Paracrinoidea Temporal range:EarlyOrdovician -Early Silurian PreꞒ Ꞓ O S D C P T J K Pg N
Comarocystites punctatus
Scientific classification
Kingdom:	Animalia
Phylum:	Echinodermata
Subphylum:	†Blastozoa
Class:	†Paracrinoidea Regnell, 1945
Orders
Comarocystitida Platycystitida

Paracrinoidea is an extinctclass ofblastozoanechinoderms. They lived in shallow seas during the EarlyOrdovician through the EarlySilurian. While blastozoans are usually characterized by types of respiratory structures present, it is not clear what types of respiratory structures paracrinoids likely had. Despite the taxon's name, the paracrinoids are not closely related tocrinoids.

Paracrinoids are characterized by a mouth with two to five feeding arms arranged asymmetrically, or somewhat bisymmetrically. They have a U-shaped gut, and their anus is located next to the mouth. They have irregularly shaped bodies (theca), and a stem, superficially similar to crinoids, and may have used the stem to attach themselves to asubstrate, although some reconstructions show them partially buried in sediment.^[1]

Only 13 to 15 genera are known. SeeList of echinodermata orders

• Order †Comarocystitida
  • ?Family †Heckeritidae
    • †Heckerites
  • Family †Amygdalocystitidae
    • †Achradocystites Volborth, 1870
    • †Amygdalocystites Billings, 1854 (=Ottawacystis) (?=Billingsocystis)
    • †Oklahomacystis Parsley & Mintz, 1975 (Bassler, 1943)
    • †Ovulocystites Frest et al., 1980
  • Family †Comarocystitidae Balther, 1899
    • †Comarocystites Billings, 1854
    • †Implicaticystis
    • †Sinclairocystis
• Order †Platycystitida
  • Family †Platycystitidae
    • Subfamily †Canadocystinae Frest, Strimple, & Coney, 1979
      • †Canadocystis (=Sigmacystis)
    • Subfamily †Platycystitinae Frest, Strimple, & Coney, 1979
      • †Globulocystites Frest, Strimple, & Coney, 1979
        • †Globulocystites rotundatus Frest, Strimple, & Coney, 1979 (type)
        • †Globulocystites cristatus (Bassler) (Referred toGlobulocystites by Frest, Strimple, & Coney, 1979)
        • †Globulocystites infundus Frest, Strimple, & McGinnis, 1977, p. 215 (Referred toGlobulocystites fromPlatycystites by Frest, Strimple, & Coney, 1979)
      • †Platycystites Miller, 1889
        • †Platycystites faberi Miller, 1889 (type)
        • †Platycystites ovalis Frest, Strimple, & Coney, 1979
        • †Platycystites sp. Frest, Strimple, & Coney, 1979 (NMNH 112086, Blackriverian, Bromide Formation, Carter County, Oklahoma)
  • †FamilyMalocystitidae
    • †Malocystites
    • †Wellerocystis
  • †FamilyBistomiacystitidae
    • †Bistomiacystis
• Orderincertae sedis
  • †FamilySpringerocystidae Bassler, 1950 (suggested as paracrinoids related toCanadacystis by Sprinkle, 1973, but Parsley & Mintz, 1975 regarded them as eocrinoids, as originally described)^[2]
    • †Columbocystis
    • †Foerstecystis
    • †Springerocystis

Doubtful paracrinoids:^{[citation needed]}

• †Allocystites (suggested as a paracrinoid related toCanadacystis by Sprinkle, 1973 but not Parsley & Mintz, 1975)
• †Paleocystites
• †Ulrichocystis

Phylogeny after Limbeck (2018)

-+--C. laevis (Cryptocrinites laevis?) `--+--Columbocystis ovata (Columbocystis ovata? Eocrinoid)    |--Columbocystis typica    `--+--+--Bistomiacystis globosa       |  |--Bistomiacystis schrantzi       |  `--Achradocystites schmidti       `--+--+--Comarocystites punctatus          |  |--Comarocystites tribrachius          |  |--Implicaticystis shumardi          |  `--Implicaticystis symmetricus          `--+--Canadocystis tennesseensis             `--+--Canadocystis barrandei                |--Canadocystis emmonsi                `--+--Malocystites murchisoni                   `--+--Sinclairocystis praedicta                      |--+--Amygdalocystites florealis                      |  |--Amygdalocystites radiatus                      |  |--Oklahomacystis bibrachiatus                      |  |--Oklahomacystis spissus                      |  |--Oklahomacystis tribrachiatus                      |  |--Oklahomacystis trigonis                      |  `--Wellerocystis kimmswickensis                      `--+--Globulocystites cristatus                         |--Globulocystites rotundatus                         |--Globulocystites (originallyPlatycystites)infundus                         |--Platycystites cristatus                         `--Platycystites faberi

This article includes a list ofgeneral references, butit lacks sufficient correspondinginline citations. Please help toimprove this article byintroducing more precise citations.(June 2020) (Learn how and when to remove this message)

• Frest, T. J.; Strimple, H. L.; Coney, C. C. (1979)."Paracrinoids (Platycystitidae) from the Benbolt Formation (Blackriverian) of Virginia".Journal of Paleontology.53 (2):380–398.
• Frest, T. J.; Strimple, H. L.; McGinnis, M. R. (1977). "A new species ofPlatycystites (Echinodermata: Paracrinoidea) from the Middle Ordovician of Oklahoma".Journal of the Washington Academy of Sciences.66:211–221.
• Limbeck, M. R. (2018)."Fossil focus: Paracrinoids".Palaeontology.8 (9):1–7. Archived fromthe original on 2024-04-21. Retrieved2020-06-21.
• Parsley, R. L.; Mintz, L. W. (1975). "North American Paracrinoidea (Ordovician: Paracrinozoa, new, Echinodermata)".Bulletins of American Paleontology.68 (288):1–115.
• Parsley, R. L. (1975). "Systematics and functional morphology ofColumbocystis, a Middle Ordovician "Cystidean" (Echinodermata) of uncertain affinities".Bulletins of American Paleontology.67 (287):349–361.
• Sprinkle, J. (1973). "Morphology and evolution of blastozoan echinoderms".Harvard University Museum of Comparative Zoology Special Publication: 284.

• Paracrinoidea
• Ordovician echinoderms
• Silurian echinoderms
• Early Ordovician first appearances
• Silurian extinctions
• Prehistoric animal classes
• Echinoderm orders

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