STL Science Center

STL Science Center

07 November 2018

Papers of Many Measures

There are many Dimetrodon papers. A significant number of those papers are descriptions of different finds of Dimetrodon from various different places. The original naming papers would be most interesting, if we had them somewhere online. We do not, to my knowledge. However, we do have the first Dimetrodon species known from Europe, the first from outside of North America actually, which was found in the Bromacker assemblage. This is a Lower Permian formation in and around the Thuringian Forest of Central Germany.

There are other descriptions of Dimetrodon as well. Some of these regard the jaw muscles of the interestingly shaped skull of Dimetrodon. Other venture into describing how Dimetrodon may have regulated its temperature using its unique sail structure. The structure of the sail is, of course, a constant subject of study. Like any other body part, the sail could be subjected to injury as well, and studies have certainly been conducted that on said injuries.

Many of these studies together have led to phylogenetic studies of Dimetrodon. The pelycosaurs, in general, are in an interesting position in the evolutionary tree of synapsids. One of the papers I enjoyed reading when I first learned systematics and began dealing with trees is this paper by Ken Angielczyk which uses Dimetrodon as an example species in how to think about trees (otherwise discussed as "tree thinking") how to use them to understand relationships between taxa.

04 November 2018

Not A Dinosaur

Pelycosaurs are not dinosaurs. As Dimetrodon is a pelycosaur, Dimetrodon is also not a dinosaur. This has mostly been eroded from the popular psyche, though there are still vestiges of Dimetrodon's inclusion in the world of dinosaurs out in the modern world. These videos will make sure that everyone knows what a Dimetrodon is and is not.

Emily Graslie (she is a professional science communicator, so expect a well delivered video) on Brain Scoop:

A top ten list of facts. This video again addresses the fact that Dimetrodon was not a dinosaur straight off the bat. It then lists some interesting facts about Dimetrodon. The video includes a lot of images and video game animations.

03 November 2018

New Old Animals

Sphenacodontids ("Wedge point tooth") are a group of synapsids that are known from fossils found across Europe and North America from ages between from the Late Pennsylvanian to the Middle Permian. The most well-known examples of not only sphenacodontids but also pelycosaurs is the large headed apex predator known from Texas and Oklahoma (mostly), Dimetrodon ("Two measures of teeth"). The genus Dimetrodon actually consists of 13 recognized valid species; though we regularly hear Dimetrodon referenced as though it is a single species (generally the type species, D. limbatus Cope 1877). The general description of Dimetrodon species is a group of animals presenting with tall laterally compressed skulls, a large dorsal sail, and a tail composed of upwards of 50 caudal vertebrae, accounting for a significant portion of the total length of the animals. The sail is what most people think of when they think of Dimetrodon, but these pelycosaurs are actually named after their teeth, which consist of 1 - 2 pairs of large caniniform teeth and large incisors in the front of the mouth and smaller teeth caudally. Also intriguing in the skulls of Dimetrodon species are primitive nasal turbinates, appearing to indicate a capability of warming and cooling air as it was inhaled and exhaled and what appears to be a transitional morphology of the ear that would give rise to the mammalian ear. The story of the mammalian ear is far more complicated than the previous sentence makes it sound, but this intermediate ear morphology is important in overall ear evolution.

There are many reasons that Dimetrodon is an interesting animal to study and, given time this week, we can get into some of the studies that have been done with disparate species of the Dimetrodon genus. Dimetrodon will always stand out because of their importance in the evolutionary history of synapsids, their unique morphology, and, personally, because the first model I ever built was of a Dimetrodon standing on a rock. It is very possible that this was the model kit (I was young and it was forever ago, but this brings up the memory of building it).
 Also, here is a nice illustration of a few of the species of Dimetrodon scaled to one another by Dmitry Bogdanov.
©Dmitry Bogdanov