Author: Bruce Neville
The phylum Chordata includes three subphyla: the Urochordata or tunicates, the Cephalochordata or lancelets, and the Vertebrata or vertebrates. All Species of the subphyla Urochordata and Cephalochordata are marine, so they do not occur in New Mexico. Members of 5 of the 7 living classes of Vertebrata occur in New Mexico.
The phylum Chordata is characterized by the presence at some stage of life of a notochord, a dorsal hollow nerve cord, and gill slits. The notochord is a stiff dorsal rod of cartilage that provides rigidity and protection for the dorsal nerve cord. It is present in adults of the subphylum Cephalochordata and the fish classes Agnatha and Chondrichthyes, but is replaced by a bony vertebral column in the other classes of the subphylum Vertebrata. The dorsal hollow nerve cord is present in adults of all classes of vertebrates. All fishes and some amphibians have gill slits as adults, but they are present only in the larvae of the other classes of vertebrates. The vertebrates are characterized by the presence of a skull that protects the brain and, in most classes, a cartilaginous or bony vertebral column that protects the spinal cord.
Vertebrates are tremendously varied in body form and include fishes, amphibians, reptiles, birds, and mammals. They range in size from some fishes only an inch long as adults to the blue whale.
Vertebrates are found worldwide, except at the very centers of the polar ice caps.
Vertebrates occur in essentially every habitat on Earth, including the open ocean, the deepest sea bottoms, the air, and the edges of the polar ice caps. They may be marine, freshwater, terrestrial, aerial, or subterranean.
Vertebrates feed on essentially every available source of food. They may be herbivores, carnivores, or omnivores.
Reproduction and Development:
Vertebrates display an amazing range of reproductive adaptations. Some Species lay eggs, while others bear live young. The live young may be nourished by the mother (as in mammals) or simply develop as eggs within the mother's body (as in rattlesnakes). Vertebrates may build a nest and care for the young to varying degrees, or they may simply release their gametes into the environment to develop without help from the parents. Most Species of vertebrate participate in sexual reproduction, but some Species of fishes and reptiles are all female and do not undergo sexual reproduction.
Vertebrates exhibit a wide variety of behaviors.
Vertebrates and arthropods are the two most important groups of animals in nearly every habitat on earth.
Many vertebrate Species have huge populations and are not endangered. Others, however, have limited ranges or have been reduced to such small populations that they are severely endangered.
Subphylum: Urochordata, tunicates (marine; not in New Mexico)
Subphylum: Cephalochordata, lancelets (marine; not in New Mexico)
The 7 living classes of vertebrates are:
Agnatha: Lampreys and hagfishes; not found in New Mexico
Chondrichthyes: Cartilaginous fishes (sharks and rays); not found in New Mexico
Osteichthyes: Bony fishes; many Species in New Mexico
Amphibia: Frogs, salamanders, and caecilians; many Species in New Mexico
Reptilia: turtles, crocodilians, lizards, snakes, and tuatara; many Species in New Mexico
Aves: birds; many Species in New Mexico
Mammalia: mammals; many Species in New Mexico
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Margulis, Lynn, and Karlene V. Schwartz. 1998. Five Kingdoms: an Illustratred Guide to the Phyla of Life on Earth. New York: W.H. Freeman and Co., 520 p.
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