STL Science Center

STL Science Center

18 October 2017

Sprawling Horned Faces

From Chudinov 1965
Estemmenosuchus has a crown of horns. The crown of horns has been hypothesized to have been used for intraspecific signalling and display short of combat; combat with the horns was probably used as an absolute last resort by these animals. The reason that it would have been used as a last resort is that the horns were massive bone structures. Unlike antlers, horns are composed of bone and insult or injury to these structures can be much more traumatic to the animals than damage to antlers (injuries to antlers are serious of course though). The horns of Estemmenosuchus were composed of extremely thick outgrowths of the frontals and cause the skull to appear even more massive than it is. Known skulls of Estemmenosuchus are approximately 65 cm (26 in) in length. That is not the only thing that is large and unique about Estemmenosuchus though. This large therapsid (approximately 3 m  or 10 ft long) also had a sprawling posture; this is somewhat typical in therapsids and Permian reptiles as well. Some have used this sprawling posture as evidence for an herbivorous diet, saying that the sprawling posture enabled the animal to hold a large fermenting gut with more support than if it had a posture like cattle or a similar mammal; this seems less than ideal given what we know about extant mammals. The canines of Estemmenosuchus are used as evidence to a different, more omnivorous but not quite carnivorous, dietary regimen.

17 October 2017

Working Hard to Find Papers

Finding papers that are about, reference, or even vaguely mention Estemmenosuchus is actually a lot more difficult than I had initially thought it would be. The majority of the papers that make mention of the interestingly shaped therapsid are descriptions of faunal assemblages of Eastern Europe, Russia, or simply Permian fauna in general. These papers are exemplified online by Chudinov's (Tchudinov) 1965 paper Deinocephalians of the U.S.S.R. and Battail's 2000 paper A comparison of Late Permian Gondwanan and Laurasian amniote faunas. Chudinov actually described the two species of Estemmenosuchus in 1960 and 1968; these descriptions are not available online. Unfortunately, Chudinov's treatments of Estemmenosuchus are possibly the best and are certainly the best online at the moment.

16 October 2017

Ugly Animals Get All the Love

Whenever a fossil animal is bizarre enough to be a little scary or to be called ugly outright it appears to gather an awful lot of attention in the media and within the general population. Estemmenosuchus is an animal that exemplifies this sort of massive interest across the lines of professional and amateur as well as including the typically disinterested portion of the population. Despite knowledge of the animal and its respected, if not well known, existence in the fossil record, it has not made am impact in the animation or documentary community that typically brings dinosaurs and other fossil animals to life. A Permian Monsters exhibit was once outfitted with an animatronic Estemmenosuchus and Gondwana Studios captured the statue in motion and displaying all the small conical teeth it was installed bearing. Seeing an interpretation in action is important to understanding how scientists envision this animal moving around its environment, regardless of the actual motions that this statue is engaged in (what I mean here is that it is roaring and moving its head around perfectly well, but there is no locomotion aspect to the animatronics). Maybe someone should have suggested this rather intriguing animal for a role in the Walking with Monsters series from 2005. It would have been contemporary with other Permian animals like Gorgonops, Dimetrodon, and  Edaphosaurus, to name a few. Perhaps this age will be revisited by television and film, but until then the movies for Estemmenosuchus are sadly lacking overall.

14 October 2017

News Then Therapsids

In the somewhat recent past I  found myself thinking that perhaps we could use a name change here at Dinosaur of the Week. The fact of the matter is that we have covered a lot of dinosaurs and fossil animals in the past 7 years (give or take a week or two off a year for vacations and conferences we are talking about ~50 animals a year for 7 years) and the number of well known, well documented, and well represented dinosaurs have become rarer and rarer for us to cover. We could easily cover only dinosaurs, but there is a point, and we are very near it, where we will start to cover dinosaurs that are represented by singular fragments of singular bones and are highly hypothetical. In exploring other fossil animals we have extended the life of this blog beyond a few years and have been able to explore a much larger range of life on the history of this planet.

Why haven't we changed the name in all that time then? I have seriously considered it a number of times in the past year or two because I realize that we discuss much more than dinosaurs. There could be any number of good names: Fossil Animal of the Week, Extinct Animal of the Week, to name a few. So far I have decided that the fact that Dinosaur of the Week is acceptable as a name, though we could rebrand ourselves without losing an audience. The reason that I am reluctant to do so at the moment is that we have recently become more widely known. The site has been cited in scientific and educational presentations at conferences and it has been used in classrooms in public schools for an extended period of time. All of that said, should a name change occur, the change would be effected in the first week of the new year. This will give me time to make a final decision on a new name, how to rebrand the site, and to illustrate all of the necessary materials for the site. Now, on with the animal for this week:

©Roland Tanglao
Estemmenosuchus is a genus of Dinocephalian ("terrible headed") therapsid. Two species are known; E. uralensis Tchudinov, 1960 (type)and E. mirabilis Tchudinov, 1968. These two species are both known from the Perm region of Russia, an area near the Ural mountains in the center of the country. The name Estemmenosuchus means "Crowned crocodile" in Greek, but therapsids like these two species are actually mammals, and not at all related to crocodiles. A body measuring approximately 3 m (10 ft) that looked something like the body of sprawling hippopotamus was attached to this crowned reptilian looking head. Important questions remain: What are all of these growths made of? What were their purpose? What did this animal eat? What makes it a therapsid?

13 October 2017

On the Nest

©Maurilio Oliveira
Guidraco venator is unique among pterosaurs in a variety of ways. The teeth are actually somewhat common in earlier pterosaurs like Dimorphodon, but the size of Guidraco is more rare for a pterosaur with those type of teeth. In terms of interpretations of Guidraco the animal is unique in that many of the illustrations of this pterosaur do not take place in the air. A number of interpretations do show Guidraco flying but we have not seen any of it diving toward food items, taking off or landing, or participating in any visibly powered flight (i.e. there are no interpretations or illustrations that appear to be showing down or upstrokes of the wings more definitively than they depict soaring. There is nothing wrong with any of these depictions, of course. However, as with any other fossil animal we discuss here, we do like to see a little variation in how animals are depicted because we know that animals engage in dynamic behaviors throughout their lifespans. There are a number of illustrations and interpretations of Guidraco walking on the ground. These are interesting, but not as interesting as the illustration we are looking at today. This illustration combines some odd perspective (like the directly facing Guidraco) and the aforementioned not seen before act of feeding (look in the background) with the pose of a sitting Guidraco and different wing positions which are showing hints of powered flight. It may look as though I set that up earlier in saying that we had not seen those things until now, but an image search with those keywords actually seems to have turned in the perfect storm of an illustration which we should look at in great detail. The behaviors that were, until I found this image, uninterpreted or at least had not been illustrated, represent a substantial portion of the life history of Guidraco and the ideas hypothesized in these representations of their lives can, potentially, tell us a lot about the pterosaur. This illustration also tells us a lot about how the researchers interpreted the life history of Guidraco based on sister taxa and the fossil that was known to them when they described it.

11 October 2017

Mouth of the Dragon

Attributed to Feng Lan
Guidraco possessed approximately 82 teeth in its 38 cm (14.9 in) long skull. Both the mandible and upper jaw (consisting of maxillae, premaxillae, and nasals) were of equal length but the upper jaw contained 23 teeth on each side whereas the mandible contained 18 teeth per side. The first teeth in each row are held almost horizontal and, as the teeth are followed caudally in the mouth, they begin to curve more and point toward the open mouth; up in the mandible and down in the upper jaw. The mandible's rostral teeth are slightly larger than their counterparts in the upper jaw and for the most part the teeth are of similar sizes caudally. These forward most teeth come together, or occlude, in such a way that they form a basket of teeth and mouth which would have been very well suited to grasping fish and other "slippery" meals. The initial description makes mention of this dietary inference as well and leans heavily on the idea that this would have been the preferred diet of Guidraco.

10 October 2017

Describing a Dragon

The description of Guidraco written by Wang, et al. in 2012 is available online with 15 different websites hosting the article or links to the article. The phylogenetic relationships of Guidraco and other pterosaurs are briefly described at the end of the paper, but the most important portion of the paper is the actual physical description of the pterosaur. This description includes a number of high detailed photographs of the fossil as well as detailed line drawings that point out individual bones of the skull. That, in turn, informs an accurate reconstruction of the skull which also accompanies the description of the fossil. The postcranial skeleton is also described in great detail in the paper, but is not illustrated in the reconstruction, but is labelled in the initial line drawing and shown in the details of the photographs.