1. Echinoids (Class Echinoidea) Burt CarterFall, 2012

2. Kingdom Animalia Phylum Echinodermata Animals with: Multi-plated skeletons of high-Mg calcite with a stereom microstructure. A water vascular system. (usually) pentameral symmetry superimposed on underlying bilaterality. Class Echinoidea Free-living echinoderms (“eleutherozoans”) with: the skeleton in the form of a test, which is usually (but not invariably) rigid. moveable spines articulated to tubercles on the test surface.

3. Taphonomy The high-Mg skeleton is mineralogically stable, allowing excellent preservation in most cases. (So-called “perfect” preservation.) Diagenetic syntaxial cementation usually obscures the stereom microstructure. Regular echinoids may have non-rigid tests, and in general the constituent plates are not as well interconnected by connective tissue as in irregular echinoids. Their fossil record is consequently not as complete. Spines are articulated to tubercles only by connective tissue and the muscles that operate the spines, thus they are often lost during biostratinomic alteration. Their function may still be inferred from the muscle scars.

4. ~2cm Periarchus pileussinensis (Ravenel, 1844) #83015 in GSW taxonomic teaching collection (labeled P. lyelli) Aboral View Oral View Anterior Posterior Anterior Posterior Petals (Petaloid Ambulacra) Interambulacra Apical System (Ocular and Genital Pores evident) Tubercles (Completely Cover Both Surfaces) Location of Anus and Periproct Location of Mouth and Peristome Food Grooves (Most of the oral surface is covered by encrusting bryozoa.)

5. Borrowed from the Tree of Life website (tolweb.org)

6. References and Bibliography Cooke, C.W., 1959, Cenozoic echinoids of eastern United States: USGS Prof. Pap. 321, 106 p. Moore, R.C. (ed.), 1966, Treatise on Invertebrate Paleontology, part U, Echinodermata 3: Lawrence, KS, Univ. KS press, 695 p. Ravenel, E., 1844, Description of some new species of organic remains from the Eocene of South Carolina: Acad. Nat. Sci. Philadelphia, Proc., v. 2, 96-98. Smith, A.B., 1984, Echinoid Palaebiology, London, George Allen & Unwin Pub., 190 p.