Key Concepts. Most animal phyla that exist today trace back to the Cambrian Period, more than 500 million years ago. Although all animal phyla originated in the oceans, members of a few phyla, including bacteria, insects, and vertebrates, have colonized the land.

What animal phylum came first?

Summary: Who came first – sponges or comb jellies? A new study reaffirms that sponges are the oldest animal phylum – and restores the classical view of early animal evolution, which recent molecular analyses had challenged.

When did animal phyla appear?

The Cambrian explosion or Cambrian radiation was an event approximately 541 million years ago in the Cambrian period when practically all major animal phyla started appearing in the fossil record.