Sensonatoridae, Lowry & Myers, 2012

Lowry, J. K. & Myers, A. A., 2012, New, mainly southern hemisphere, freshwater families of Amphipoda (Crustacea), together with a description of the first freshwater calliopiid, Lutriwita bradburyi gen. nov. et sp. nov., Zootaxa 3499, pp. 27-45 : 38-39

Sensonatoridae fam. nov.

Type genus. Sensonator Notenboom, 1986 .

Included genera. Sensonator Notenboom, 1986 .

Diagnostic description. Head eyes absent. Calceoli present. Antenna 1 shorter than antenna 2; peduncular article 1 longer than article 2; accessory flagellum short. Antenna 2 peduncular article 1 bulbous. Mandible incisor smooth plate. Labium without inner plates. Maxilla 1 inner plate setose apically; palps alike. Maxilla 2 inner plate without oblique setal row. Maxilliped inner plate reduced; outer plate small. Body laterally compressed. Coxal gills present on coxae 2 to 6, stalked, with proximal suture. Sternal gills absent. Gnathopods 1 and 2 not sexually dimorphic. Gnathopod 1 smaller than gnathopod 2; Gnathopod 1 propodus with single row of simple or bifid robust setae along palmar margin. Pereopod 4 without posteroventral lobe. Pereopods 5–7: pereopod 5 shorter, pereopods 6 and 7 similar length; dactyli with a few subterminal setae. Pereopod 5 coxa with small anteroventral lobe; basis slightly expanded. Urosomites 1 to 3 free, with robust dorsal setae. Urosomite 1 with distoventral robust seta. Urosomite 2 without paired dorsal setae. Uropod 1 peduncle without basofacial robust seta; without ventromedial spine. Uropod 3 biramous; rami not sexually dimorphic; with fringing plumose setae; inner ramus subequal in length to outer ramus; outer ramus 2-articulate, article 2 short. Telson deeply cleft, with robust setae.

Remarks. Notenboom (1986) originally hypothesised that Sensonator penetrated continental ground waters from a pelagic marine ancestor. Notenboom considered that Sensonator was more similar to the Gammaridae than to other freshwater northern hemisphere families such as the crangoyntids and niphargids. However he pointed out that, unlike gammarids, in Sensonator the males are not larger than the females, the gnathopods are similar in size and not sexually dimorphic. Probably Sensonator does not amplex. Notenboom (1986) also considered similarities to bogidiellid, liljeborgiid and pardaliscid amphipods.

The monotypic family Sensonatoridae appears to be most similar to the northern shield freshwater gammarid and luciobliviid amphipods. They all share the gammarid-type calceolus, a bulbous first article on the peduncle of antenna 2, stalked coxal gills on pereopods 2 to 6, urosomites 1 to 3 with dorsal robust setae and deeply cleft telsons. But sensonatorids have a shortened first antenna and third uropods with plumose setae unlike these family groups.

Distribution. Europe.