rtebrates originated about 525 million years ago during the Cambrian explosion, which saw a rise in organism diversity. The earliest known vertebrate is believed to be Myllokunmingia. One of many early vertebrates are 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.[page needed] 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. From fish to amphibians Acanthostega, a fish-like early labyrinthodont. The first jawed vertebrates may have appeared in the late Ordovician (~450 mya) and became common in the Devonian, often known as the "Age of Fishes"
. The two groups of bony fishes, the actinopterygii and sarcopterygii, evolved and became common. The Devonian also saw the demise of virtually all jawless fishes save for lampreys and hagfish, as well as the Placodermi, a group of armoured fish that dominated the entirety of that period since the late Silurian. The Devonian also saw the rise of the first labyrinthodonts, which was a transitional form between fishes and amphibians. Mesozoic vertebrates Amniotes branched from labyrinthodonts in the subsequent Carboniferous period. The Parareptilia and synapsid amniotes were common during the late Paleozoic, while diapsids became dominant during the Mesozoic. In the sea, the bony fishes became dominant. Birds, a derived form of dinosaur, evolved in the Jurassic. The demise of the non-avian dinosaurs at the end of the Cretaceous allowe