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Saurosuchus

Saurosuchus was a 20-foot pseudosuchian (a distant ancestor of crocodiles) which lived in Argentina during the middle Triassic Period about 230 million years ago. It was the largest carnivorous animal in its environment in terms of both length and weight, and it was likely the top predator within the Ischigualasto Formation, but that was before the dinosaurs arrived. Saurosuchus lived side-by-side with the meat-eating dinosaurs, but eventually carnivorous dinosaurs like Herrerasaurus, which were faster, more agile, and possibly more intelligent, drove these creatures to extinction.

Skull of Saurosuchus. Drawn in Crayola black marker. © Jason R. Abdale. March 11, 2021.

 

Panphagia, the Oldest-Known Sauropodomorph Dinosaur

For decades, South America has been regarded by paleontologists as the place where dinosaurs originated. It is here that we have our clearest record of what the oldest dinosaurs looked like. Specifically, Brazil and Argentina hold the record for the countries that possess the oldest-known dinosaur fossils. Based upon the fossils that have been uncovered in Brazil’s Santa Maria Formation and Argentina’s Ischigualasto Formation (in particular a locality known as “the Valley of the Moon”), dinosaurs are believed to have appeared during the middle of the Triassic Period about 235-230 million years ago.

Prior to the appearance of dinosaurs in the middle Triassic, smaller dinosaur-like animals scurried about within the jungles of South America. These proto-dinosaurs are known as “dinosauromorphs”. They first appeared during the early Triassic Period, and continued into the late Triassic, well after dinosaurs had appeared and established themselves. Probably the most well-known of these early dinosauromorphs is Lagosuchus, a small reptile about the size of a chicken. What made Lagosuchus and its kind different from the other reptiles which were around at the time was the fact that Lagosuchus and its close relatives ran around on two legs instead of four. This would be a major innovation which would be exploited by the earliest dinosaurs.

File:Marasuchus.JPG

The skeleton of Marasuchus, an advanced “dinosauromorph” from Argentina, dated to the middle Triassic Period about 235 MYA. It has been hypothesized that Marasuchus and Lagosuchus are in fact the same animal. Photograph by Michelle Reback (July 28, 2008). Public domain image, Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Marasuchus.JPG

For a long time, our idea of what the earliest dinosaurs looked like was shrouded in mystery. However, it seemed that the first dinosaurs were carnivores. From the 1950s until the very early 1990s, creatures like Staurikosaurus of Brazil and Herrerasaurus of Argentina were the oldest-known dinosaurs, and they were also believed to be the most evolutionarily primitive. Still, despite their supposedly archaic nature, these were fairly large animals – Staurikosaurus reached 6 to 8 feet long, and Herrerasaurus was even bigger, reaching 12 feet long. Both of these animals, and Herrerasaurus in particular, clearly would have been formidable competitors to the other carnivorous four-legged reptiles which were alive at the time. This was quite an upgrade from small chicken-sized creatures like Lagosuchus, which had existed only a short time earlier. Considering the very short time difference between the appearance of small creatures like Lagosuchus and the subsequent appearance of large meat-eating dinosaurs like Herrerasaurus, it appeared as though one of two options applied here: either dinosaurs managed to evolve into a large size within a very short length of time, or there was some intermediate species which hadn’t been discovered yet. Was it possible that there was another dinosaur, as yet undiscovered, which could fill the gap between the primitive dinosauromorphs and creatures like Herrerasaurus?

In 1991, the skeleton of a new dinosaur was discovered in Argentina by Dr. Ricardo Martinez, a paleontologist from the University of San Juan. This animal was far smaller, and it seemed more primitive, than Herrerasaurus. It measured only 3 feet long, and it appeared to have an anatomy which was less advanced than either Staurikosaurus or Herrerasaurus. In 1993, the animal was named Eoraptor, “the dawn thief”. For nearly two decades, this little animal held the title of being the oldest-known dinosaur.

However, complications arose. A closer examination of the skeletons of both Herrerasaurus and Eoraptor created doubts as to whether or not Eoraptor really was the oldest and most primitive dinosaur ever found. For example, the fewer sacral vertebrae an animal has, the more primitive it’s believed to be. Eoraptor possessed three sacral vertebrae, but Herrerasaurus had only two. This indicated that Herrerasaurus, despite being five times larger, was actually more primitive than Eoraptor. Another point of contention was the structure of the lower jaw. When Eoraptor was first discovered and described, it was believed that it possessed a less-evolved jaw structure than Herrerasaurus, but this turned out to be false. Gradually, concerns began to be raised that Eoraptor, despite its small size, was actually not as primitive as it first appeared to be. Special attention was given to the skull and the teeth. Eoraptor possessed different kinds of teeth in its mouth, indicating that it was an omnivore. A close examination of both the skull structure and the teeth made some wonder if Eoraptor was as primitive as we initially believed. In fact, there were some aspects of its anatomy that bore a bit of a resemblance to the sauropodomorph dinosaurs – the long-necked long-tailed creatures that we typically associate with the word “dinosaur” – rather than the fleet-footed meat-eating theropod dinosaurs.

In 2011, Dr. Ricardo Martinez (the same man who had found Eoraptor’s skeleton in 1991) re-classified Eoraptor as a primitive sauropodomorph. This claim was met with skepticism by the scientific community. In a subsequent study, Martinez changed his mind again and stated that Eoraptor was so archaic that it could not be placed into any definite group of saurischian dinosaurs and ought to be placed at the very base of Saurischia. However in 2013, Dr. Paul Sereno did his own evaluation of Eoraptor’s skeleton and concluded that indeed it was a primitive sauropodomorph, distantly related to other prosauropods like Plateosaurus and Anchisaurus. Even so, the overwhelming majority of the scientific community has refuted this claim. Numerous studies have been conducted on Eoraptor since it was discovered and named, and most of them state that Eoraptor is either a very primitive theropod dinosaur or else it is the earliest saurischian, appearing before the saurischians split into theropods and sauropodomorphs.

All of this raises an interesting question. If Eoraptor was not the earliest sauropodomorph, then what was?

In 2006, Dr. Ricardo Martinez was once again exploring the middle Triassic rock layers of the Ischigualasto Formation, dated to 228.3 million years ago, when he found another skeleton. It looked similar to Eoraptor, but it was noticeably larger, measuring 4.25 feet (1.3 meters) in length; Martinez thought that the skeleton was of a juvenile, and that the adult would be larger, say perhaps 6 feet long. The skeleton was incomplete, including only a partial skull. Teeth were only found in the lower jaw. The skull was clearly similar to Eoraptor’s, but it also showed some features which can be seen in very primitive sauropodomorphs like Plateosaurus. For example, the lower jaw curves downwards towards the front, which is a tell-tale feature of that group. The teeth were also very similar to those seen in prosauropods. Based upon the skull structure and the shape of the teeth, this animal seemed to be more closely related to sauropods than theropods. In 2009, the animal was named Panphagia, which is ancient Greek for “eats everything” in reference to its supposedly omnivorous diet.

Reconstruction of the skeleton of Panphagia protos. Photograph by Eva Kröcher (December 5, 2010). Creative Commons “Attribution Non-Commercial Non-Derivative 3.0 (US)”, GNU Free Documentation License (GFDL), and Free Art License. https://commons.wikimedia.org/wiki/File:Panphagia_fossil_DSC_6168.jpg.

A complete skull was not found with the skeleton, but we have enough of the bones to give us an idea of the skull’s outline. Below is an illustration that I made of what the complete skull of Panphagia might look like, based upon what was seen in the photograph that you see above. The drawing was made with a black Crayola marker.

Skull of Panphagia protos. © Jason R. Abdale (February 9, 2021).

Based upon this skeleton and the description that Ricardo Martinez and Oscar A. Alcober gave in their paper on this animal, I have reconstructed what the entire animal might look like. The creature bears a slight resemblance to prosauropods like Plateosaurus and Anchisaurus. No hands were found with the specimen. However, the illustration which accompanied Martinez and Alcober’s paper showed Panphagia sporting hands with four fingers, although the fourth digit was so small that it was probably incorporated into the wrist and wasn’t seen on the outside. The fingers themselves were longer the more distal they were to the body (in other words, the middle finger was longer than the thumb, and the pinky was even longer than the middle finger), and this was repeated in the skeletal reconstruction seen above. Since this was the reconstruction seen in both sources, I incorporated it into my own illustration.

I think that there are two issues with the illustrated reconstruction of Panphagia’s skeleton seen in the scientific paper and in the physical reconstruction seen in the photo above. Firstly, I think that the tail is too short. The animal looks conspicuously front-heavy, and the tail ought to be longer to give it better balance. Secondly, I believe that the hand structure is incorrect. Prosauropods like Plateosaurus, Massospondylus, and Anchisaurus had hands with five fingers and large thumb claws. However, it must be noted that all three of those species came from the late Triassic and early Jurassic Periods, nearly twenty to thirty million years after Panphagia’s appearance, and their hand structure may have been more evolved than that seen in archaic animals like Panphagia. However, until a more complete specimen of this animal is found, I think my reconstruction is going to remain as it is.

My drawing was made with No. 2 pencil on printer paper.

Panphagia protos. © Jason R. Abdale (February 14, 2021).

 

For more information, please read Martinez’ and Alcober’s paper on this animal, which you can see here:

Martínez, Ricardo N.; Alcober, Oscar A. (February 16, 2009). “A basal sauropodomorph (Dinosauria: Saurischia) from the Ischigualasto Formation (Triassic, Carnian) and the early evolution of Sauropodomorpha”. PLoS ONE, volume 4, issue 2. Pages 1-12. doi:10.1371/journal.pone.0004397.

https://storage.googleapis.com/plos-corpus-prod/10.1371/journal.pone.0004397/1/pone.0004397.pdf?X-Goog-Algorithm=GOOG4-RSA-SHA256&X-Goog-Credential=wombat-sa%40plos-prod.iam.gserviceaccount.com%2F20210301%2Fauto%2Fstorage%2Fgoog4_request&X-Goog-Date=20210301T093333Z&X-Goog-Expires=3600&X-Goog-SignedHeaders=host&X-Goog-Signature=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.

 

Keep your pencils sharp, everyone.

 

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 during the late Triassic Period, who in turn would be replaced by crocodilians during the Jurassic Period.

Alamosaurus

alamosaurus

I know that it’s been a while, but here is my latest addition of paleo-art to this blog. Behold – Alamosaurus, a behemoth of a sauropod that roamed Texas during the late Cretaceous Period. Alamosaurus was a member of the “titanosaur” family, which is more well-known from species found in South America, Europe, and Africa. No complete skeleton of Alamosaurus has ever been found, so we only have a rough idea about what it looked like, and we’re not even sure how big it was when it was fully grown. The most common estimate that I’ve seen is that it was somewhere around 65 – 70 feet long, but it might have been bigger than that.

Because no complete specimen of Alamosaurus has been found, you’re going to see a lot of variation in paleo-art reconstructions of this animal. From what I’ve gathered, a lot of the pictures that are visible on the internet these days are inaccurate. Alamosaurus had a massively thick neck, but its tail was not correspondingly long or massive. The presence of osteoderms along its back are a guess, since other titanosaurs, notably Saltasaurus, were known to have had them.

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.