Scutosaurus

Scutosaurus is a genus of extinct reptiles that existed during the Permian Period. It was a large reptile covered in plates of armor. This feature has earned it an alias of “the shield lizard.” Another distinctive feature of Scutosaurus is the position of its legs. Unlike most reptiles, the legs of the Scutosaurus were located under its body. The unique position of its leg supported the massive weight of this reptile. Remains of the animal have been discovered in the Malokinelskaya Formation in European Russia. They have been dated to be about 264 million years old.

Description and Size

Scutosaurus is a type of parareptile that lived about 264 to 252 million years ago during the Permian. Only one species, Scutosaurus karpinskii, has been identified so far. The generic name translates as “shield lizard.” This refers to the large armor on this dinosaur’s entire back and other parts.  

The species belong to a family of parareptiles known as pareiasaurs. Members of this family were among the largest reptiles that lived during the Permian. Scutosaurus was massive, and fossil evidence shows it was one of the largest dinosaurs in the pareiasaurs family. 

It weighed up to 2,560 pounds, which is around the same size as a modern-day black rhinoceros. The body length ranged from about eight to nine feet (2.5 to 3 meters). The entire body of this reptile was covered by osteoderms. The bony osteoderms were separate from each other instead of forming a single continuous plate. However, they were closely packed too. 

Like other pareiasaurs, Scutosaurus had a barrel-shaped rib cage with massive limbs. It had a short, stout body with a very short tail. Scutosaurus karpinskii had an extremely thick skull with unusual bony bumps. The weird projections make them look like the early horned dinosaurs (e.g., Triceratops). Scutosaurus had a broad torso to accommodate an expansive digestive system.

The snout of this reptile was broad and had rows of blade-like heterodont teeth. The upper jaw had 18 teeth, while the lower jaw had 16. The species also has a small bony projection (tubercule) behind its skull, a feature absent in other pareiasaurs. 

History and Evolution 

All fossils of the Scutosaurus found so far date back to the Lopingian epoch of the Upper Permian Period. This means they might have evolved about 259 years ago—growing to rather large sizes compared to other members of the pareiasaur family. 

In addition to evolving into bigger sizes, another interesting evolutionary adaptation seen in the Scutosaurus is the absence of cleithrum along their shoulder blade. This membrane bone first appeared in primitive fish species and was present in all their descendants, including the earliest pareiasaurs. 

However, later pareiasaurs, including the Scutosaurus, lost this structure. Losing this structure may have contributed to the development of a freely movable neck in animals that evolved afterward. 

Diet—What Did the Scutosaurus Eat?

Despite the intimidating build of this reptile, Scutosaurus was an herbivore. It lived in a semi-arid environment, which means it either had to trek long distances to find food or stay close to floodplains and riverbanks where plants to forage on would have been more abundant. 

The rows of sharp flat teeth of the Scutosaurus were adapted to chewing leaves and young branches of plants. The species also digested food with the aid of gastroliths (stomach stones). Due to its massive weight, this reptile would have needed a steady supply of food as it could not survive long periods without food. 

Habitat — When and Where Scutosaurus Lived

Scutosaurus lived about 264-252 million years ago in an area that is now in present-day Russia. Generally, the absence of modern anatomical analogs has made it difficult to know precisely how pareiasaurs lived. However, scientists have theorized that the region where they were found had a semi-arid climate back in the Permian. As plant-eaters, they probably preferred to live close to the sparse water bodies and in the few floodplains available at the time. 

During periods of drought, this animal would have had to stray far away from its home to find food. Experts think they lived a solitary lifestyle or formed very small herds. Some theories propose an aquatic or amphibian lifestyle for this reptile. However, a terrestrial habitat is more supported. 

Threats and Predators

The parareptiles, like the Scutosaurus, had the disadvantage of having relatively short legs. Due to their build, they could only run fast for a short time. This would have made them a target for larger predators. In compensation, they had thick skeletons and strong muscles, particularly in their necks. Predatory animals would have had difficulty killing a Scutosaurus despite how easy-to-catch they were. This animal also had solid bony plates that formed some sort of armor under its skin as an additional defense mechanism. Despite these defenses, large predators such as Inostrancevia (a large therapsid with enormous saber-like teeth) preyed on this reptile. 

Discoveries and Fossils

Vladimir Prokhorovich Amalitskii, a Russian paleontologist, discovered the first fossils of Scutosaurus in 1899. He made the discovery in the Upper Permian deposits of the Northern Dvina River in Russia. The site was fossil-rich, and Amalitskii continued to dig for other fossils for over 15 years, recovering almost complete remains of a wide range of animals. 

Despite finding the fossil in 1899, the official description was delayed until 1917. The 1899 discovery included a nearly complete skeleton and three partial skulls. Although the partial skulls were initially identified as a different species, later studies revealed all the bones belonged to a single species. 

More Scutosaurus remains have been found at the North Dvina site in Russia. It is the most well-known member of the pareiasaur family, with at least six fairly complete individuals recovered so far. 

Extinction—When Did Scutosaurus Die Out?

Scutosaurus went extinct around 252 million years ago, towards the end of the Permian Period. Their disappearance has been linked to the mass extinction event that took place at the end of the period. The event killed off about 65% of the vertebrate population at that time. Fossil records show the pareiasaurs diversified into several genera close to the end of the period. However, none of these genera made it into the Mesozoic.

Similar Animals to the Scutosaurus

Similar animals to Scutosaurus include: 

• Mesosaurus — This reptile lived in Africa and South America during the Early Permian. Some scientists believe this animal was one of the earliest marine reptiles to have ever lived. 
• Limnoscelis -Limnoscelis is a genus of extinct carnivorous reptiles that lived in western North America during the Late Carboniferous Period. It looked like an iguana with its slender frame, short limbs, and long tail. Limnoscelis had both amphibian and reptilian features,
• Tseajaia – Tseajaia lived in the swamps of North America about 300 million years ago. It was a reptile-like amphibian believed to have been an herbivore. 

Related Animals 

• Elasmosaurus
• Hovasaurus
• Seymouria