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Promastodonsaurus

This is Promastodonsaurus, literally meaning “before Mastodonsaurus”. Despite its saurian name, it was not a dinosaur, or even a reptile. It was actually a large amphibian. Fossils of Promastodonsaurus were found in Argentina within the rocks of the Ischigualasto Formation, dated to the middle Triassic Period approximately 230 million years ago. The species was officially named in 1963 by the famed South American paleontologist José Bonaparté, in reference to another large amphibian named Mastodonsaurus which lived in Europe during a slightly later time.

Cladistically-speaking, this animal belonged to a large group of amphibians called the “labyrinthodonts”, so-named because a cross-section of their teeth looked like a maze. Within this broad group is a sub-division called the “temnospondyls”, “the cut vertebrae” because each of their backbones is divided into several parts. The temnospondyls were a diverse group of labyrinthodont amphibians which first appeared during the Carboniferous Period and lasted into the Cretaceous Period – a span of nearly 200 million years. Within the order Temnospondyli is the sub-order “Stereospondyli”, and within this is a division called the capitosaurians, “the head lizards”, so-named due to their freakishly huge heads. Promastodonsaurus was a member of this group. It was essentially a giant meat-eating salamander with the head of an alligator.

The only evidence that we have of this animal is a single partial skull. Based upon its similarity to the skulls of other temnospondyl amphibians within its family, it is believed that the animal’s head measured 45 centimeters long (Hans-Dieter Sues and Nicholas C. Fraser, Triassic Life on Land: The Great Transition. New York: Columbia University Press, 2010. Page 69). This in turn would make the entire animal somewhere in the vicinity of 6 feet long, as big as a medium-sized alligator.

Promastodonsaurus bellmani. © Jason R. Abdale. February 9, 2021.

During the middle Triassic Period, crocodilians did not exist, so the capitosaurians like Mastodonsaurus and Promastodonsaurus essentially filled in that ecological niche as crocodilian analogs. Large amphibians like these would continue to dominate freshwater environments until they were replaced by the phytosaurus, who in turn would be replaced by crocodilians.

 

Giganotosaurus head study

Giganotosaurus head study

This was the first illustration that I made which was actually published. I drew this last year for Prehistoric Times Magazine, and it was accepted by Mr. Michael Fredericks, the magazine’s editor. It appeared in print in issue #102 (Summer 2012). Needless to say, I was excited when I was told that one of my drawings would appear in a magazine. I was even more excited when I actually saw it in print. Giganotosaurus carolinii lived in Argentina about 100 million years ago (or MYA as it is commonly abbreviated) during the middle Cretaceous Period. Giganotosaurus, which means “giant southern lizard”, was slightly larger than T. rex, but it also evolved from a more primitive ancestry. Because it was more evolutionarilly primitive than T. rex, I wanted to give it more crocodile-like skin. This drawing took me three whole weeks to complete, working non-stop. By contrast, my “Tyrannosaurus rex head” drawing, which is equally detailed and is the same size, only took me three days. Why did this drawing take so long? It’s because each scale had to be drawn individually and given special individual attention.

I have an interesting quirk when it comes to illustrating creatures with this type of skin texture. I use regular copy paper for most of my drawings. It may look smooth, but if you get really up close to it, you can see that it actually has a rather rough and imperfect surface – it is covered in very small wrinkles and dents. The human eye and brain has a tendency to recognize patterns, whether they actually exist in reality or not. When I saw the dents and wrinkles in the paper, my eye simply connected the dots. The result is what you see. This is why many of the scales, if you examine them closely, have facets with straight sides. It’s a very time-consuming process, but it produces great effects. I love all of my drawings, but this one is definitely one of my favorites, and I’m sure that it will be one of your favorites as well.