Megabathynella Camacho & Abrams, 2024

Camacho, Ana I., Abrams, Kym M. & Moulds, Tim, 2024, New giant genus of Parabathynellidae (Crustacea: Bathynellacea): first record of Bathynellacea in an Australian cave, European Journal of Taxonomy 935, pp. 54-80 : 58-59

Genus Megabathynella Camacho & Abrams gen. nov.

urn:lsid:zoobank.org:act:0A114DE6-1E02-47CF-A1B0-366CE8EE03F7

Type species

Megabathynella totemensis Camacho & Abrams gen. et sp. nov. (here designated).

Diagnosis

AI multisegmented with more than 12 articles with terminal aesthetascs present on fifth to last segments. AII 7-segmented. Labrum flat, free margin dentate. Md pars molaris (molar process) protruding; proximal tooth present; mandibular palp bi-segmented with several setae (more than six). Proximal endite of MxI with four claws; ten to 11 claws present on distal endite. Exopod of ThI to ThVII multisegmented (more than 11 articles); epipod present from ThI to ThVII; first and second article of endopod of ThI to ThVII each with a plumose dorsal seta. Male ThVIII unusually large, twice as long as wide; basal region of penial complex supports three independent lobes: inner lobe, outer lobe and dentate lobe; dentate lobe as inner lobe, rounded and as long as the outer lobe; very long curved outer lobe, as a finger; large basipod with a seta and a pronounced crest-like on internal face; dentate small exopod; endopod large with two setae and with the distal end rounded with four teeth and two setae of different sizes, the longest barbed. Female ThVIII one-segmented, almost triangular with three long barbed terminal setae. Pleopods absent. Inhomonomous sympod of uropod, with more than 50 spines, distalmost 25% longer than the rest; endopod with spines, the two terminal spines stronger than the rest, and setae, two barbed apical setae and one subterminal and two basal plumose setae; exopod with more than 16 setae. Furca very enlarged with more than 35 spines. Giant species, more than 4 mm long.

Differential diagnosis

Megabathynella Camacho & Abrams gen. nov. bears some resemblance to the giant genera Billibathynella , Brevisomabathynella and Kampucheabathynella (see Table 2 ). The new genus has more than 12 segments in AI, while the other genera have seven or 10; however, the new genus shows few teeth on the labrum, 12 to 14 with few lateral denticles, less than the other giant genera (between 12 and 63 teeth); the new genus presents a two-segmented mandibular palp with more than six setae, the general condition is one or up to three setae found in some species of Billibathynella and Brevisomabathynella ; the new genus has up to 18 articles in the exopod of the Ths and always more than 10, while the largest number found never exceeded 13 articles. The maximum number of spines found in the furca of giant species is 23, while the new genus always has more than 35. Similarly, the sympod of the uropod of the new genus has more than 50 spines, in comparison, the maximum counted to date is 28 spines in species of Billibathynella . The male ThVIII of the new genus also shows several significant differences: it is very large, with a very special endopod, the rounded and protruded distal end with small teeth and setae is totally novel.

Etymology

This prefix ‘ Mega -’ comes from the Greek ‘μέγας’, which means ‘big’. The name Megabathynella refers to the unusually large size of the new genus.

Distribution

Australia, Northern Territory (present study).