The identity of the British Ordovician cystoid ‘Hemicosmites rugatus Forbes‘

Abstract

New articulated specimens of the British Ordovician cystoid first mentioned under the name ‘Hemicosmites rugatus Forbes’ in 1848 allow its morphology and systematic affinities to be established for the first time. Despite being based on isolated plates, ‘H. rugatus Forbes’ has been reported from England and Wales, Belgium, France, Spain and Thailand, and has been attributed to four genera. It is characterized by a heteromorphic, circular stem, a theca with four basal, six infra‐lateral and eight lateral plates, all with sharp‐crested ridges running to plate angles, multiple arms in each ambulacrum and an extensive tegmen. These characters indicate it belongs in the family Caryocrinitidae and genus Caryocrinites. Caryocrinites rugatus had arms with lateral brachioles that folded in against the main arm axis, as in the type species C. ornatus Say. It is the first Ordovician species known to possess this character. Isolated plates show sorting and a few may represent other species of Caryocrinites s.l. Copyright © 2013 John Wiley & Sons, Ltd.

Testing for homologies in the axial skeleton of primitive echinoderms

“…6 and 7) was a useful initial concept, but it can be extended. For example, their figure 6 implies that all triradiate echinoderms have an ambulacral pattern of A, B + C, D + E. This is true of the hemicosmitoid rhombiferans Hemicosmites von Buch, 1840, Caryocrinites Say, 1825, Juglandocrinus von Koenen, 1886, Paracaryocrinites Chen and Yao, 1993, and Stribalocystites Miller, 1891(Lanc et al, 2015 (Fig. 9), but not of the caryocystitoid rhombiferans Caryocystites, Echinosphaerites, and Heliocrinites with three ambulacra because ambulacrum A is never present in these genera (Bockelie, 1982) (Fig.…”

“…The first few appendage plates are still attached in some species of Hemicosmites (see Bockelie, 1979b). They are biserial and the facets are assumed to have given rise to large arms with biserial brachioles alternating on either side, as in the related genus Caryocrinites (see Sprinkle, 1975;Lanc et al, 2015). The mouth is a three-rayed opening (Fig.…”

Primitive Ordovician (Floian) echinoderms from Sandu, Guizhou Province, South China, and their significance

“…Currently, three families are recognized within the Hemicosmitoida, namely the Hemicosmitidae, Caryocrinitidae and Thomacystidae (see Paul, 1984, p. 84, fig. 57;Lanc et al, 2013). The last is based on the unique genus and species Thomacystis tuberculata Paul, 1969, which is characterized by having three basal, six infra-lateral and eight lateral plates, four ambulacra developed on the oral surface, and the periproct between two lateral and two 'adoral' plates.…”

An association of problematic corals, crinoids and parasites from the Sholeshook Limestone Formation (Ordovician) of Wales

“…3;McDermott and Paul, 2014, fig. The strata are of Cautleyan (Ashgill Series, Zone 2) age of British usage, referable to the Katian Stage of the Upper Ordovician (Ingham and Wright, 1970;Lanc et al, 2013;Ferretti et al, 2014). 1).…”