section_path: Evolutionary history/First vertebrates
section_name: First vertebrates
paragraph_text: First vertebrates
  
  Vertebrates originated during the Cambrian explosion, which saw a rise in organism diversity. The earliest known vertebrates belongs to the Chengjiang biota and lived about 518 million years ago. These include Haikouichthys, Myllokunmingia, Zhongjianichthys, and probably Haikouella. 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.