Open AccessTracing the evolution of the holothurian body plan through stem‐group fossils
Author(s) -
Smith Andrew B.,
Reich Mike
Publication year - 2013
Publication title -
biological journal of the linnean society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.906
H-Index - 112
eISSN - 1095-8312
pISSN - 0024-4066
DOI - 10.1111/bij.12073
Subject(s) - biology , body plan , echinoderm , coelom , devonian , deuterostome , paleontology , phylogenetics , phylogenetic tree , anatomy , evolutionary biology , group (periodic table) , zoology , gene , biochemistry , chemistry , organic chemistry
The fossil echinoderm P alaeocucumaria , from the early D evonian H unsrück S late of southwestern G ermany, has been studied using both traditional techniques and X ‐ray microtomography, and its anatomy clarified. Phylogenetic analysis shows that it is a stem‐group holothurian with a combination of characters that help understand how the modern (crown‐group) holothurian body plan developed. Echinoids and holothurians have evolved along different paths, by differential growth of the larval‐ and rudment‐derived body regions. P alaeocucumaria shows that late stem‐group holothurians had a water vascular organization with a single external madreporite and calcified stone canal leading to the aboral end of the peripharyngeal coelom, and five primary radial water vessels that gave rise to tentacle‐like tube‐feet. This fossil data, in combination with a molecular phylogeny based on 18 s‐like r RNA gene sequence data, is used to order evolutionary steps in the making of the crown‐group holothurian body plan. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society , 2013, 109 , 670–681.