Using growth models to test the vendobiont hypothesis for the Ediacara Biota
*Renee S. Hoekzema1 and Martin Brasier1
1Department of Earth Sciences, University of Oxford
Although macrofossils from the Ediacara biota (575-542 Ma) have often been interpreted as containing the ancestors of various different metazoan clades, many were united by Seilacher (1989) into a single clade he called the Vendozoa, on the basis of a shared, ‘quilted pneu’ manner of construction. We here test this ‘vendobiont’ hypothesis by comparing the growth mechanisms of macroscopic branches within three iconic and distinct Ediacaran fossil taxa: Dickinsonia costata, Charnia masoni and Charniodiscus spp. These have often been regarded as representatives of distinct clades. We find, however, that these three seemingly disparate forms share very similar modes of growth, involving not only apical insertion of branches either side of a growth axis but also branches that grew in two distinct stages. For every branch in each of these taxa, we can distinguish a juvenile phase of fast growth and a mature phase of slower inflationary growth, for which the ratio remains similar throughout ontogeny. Our evidence strengthens the view that many macro-organisms of the Ediacara biota should be re-considered as members of a single vendobiont clade, as yet lacking clear relationships with modern metazoan groups.
A presentation abstract from the Palaeontological Association 58th Annual Meeting.