"Like many modern-day animal groups, ecdysozoans were prevalent in the Cambrian fossil record and we can see evidence of all three subgroups right at the beginning of this period, about 540 ...
Fossil of Protorosaurus speneri. Image by suvuk79 - Own work, Copyrighted free use, https://commons.wikimedia.org/w/index.php?curid=86190644, via Wikimedia Commons ...