Earth and Atmospheric Sciences, Department of


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Published in Diatom Research, 2022



Copyright © 2022 The International Society for Diatom Research; published by Taylor & Francis. Used by permission.


Late Cretaceous (late Campanian) diatom assemblages from the Campbell Plateau (Zealandia), southwest Pacific Ocean, obtained from Deep Sea Drilling Project (DSDP) Leg 29 Site 275, contain well-preserved specimens of two enigmatic diatom species currently assigned to the genus Ktenodiscus; Micrampulla parvula originally described from the Maastrichtian-age Moreno Shale, California, and Pterotheca cretacea from DSDP Site 275. In general, the two species share a number of common features with modern Corethron (domed valves, probable heterovalvate frustules, T-shaped serrated articulated spines, marginal sockets), but differ in the location of the sockets (i.e. vertically at the base of the valve dome and not on the rim), the design of the spines and sockets, and the hollow structure extending from the valve center. Although hooked spines are absent, equivalent 1-spine and 2-spine valves can be recognized in these two species. The recently described genus Praecorethron from the same late Campanian sediments shares many features with Micrampulla, but lacks the inflated central valve structure. As a result of our studies, the relevant subclass, order and family definitions are emended, as well as those of Micrampulla, M. parvula and M. cretacea comb. nov., and a new family, Micrampullaceae fam. nov., is erected to distinguish the ancient genera (Micrampulla and Praecorethron) from modern Corethron.