Spiny-skinned Invertebrates
Echinoderm, any of a variety of invertebrate marine animals belonging to the phylum Echinodermata, characterized by a hard, spiny covering or skin. Beginning with the dawn of the Cambrian Period (542 million to 488 million years ago), echinoderms have a rich fossil history and are well represented...
Spiny-skinned Invertebrates Encyclopedia Articles
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brittle star
Brittle star, any of the 2,100 living species of marine invertebrates constituting the subclass Ophiuroidea (phylum Echinodermata). Their long, thin arms—usually five and often forked and spiny—are distinctly...
urchin
Urchin, any of several marine invertebrates of the class Echinoidea (phylum Echinodermata), including the cake urchin, heart urchin, and sea urchin
sea cucumber
Sea cucumber, (class Holothuroidea), any of 1,200 species of marine invertebrates that constitute a class within the phylum Echinodermata. The soft cylindrical body, 2 to 200 cm (about 0.75 inch to 6.5...
echinoderm
Echinoderm, any of a variety of invertebrate marine animals belonging to the phylum Echinodermata, characterized by a hard, spiny covering or skin. Beginning with the dawn of the Cambrian Period (542 million...
sand dollar
Sand dollar, any of the invertebrate marine animals of the order Clypeastroida (class Echinoidea, phylum Echinodermata) that has a flat, disk-shaped body. They are close relatives of sea urchins and heart...
feather star
Feather star, any of the 550 living species of crinoid marine invertebrates (class Crinoidea) of the phylum Echinodermata lacking a stalk. The arms, which have feathery fringes and can be used for swimming,...
sea star
Sea star, any marine invertebrate of the class Asteroidea (phylum Echinodermata) having rays, or arms, surrounding an indistinct central disk. Despite their older common name, they are not fishes. The...
carpoid
Carpoid, member of an extinct group of unusual echinoderms (modern echinoderms include starfish, sea urchins, and sea lilies), known as fossils from rocks of Middle Cambrian to Early Devonian age (the...
cystoid
Cystoid, any member of an extinct class (Cystoidea) of primitive echinoderms (animals with a hard, calcareous external skeleton, related to the modern sea lily and starfish) that first appeared during...
crinoid
Crinoid, any marine invertebrate of the class Crinoidea (phylum Echinodermata) usually possessing a somewhat cup-shaped body and five or more flexible and active arms. The arms, edged with feathery projections...