Vertebrates originated around 525 million years ago during the Cambrian explosion, with the earliest known being the Myllokunmingia. Early vertebrates all had a notochord, vertebrae, and a well-defined head and tail, and lacked jaws, instead filter feeding. Jawed vertebrates first appeared in the Ordovician period and diversified greatly in the Devonian era, when amphibians also emerged and bony fishes split into two groups.

1. Vertebrates Evolutionary History
Vertebrates originated about 525 million years in the Cambrian explosion. The earliest known
vertebrate is the Myllokunmingia, which was a creature that was a fish with a skeleton made of
cartilage. All of the vertebrates had the same body type: notochord, vertebrae, and well-defined
head and tail. All of the early vertebrates lacked jaws and filter fed. The first jawed vertebrates
appeared during the Ordivician period and the group significantly grew in the Devonian period.
Both groups of bony fishes appeared. During the Devonian, all of the jawless fishes disappeared
except for lampreys and hagfish, and amphibians appeared. Reptiles appeared in the
Carboniferous period. From dinosaurs arose the birds during the Jurassic period. After the
dinosaurs died at the end of the Cretaceous period, mammals became prominent. Since the
demise of the dinosaurs, all the classes of vertebrates have greatly diversified.