Figure 3

Fig. 3. Stem-group (A to E) and crown-group (F to H) echinoderms. (A) Thestylophoran Cothurnocystis bifida (Middle Cambrian, Utah, USA). The putative gill skeletons as viewed from the back side are indicated with an arrowhead. M is the putative mouth. The arrow indicates the posterior appendage. (B) The solute Coleicarpus sprinklei (Middle Cambrian, Utah, USA). The arrow indicates the posterior appendage, and the double arrow points to the single ambulacrum. (C) The helicoplacoid Helicoplacus (Early Cambrian, California, USA). The double arrow points to one of the ambulacral grooves. (D) The eocrinoid Gogia spiralis (Middle Cambrian, Utah, USA). The double arrow points to one of the five arms. (E) The edrioasteroid Edriophus bigsbyi (Ordovician, Ontario, Canada). It displays conspicuous pentameral symmetry; one of the arms is indicated by the double arrow. (F) The crinoid Dorycrinus mississippiensis (Mississippian, Indiana, USA). (G) The asteroid Furcaster palaeozoicus (Devonian, Budenbach, Germany). (H) The echinoid Bothriocidaris (Ordovician, Estonia) [reprinted with permission from A. B. Smith, from (30)]. Scale bar, 0.5 cm in (A); 0.75 cm in (B) to (E); 2 cm in (F); 1.3 cm in (G); and 0.15 cm in (H). Part of a penny is shown for scale in (C). [View Larger Version of this Image (263K JPEG file)]

 

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