The skull names come from the word "apse," a Latin word that means "arch." The number and type of arches, or "fenestrae" (Latin for "windows"), give the skull types their names. "Why would you want to have a hole or an arch in your skull?" you may ask. These openings actually give the skull extra space for the attachment of jaw muscles, allowing animals to snap their jaws shut more forcefully.
For reasons of length, this article will provide a rather cursory look at the types of skulls that we see in the reptiles; there is simply no way that I could go into great detail about skulls without writing a book! For more information, I recommend Prehistoric Life: The Rise of the Vertebrates by David Norman, which has much more extensive information about the development of the different skull types, as well as other information about the development of vertebrates through time.
The anapsids were the first reptiles to appear in the fossil record in the Carboniferous Period (345 to 280 million years ago). "Anapsid" means "without an arch", and the anapsids have no fenestrae in their skulls. The anapsids were first represented by the small, herbivorous Procolophonids, and the much larger, herbivorous Pareiasaurs. These two groups were never particularly successful, and were displaced by the synapsids toward the end of the Carboniferous Period. One group of anapsid animals that still survive today are the turtles, who first arose during the Triassic Period (230 to 195 million years ago).
The next group are the synapsids, who have one fenestra low on either side of the skull. "Synapsid" means "together arch." The synapsids were the dominant land vertebrates from the Late Carboniferous Period (280 to 230 million years ago) to the end of the Triassic Period (230 to 195 million years ago). Although the syanpsids are reptiles, they gave rise to mammals, and are usually referred to as "mammal-like reptiles." Dimetrodon is probably the most famous of the synapsids (see my article "Dimetrodon" for more information).
Go To Page: 1 2
