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A stalked crinoid (white) and a comatulid (red) in deep sea, showing the differences between these two sister groups. Most modern crinoids, i.e., the feather stars, are free-moving and lack a stem as adults. Examples of fossil crinoids that have been interpreted as free-swimming include Marsupites, Saccocoma and Uintacrinus. [23]
One proposal for the cladistic placement of the Homalozoan classes groups Stylophora together with crinoids to form Crinozoa. [7] A 2024 survey of recent research finds more support for Homalozoa as a paraphyletic assemblage along the echinoderm stem group, but noted that the position of Stylophora in particular was uncertain. [8]
Articulata are a subclass or superorder within the class Crinoidea, including all living crinoid species. They are commonly known as sea lilies (stalked crinoids) or feather stars (unstalked crinoids). The Articulata are differentiated from the extinct subclasses by their lack of an anal plate in the adult stage and the presence of an ...
Pentacrinites is an extinct genus of crinoids that lived from the Hettangian to the Bathonian of Asia, Europe, North America, and New Zealand.Their stems are pentagonal to star-shaped in cross-section and are the most commonly preserved parts. [1]
Pentacrinoidea includes most major crinoid groups, such as the living Articulata and extinct Flexibilia (together forming the parvclass Cladida) as well as the extinct Disparida. It is a stem-based taxon , defined as including all crinoids closer to Pentacrinites (a Jurassic articulate) or Apektocrinus (an Early Ordovician cladid ) than to ...
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.
Three infrabasal plates (in contrast to the five found in other dicyclic crinoids). Two of these plates (the zygous plates) are the result of fusion, and are larger than the remaining (azygous) plate. The azygous infrabasal is almost always located under the C ray. 5 basal plates and 5 radial plates in the calyx.
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