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Proc Biol Sci. 2017 Sep 13;284(1862). pii: 20171189. doi: 10.1098/rspb.2017.1189.

An edrioasteroid from the Silurian Herefordshire Lagerstätte of England reveals the nature of the water vascular system in an extinct echinoderm.

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Department of Geology and Geophysics, and Yale Peabody Museum of Natural History, Yale University, PO Box 208109, New Haven, CT 06520-8109, USA
Oxford University Museum of Natural History, Oxford OX1 3PW, UK.
Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK.
Department of Geology, University of Leicester, Leicester LE1 7RH, UK.
Department of Earth Sciences and Engineering, Imperial College London, London SW7 2BP, UK.


Echinoderms are unique in having a water vascular system with tube feet, which perform a variety of functions in living forms. Here, we report the first example of preserved tube feet in an extinct group of echinoderms. The material, from the Silurian Herefordshire Lagerstätte, UK, is assigned to a new genus and species of rhenopyrgid edrioasteroid, Heropyrgus disterminus The tube feet attach to the inner surface of compound interradial plates and form two sets, an upper and a lower, an arrangement never reported previously in an extant or extinct echinoderm. Cover plates are absent and floor plates are separated creating a large permanent entrance to the interior of the oral area. The tube feet may have captured food particles that entered the oral area and/or enhanced respiration. The pentameral symmetry of the oral surface transitions to eight columns in which the plates are vertically offset resulting in a spiral appearance. This change in symmetry may reflect flexibility in the evolutionary development of the axial and extraxial zones in early echinoderm evolution.


Echinodermata; Edrioasteroidea; Herefordshire Lagerstätte; Silurian; water vascular system

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