Australia: The Land Where Time Began

A biography of the Australian continent 

Sponges (Porifera) - Living Metazoans from the Neoproterozoic, Biomineralisation and the Concept of Their Evolutionary Success

The earliest known metazoans date from the Neoproterozoic Era, comprising the Cryogenian Period, which is comprised of 2 (or 3?) major glaciations, the Sturtian Glaciation and the Varanger-Marinoan Glaciation. It was at this time that the Phylum Porifera (sponges), the first animals, evolved and developed a hard skeleton. Hexactinellida and Demospongiae, were 2 classes of siliceous sponges that already had the major gene repertoire and gene regulatory networks that are present in multicellular animals of the present. As well as having these metazoan features the siliceous sponges also had silicatein, an enzyme mediating the formation of biosilica, an autapomorphic character. Fossils of siliceous sponges that are well-preserved have been excavated from the Cambrian age Burgess Shale and Chengjiang Deposits. The Porifera have continued to evolve and survive for the 500 My to the present,

Sources & Further reading

1. Wang, Xiaohong, Shixue Hu, Lu Gan, Matthias Wiens, and Werner E. G. Müller. "Sponges (Porifera) as Living Metazoan Witnesses from the Neoproterozoic: Biomineralization and the Concept of Their Evolutionary Success." Terra Nova 22, no. 1 (2010): 1-11.