This is a simplified evolutionary tree of six representative animal phyla, illustrating differences in body form, habitat, and species numbers among them. This visual may only be used in ...

Our collections cover all of the living invertebrate phyla, including Onychophora (velvet worms), Chaetognatha ... (horseshoe worms), Priapulida (penis worms), Rotifera (wheel animals) and Tardigrada ...

But then in the blink of an eye on a geological timescale, the first major animal phyla appeared, including arthropods, mollusks, echinoderms, and early vertebrates. This was a period of intense ...

Q: How did these different kinds of eyes evolve? A: The traditional idea is that the eyes evolved separately into separate animal phyla. An insect eye looks so different from a human eye that one ...