Anambulacralia Paul & Toom, 2021

Order Anambulacralia Paul & Toom, 2021

Diagnosis.—Stemless diploporites with an oral frame composed of either or both radial circumorals and interradial periorals, outside the peristome food grooves lie directly on thecal plates and lack both floor and cover plates ( Paul and Toom 2021: 228).

Remarks.—The Anambulacralia includes four families, the Aristocystitidae Neumayr, 1889 , Holocystitidae Miller, 1889 , Parasphaeronitidae Bockelie, 1984, and Sphaeronitidae Neumayr, 1889 . Anambulacralians entirely lack a stem, but were directly attached by an aboral attachment area to solid, or at least firm, substrates. They are distinguished from the other diploporites by the lack of a definite ambulacral structure. All other diploporites, whether directly attached or stem-bearing have ambulacra in which each ambulacral plate supported a single, erect feeding structure (commonly a brachiole). Rows of adambulacral plates either formed part of the thecal wall (mural ambulacra) as in the Protocrinitidae Bather, 1899 , or were recumbent on thecal plates, as in the Mesocystidae Bather, 1899 .