Today holasteroids live exclusively in the deep-sea, and include the deepest dwelling of all known echinoid species. Little is known about their biology other than they are deposit feeders, apparently collecting surface organic matter via their frontal groove as they move over the sediment surface. Growth and population structure is best known for, Echinosigra, due to the work of Gage (1984).
However, in the Cretaceous many groups are found living in shallow water settings. They resemble spatangoids in many ways, and many were almost certainly infaunal. However, unlike spatangoids, none appear to have developed funnel-building tube-feet. Thus holasteroids could only have lived fully infaunally in moderately porous and permeable sediments. Flat-based forms such as Echinocorys and the stegasterids were probably exclusively epifaunal, while those with more ovate tests such as Infulaster and Cardiaster, may have lived partially buried (see Gale & Smith 1982). Most Cretaceous and many Tertiary holasteroids have enlarged pore-pairs around the mouth identical to those bearing penicillate tube-feet in spatangoids. It seems likely, therefore, that they were selective particle feeders using penicillate tube-feet to pass suitable particles to the mouth.
Gage, J. D. 1984. On the status of the deep-sea echinoids Echinosigra phiale and E. paradoxa. Journal of the Marine Biological Association UK 64, 157-170.
Gale, A. S. & Smith, A. B. 1982. The palaeobiology of the Cretaceous irregular echinoids Infulaster and Hagenowia. Palaeontology 25, 11-42.