Terminal Ediacaran metazoan reefs (c. 548–541 Ma) can be locally substantial and the skeletal metazoans Cloudina riemkeae, C. hartmannae, Namacalathus and Namapoikia produced diverse reef types with complex ecologies in association with varied microbialite support or influence. In the Nama Group, Namibia, metazoan reefs grew in three associations with differing dominant frameworks: (1) monospecific aggregations of Cloudina; (2) Cloudina–Namacalathus–thrombolite assemblages; and (3) thrombolite-dominated metazoan communities. Cloudina hartmannae formed monospecific reefs up to 7 m wide and 3 m high with no microbialite component. The synoptic relief was probably <1 m. Cloudina riemkeae formed densely aggregating assemblages associated with microbialites and thrombolites, each from 30 to 100 mm high, which successively colonized former generations. Isolated Namacalathus either intergrew with C. riemkeae or formed dense, low-relief, monospecific aggregations succeeding C. riemkeae frameworks. Thrombolite-dominated metazoan reefs reached up to 20 m in height and width, with a synoptic relief of up to several metres. Cloudina and Namacalathus grew closely associated with these framework thrombolites and Namapoikia, which was encrusting and modular, reached up to 1 m in size and occupied neptunian dykes and fissures. Cloudina and Namacalathus also grow cryptically, either as pendent aggregations from laminar crypt ceilings in microbial framework reefs, or as clusters associated with thrombolite attached to neptunian dyke walls.
Figures & Tables
This volume in memory of Professor Martin Brasier, which has many of his unfinished works, summarizes recent progress in some of the hottest topics in palaeobiology including cellular preservation of early microbial life and early evolution of macroscopic animal life, encompassing the Ediacara biota. The papers focus on how to decipher evidence for early life, which requires exceptional preservation, employment of state-of-the-art techniques and also an understanding gleaned from Phanerozoic lagerstätte and modern analogues. The papers also apply Martin’s MOFAOTYOF principle (my oldest fossils are older than your oldest fossils), requiring an integrated approach to understanding fossils. The adoption of the null-hypothesis that all putative traces of life are abiotic until proven otherwise, and the consideration of putative fossils within their spatial context, characterized the work of Martin Brasier, as is well demonstrated by the papers in this volume.