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  • chordates
  • Schematic phylogeny of the chordates, indicating the time of origin of molecules involved in specific immunity in vertebrates. (els.net)
  • The defining characteristic of a vertebrate is the vertebral column, in which the notochord (a stiff rod of uniform composition) found in all chordates has been replaced by a segmented series of stiffer elements (vertebrae) separated by mobile joints (intervertebral discs, derived embryonically and evolutionarily from the notochord). (wikipedia.org)
  • Devonian
  • Furthermore, the late Devonian event is only significant in that it was the first land invasion by vertebrate organisms, and that it resulted in an explosion of vertebrate biodiversity due to the many different niches that these species were able to exploit. (wikipedia.org)
  • traits
  • Vertebrates share other traits as well: an internal skeleton, muscles, a protective skin, blood that circulates through vessels, and an advanced nervous system, including a head with a brain. (amnh.org)
  • early
  • Cephalaspis, one of an early group of vertebrates called ostracoderms, possessed an external bony head shield, but probably its internal skeleton was not ossified to any great extent. (britannica.com)
  • comparable
  • A slight swelling of the anterior end of the nerve cord is found in the lancelet, a chordate, though it lacks the eyes and other complex sense organs comparable to those of vertebrates. (wikipedia.org)