<P> Vertebrates originated about 525 million years ago during the Cambrian explosion , which saw the rise in organism diversity . The earliest known vertebrate is believed to be the Myllokunmingia . Another early vertebrate is Haikouichthys ercaicunensis . Unlike the other fauna that dominated the Cambrian , these groups had the basic vertebrate body plan : a notochord , rudimentary vertebrae , and a well - defined head and tail . All of these early vertebrates lacked jaws in the common sense and relied on filter feeding close to the seabed . A vertebrate group of uncertain phylogeny , small - eel - like conodonts , are known from microfossils of their paired tooth segments from the late Cambrian to the end of the Triassic . </P>
when did the first vertebrates appear on earth
about 525 million years ago during the Cambrian explosion