Dimetrodon was one of the mammal-like reptiles, and belonged to the group of reptiles we call the Pelycosaurs. Dimetrodon is often mistakenly called a dinosaur, and I will discuss why it was not really a dinosaur in this article.
The Pelycosaurs first appeared in the late Carboniferous Period (about 300 million years ago), soon after the first reptiles colonized the land. They started out as small, lizard-like reptiles, but rapidly developed into many different types. The Pelycosaurs are grouped into four families, the first family was the Ophiacodontia, and the other three families arose from this group. Two families were herbivorous (plant eating), the Edaphosauria and the Caseids. The fourth family, the Sphenacodontia, was carnivorous (meat eating); the Sphenacodontia are the direct ancestors of the therapsids (the group that mammals are in), and is the family that Dimetrodon is placed in. (See my article "Biological Nomenclature" for more information about how biologists divide animals into groups.)
The Pelycosaurs were the dominant land animals of the lower Permian Period (about 280 to 260 million years ago), and Dimetrodon was probably the dominant predator during that time. Dimetrodon, whose name means "two kinds of teeth", is considered to represent the culmination of Spenacodontian development. It was about 3.5 meters (11.5 feet) in length, and weighed about 200 kilograms (about 440 pounds). Dimetrodon is best known for its enormously elongated neural spines that are believed to have supported a "sail" on its back. Paleontologists believe that the neural spines were connected by a membrane which was supplied with blood vessels, allowing Dimetrodon better temperature regulation than other Pelycosaurs.
The Pelycosaurs and other reptiles, including dinosaurs, are "cold-blooded" or ectothermic. ("Warm blooded" animals are endothermic.) This means that they use the outside world to regulate their body temperature. You may have seen documentaries of crocodiles basking in the sun, they do this to raise their body temperature enough so they can move around quickly. If they do not bask, and their body temperature drops, they become sluggish and move slowly. Dimetrodon would have an advantage over the other reptiles with its temperature-regulating sail. By turning its sail filled with blood vessels to catch the morning sun, it could warm its body temperature from 26 to 32 degrees Celsius (79 to 90 degrees Fahrenheit) in only about an hour and a half. An animal the same size without a sail would have taken more than three and a half hours to warm up this same amount! By warming up quickly in the morning sun, Dimetrodon would then be able to catch other reptiles that were still cool and sluggish.
 |
 |
Go To Page: 1 2
