Austrothelphusa wasselli, Naser & Davie & Waltham, 2018

Naser, Murtada D., Davie, Peter J. F. & Waltham, Nathan J., 2018, Redescription of Austrothelphusa wasselli (Bishop, 1963) (Crustacea: Brachyura: Gecarcinucidae), and designation of a new species from the Gilbert River, north Queensland, Australia, Zootaxa 4369 (1), pp. 109-127 : 114

Austrothelphusa wasselli species-complex

Diagnosis. Carapace broadly oval, moderately convex; surface medially punctate; gastro-cardiac (H-shaped) grooves present but not strongly marked; epigastric regions separated by median groove; epigastric crests absent or poorly developed; postorbital crests low or absent; branchial regions not markedly swollen, lacking anterolateral striations, punctate; cervical grooves shallow, poorly marked; anterolateral margins smoothly cristate, evenly convex, with one, more or less distinct, but always small epibranchial tooth. Frontal and orbital margins with raised rim. Exorbital angle spine moderately blunt. Posterolateral borders straight, convergent posteriorly, bearing oblique striations. Front more or less bilobed. Male pleon broadly triangular; somites 4 and 5 strongly tapering; somite 6 slightly tapering; telson length subequal to breadth at base, tongue-shaped. Small species, typically less than 25 mm maximum carapace width; females with mature pleon by 13 mm CW.

Remarks. Justification for using the term “species-complex” to treat a group of samples from various river catchments from across Cape York, is given elsewhere in this paper, and will not be repeated here. Suffice to say that we have found discrete morphological patterns within the broad geographic range currently ascribed to A. wasselli sensu lato, and these differences are supported by significant genetic divergence. It is intended to describe a number of further new species as a result of our ongoing study exploring the phylogeny of this group using both mitochondrial and nuclear genetic markers.

The members of the A. wasselli species-complex are easily recognisable from other Austrothelphusa species by: the relatively unswollen anterolateral branchial regions that lack obvious oblique striations; the telson of the male pleon being about as long as wide at base; and the small size when fully grown, especially the small size of females at sexual maturity.

Based on pleon shape, A. wasselli sensu lato is closest to A. raceki ( Bishop 1963: fig. 2A). Preliminary unpublished genetic results (P.J.F. Davie & D. Gopurenko) also indicate that A. raceki samples form the sister clade to A. wasselli sensu lato.