Characteristic of the Neoproterozoic and Cambrian epochs, the heterogeneous group called calcimicrobes are calcareous colonial microfossils, which include many morphologically dissimilar organisms, whose effect in massive aggregations, in association with shelly metazoans, was to lay down the earliest recognizable reef systems: compare Archaeocyathids. The earliest recognizable patch reefs date to the Tommotian. Individual calcimicrobes laid down calcium carbonate in tubules, threads, chambered structures and other forms. The term calcimicrobe is useful in recreating the paleoecology of these systems. The term was first applied by N.P. James and D.I. Gravestock in 1990. The Neoproterozoic is the geological era from 1000 Ma to 542 Ma (million years ago). ... The Cambrian is a major division of the geologic timescale that begins about 542 Ma (million years ago) at the end of the Proterozoic eon and ended about 488. ... Phyla Radiata Cnidaria Ctenophora - Comb jellies Bilateria Protostomia Acoelomorpha Platyhelminthes - Flatworms Nemertina - Ribbon worms Gastrotricha Gnathostomulida - Jawed worms Micrognathozoa Rotifera - Rotifers Acanthocephala Priapulida Kinorhyncha Loricifera Entoprocta Nematoda - Roundworms Nematomorpha - Horsehair worms Cycliophora Mollusca - Mollusks Sipuncula - Peanut worms Annelida - Segmented worms Tardigrada - Water bears Onychophora - Velvet worms Arthropoda - Insects, etc. ... A reef surrounding an islet. ... The Archeocyatha, also called Archaeocyathids, were sessile, reef-building marine organisms that lived during the Lower Cambrian period (500-600 million years ago). ... The Tommotian Age is an early part of the Cambrian period. ... Calcium carbonate is a chemical compound, with chemical formula CaCO3. ... you doedd you flydndoedd ha ha ha ha aha ...

References

• James, ,N.P.and D.I.Gravestock.1990. "Lower Cambrian shelf and shelf margin buildups, Flinders Ranges, South Australia." Sedimentology 37:455–480.