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An echinoderm (/ ɪ ˈ k aɪ n ə ˌ d ɜːr m, ˈ ɛ k ə-/) [2] is any animal of the phylum Echinodermata (/ ɪ ˌ k aɪ n oʊ ˈ d ɜːr m ə t ə /), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". [3]
Ambulacraria / ˌ æ m b j uː l ə ˈ k r ɛər i ə /, or Coelomopora / s iː l ə ˈ m ɒ p ə r ə /, is a clade of invertebrate phyla that includes echinoderms and hemichordates; [1] a member of this group is called an ambulacrarian. Phylogenetic analysis suggests the echinoderms and hemichordates separated around 533 million years ago. [2]
Ambulacral is a term typically used in the context of anatomical parts of the phylum Echinodermata or class Asteroidea and Edrioasteroidea. [1] [2] Echinoderms can have ambulacral parts that include ossicles, plates, spines, and suckers.
Sea urchins or urchins (/ ˈ ɜːr tʃ ɪ n z /) are typically spiny, globular animals, echinoderms in the class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal to 5,000 metres (16,000 ft; 2,700 fathoms). [1]
The echinoderms are mainly distinguished from other phyla by their body plan and organization. The earliest sea cucumbers are known from the middle Ordovician , over 450 million years ago. [ 35 ] The apodida is the sister group to the other orders of sea cucumbers.
Echinoderms (sea urchins, sea lilies, sea stars, crinoids, ...) are animals in the phylum Echinodermata. There are 5 subphyla, some of them being extinct: †Homalozoa, Crinozoa, Asterozoa, Echinozoa and †Blastozoa.
Pedicellaria of Acanthaster planci Generalized pedicellaria of an (a) asteroid and (b) echinoid. A pedicellaria (pl.: pedicellariae) is a small wrench- or claw-shaped appendage with movable jaws, called valves, commonly found on echinoderms (phylum Echinodermata), particularly in sea stars (class Asteroidea) and sea urchins (class Echinoidea).
A brittle star, Ophionereis reticulata A sea cucumber from Malaysia Starfish exhibit a wide range of colours. This List of echinoderm orders concerns the various classes and orders into which taxonomists categorize the roughly 7000 extant species [1] as well as the extinct species of the exclusively marine phylum Echinodermata.