Facing the taxonomic impediment — a reassessment of Merulanella Verhoeff, 1926 (Oniscidea, Armadillidae) through historical specimens

The taxonomic impediment has been identified as a problem for conservation biology since 1988. Although several measures have been developed to overcome it, major non-specialized scientific publishers have not fully addressed it. One of the more challenging solutions relies on the identification of taxonomic needs and priorities hampered by the scarcity and inaccessibility of resources. Currently, publishers often consider taxonomy on its own not worth publishing unless supplementary to additional work, such as genetic analyses, pushing publication to a restricted space in specialized journals. A revision of the terrestrial isopod genus Merulanella , through the literature and historical specimens, shows that taxonomies outlined before the development of certain key concepts in evolutionary biology need to be urgently revisited before new studies are done on them. Furthermore, some species in this genus are considered endangered due to the pet trade, albeit they are not included on the IUCN Red List. The taxonomy of the genus Merulanella was developed before and during the development of zoogeography and before the modern concept of vicariance, explaining the wide distribution of this genus with seven species spanning over three biogeographic realms: M. carinata , M. wahrbergi , M. dollfusi (Australasia), M. bicolorata , M. gibbera , M. lattissima (Indomalay), and M. peltata (Afrotropics). After revising the literature, the context of the produced taxonomy, and assessing the type material, first-hand and through photographs, the morphological dissimilarity justifies restricting Merulanella to the species from New Caledonia (Australasian realm), namely M. carinata , M. wahrbergi , and M. dollfusi . A new genus is proposed for the species from Flores, Indonesia, erecting Floresiodillo gibberum gen. et comb. nov. , and F. latissimus gen. et. comb. nov. , a new genus is erected for the species in Myanmar, Ardentiella bicolarata , gen. et comb. nov. and A. caerulea gen. et comb. nov. (both in the Indomalayan realm), and a new genus is erected for the species in Seychelles, Acutodillo peltatus gen. et comb. nov. (Afrotropical realm). Further studies will be needed to determine the phylogenetic relationships between these new genera and the history of their distribution. Still, this new framework better captures the diversity of the family Armadillidae for its conservation.