The Echinoid Directory

Little is known of the biology of this entirely extinct group. The most primitive members are close in form to contemporary cassiduloids, and were presumably like them bulk sediment swallowers. However, later members are much closer in morphology to holasteroids, with poorly developed phyllodes and subanal tube-feet. Many of the Upper Jurassic and Lower Cretaceous forms are apetaloid and appear to have inhabited deeper water settings.

The earliest known disasterid is Lower Jurassic. Although there remains some uncertainty about whether a Pleinsbachian record is valid (Vadet et al. 1995), there is an undoubted Toarcian disasterid. The group never achieved high diversity but was usually represented by a small number of genera at any one time. Disasterids continued through the Jurassic and into the Lower Cretaceous, with the last included member extending into the Albian. Mintz (1968) provided a summary of generic diversity.

Vadet, A., Thierry, J., Rioult, M. & Guitton, M. 1995. Presence de Pygomalus ovalis dans le Carixien superieur. Memoires de la Societe academique de Boulonnais 16, 60-62.

Mintz, L. W. 1968. Echinoids of the Mesozoic families Collyritidae d'Orbigny, 1853 and Disasteridae Gras, 1848. Journal of Paleontology 42, 1272-1288.