Extract

Recent study of the syntype material of the type species of the monotypic genus Ankumia van Veen, 1932 (A. bosqueti van Veen, 1932) confirmed a pathological retention of moults, expressed by multilayered ridge-like structures, used for the original diagnosis of the genus (Jones, 2003). For this reason, it was proposed that the genus Ankumia should be abandoned as a nomen dubium in favour of Platella Coryell & Fields, 1937. This interpretation was challenged by Malz & Lord (2004), who saw no reason to treat Ankumia as nomen dubium and, acknowledging the unequivocal cytherellid nature of the species, posed and addressed two taxonomical questions: (1) do pathological individuals of cytherellids justify specific and/or generic ranking?; (2) why should Ankumia be abandoned in favour of Platella?

In addressing their first question, Malz & Lord (2004) correctly answered in the negative. However, they claimed that ‘... demonstration of a corresponding “normal” species (including “pathological individuals”) among the associated cytherellids is wanting’. The author disagrees with this statement because he described and illustrated two morphological shell-types among the specimens assigned as syntypes of Ankumia bosqueti in the van Veen/Bonnema collection. They are the ‘Cytherella shell-type’ (Jones, 2003, pl. 1, figs 2–8) and the ‘Ankumia shell-type’ (Jones, 2003, pl. 1, fig. 1; pl. 2 figs 1–14), which correspond to the ‘normal’ species, and to the pathological individuals of that species, respectively. The Ankumia shell-type possesses concentric ribs that become progressively thinner from the adult to the juvenile stages. Of the 22 syntypes studied, 13 …