ORGANIC MATRIX IN THE EARLY CAMBRIAN: PHYSICAL EVIDENCE AND SIGNIFICANCE

The organic matrix associated with biomineralization processes in carbonate skeletons has previously been reported in representatives of modern mollusks, brachiopods, bryozoans, cirriped arthropods, corals, sponges, and foraminifera, and in degraded form in fossil representatives of some of these groups as old as Silurian.

The fundamental structure of this organic matrix is a nodular strand, with a typical nodule diameter of approximately 30 nanometers. This is generally built into a two-dimensional, lace-like mesh, and in advanced forms this mesh can be further configured into complex structural units. During fossilization, even the more complex units gradually degrade, first into a mesh and later into individual strands. Remarkably, the degraded matrix is sometimes preserved even in recrystallized fossil skeletons.

I can now add evidence for such matrix, including degraded fragments of mesh, in the skeletal elements of archaeocyathids from the Lower Cambrian Poleta formation in Esmeralda County, Nevada. This, together with the multi-phylum distribution of the organic matrix, has significant implications for the origins and evolution of matrix-based carbonate biomineralization in the early Phanerozoic.