A pipiscid-like fossil from the Lower Cambrian of south China

Abstract

Exceptional fossil preservation is critical to our understanding of early metazoan evolution. A key source of information is the Burgess Shale-type faunas1,2,3,4,5. Fossils from these deposits provide important insights into metazoan phylogeny, notably that of stem-group protostomes2,3,6, and related topics such as trophic specialization7. Metazoan relationships are also being significantly reappraised in terms of molecular-based phylogenies8,9, but integration of these data with palaeontological systematics is not straightforward10,11. Moreover, molecular phylogenies are silent concerning the anatomies of stem-groups and the functional transitions that underpin the origin of different body plans2,6. Some hitherto enigmatic fossils possess unique character–state combinations that, although they can be shoe-horned into extinct phyla12, may be more profitably interpreted as defining major stem-groups2,3. Here we describe a possible pipiscid, a metazoan previously known only from the Upper Carboniferous13,14, from the Lower Cambrian of south China. Pipiscids are currently interpreted as being agnathan chordates13,14,15, but this discovery from the Chengjiang fossil-Lagerstatte indicates that the assignment of pipiscids to the Agnatha deserves to be reconsidered.