Xl dating Odense
Phylogenomic extrapolations indicate the last common ancestor of sponges and eumetazoans existed deep in the Cryogenian, perhaps 200 million years (Myr) before the Cambrian (541 Ma).
In addition, the recovery from Cryogenian-aged rocks of an organic sterol biomarker that is synthesized by marine demosponges suggested the early presence of this poriferan clade (12), although the conclusion that the provenance of this fossil sterol indicates the existence of Cryogenian sponges is now also questioned (7).
Despite phylogenomic extrapolations that indicate divergence of sponge lineages from eumetazoan lineages deep in Precambrian time, lack of substantial paleontological evidence directly supporting this prediction has thus remained frustrating.
A dense patch of external structures that display the form of a lawn of sponge papillae has also survived.
Within the main funnel, an area where features of the inner surface are preserved displays a regular pattern of uniform pits.
This sponge/eumetazoan ancestor is predicted by phylogenomics to have lived deep in the Cryogenian (6), the geological period that terminated with the end of the Snowball Earth glaciations at 635 Ma, although how deep is not clear at present (7).