What was the 2nd animal on Earth?

What was the 2nd animal on Earth? Sea sponges have been around a long time, but they are at least old enough to be the longest-existing creatures on Earth. The second animal on earth would be the jellyfish, it existed even 505 million years ago. New fossil evidence of jellyfish goes back over half a billion years.

Sea sponges have been around a long time, but they are at least old enough to be the longest-existing creatures on Earth. The second animal on earth would be the jellyfish, it existed even 505 million years ago. New fossil evidence of jellyfish goes back over half a billion years.