Evolution What the Fossils Say and Why it Matters

Porifera

Ctenophora

Cnidaria

Lobopodia

Tardigrada

Chelicerata

Crustacea

Myriapoda

Insecta

Nematoda

Rotifera Platyhelmintha

Nemertini

Annelida

Mollusca

Hemichordata

Tunicata

Vertebrata

Bryozoa

Chengjiang Burgess Shale

Crown Group Bilaterians Total Bilaterians

Crown Group Metazoans

Vendian Cambrian Ordovician Silurian Devonian Carboniferous Permian

Priapulida

Chaetognatha

Brachiopoda

Echinodermata

Cephalochordata

FIGURE 5.7. The branching history of the animals, based on molecular data. (Drawing by Carl Buell; modified
from Briggs and Fortey 2005: fig. 2)