7 things you never knew about Dimetrodon

1. Dimetrodon is pronounced die-MET-row-don. Everyone’s favourite dinosaur with a large sail on its back. Except they are not dinosaurs, they are a Synapsid and are more closely related to mammals than dinosaurs. Inside their large skulls, behind the eye socket there is one large hole called the temporal fenestra. Some of the lower jaw muscles were attached to the head at this point. Dinosaurs have two holes in the same place and are called diapsids. Strange as it seems Dimetrodon is a distant relative of ours and not the dinosaurs.
2. Dimetrodon lived 40 million years before dinosaurs in the early Permian (299 – 270 Million years ago). Their fossils were first discovered in 1878 in the south-western United States and most have been found in Texas and Oklahoma. Some have also been found in Germany, and fossilised footprints have been found in Nova Scotia, Canada.
3. With a huge sail on their backs, you might have thought that their name would refer to that. In fact, the name refers to the fact that their teeth size varies considerably from front to back with the largest ones at the front. The name means “two shapes of tooth”.
4. Did I mention that they have a huge sail on their backs? Bony spines up to 6 feet long rose vertically from its backbone and supported flaps of skin that gave a sail-like appearance. Scientists think that the sail was used to regulate their temperature, heating the animal up in the morning and allowing it to cool down if required later in the day. The sail could also be used for display to attract mates or make it look larger to potential predators. It has also been suggested that the sail would act as camouflage when the animal was in reed beds, or used as a sail when swimming.
5. Like a modern crocodile, Dimetrodon had four legs that splayed out at the sides. Dinosaurs have legs extended under their bodies. Dimetrodon was probably a relatively fast runner. As it was a carnivore, this would have helped it catch its prey.
6. At over 11 feet long (~3.5m) and weighing about 500 pounds (~250kg), these were the top predators of their day. Animals on their menu would probably include another Synapsid, the vegetarian Edaphosaurus, which also sported a sail but was only half the size of Dimetrodon. Another cousin probably on the menu was the Casea, another vegetarian Synapsid. Casea was only 4 feet long (~1.3m) and lacked the distinctive sails of its relatives.

Dimetrodon sunning itself

Dimetrodon sunning itself

7. There are at least 13 different types of Dimetrodon, ranging in size from the 11ft (~3.5m) of D. grandis to the 2ft (~0.6m) D. teutonis. The animal was first described by the American fossil hunter Edward Drinker Cope in the 1870’s. Several more new species were described by E. C. Case in the early 20th century while another American palaeontologist, Alfred Romer, also added to the list of known Dimetrodon.

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