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The name echinoderm is from Ancient Greek ἐχῖνος (ekhînos) 'hedgehog' and δέρμα (dérma) 'skin'. [5] Echinoderms are bilaterians , meaning that their ancestors were mirror-symmetric. Among the bilaterians, they belong to the deuterostome division, meaning that the blastopore , the first opening to form during embryo development ...
The name urchin is an old word for hedgehog, which sea urchins resemble; they have archaically been called sea hedgehogs. [6] [7] The name is derived from the Old French herichun, from Latin ericius ('hedgehog'). [8] Like other echinoderms, sea urchin early larvae have bilateral symmetry, [9] but they develop five-fold symmetry as they mature ...
Hemichordata (/ ˌhɛmɪkɔːrˈdeɪtə / HEM-ih-kor-DAY-tə) is a phylum which consists of triploblastic, eucoelomate, and bilaterally symmetrical marine deuterostome animals, generally considered the sister group of the echinoderms. They appear in the Lower or Middle Cambrian and include two main classes: Enteropneusta (acorn worms), and ...
Torquaratoridae. The acorn worms or Enteropneusta are a hemichordate class of invertebrates consisting of one order of the same name. [2] The closest non-hemichordate relatives of the Enteropneusta are the echinoderms. [3] There are 111 known species of acorn worm in the world, [4] the main species for research being Saccoglossus kowalevskii.
Ctenocystoidea is an extinct clade of echinoderms, which lived during the Cambrian and Ordovician periods. Unlike other echinoderms, ctenocystoids had bilateral symmetry, or were only very slightly asymmetrical. They are believed to be one of the earliest-diverging branches of echinoderms, with their bilateral symmetry a trait shared with other ...
Helicoplacus. Helicoplacus (often misspelled Helioplacus) is the earliest well-studied fossil echinoderm. Fossil plates are known from several regions. Complete specimens were found in Lower Cambrian strata of the White Mountains of California. The animal was a cigar-shaped creature up to 7 centimetres (2.8 in) long that stood upright on one end.
Pages in category "Echinoderm anatomy" The following 15 pages are in this category, out of 15 total. This list may not reflect recent changes. A. Ambulacral;
Sea urchins, by Nick Hobgood (edited by Lycaon) Echinaster sepositus, by Poco a poco. Sphaerechinus granularis, by Poco a poco. Luidia senegalensis, by Andrea Westmoreland. Acanthaster brevispinus, by Matt Kieffer (edited by Cangadoba and Archaeodontosaurus) Anatomical diagram of a starfish, by Hans Hillewaert (edited by Slashme) Eucidaris ...