Dimetrodon

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{{Taxobox | color = pink | name = Dimetrodon | status = Conservation status: Fossil | image = Dimetrodon.jpg | image_width = 250px | image_caption = Dimetrodon grandis skeleton at the </br> National Museum of Natural History | regnum = Animalia | phylum = Chordata | classis = Synapsida | ordo = Pelycosauria | familia = Sphenacodontidae | genus = Dimetrodon | genus_authority = Cope, 1878 }} Dimetrodon (Template:IPA) was a predatory synapsid (mammal-like "reptile") genus that flourished during the Permian period, living between 280 and 260 million years ago. It was more closely related to mammals than to true reptiles (Sauropsida) like dinosaurs, lizards and birds. Dimetrodon was not a dinosaur, despite being popularly grouped with them; rather, it is classified as a pelycosaur. It is surprisingly well known to the general public: it makes an appearance in the James Mason film Journey to the Center of the Earth.

1 Characteristics
2 Sail
3 Relationship with modern mammals
4 In popular culture
5 External links

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Characteristics

Dimetrodon was a dominant carnivore, the largest of its day. It grew to up to 3 meters, 10 feet, in length. Dimetrodon means "two-measure teeth"; it is so named because it had a large skull with two different types of teeth (shearing teeth and sharp canine teeth), unlike reptiles. It walked on four side-sprawling legs and had a large tail. Dimetrodon may have moved in a manner similar to reptiles.

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Sail

The most distinctive characteristic of Dimetrodon was the spectacular sail on its back. The sail was probably used to regulate body temperature; the surface area would allow it to warm up or cool off more efficiently. It may also have been used in mating rituals and to ward off other predators. The sail was supported by neural spines, each one sprouting from an individual vertebra.

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Relationship with modern mammals

As a synapsid, Dimetrodon was distantly related to humans and all other modern mammals. Synapsids were the first "reptiles" to evolve different types of teeth. Whereas reptiles hardly chew their food, simply gulping it down, synapsids like Dimetrodon developed canine teeth to help shear meat into smaller pieces for easier ingestion. These "two-measure teeth" eventually gave rise to the various kinds of teeth present in modern mammals. For more information on human ancestry, see timeline of human evolution.

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In popular culture

In the television documentary Before the Dinosaurs (called Walking With Monsters in the US), baby Dimetrodon were shown hatching with sails, fully independent. In fact, no Dimetrodon eggs have yet been found, and it's entirely possible that the sail, which would be hard to store in an egg, was either absent or not rigid upon hatching. The program also stated that Dimetrodon consumed 90% of a carcass, while lions today ate 70%, and that Dimetrodon would only eat intestines after shaking out the waste inside, since "dung is one thing a Dimetrodon can't stomach." These "facts" are almost entirely speculative on the part of the producers, who invented behaviors and presented them as fact in order to highten the sense of realism.