458.