Disparida

{{Short description|Extinct clade of crinoids}}

{{Automatic taxobox

| fossil_range = {{fossilrange|Tremadocian|Middle Permian}}

| image = Synbathocrinus fossil crinoid (Burlington Limestone, Mississippian; Missouri, USA) 1 (17383990962).jpg

| image_upright = 0.5

| image_caption = Synbathocrinus from the Mississippian of Missouri, USA

| taxon = Disparida

| authority = Moore & Laudon, 1943

| subdivision_ranks = Orders

| subdivision = *Calceocrinida

• Eustenocrinida
• Homocrinida
• Maennilicrinida
• Myelodactyla
• Pisocrinoidea
• Tetragonocrinida

| subdivision_ref =

}}

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{{Cite journal |last=Wright |first=David F. |last2=Ausich |first2=William I. |last3=Cole |first3=Selina R. |last4=Peter |first4=Mark E. |last5=Rhenberg |first5=Elizabeth C. |date=2017 |title=Phylogenetic taxonomy and classification of the Crinoidea (Echinodermata) |url=https://www.cambridge.org/core/product/identifier/S0022336016001426/type/journal_article |journal=Journal of Paleontology |language=en |volume=91 |issue=4 |pages=829–846 |doi=10.1017/jpa.2016.142 |issn=0022-3360|doi-access=free }} 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.{{Cite journal |last=Ausich |first=William I. |date=2018-12-01 |title=Morphological paradox of disparid crinoids (Echinodermata): phylogenetic analysis of a Paleozoic clade |url=https://doi.org/10.1007/s13358-018-0147-z |journal=Swiss Journal of Palaeontology |language=en |volume=137 |issue=2 |pages=159–176 |doi=10.1007/s13358-018-0147-z |issn=1664-2384|url-access=subscription }}

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:{{Cite book |last=Moore |first=Raymond C. |url=http://paleo.ku.edu/treatise2/parts/t1.html |title=Part T, Echinodermata 2, Crinoidea, vol. 2 |date=1978 |publisher=University of Kansas and Geological Society of America |others=By Georges Ubaghs, R. C. Moore, H. Wienberg Rasmussen, N. Gary Lane, Albert Breimer, H. L. Strimple, J. C. Brower, Russell M. Jeffords, James Sprinkle, R. E. Peck, D. B. Macurda Jr., D. L. Meyer, Michel Roux, Hertha Sieverts-Doreck, R. O. Fay, and R. A. Robison |isbn=978-0-8137-3021-9 |editor-last=Moore |editor-first=Raymond C. |series=Treatise on invertebrate paleontology |volume= |location=Boulder, CO and Lawrence, KS |page= |oclc=531991 |editor-last2=Teichert |editor-first2=Curt}}

• 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.