Fixed, free, and fixed: The fickle phylogeny of extant Crinoidea (Echinodermata) and their Permian–Triassic origin

Sea Lily Muscle Lacks a Troponin-Regulatory System, While it Contains Paramyosin

“…Moreover, troponin has been detected in actin filament networks in non-striated muscle of the tardigrades (water bears) (Obinata et al, 2011) and in gonad myoepithelial cells of nematodes (Ono and Ono, 2004;Obinata et al, 2010), suggesting the possibility that troponin is involved in the regulation of a variety of motile cells. In this study, we focused on an isocrinid sea lily (stalked crinoid), a taxon that constitutes the most basal group of extant echinoderms (Rouse et al, 2013) and a member of subphylum Pelmatozoa, to clarify whether troponin is lacking from the beginning of the evolution of echinoderms. According to microscopic observations, crinoids, some feather stars, have obliquely striated muscle as many invertebrates of protostomes but an unusual Z-system exists in the crinoid muscle (Candia Carnevali and Saita, 1985;Candia Carnevali et al, 1986).…”

Crinoids from Svalbard in the aftermath of the end−Permian mass extinction

“…For instance, according to the latest edition of the Treatise on In− vertebrate Paleontology, the Articulata is retained as a monophyletic, post−Paleo− zoic clade (Hess and Messing 2011). In accordance with this, recent molecular clocks suggest that articulate crinoids have roots in the Middle-Late Triassic (Rouse et al 2013). The latter study suggested that articulate crinoids likely radi− ated from a small clade that passed through the end−Permian extinction rather than from several surviving lineages.…”

“…From a palaeo− geographic perspective, the Svalbard roveacrinid occurrence is consistent with the circum−Tethyan distribution of this crinoid order, extending far north into the Arctic realm due to surface water circulation that allowed the dispersal of somphocrinid lar− vae as well as of adults during the Late Triassic. The most intriguing discovery may be that of the comatulid−like plates: if these prove to be centrodorsals, they will force a reassessment of previous hypotheses of their Late Triassic origins and imply that the crinoid stalk might have been lost multiple times as previously suggested by mo− lecular data (Rouse et al 2013). Furthermore, discovery of encrinid−like ossicles in the Lower Triassic may solve a long−standing problem concerning the similarities between the late Paleozoic cladid Erisocrinidae and the Triassic encrinids that were long attributable to convergent evolution.…”

“…The latter study suggested that articulate crinoids likely radi− ated from a small clade that passed through the end−Permian extinction rather than from several surviving lineages. However, it should be pointed out that the 95% confidence limits on the Beast analyses extend into the Permian (Rouse et al 2013). Indeed, as highlighted by Roux et al (2013), molecular data of extant cri− noids need to be treated with caution because they can only support the monophyly of the class Crinoidea, not that of the subclass Articulata.…”

Persistent and widespread occurrence of bioactive quinone pigments during post-Paleozoic crinoid diversification

“…verrucosus) with ethanol (Table S2). For reference, authentic samples of gymnochrome B (containing small amounts of gymnochrome A) from N. richeri Recent investigations based on molecular data support the hypothesis that all living crinoids radiated from a small clade that passed through the end-Permian mass extinction, but suggest an earlier divergence of the order Comatulida from other clades (22,23). In present-day comatulids the most abundant pigments are anthraquinones, pyrones, and bianthrones, whereas hypericinoid pigments have been detected only as minor pigments (4).…”