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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]
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 ...
This list of crinoid genera is an attempt to create a ... it is hoped that things will improve and a classification will emerge that is based on the whole animal. ...
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 ...
Sea lilies are crinoids with a calyx and five pairs of feather-like arms standing on a long stalk which is retained throughout the animal's life. This stalk is attached to the substrate by means of an enlarged, terminal disc or alternatively by means of several branching, irregular radicular cirri arising from the lowest part of the stem. [ 3 ]
The passion flower feather star is a robust crinoid with a diameter of about 12 cm (5 in) when fully extended. It has eighteen to twenty jointed arms which can be coiled up when the animal is not feeding. These are attached to a cup-shaped body or calyx. The arms are edged by feathery appendages known as pinnules.
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]
Like extant crinoids, Agaricocrinus americanus was anchored to a hard surface by a holdfast out of which grew an articulated stalk. On top of this was a calyx with a number of feather-like arms. Each arm bore short branches known as pinnules and from these cirri were extended which sifted plankton from the water flowing past.