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Crinoidea - Hybocrinida
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
|D. F. Wright et al. 2017||The Hybocrinida is stem-defined as the most inclusive clade containing Hybocrinus conicus Billings, 1857 and Hybocystites problematicus Wetherby, 1880 but not Porocrinus conicus Billings, 1857 and Carabocrinus radiatus Billings, 1857.
In addition to having a pseudomonocyclic calyx (infrabasals absent), hybocrinids are characterized by a number of unusual apomorphies that distinguish them from Porocrinids (and all other crinoids). Many of these traits are similar to those typically present in blastozoan echinoderms, including reduction in the number of arms, modification of food-gathering appendages to be recumbent (sometimes extending downward
over calyx plates), and reduction in the number of calyx plates (Sprinkle and Moore, 1978).
[Wright et al., 2017]