Late Cretaceous-Early Palaeogene echinoderms and the K/T boundary in the southeast Netherlands and northeast Belgium —

The present paper is divided into two parts. In the first, all Campanian, Maastrichtian and Danian ophiuroids known to date from the extended type area of the Maastrichtian Stage, are described and illustrated. The geographic and stratigraphic distribution of this diverse echinoderm group are documented. A total of twenty-one genera (one of them new) and thirty-seven species (seven of them new) are recorded from the Campanian-Danian of Liège-Limburg and the Aachen area (Germany). The following taxa are new: Ophiocten? yvonnae sp. nov., Stegophiura? trispinosa sp. nov., Deckersamphiura inusitata gen. et sp. nov., Ophiarachna? martinblomi sp. nov., Ophiolepis? falsa sp. nov., Ophiomusium lux sp. nov., and Mesophiomusium decipiens gen. et sp. nov. Additional species, recorded here in open nomenclature, may prove to be new as well, but limited material precludes their formal naming. Many ophiuroid species from Liège-Limburg are also known from the Lower Maastrichtian of Rügen and Møn (Denmark). In general, material from those localities is much better preserved, which is why type specimens of additional new taxa have been selected from samples collected there. In the second part of the present paper a total of twenty-four new species and one new genus are described: Ophiosmilax? alternatus sp. nov., Asteronyx? spinulosa sp. nov., Ophiomyxa? curvata sp. nov., Ophiomyxa? rhipidata sp. nov., Ophioscolex? clivulus sp. nov., Ophioscolex? cretaceus sp. nov., Ophiacantha? punctata sp. nov., Ophiacantha? rugosa sp. nov., Ophiacantha? striata sp. nov., Sinosura jasmundensis sp. nov., Hemieuryale? parva sp. nov., Amphiura? plana sp. nov., Ophiothrix? bongaertsi sp. nov., Ophiothrix? cristata sp. nov., Ophiothela? semirotunda sp. nov., Ophiactis? sulcata sp. nov., Ophiocoma? ishidai sp. nov., Ophioderma? radiatum sp. nov., Ophiolepis? granulata sp. nov., Ophiolepis? linea sp. nov., Ophiomusium biconcavum sp. nov., Ophiomusium sentum sp. nov., Ophiomusium sinuatum sp. nov., and Mesophiomusium moenense gen. et sp. nov. Four additional species (Trichaster? sp., Ophiacantha? sp., Sinosura sp., and S. aff. schneideri Kutscher, 1987) are left in open nomenclature; these may prove to be new as well, but not enough material is currently available to erect new species upon. Previously described ophiuroid species, some of which are here reassigned to other genera, in all of these faunas include: Asteronyx? simplex A.H. Müller, 1950, Trichaster? ornatus (Rasmussen, 1950), Ophiomyxa? jekerica (Berry, 1938), Ophiacantha? danica Rasmussen, 1952, Stegophiura? hagenowi (Rasmussen, 1950), Felderophiura vanderhami Jagt, 1991, Ophioplinthaca? fuerstenbergii (J. Müller, 1847), Ophiocoma? senonensis (Valette, 1915), Ophiocoma? rasmusseni Hess, 1960b, Ophioderma? substriatum (Rasmussen, 1950), Ophiotitanos serrata (Roemer, 1840), and Ophiomusium granulosum (Roemer, 1840). Ophiomusium subcylindricum (von Hagenow, 1840) and O. danicum Brünnich Nielsen, 1926 are considered to be junior synonyms of O. granulosum. With very few exceptions, species assignment to extant genera is fraught with difficulties, even in those cases where more or less complete discs with arms attached are available. Most of our taxa are based on dissociated ossicles, or portions of arms at best, which are preferentially placed in the nomipp nal genera of the various ophiuroid families. Despite this present paper demonstrates that Late Cretaceous-Early exceeds previous estimates, and that the white chalk facies benthic inhabitation than assumed by earlier authors.