Disparida is an parvclass of extinct marine animals in the class Crinoidea.W. I. Ausich, D. F. Wright, S. R. Cole and J. M. Koniecki. 2018. Disparid and hybocrinid crinoids (Echinodermata) from the Upper Ordovician (lower Katian) Brechin Lagerstätte of Ontario. Journal of Paleontology 92(5):850-871 [S. Cole/S. Cole]Y. Y. Mao, G. D. Webster, W. I. Ausich, Y. Li, Q. L. Wang and M. Reich. 2018. A new crinoid fauna from the Taiyuan Formation (early Permian) of Henan, North China. Journal of Paleontology 92:1066-1080 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.
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.
Major traits of Disparida include:
Small monocyclic calyx, without interbasal plates. Radial plates are proportionally large and may be compound (with multiple components), while basal plates are often reduced. Proximal branchial plates tend to fuse with their respective radials. Thin, uniserial arms without pinnules. Branching is typically frequent. Redevelopment of prominent bilateral symmetry via an axis aligned to one of the five rays making up the crown. This axis of symmetry may lie along the E ray (homocrinoid symmetry), D ray (heterocrinoid symmetry), C ray (isocrinoid symmetry), or A ray (crinoid/belemnocrinoid symmetry, which is developed to a lesser degree in other crinoids). Posterior plates lie above the C radial.
List of families and genera Disparida classification is undergoing revision. Many proposed families are paraphyletic or polyphyletic.
Family Acolocrinidae
Acolocrinus Paracolocrinus
Family Allagecrinidae
Allagecrinus Isoallagecrinus Kallimorphocrinus Litocrinus Metallagecrinus Wrightocrinus
Family Alphacrinidae
Alphacrinus
Family Anamesocrinidae
Anamesocrinus
Family Anomalocrinidae
Anomalocrinus Geraocrinus
Family Aptocrinidae
Othneiocrinus
Family Athenacrinidae
Athenacrinus
Family Belemnocrinidae
Belemnocrinus Whiteocrinus
Family Calceocrinidae
Anulocrinus Calceocrinus Catatonocrinus Charactocrinus Chirocrinus Chiropinna Corvucrinus Cremacrinus Cunctocrinus Darraghcrinus Deltacrinus Diaphorocrinus Dolerocrinus Eohalysiocrinus Epihalysiocrinus Espanocrinus Grypocrinus Halysiocrinus Minicrinus Paracremacrinus Senariocrinus Stibarocrinus Synchirocrinus Trypherocrinus
Family Catillocrinidae
Allocatillocrinus Catillocrinus Eucatillocrinus Kolvacrinus Isocatillocrinus Metacatillocrinus Mycocrinus Neocatillocrinus Notiocatillocrinus Paracatillocrinus Taucatillocrinus Ufacrinus Xenocatillocrinus
Family Cincinnaticrinidae (i.e. Heterocrinidae, paraphyletic / polyphyletic)
Atyphocrinus Cincinnaticrinus Doliocrinus Dystactocrinus Glaucocrinus Heterocrinus Isotomocrinus Ohiocrinus Serendipocrinus Tenuicrinus Tryssocrinus
Family Columbicrinidae
Columbicrinus Praecursoricrinus
Family Dulkumocrinidae
Dulkumocrinus
Family Eustenocrinidae
Cataractocrinus Coralcrinus Eustenocrinus Inyocrinus Peniculocrinus Pogonipocrinus Virucrinus
Family Haplocrinitidae
Haplocrinites
Family Homocrinidae (paraphyletic / polyphyletic)
Apodasmocrinus Bodacrinus Cataraquicrinus Daedalocrinus Difficilicrinus Drymocrinus Ectenocrinus Homocrinus Ibexocrinus Kastorcrinus Penicillicrinus Sygcaulocrinus Tunguskocrinus
Family Iocrinidae (paraphyletic)
Caleidocrinus Grammocrinus Iocrinus Margoiocrinus Muicrinus Pariocrinus Peltacrinus Ristnacrinus Schaldichocrinus Tornatilicrinus Westheadocrinus
Family Maennilicrinidae
Heviacrinus Maennilicrinus Putilovocrinus Vosekocrinus
Family Myelodactylidae
Brachiocrinus Crinobrachiatus Eomyelodactylus Herpetocrinus Musicrinus Myelodactylus
Family Pisocrinidae
Cicerocrinus Eocicerocrinus Parapisocrinus Pisocrinus Playfordicrinus Triacrinus Trichocrinus
Family Pygmaeocrinidae (polyphyletic)
Kroppocrinus Pygmaeocrinus Storthingocrinus
Family Synbathocrinidae
Abyssocrinus Phimocrinus Ramacrinus Stylocrinus Synbathocrinus Taidocrinus Theloreus
Family Tetragonocrinidae
Ramseyocrinus Tetragonocrinus
Family Zophocrinidae
Parazophocrinus Tiaracrinus Zophocrinus
Incertae sedis
Agostocrinus? Aureocrinus Brutopisocrinus Calcycanthocrinus Changinocrinus Claviculacrinus Desmacriocrinus Gongrocrinus Heracrinus Holynocrinus Hypsocrinus Jaekelicrinus Junocrinus Macnamaratylus Paradoxocrinus Perissocrinus Perittocrinus? Quiniocrinus Regnellicrinus Resetocrinus Stereobrachicrinus Tetracionocrinus? Thaminocrinus Trophocrinus Xisoallegocrinus
References