Abderaz Formation is one of the Upper Cretaceous formations in the Kopet-Dagh sedimentary basin. A stratigraphic section from the mentioned formation is selected for detailed systematic description with regard to echinoids. Numerous well preserved representatives of the families Mircrasteridae wright, 1857 and Echinocorythidae Lambert, 1920 are described from the Ghaleh-Zoo stratigraphic sectio...

Populations of sea urchins often fluctuate greatly in density. The density of sea urchins is usually inversely correlated with the abundance of macrolagae. It is argued that fluctuations in density are a predictable consequence of the unique morphology and physiology of sea urchins. An extraordinary ability to accomodate food Limitation through variations in growth rate means that surv~vorship ...

Two new echinoid genera and species, Salvaster roberti gen. et sp. nov. and Pygolampas edita gen. et sp. nov. are described. They were collected in the Calcaires à Spatangues Formation (CSF) that consists of limestone and clay sediments deposited in the southeast of the Paris Basin (France) during the Early Hauterivian (Early Cretaceous). The CSF is dated from the Acanthodiscus radiatus chronoz...