Letters to Nature

Nature 417, 841-844 (20 June 2002) | doi:10.1038/nature00805; Received 26 July 2001; Accepted 12 March 2002

Paired gill slits in a fossil with a calcite skeleton

Patrício Dominguez1,2, Antone G. Jacobson3 & Richard P. S. Jefferies1

  1. Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
  2. Patterson Labs, MCDB, The University of Texas, Austin, Texas 78712, USA
  3. Departamento de Paleontologia, Universidad Complutense de Madrid, Ciudad Universitaría, 28040 Madrid, Spain

Correspondence to: Richard P. S. Jefferies1 Correspondence and requests for materials should be addressed to R.P.S.J. (e-mail: Email: r.jefferies@nhm.ac.uk).

The chordates, hemichordates (such as acorn worms) and echinoderms (such as starfish) comprise the group Deuterostomia, well established as monophyletic1, 2. Among extant deuterostomes, a skeleton in which each plate has the crystallographic structure of a single crystal of calcite is characteristic of echinoderms and is always associated with radial symmetry and never with gill slits. Among fossils, however, such a skeleton sometimes occurs without radial symmetry. This is true of Jaekelocarpus oklahomensis, from the Upper Carboniferous of Oklahoma, USA, which, being externally almost bilaterally symmetrical, is traditionally placed in the group Mitrata (Ordovician to Carboniferous periods, 530–280 million years ago), by contrast with the bizarrely asymmetrical Cornuta (Cambrian to Ordovician periods, 540 to 440 million years ago). Using computer X-ray microtomography, we describe the anatomy of Jaekelocarpus in greater detail than formerly possible, reveal evidence of paired gill slits internally and interpret its functional anatomy. On this basis we suggest its phylogenetic position within the deuterostomes.