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Role in Cambrian
Last modified : 26 October 2012
- ARCHAEOCYATHA - A knowledge base
IntroductionArchaeocyaths are exclusively Cambrian fossils. They built the first metazoans bioconstructions. Since the discovery of living aspiculate sponges, their systematic position has been controversial but now a consensus has been found: archaeocyaths represent an extinct class of the phylum Porifera, closed to the Demospongiae. (Debrenne & Vacelet 1984).
The archaeocyathan skeleton is often composed of two inverted porous cones, fitting into each other, interpreted as outer and inner walls delimiting the intervallum. Vertical radial elements (septa, taeniae...) and/or horizontal elements (tabulae) connect the two walls.
Figure 1: Stylized archaeocyathan skeleton (DEBRENNE 1964, modified)The archaeocyathan cups display various architectural types: one-walled conical, single-chambered subspherical, multi-chambered conical (thalamid), chaetetid, and syringoid.
Figure 2: Different architecture of archaeocyathan cups
Figure 3: Examples of solitary and modular archaeocyathan (A.KERNER)Archaeocyathan systematics is based on skeletal ontogeny determining the order of appearance of skeletal elements, their complexification and the stabilization of adult features (Debrenne et al. 1990, Debrenne & Zhuravlev 1992b and Debrenne et al. 2002)