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Echinoderms are deuterostomal animals with radial symmetry and a calcareous endoskeleton. They include starfish, sea urchins, sea cucumbers and others. Learn about their taxonomy, evolution, diversity and ecological importance.
Ctenocystoids are likely among the most basal stem-group echinoderms. [1] They have also been interpreted as aberrant blastozoans and as stem-group hemichordates . [ 7 ] [ 8 ] The presence of stereom plates indicates that they most likely belong to the echinoderm total group, rendering a hemichordate affinity unlikely.
Ambulacraria is a clade of invertebrate phyla that includes echinoderms and hemichordates. Learn about their evolution, fossil record, ontogeny, and phylogenetic relationships with other deuterostomes.
Instead, there is a spiral food groove on the outside along which food was moved to a mouth that is thought to be on the side. The respiratory system appears to be primitive. Although the animal does not look like a typical echinoderm, the plates are composed of the characteristic calcareous plates known as stereom that are common to all ...
Eucidaris tribuloides, the slate pencil urchin (named after slate pencil), is a species of cidaroid sea urchins that inhabits littoral regions of the Atlantic Ocean.As a member of the basal echinoid order Cidaroida, its morphological, developmental and molecular genetic characteristics make it a phylogenetically interesting species.
Learn about the hydraulic system used by echinoderms, such as sea stars and sea urchins, for locomotion, food and waste transportation, and respiration. Compare the structure and function of the water vascular system in different classes of echinoderms, such as ophiuroids, crinoids, and holothuroids.
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.
Sea urchins are spiny, globular animals that feed on algae and other organisms. They have fivefold symmetry, tube feet, and a hard shell called a test. Learn about their diversity, anatomy, ecology, evolution, and relation to humans.