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Disparida Temporal range:
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Synbathocrinus from the Mississippian of Missouri, USA | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Echinodermata |
Class: | Crinoidea |
Infraclass: | Inadunata |
Parvclass: | †Disparida Moore & Laudon, 1943 |
Orders[1] | |
Disparida is an parvclass of extinct marine animals in the class Crinoidea.[2][3][1] Disparids are a speciose and morphologically diverse group of crinoids distinguished by their monocyclic calyx and slender arms without pinnules. They range from the Early Ordovician (Tremadocian) to Middle Permian, reaching their highest diversity during the Late Ordovician.[4]
While many disparids had a generalized shape typical of other stalked crinoids, some subgroups achieved strange forms. The long-lasting Calceocrinidae were recumbent forms, with a flattened crown bent back onto a stalk which rested on the seafloor. Other unusual disparid families include the armless Zophocrinidae, the spiral-armed Myelodactylidae, and the diminutive, simplified Pisocrinidae. Disparids have long been classified by the structure of their radial plates and different planes of symmetry, but a cumulative phylogenetic approach has failed to confirm the validity of many proposed subgroups. Nevertheless, Disparida itself is well-supported as a distinct monophyletic group.[4]
Major traits of Disparida include:[1][5]
Disparida classification is undergoing revision. Many proposed families are paraphyletic or polyphyletic.[5][6][4]
Family Acolocrinidae
Family Allagecrinidae
Family Alphacrinidae
Family Anamesocrinidae
Family Anomalocrinidae
Family Aptocrinidae
Family Athenacrinidae
Family Belemnocrinidae
Family Calceocrinidae
Family Catillocrinidae
Family Cincinnaticrinidae (i.e. Heterocrinidae, paraphyletic / polyphyletic)
Family Columbicrinidae
Family Dulkumocrinidae
Family Eustenocrinidae
Family Haplocrinitidae
Family Homocrinidae (paraphyletic / polyphyletic)
Family Iocrinidae (paraphyletic)
Family Maennilicrinidae
Family Myelodactylidae
Family Pisocrinidae
Family Pygmaeocrinidae (polyphyletic)
Family Synbathocrinidae
Family Tetragonocrinidae
Family Zophocrinidae