Cryptostomata

(paleontology) An order of extinct bryozoans in the class Gymnolaemata.

An extinct order of Bryozoa in the class Stenolaemata. Cryptostomes had basally attached, erect, calcified colonies made of sheets or delicate branches composed of short tubular or box-shaped feeding zooids (individual units that constitute these colonial organisms) and commonly extra-zooidal skeletal deposits. Overall colony morphology is the basis for dividing cryptostomes into four subgroups that commonly are treated as orders: Rhabdomesina, Ptilodictyina, Fenestellina, and Timanodictyina.

Cryptostomes were exclusively marine and lived in a wide variety of relatively low-energy environments on continental shelves and seas. They were important contributors to the growth of organic mounds during the Late Ordovician and early Carboniferous.

Phylogenetic relationships among the four subgroups are not clear. Probably the Rhabdomesina is paraphyletic and gave rise to the other three groups, each of which apparently is monophyletic. See also Bryozoa; Stenolaemata.