Real Fossil Algae Receptaculites oweni

Description: These are often described as sunflower coral, which is dead wrong. Previously assigned to sponges, they are now widely accepted as fossil algae colonies. They are found throughout North America in lower Ordovician through the Permian formations, and typically measure from a few inches to a foot in diameter. Interestingly, stromatolites are often mistakenly called fossil algae that is obsolete science, as algae probably did not evolve until the late Proterozoic. Also interesting is that some scientists, based on sequencing, dispute that algae which lacks a vascular system should be grouped with Kingdom Plantae.

This is both a finely detailed and huge Receptaculites. It is the skeletal remains, so to speak, of a colony of algae. By the Ordovician, stromatolites formed by prokaryotic bacteria has undergone steep decline, and stromatolites were then being formed by microbial mats of algae. Seldom do you see them this large and complete.