Clarification of the taxonomic status of Acanthochitona discrepans (Brown, 1827) with new data for the North-East Atlantic Acanthochitona (Polyplacophora, Acanthochitonidae)

Abstract

The genus Acanthochitona can be easily distinguished from other chitons by having eighteen tufts of bristles on the dorsal side of the densely spiculose girdle. In the North-East Atlantic, five species of this genus have been recognised so far: A. crinita (Pennant, 1777), A. discrepans (Brown, 1827), A. fascicularis (Linnaeus, 1767), A. oblonga Leloup, 1968 and A. pilosa Schmidt-Petersen, Schwabe et Haszprunar, 2015. The nomenclature of A. crinita, A. discrepans and A. fascicularis was confused for a very long time until Kaas (1985) designated type specimens for them and provided a brief key. However, his work lacked detailed descriptions of the three species and some authors doubted that A. discrepans constitutes a separate species. Subsequently, the taxonomic status of A. discrepans has remained unclear. Here, we implemented an integrative approach which combined morphology and molecular evidence to show that Acanthochitona discrepans is, indeed, a valid species and we present re-descriptions for A. crinita, A. discrepans and A. fascicularis.