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Echinoderms are among the marine invertebrates that underwent the most severe losses at the end-Permian extinction. The prevailing paradigm claims an extreme bottleneck with only very few, if not single, holdovers ("hangovers" herein) sparking the post-Paleozoic radiation. Here we identify previously overlooked Triassic echinoids, ophiuroids, and asteroids as unambiguous members of Paleozoic stem groups. These echinoderm hangovers occurred almost worldwide and had spread into a wide range of paleoenvironments by the Late Triassic. Our discovery challenges fundamentals of echinoderm evolution with respect to end-Permian survival and sheds new light on the early evolution of the modern clades, in particular on Triassic ghost lineages (i.e., inferred but undocumented fossil record) of the crown-group look-alikes of the Paleozoic hangovers. [ABSTRACT FROM AUTHOR]

Abstract: Colonies of Traumatocrinus (Echinodermata, Crinoidea, Encrinida) attached to driftwood from the Late Triassic (Carnian) Xiaowa Formation of the Guanling area (Guizhou, Southwest China) give evidence for a pseudoplanktonic lifestyle of this specialized offshoot of the otherwise benthic Middle Triassic family Encrinidae. The stem of Traumatocrinus individuals may exceed 11 m in length. Colonies attached by root cirri to logs of driftwood may consist of more than 150 individuals. After the end-Carnian extinction of Traumatocrinus, its ecological niche was taken over in Norian times by Seirocrinus and Pentacrinites with convergent morphological modifications. Seirocrinus and Pentacrinites were derived from the Middle Triassic benthic articulate crinoid family Holocrinidae. After the Toarcian (Lower Jurassic), the niche occupied by Pentacrinitidae disappeared, possibly because of the emergence of wood-boring bivalves and their destructive impact. Due to a larval and adult planktonic and pseudoplanktonic lifestyle, the pelagic Traumatocrinidae were dispersed over the Triassic seas. While genus Traumatocrinus was a Palaeo-Tethys faunal element, its sister genus Vostocovacrinus inhabited the Boreal realm. [Copyright &y& Elsevier]

The article presents author's comments on the Paleozoic stem-group echinoderms that survived the end-Permian extinction. It mentions that the holdovers in post-extinction strata has to be supported by collection of sedimentologic and taphonomic observations. It mentions that the redeposition of echinoderms from older deposits has been excluded.