ABSTRACT
The evolutionary history of the Collyritidae of the Paris Basin, from the Upper Bajocian to the Middle Oxfordian (Middle and Upper Jurassic), is considered with respect to several data: changes in body shape and anatomy in space and time; sediment characteristics; stratigraphical and geographical distribution of populations; paleogeography and its variations in time; relative importance of the taxon in relation to other fossil echinoid groups. The morphological variations appear closely related to the grain size of the sediment and its carbonate content. Furthermore, this echinoid family is restricted to shallow but open and quiet environments; it is totally missing from very shallow low energy and sheltered environments and from high energy ones as well as from quiet and deeper environments. The settling occurs in several stages correlated with transgressive periods. Except in a few cases, collyritids occur to the exclusion of other regular or irregular echinoids.
