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

30 October 2018

Too Many Choices

Probably because Simosuchus has such an interesting skull and teeth for a crocodilian relative there are a number of papers and studies of Simosuchus. The odd shape and the intriguing phylogenetic position of Simosuchus are also often studied topics as well. I know that a number of the readers here have read a lot of these papers, and maybe even know them by heart. The discussions here lately have been quite vibrant and I hope they continue, so if anyone reads these papers and has questions please feel free to ask them. I am sure someone can answer them. Instead of describing each paper and then linking them, I am simply going to link them by subject here. As a fair warning, many of these papers come from a 2010 Memoir edition of the Journal of Vertebrate Paleontology specifically about Simosuchus (read as you may need to look for additional links to read these):

Description paper by Buckley et al (2000)

Phylogeny of Simosuchus by Turner and Sertich (2010)

Craniofacial morphology by Kley et al (2010)

Postcranial skeleton:
Appendicular by Sertich and Groenke (2010)
Axial skeleton by Georgi and Krause (2010)

Osteoderms by Hill (2010)

28 October 2018

Well Done Videos

Probably not the group that we would normally turn to here to get facts and videos, the Expeditioner's Discovery Guild is a channel on YouTube that has a lot of wide-ranging videos. One of their videos is the 7:21 second description and artwork compilation addressing Simosuchus. There is a lot of good information here and it is worth watching. It actually directly answers some of questions that people have asked in the last 24 hours as well.

27 October 2018


The pug nosed crocodile, Simosuchus clarki (Buckley et al. 2000) is named for its short and blunt snout. Recovered from the Mahajanga Province of Madagascar, the small (2.5 ft; 0.75 m) crocodylomorph had small leaf shaped teeth and is thought to have been one of a number of early suchians that was actually herbivorous rather than carnivorous. There are quite a few interesting facts about this suchian and its lifestyle that tell us a lot about the evolution of crocodiles. Stick with us to see tomorrow what kinds of interesting facts we will share tomorrow.
Photo of ROM display specimen by D. Gordon E. Robertson

23 September 2018

Pseudosuchian Archosaurs

Rather than spend today telling the intrepid readers (and viewers of videos) what a pseudosuchian is and is not, I present to you today videos that show, describe, and discuss Revueltosaurus.The genus Revueltosaurus consists of three recognized species: R. callenderi Hunt, 1989 type; R. olseni Hunt and Lucas, 1994; R. hunti Heckert, 2002. The first video comes from Petrified Forest and the National Park Service. It describes the finds at the park and where some of those bones come from on the skull of this crocodile relative. The second video features NMMNH Chief Scientist Spencer Lucas talking about what exactly Revueltosaurus is and is not, in a very short manner of time (the clip lasts approximately 90 seconds).