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Ophiocistioidea
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<p>Ophiocistioidea is a class of extinct <a href="/facts/Echinoderm/j2rd8qwt">echinoderms</a> from the <a href="/facts/Palaeozoic/5qe2wz7U">Palaeozoic</a> and early <a href="/facts/Mesozoic/yYsvXGPa">Mesozoic</a>. They most likely form a <a href="/facts/Paraphyletic/tmTWjACz">paraphyletic</a> <a href="/facts/Evolutionary_grade/ssv1Meoz">grade</a> along <a href="/facts/Sea_cucumber/1ruJ7ePx">sea cucumber</a> stem lineage, although some sources still consider the question of ophiocistioid <a href="/facts/Monophyly/pD8Yrrn6">monophyly</a> unresolved. </p>