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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 ...
The columnals usually became disarticulated after the animal died. Articulated crinoid fossils are relatively rare, but disarticulated columnals are quite common in the fossil record. They may be extracted from their matrix (often limestone ) or, in the case of exposures in coastal cliffs, they can sometimes be found washed out of the matrix ...
They are found in different forms and arrangements in sea urchins, starfish, brittle stars, sea cucumbers, and crinoids. The ossicles and spines (which are specialised sharp ossicles) are the only parts of the animal likely to be fossilized after an echinoderm dies.
Crinoids catch food particles using the tube feet on their outspread pinnules, move them into the ambulacral grooves, wrap them in mucus, and convey them to the mouth using the cilia lining the grooves. [83] The exact dietary requirements of crinoids have been little researched, but in the laboratory, they can be fed with diatoms. [88]
The stomachs of C. mican collected around E. parrae contained large amounts of crinoid stems and soft tissue. In response to this, Endoxocrinus parrae have been observed detaching itself and using its cirri to move across the bottom of the ocean away from the predator.
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 ...
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.