[3] The evidence for this claim lies within the highly morphologically diverse body plans of the diploporitans: there are major differences in the makeup of the attachment structure (e.g., stem or holdfast), in the makeup of the feeding grooves, and even major differences in the construction of the group-defining diplopore respiratory structures.

This group is characterized by short ambulacral feeding grooves and holdfasts that cement directly to a hard substrate, instead of a stem.

The following cladogram, representing a strict consensus of the 18 most parsimonious trees with a length of 99 steps, shows the monophyly of Sphaeronitida and (within it) Holocystidae.

[6] Gogia spiralus (Gogiid Eocrinoid) Rhopalocystis destombesi (Ascocystitid Eocrinoid) Eurekablastus rozhnovi (Parablastoid) Asteroblastus stellatus Hybocrinus nitidus (Crinoid) Eumorphocystis multiporata Cheirocystis fultonensis (Glyptocystitid Rhombiferan) Hemicosmites grandis (Hemicosmitid Rhombiferan) Stephanocrinus angulatus (Coronate Blastoid) Canadocystis barrandei (Paracrinoid) Dactylocystis schmidti Fungocystites rarissimus Estonocystis antropoffi Glyptosphaerites leuchtenbergi Tristomiocystis globossus Sphaeronities rossicum Eucystis angelini Haplosphaeronites oblonga Triamara ventricosa Aristocystites bohemicus Trematocystis magniporatus Pustulocystis pentax Pentacystis gibsoni Paulicystus densus Holocystites cylindricus Holocystites scutellus Holocystites salmoensis Information concerning the distribution of diploporitan fossils is constantly changing, as more field sites are found and fossils from these are described.

[7] Diploporitans are routinely found preserved from the Ordovician in Gondwana (i.e., southern Europe, northern Africa, the Middle East), Baltica, South China, and European Laurentia (e.g., United Kingdom).

These diploporitans, representing multiple genera, all share the same basic features: reduced food grooves, large plates to support feeding structures that branched off of the surface of the body, and specialized diplopore respiratory structures, called humatipores (diplopores that are connected by multiple canals below the surface of the plate).

[9] The Holocystites Fauna is mostly found in the midcontinental United States (e.g., Indiana, Wisconsin, Tennessee) and does not survive past the end of the Silurian.