First Animals on Earth?

Eoporpita – A radially symmetrical specimen about 6 cm in diameter. Most scientists believe it was similar to Cyclomedusa, a bottom dwelling Cnidarian. It has a medusa-shaped body, with clearly visible tentacles hanging down from the sides, although Eoporpita may be a Hydroid colony, not one single animal, similar to today’s Man-O’-War “Jellyfish” (although not one).

Nemiana – an elusive, globular fossil that appears to be extremely rudimentary and simple. Little can be made of its simple anatomy, but some researchers speculate that they may be some sort of anemone, although it lacks tentacles. Some say that it could even be a massive protist or perhaps an alga.

Pteridinium – Perhaps an ancient Cnidarian or even belonging to an unknown phylum, Pteridinium has an elongated body with the appearance of ribs running down its body. It does not resemble any extant life on this planet.

Arkarua – The best bet for Arkarua’s identity is an echinoderm. You can barely make out the classic 5-fold symmetry of Echinoderm’s in the fossil, though this is far from proven. If this guess is true, then it is the oldest known echinoderm fossil in record.

Dickinsonia – looking like a ovular footprint, Dickinsonia fossils has been found in south Australia and in northern Russia. It looks somewhat like an annelid, because of resemblances with the extant polychaete genus, Spinther, or others may conclude that it is a Cnidarian polyp.

Spriggina – also a very controversial fossil, it appears that Spriggina may have affinities with either the Annelida (as was originally proposed) or the Arthropoda (recently popular idea). Although the Arthropoda are strictly a phylum of hard-bodied organisms, Spriggina is most likely soft-bodied. It has a crescent-shaped head, and little is known of its appendages. A key feature of Spriggina is its segments running throughout its body, which is a characteristic of both the Annelida (earthworms, polychaetes, etc.) and the Arthropoda (”bugs”, ants, moths, and the like).

Tribrachidium – a fossil of its own eccentricity, Tribrachidium is a triradially symmetrical animal. It has been linked to either phylum Cnidaria (jellies, etc.) or phylum Echinodermata (starfish, crinoids, etc.).

Kimberella – a very interesting and controversial Ediacaran fossil. Originally thought to be a Box Jellyfish from the looks of a few specimens from Australia, a group of researchers found the same fossils in Russia, but proved them to be bilateral animals, possibly Molluscs, although little can be made of their fossils.