were jellyfish and worms the first animals???

Question

[edit] Timeline
Period Animals Year
Precambrian Jellyfish, Worms 3500 mya (mya - million year ago)
Cambrian Sellfish, corals, jawless fish 570 mya
Ordovician 505 mya
Silurian First land plants 438 mya
Devonian Insects, spiders 408 mya
Carboniferous First reptile 360 mya
Permian 286 mya
Triassic Dinosaurs, mammals, frogs 245 mya
Jurassic First birds 208 mya
Cretaceous Snakes, first mordern animals 144 mya
Palaeocene Owls, shrews 65 mya
Eocene Horses, dogs, cats, elephants, rabbit 58 mya
Oligocene Deer, pigs, monkeys, rhino 37 mya
Miocene Mice, rats, apes 24 mya
Pliocene Cattle, sheep 5 mya
Pleistocene (ice age) Homo sapien 2 million years ago



from wikipedia

Answer 1

This is a very interesting question. No one knows the answer to this since there are no fossils to guide us. However, it seems that the earliest multicellular animals were probably somewhat like "Hydra", which are the earliest animals that share Hox genes with us. These animals were likely to be free swimming and having only one "hole" that served as both mouth and anus. Subsequently these creatures evolved into Jellyfish-like creatures and then later to worm-like creatures, which became eel-like creatures, then shark-like creatures, etc, etc.The embryologic remnant of this hole is likely to be your belly button. If you are further interested in this subject, I highly recommend the book "The Ancestor's Tale" by Richard Dawkins.