Evolutionary Exploitation of Design Options by the First Animals with Hard Skeletons
R. D. K. Thomas,
*
Rebecca M. Shearman,
Graham W. Stewart
The set of viable design elements available for animals
to use in building skeletons has been fully exploited. Analysis of animal skeletons in relation to the multivariate, theoretical "Skeleton Space" has shown that a large proportion of these options are used in each phylum. Here, we show that structural elements deployed in the skeletons of Burgess Shale animals (Middle Cambrian) incorporate 146 of 182 character pairs defined in this morphospace. Within 15 million years of the appearance of crown groups of phyla with
substantial hard parts, at least 80 percent of skeletal design elements
recognized among living and extinct marine metazoans were exploited.
Department of Geosciences, Franklin & Marshall College, Lancaster,
PA 17604, USA.
*
To whom correspondence should be addressed. E-mail:
r_thomas{at}acad.fandm.edu
Present address: Department of Organismal Biology and
Anatomy, University of Chicago, 1027 East 57 Street, Chicago, IL 60637, USA.
Present address: Rose Center for Earth and Space,
American Museum of Natural History, 200 Central Park West, New York, NY 10024, USA.
