Phylum Chordata. A Tribute to the Diversity We Know. Introduction. Members of the Phylum Chordata include animals with which we are probably most likely familiar (including fish, birds, reptiles, amphibians and beasts like ourselves)
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A Tribute to the Diversity We Know
Four structural characteristics set chordates apart from all other phyla:
a pharyngeal gill slits
a hollow dorsal nerve cord
These attributes are always found in the larval forms or early embryo (although they may be absent in the adult).
The notochord is mainly composed of fibrous connective tissue
For those animals in which it persists into the adult form, the notochord provides support (it acts like our backbone) and increases swimming efficiency
In animals like ourselves, bony structures called vertebrae develop near the notochord and eventually replace it during embryogenesis
Pharyngeal gill slits are cuts in the pharynx that connect to a cavity surrounding the pharynx
For organisms in which they remain in the adult, they are often elaborated into respiratory structures (and are sometimes involved in filtering food during feeding).
The morphological equivalent of gill silts are seen briefly during our own development (weeks 4-5), but they usually close or develop into other structures
Occasionally, the slits do not close, resulting in the newborn having an opening in the neck area (a cervical fistula).
In all the phyla we have studied up to this point, the anus was terminal (at the tip of the tail)
Chordates, on the other hand, follow the anus with a tail of variable length (again, an adaptation for locomotion).
In us, the tail is short and fused (the coccyx at the base of your spine).
Superclass Gnathostomata can be broken up into the following classes:
Subclass Actinopterygii Subclass Sarcopterygii
(ray-finned fishes) (lobe-finned fishes)
absence of certain temporal openings:
You need to know the Eutherian orders:
Artiodactyla (deer, goat, pig)Macroscelidea (elephant shrews)
Carnivora (bears, wolves)Perissodactyla (horses, rhinos)
Cetacea (whales, dolphins)Pholidota (the pangolin)
Chiroptera (bats) Primates (monkeys, apes)
Edentata (armadillo, sloth) Proboscidea (elephants)
Hyracoidea (hyraxes)Rodentia (rats, mice)
Insectivora (shrew, hedgehog)Sirenia (manatees)
Lagomorpha (rabbits)Tubulidentata (aardvarks)
Pinnipedia (seal, walrus)