Gustavus Ahyong & Ng, 2009 Type species. Gustavus mecognathus Ahyong & Ng, 2009. Other species included. Gustavus holthuisae sp. nov. Remarks. Števčić (2011) recognised a new tribe, Gustavini, placing it under the Aphanodactylinae in his concept of Asthenognathidae Stimpson, 1858. Whereas the morphological features of Gustavus, in particular the somewhat peculiar Mxp3, are unusual within Aphanodactylidae, members of this family are so diverse in form that a suprageneric grouping just for Gustavus would not be taxonomically meaningful, even with discovery of a second species of the genus (described below). In addition, the subtriangular Mxp3 ischium of Gustavus, being slender and distinctly tapering proximally, is a feature also present in Takedactylus Naruse & Maenosono, 2012. Takedactylus, however, has a completely different carapace form and much longer walking legs, the latter also with a distinctive dactylus armed with an accessory spine (cf. Naruse & Maenosono 2012; Naruse & Yoshida 2018).

Published as part of Ng, Peter K. L. & Anker, Arthur, 2024, A second species in the polychaete-associated crab genus Gustavus Ahyong & Ng, 2009 (Decapoda: Brachyura: Aphanodactylidae), pp. 369-380 in Zootaxa 5497 (3) on page 370, DOI: 10.11646/zootaxa.5497.3.3, http://zenodo.org/record/13618519