page_title: Diploporita
section_title: Silurian
hierarchical_section_title: Diploporita / Distribution / Silurian
caption_attribution_description: English: Paulicystis sparsus, a diploporitan from middle Silurian deposits of Indiana. This taxon belongs to the holocystitid group, meaning that it has humatipores, instead of diplopores. Note the humatipores that are pores connected by multiple canals are located on all of the plates of the body wall. Specimen from The University of Iowa Paleontology Repository (SUI 48164)
context_page_description: Diploporita is an extinct class of blastozoan that ranged from the Ordovician to the Devonian. These echinoderms are identified by a specialized respiratory structure, called diplopores. Diplopores are a double pore system that sit within a depression on a single thecal plate; each plate can contain numerous diplopore pairs.
  The diploporitans likely represent a polyphyletic group. 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, in the makeup of the feeding grooves, and even major differences in the construction of the group-defining diplopore respiratory structures. The only phylogenetic analysis of Diploporita to date indicates that Diploporita is not a natural evolutionary group. Rather, Diploporita is an artificial grouping based on the presence of diplopores, that have re-evolved multiple times throughout the echinoderm evolutionary tree.
context_section_description: The end-Ordovician extinction represented a large-scale extinction for diploporitans. The majority of diploporitan species went extinct during this period and they never returned to their high species numbers after this time. During the Silurian, there was a much larger presence of diploporitans in North American than during the Ordovician. These diploporitans, called the Holocystites Fauna, appeared in North America during the middle of the Silurian. 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). 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. 
  Other Silurian occurrences of diploporitans worldwide are rare and limited to only a few species (e.g., Eucystis). These occurrences are largely restricted to southern Europe.
caption: Paulicystis sparsus, holocystitid diploporitan from middle Silurian rocks of Indiana. Note the humatipore respiratory structures that pierce the plates of the body wall. (University of Iowa Paleontology Repository, SUI 48164)
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