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There are about 7,600 extant species of echinoderm as well as about 13,000 extinct species. [ 9 ] [ 10 ] All echinoderms are marine , but they are found in habitats ranging from shallow intertidal areas to abyssal depths.
The Eocrinoidea were an extinct class of echinoderms that lived between the Early Cambrian and Late Silurian periods. They are the earliest known group of stalked, brachiole-bearing echinoderms, and were the most common echinoderms during the Cambrian. The earliest genera had a short holdfast and irregularly structured plates. Later forms had a ...
Blastoids (class Blastoidea) are an extinct type of stemmed echinoderm, often referred to as sea buds. [1] They first appear, along with many other echinoderm classes, in the Ordovician period, and reached their greatest diversity in the Mississippian subperiod of the Carboniferous period. However, blastoids may have originated in the Cambrian.
Edrioasteroidea is an extinct class of echinoderms.The living animal would have resembled a pentamerously symmetrical disc or cushion. They were obligate encrusters and attached themselves to inorganic or biologic hard substrates (frequently hardgrounds or brachiopods). [1]
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.
Cystoidea was defined as a class of extinct paleozoic blastozoan echinoderms established to encompass stalked taxa that were neither crinoids nor blastoids. It was shown to be polyphyletic in the late 1960s but continues to be used even in recent (as of 2022) literature to discuss both rhombiferans and diploporitans. [1]
Yanjiahella biscarpa is an extinct species of Early Cambrian deuterostome which may represent the earliest stem group echinoderm. [1] [2]This species is known from the Fortunian Yanjiahe Formation (~541.0–534.6 Ma) in Hubei province, China and was first described by Guo et al. [3] who had difficulty in assigning a taxonomy to the animal due to the shared nature of its features between the ...
Cornuta is an extinct order of echinoderms. Along with the mitrates, they form the Stylophora. Their first (probable) representative is Ponticulocarpus from the Spence Shale (mid Cambrian);, [1] Ordovician examples also exist.