Fossil History

From hydrocarbon remains of sterols produced by marine demospongiaes, a record is present for metazoans in the geological records >635MYA. This is based on new high precision geochronology that constitutes a continuous 100MY-long chemical fossil record of Demospogiae (Love et al. 2009).  As they go back so far in the fossil they are sometimes referred to as living fossils (Muller 1998), as they currently represent the oldest evidence of fossils in the fossil record (Love et al 2009).