Ankumia van Veen, 1932 (nomen dubium): pathological moult retention in the Cytherellidae (Platycopida: Ostracoda)

Peter J. Jones
2003 Journal of Micropalaeontology  
<p><strong>Abstract.</strong> The monotypic genus <i>Ankumia</i> is associated with the rich cytherellid fauna described by van Veen (1932) from the Upper Cretaceous (late Maastrichtian) rocks of South Limburg, The Netherlands. The type species (<i>A. bosqueti</i> van Veen, 1932) is redescribed because the genus possesses the enigmatic combination of cytherellid (posterior sex-dimorphism and R/L overlap) and eridostracan (several concentric bands) characters. As no holotype was designated, the
more » ... edescription is based on a detailed SEM examination of the syntypes in the Bonnema/van Veen composite collection. Most syntypes show that the outer layer of coarse, concentric, rings, which form an oblique cone, are retained moults of a species of cytherellid. The point of retention in the early instars is along the posteroventral margin, contrary to the dorsal position of successive lamellae in eridostracan <i>Cryptophyllus.</i> Other syntypes possess the typical lateral outline of adult species of Cytherellidae. The ontogeny of each individual of retained moults <i>('Ankumia')</i> has a nine-instar pattern, with a growth increment between successive moults about 1.15, slightly less than that (about 1.20) observed by Shaver (1953) for <i>Cytherella bullata.</i> The name <i>Ankumia</i> is abandonned, and a new combination proposed for the previous type species, <i>Platella bosqueti</i> (van Veen, 1932).</p>
doi:10.1144/jm.22.1.85 fatcat:rkkyt7uc7fbjtk4jsyisttlv5i