ABSTRACT
The most of Cretaceous Holasteroids lack the fascioles or have the marginal one only. The first genera with subanal fasciole Giraliaster and Galeaster appeared in Maastrichtian. Evolutionary trends of the latter, that became extinct in Paleocene, are the following: disjunction of apical system, coalescence of 2 and 3 genital plates, disjunction of 1, 4 and 5 interambulacra on the oral side, development of the frontal sinus. It suggests its close affinity to recent Pourtalesiidae. Basseaster, Garumnaster, Pomaster with meridoplaeous 1, 4, 2 and 3 interambulacra occured in Paleocene. These genera are evidently the most ancient ones of the family Urechinidae. The genera Corystus, Cardabia, Huttonechinus (Paleocene — Miocene) and recent Stereopneustes with single rostral plate in plastron belong to the family Corysitidae. One may assume that all these Holasteroids share the synapomorphy — subanal fasciole and form monophyletic group.
