Dimetrodon

Mammals are all around us today and even if you have lived under a rock for your entire life you've probably seen a mammal. Why? Because you, yourself, are a mammal. But did you know that you were also a synapsid?

You see mammals are themselves part of a larger group called Synapsida which is one of the two groups of amniotes (animals that had protective coverings around their eggs, oh and the other group is called sauropsida or reptiles) and has existed since animals evolved to lay eggs on land.

Earlier synapsids however did not look like mammals at all and can only be identified by skeletal features. This meant that early synapsids would have looked more like reptiles then what your recoignize as a mammal today. This had lead to the naming of the term mammal-like reptile. This is of a wrong term as these so called mammal-like reptiles are not related to reptiles aside from skeletal traits that all amniotes have and their similarity to reptiles is due to convergence (this is anatomist speak for when two or more creautres independantly aquire some of the same traits that they poses).
Two skeletons of a pair of dimetrodons along with a painted background and a little text box

Early Synapsids flurished in the Permian period around 299 to 251 million years ago. During that time land animals for the first time grew big. And as prey got bigger, so did the predators. Which links us neatly to dimetrodon.

Discovered in 1902 by an influencial paleontologist named Cope who I hope to be covering in another blog post. Dimetrodon has been found mainly in texas where many complete specimens along with skeletons of other creautres have allowed an extremely accurate depcition of the ecosystem compard to other fossil sites.

Dimetrodon was around 11 feet and weighed approximatly 550 kilograms and was the biggest predator in it's ecosystem. In addition to it's basic body size dimetrodon also have a sizeable sail that has gained it fame. But this was not its' only interesting trait. Indeed while earlier creatures had skulls that consisted of many different smaller bones dimetrodon was different. You see, during mammal evolution the smaller bones in the lower jaw became, well smaller until they were absorbed into one single large bone. This bone became connected to the ear forming the inner ear bone. Eventually mammals evolved different types of teeth in the jaw and dimetrodon shows the begining of this design.
Comparision of pelycosaur skulls (1=spehnacodontid 2=ophiacodont 3=casied the various colour represent different bones green=quadratojugal red=squamosale blue=jugal

Dimetrodon itself is actually part of a group called the sphenacodontids which are joined with another group called the edaphosaurids and together they form the clade pelycosauria. Interestingly the large sail that is seen in dimetrodon and perhaps also in perhaps more sphenacodontids is also seen in atleast one edaphosaurid meaning that both types of pelycosaurs evolved sails.

Anyway lets get back to that sail. Many different species of dimetrodon had different sail shapes althrough this may be do to otogeny or the changes that occur in organisms as they grow. But we're not here to discuss that so lets talk about the purpose of such a sail. There are two main ideas that I will discuss seeing as they're the only two I am aware of. The first is the radiator theory. The idea is that a dimetrodon could angle it's sail to either collect large amounts of sun to warm itself up (dimetrodon is thought to be cold-blooded so it would require other sources to monitor its' heat) or to block out sunlight. The problem is that other creatures of dimetrodons size and age do not have such elaborate measures of temperature control.

The second idea is the display idea. This idea is based on the idea that the sail would be large and noticable meaing that a dimetrodon could use it's sail to attract a mate or to deter a rival. The problem with this idea is that the sail was very large and since most sexual display devices are relativy small or unoticable and dimetrodons sail was very large so it makes sense for it to have had another function.

My personal thought on this is that dimetrodon used both ideas. I base this on the fact that modern organisms pretty much always develop traits to take advantage of more then one and if dimetrodon could have used it's sail as either a display device or a thermoregulation tool, then why couldn't it have done both.

Well thats it from me. I would just like to point out that I am coming from a more common knowledge background so there may be a lot of anatomical knowledge that I missed. I sense however and I will just end the post here.

References:
http://en.wikipedia.org/wiki/Pelycosaur
http://en.wikipedia.org/wiki/Dimetrodon

The start of something new

Hello, I would like to welcome you to my new blog Prehistoric Creatures (should have capitalized the "c" in creatures in the title....). This is my first blog and I hope that it will be a success.

I guess it is time to discuss what this blog will be about. In short I intend this blog to be a brief discussion of prehistoric animals, i.e. dinosaurs, mammoths, and dimetrodon. I am not an actual paleontologist (yet) so I intend to discuss things that are more common knowledge like history and all that kind of stuff.

Anyway I would like to once again welcome you to the new blog Prehistoric Creatures!