Chordates, members of the animal phylum Chordata, which includes all mammals, birds, amphibians, reptiles, and fish. There are about 45,000 species of chordates. They are classified in four subphyla, the largest of which contains the vertebrates. All chordates share three basic characteristics. The first characteristic is a single dorsal nerve cord, which in mammals takes the form of the brain and spinal cord. The second is a flexible rod of cells called a notochord, which in vertebrates takes the form of the backbone. The third is the presence of gill slits at some stage during the development of the animal. All chordates have bilateral symmetry.
Cahow, or Bermuda Petrel is an ocean bird that nests only in Bermuda. Like other petrels, the bird lives at sea for seven or eight months, returning to shore to nest in burrows and raise its young.
Gallimimus ("chicken mimic") was the largest of the ornithomimids (the "ostrich dinosaurs") known. It has been found only in the Late Cretaceous Nemegt Formation of Mongolia. Learn more about the Gallimimus and other Late Cretaceous dinosaurs.