Dimetrodon

From Palaeos

The pelycosaur Dimetrodon grandis meeting the amphibian Platyhystrix rugosus for a lunch date of destiny in Permian Texas

[edit] Introduction

Dimetrodon was a large predatory pelycosaur that flourished during the Early Permian Period, living between about 280 and 260 million years ago. It was more closely related to mammals than to true reptiles (Sauropsida), like dinosaurs, lizards and birds.

Fossils of Dimetrodon have been found in North America and (more fragmentarily) Europe. It is best known from the Texas deltas of the time. The climate of Europe and North America in the Early Permian, was probably arid to continental, so Dimetrodon was probably adaptable.

[edit] Information

Linnaean taxonomy:

• Phylum: Chordata
  • Class: Reptilia (paraphyletic)
    • Subclass (or monophyletic or paraphyletic class): Synapsida
      • Order: Pelycosauria
        • Family: Sphenacodontidae
          • Genus: Dimetrodon

Author: Cope, 1878

Species:

• D. milleri
• D. natalis
• D. limbatus
• D. booneorum
• D. gigashomogenes
• D. grandis
• D. loomisi
• D. angelensis
• D. teutonis

Stratigraphic Range: Asselian to Early Kungurian (Permian)

Known Distribution: Equatorial west Euramerica

Lifestyle: Terrestrial apex predator

[edit] Characteristics

Dimetrodon was a dominant carnivore, the largest known of its day. It grew to up to 3 meters (10 feet) in length. The name Dimetrodon means 'two-measure teeth', so named because it had a large skull with two different types of teeth (shearing teeth and sharp canine teeth), unlike reptiles. Dentition showing this differentiation of teeth is called heterodonty.

Dimetrodon had a sprawling posture and may have moved in a manner similar to present-day lizards.

[edit] 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. In this way, it could have easily picked off slower prey that was still warming up. The sail may also have been used in mating rituals and to warn off other predators. The sail was supported by neural spines, each one sprouting from an individual vertebra. Bramwell and Fellgett (1973) calculate that a 200 kg Dimetrodon would heat up from 26° C to 32° C in 205 minutes without a sail and in only 80 minutes with a sail.

[edit] Relationship with modern mammals

As a synapsid, Dimetrodon was distantly related to humans and all other modern mammals. Synapsids were the first tetrapods to evolve differentiated (or heterodont) teeth. Whereas most reptiles hardly chew their food, simply gulping it down, synapsids like Dimetrodon developed 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.

[edit] References

1. Bramwell, C. D. and Fellgett, P. P., 1973, Thermal regulation in sail lizards. Nature, v. 242, p. 203-205.

[edit] Credit

This page MAK061125