Cincta

Trochocystites bohemicus, photographed by J. R. Barbour.

Belongs within: Echinodermata.

The Cincta are a Middle Cambrian group of non-pentamerous echinoderms, with a shape broadly reminiscent of a frying pan or a tennis racquet. The flattened theca bears an elongate, rigid stele; cinctans possibly lived with the stele angled into the sediment to anchor the animal in place.

Characters (from Ubaghs 1967): Homalozoa with skeleton composed of theca and stele; theca depressed in plane (extension plane) passing through main orifices and stele attachment, with convex surface (superior face) and opposite flat or slightly concave surface (inferior face) united in girdling frame of thick marginal plates; superior face formed within marginals by numerous loosely joined plates termed supracentrals except near pole opposed to stele where they fuse or are replaced by row of stout suranal plates; at absteleal pole and excavated in marginal frame is large thecal orifice inferred to mark location of anus; it is protected by apparently movable plate designated as operculum; adjacent is smaller circular orifice that probably represents mouth; periphery of theca adjacent to presumed mouth bearing one or generally two epithecal grooves hollowed in outer face of marginals, grooves conpected to mouth and protected by multitude of minute cover plates; inferior thecal face formed within marginals of close-fitting polygonal infracentrals, without orifices. Stele tapered, depressed in same plane as theca, with convex superior face in form of ridge and flat or slightly convex inferior face which meet laterally as angled keels, constructed of two rows of opposed or alternating ossicles (dimeres) between which variable number of small irregular platelets commonly are intercalated on superior and inferior faces; narrow axial cavity of stele confluent with thecal cavity.

<==Cincta [Homostelea, Marginata]
    |  i. s.: Asturicystis EL11
    |         Protocinctus EL11
    |--Gyrocystidae U67
    |    |--Decacystis Gislén 1927 U67
    |    |    `--*D. hispanica Gislén 1927 U67
    |    `--Gyrocystis Jaekel 1918 [incl. Sucocystis Termier & Termier 1958] U67
    |         |--G. barrandei (Munier-Chalmas & Bergeron 1889) (see below for synonymy) U67
    |         `--‘*Sucocystis’ theronensis Termier & Termier 1958 U67
    `--Trochocystitidae [Trochocystidae] U67
         |--Trochocystoides Jaekel 1918 U67
         |    `--*T. parvus Jaekel 1918 U67
         `--Trochocystites Barrande 1887 [=Trochocystis Haeckel 1896; incl. Trigonocystis Haeckel 1896] U67
              |--*T. bohemicus Barrande 1887 [=*Trochocystis bohemicus] U67
              |--T. longifossatus Jaekel 1918 J18
              `--‘*Trigonocystis’ trigona Haeckel 1896 U67

Gyrocystis barrandei (Munier-Chalmas & Bergeron 1889) [=Trochocystites barrandei; incl. T. occidentalis Jaekel 1901, *Gyrocystis platessa Jaekel 1918] U67

*Type species of generic name indicated

REFERENCES

[EL11] Erwin, D. H., M. Laflamme, S. M. Tweedt, E. A. Sperling, D. Pisani & K. J. Peterson. 2011. The Cambrian conundrum: early divergence and later ecological success in the early history of animals. Science 334: 1091-1097.

[J18] Jaekel, O. 1918. Phylogenie und System der Pelmatozoen. Paläontologische Zeitschrift 3: 1-128.

[U67] Ubaghs, G. 1967. Homostelea. In Treatise on Invertebrate Paleontology pt. S. Echinodermata 1. General characters. Homalozoa-Crinozoa (except Crinoidea) (R. C. Moore, ed.) vol. 2 pp. S565-S581. The Geological Society of America, Inc., and The University of Kansas: Lawrence (Kansas).