Cuttlefishes (Cephalopoda, Sepiidae): the bare bones—an hypothesis of relationships

Based on a comprehensive analysis of molecular sequence data, the Sepiidae genera Acanthosepion Rochebrune, 1884; Ascarosepion Rochebrune, 1884; Aurosepina Jothinayagam, 1987; Decorisepia Iredale, 1926; Doratosepion Rochebrune, 1884; Rhombosepion Rochebrune, 1884 and Spathidosepion Rochebrune, 1884 are here re-instated and formally recognised as valid. Sepia Linnaeus, 1758 and Sepiella Gray, 1849 are retained, but Metasepia Hoyle, 1885 is placed in alternative combination with Ascarosepion . The subgenus Digitosepia Lipiński, 2020 is well supported and is herein elevated to generic status. Sepia trygonina (Rochebrune, 1884) and Sepia hieronis (Robson, 1924) are placed in new monotypic genera Erythalassa gen. nov. and Lusepia gen. nov. respectively. Hemisepius Steenstrup, 1875, also monotypic, is recognised as valid based on a unique synapomorphy: the presence of a fleshy ridge on each side of the antero-ventral mantle that bears a longitudinal row of black pores, however, H. typicus Steenstrup, 1875, was not included in our molecular analysis as tissue samples could not be obtained. Sepia tuberculata Lamarck, 1798, the type species for the nominal genus Spathidosepion , was not included for the same reason . Based on the morphological similarity between S. tuberculata and the sequenced taxa, S. papillata Quoy & Gaimard, 1832 and S. angulata Roeleveld, 1972 we tentatively assign these two taxa to Spathidosepion pending future confirmation. Where possible, each genus is diagnosed based on a combination of morphological and molecular characters.