Dimetrodon is one of the most recognizable prehistoric animals and is often mistaken for a dinosaur. It looks like a cross between a lizard and a dog and has the teeth to match, thus its name that translates to, “Two shapes of Teeth.” Despite the fact that popular culture mistakes this animal for a member of Dinosauria, it had many features that differentiate it from the dinosaurs including; Semi-Squat legs, a thin sail on its back, and mammalian dentition. All these aspects and more make this a very interesting animal, and one of the most common predators of Permian North America and Europe.
Dimetrodon lived during the period known as the Early Permian, more specifically 295–272 million years ago, in a wide range of the world. Fossils of the animal have been discovered in USA (Texas, Oklahoma, Utah, Arizona, Ohio, New Mexico, and Arizona) and Europe (Germany). The first instance of this animal’s discovery came about in the 1870s by esteemed Paleontologist, Edward Drinker Cope, after receiving the initial specimens from an area of Texas called the Red Beds. Cope acquired the material from collectors excavating the area including Swiss naturalist Jacob Boll, geologist W. F. Cummins, and amateur paleontologist Charles Hazelius Sternberg. Edward Drinker Cope sent his material to the American Museum of Natural History while his rival, Othniel Charles Marsh, sent his Dimetrodon material to the Walker Museum in Chicago (Now annexed to the Field Museum). The list of valid species is long and consists of; D. angelensis, D. borealis, D. booneorum, D. dollovianus, D. giganhomogenes, D. grandis, D. limbatus, D. loomisi, D. macrospondylus, D. milleri, D. natalis, D. occidentalis, and D. teutonis. Michigan Paleontologist, Ermine Cowles Case, completed a study on Dimetrodon in which he named a great many species with the aide of The American Museum of Natural History, which granted him funding to conduct his research. Searching through the material that Edward Drinker Cope had discovered and labeled Dimetrodon, Case found that many of these finds were of new species. After Case’s study, new specimens of Dimetrodon were discovered in other localities of the United States including Utah, Arizona, and Ohio. One of the recent discoveries occurred in 2001, when a new species of Dimetrodon had been uncovered from the Thuringian Forest of Germany. And then again in 2015 a species previously known as Bathygnathus uncovered in Canada went through a name change, being a nomen dubium (a scientific name that is of unknown or doubtful application.) to Dimetrodon, and is now categorized under D. borealis. These more recent finds extend the range of the Permian predator farther than had ever been known. But this pays no homage to the raw power that Dimetrodon housed.
Although Dimetrodon remains a very unusual animal, it loses its uniqueness when compared with the other animals it shared its environment with; Diplocaulus, Eryops, Ophiacodon, Edaphosaurus, Xenacanthus, Diadectes, and many more. Since Dimetrodon would have lived in a very swampy biome, it would likely have preyed upon amphibians and fish of the lakes and streams of its environment. Theories have been proposed by Paleontologists, Robert Bakker and Everett Olson, that Dimetrodon would have been an expert hunter of these aquatic prey and may have been the reason the odd amphibian Diplocaulus evolved its boomerang-shaped headgear; in order to make it difficult for a predator such as Dimetrodon to swallow it whole.
The anatomy of Dimetrodon is rather odd as well; it showcases adaptations similar to both mammals and reptiles. The skull of Dimetrodon is deep and compressed laterally. The skull has only one pair of holes, called fenestrae, on either side of the skull which is a telltale sign of the animal’s heritage; Dimetrodon was a Synapsid, an early mammal-like-reptile and ancestor to modern mammals. Dimetrodon’s relatives consist of; Sphenacodon, Secodontosaurus, and Cryptovenator. Dimetrodon was also the ancestor of therapsids, another line of Mammal-like-reptiles that eventually led to modern mammals. Dimetrodon teeth were another sign of its relation to mammals. Unlike most reptiles and amphibians it shared its environment with, Dimetrodon’s teeth changed shape along the jawline. Canine and incisor teeth were at the front of the jaws, and then smaller teeth lined the rest of the jaw becoming smaller in size. All of the teeth of Dimetrodon are serrated and would have helped hold on to and slice through struggling prey.
One of the most obvious traits that Dimetrodon had is its enormous sail. Along the vertebrae of the animal, a line of tall and thin neural spines juts upwards. It is unknown whether or not the animal truly had a span of skin covering the sail; however this is a very likely hypothesis and has been in use for as long as Dimetrodon has been known to science. The spines are compressed in a rectangular shape from the sides and on many specimens, preserve a figure-eight shape in cross-section. On many specimens, the spines stop at a certain point and start to point in odd directions. This, coupled with the fact that the points of the spine near their end bend sharply, suggests that the sail of skin would only have reached a certain point and then stopped, shortening the sail to be much smaller than usually portrayed. The exact use of this spine, like the integument (external covering) of most prehistoric animals, is unknown; however, theories exist for its use. One such theory is that the sail could have helped the animal warm up by facing the sun, or cool down by facing away from it. The other, slightly more excepted theory, is that the sail might have been a sexual display to help attract mates. Perhaps the animal could have fed blood into the sail to change its color and help it attract more mates, but these are theories that may never be tested due to the animal being extinct.
Despite the fact that Dimetrodon is long extinct, it has stayed in the public’s mind as that “other dinosaur.” Commonly portrayed in books about dinosaurs, the common misconception is that this ancient animal is a Dinosaur, of which it is far from it. In fact, Dimetrodon has more in common with humans than it does with Dinosaurs. However, as 99% of all other life forms that have ever existed, it is extinct and the only evidence of it having ever existed is in its fossilized remains. Dimetrodon remains a strange animal, from an even stranger time.
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