New species of Mesamphisopus, an endemic South African freshwater isopod genus (Isopoda: Phreatoicidea: Mesamphisopidae) Author Gouws, Gavin text Zootaxa 2008 2008-01-25 1690 1 62 journal article 1175­5334 Key to the known species of Mesamphisopus 1 Antennal basal articles sparsely to moderately setose ............................................................................... 2 – Antennal basal articles heavily setose ....................................................................................................... 3 2 Pleotelson dorsal margin straight, apex continuous with and at same level as anterior dorsal margin (ventral inflection absent or very shallow), apex long and not up-turned .................................... M. paludosus – Pleotelson dorsal margin gradually curving downwards with deep ventral inflection, apex below level of anterior dorsal margin, apex long and up-turned or very short ........................................... M. penicillatus 3 Uropodal protopod dorsomesial margin/ridge produced to some extent and plate-like ............................ 4 – Uropodal protopod dorsomesial margin approximately linear, not produced ........................ M. tsitsikamma 4 Pleotelson with subapical pair of dorsal robust setae ................................................................................ 5 – Pleotelson without subapical pair of dorsal robust setae ........................................................................... 6 5 Cephalon and pereon sparsely to moderately setose; antennula with 5 or 6 articles; pleotelson abrupt, stubby, dorsal margin sloping steeply with shallow ventral inflection, apex indefinite and hardly upturned; elongate setae abundant on uropodal rami ............................................................. M. abbreviatus – Cephalon and pereon with abundant elongate setae, particularly laterally; antennula with 7 or 8 articles; pleotelson dorsal margin sloping gradually, ventral inflection deep, apex broad, small and up-turned; elongate setae sparse on uropodal rami or absent .......................................................................... M. depressus 6 Eyes small, diameter less than half the width of proximal antennal article and <0.10 head depth; body lacking pigmentation ................................................................................................................. M. albidus – Eyes larger, diameter approximately half width of proximal antennal article and> 0.10 head depth; body pigmented or weakly pigmented ................................................................................................................ 7 7 Antennula short (<0.15 body length); antenna long (> 0.60 body length); pereopod I with distoventral cuticular process on propodal palm;> 10 robust setae on each of uropodal rami; body weakly pigmented ..................................................................................................................................................... M. setosus – Antennula long (> 0.15 body length); antenna short (<0.60 body length); pereopod I without distoventral cuticular process on propodal palm; <6 robust setae on each of uropodal rami; body strongly pigmented .................................................................................................................................................................... 8 8 Pereopod I dactylus distoventral row of scale-like spines absent or weakly developed; pleotelson lateral uropodal ridge absent/weakly developed; abundant elongate setae on uropodal protopod and rami .......... ................................................................................................................................................... M. kensleyi – Pereopod I dactylus distoventral row of scale-like spines well developed; pleotelson lateral uropodal ridge well developed; elongate setae on uropodal protopod and rami sparse to common ................................. 9 9 Antennular and antennal articles short, broad, inflated and bulbous; setae common to abundant on pereon and pleon .................................................................................................................................. M. baccatus – Antennular and antennal articles long, slender, broadly rectangular; pereon and pleon sparsely setose ..... .................................................................................................................................................. M. capensis