Diploporita
| Diploporita | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Subphylum: | Blastozoa |
| Class: | Diploporita |
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 (body) 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 (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.
There are three major groups of Diploporita that have been traditionally proposed: the Asteroblastida, Glyptosphaeritida, and the Sphaeronitida. These three groups, which are markedly different from one another, are found in approximately the same age strata in the Early Ordovician of the Prague Basin. Of these proposed groups, only one has been thought to be monophyletic: the Sphaeronitida. This group is characterized by short ambulacral feeding grooves and holdfasts that cement directly to a hard substrate, instead of a stem.
At this time, it is not clear to which group Diploporita is most closely related. It has been suggested that the paraphyletic group Eocrinoidea could have given rise to diploporitans, as well as other groups of blastozoans, but the evidence for this is inconclusive at this time.
Information concerning the distribution of diploporitan fossils is constantly changing, as more field sites are found and fossils from these are described. This description of diploporitan fossil occurrences is only meant to be a general introduction and is not an exhaustive list.
Diploporitans in the Ordovician were very diverse, with a high estimate of 176 species. 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). Ordovician Occurrences of diploporitans in North American Laurentia are limited to only a very small number of instances. The Late Ordovician Bromide Formation is one of the few, and likely the most well-known, outcrops of diploporitan fossils, Eumorphocystis multiporata
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