Timeline of Discovery and Extinction
1822
First description of *Mesosaurus* by Cuvier. Initially, it was considered a fossil of a living reptile, leading to much debate amongst early paleontologists regarding the validity of fossil evidence and the concept of extinction. The initial classification highlighted its unique features – a flattened body, paddle-like limbs, and small size – which contrasted sharply with known marine reptiles.
1852
Georges Cuvier publishes *Lecons de paleontologie*, formally establishing the concept of extinction and using fossil evidence to understand evolutionary relationships. *Mesosaurus* becomes a key example in his arguments, demonstrating that organisms could disappear from the Earth entirely. This marked a pivotal shift in scientific thought.
1870s - 1920s
Numerous expeditions to the Triassic formations of South America (Brazil, Argentina, Uruguay) yield countless *Mesosaurus* fossils. These finds cemented its place as a defining species of the period and fueled further research into the geological history of Gondwana. The discovery sites were often associated with ancient river systems that eventually flowed into shallow seas.
20th Century - Present
Paleontologists continue to study *Mesosaurus* remains, refining our understanding of its paleoecology and the environmental conditions in which it lived. Research focuses on reconstructing the ancient river systems that supported this species and analyzing trace fossils (footprints) to gain insights into its behavior – likely a bottom-dwelling predator. The fossil record provides crucial data for climate modeling during the Triassic period.
Characteristics of *Mesosaurus*
Physical Description
*Mesosaurus* was a small, flattened reptile, typically around 1 meter (3.3 feet) in length and weighing approximately 60-80 kilograms (132-176 pounds). Its most distinctive features included:
- A streamlined, paddle-shaped body – ideal for navigating shallow waters.
- Two short, stout limbs with broad, flattened feet resembling paddles.
- Small, reduced eyes, suggesting a primarily bottom-dwelling lifestyle.
- A relatively large head with sharp teeth adapted for catching small invertebrates and fish.
Paleoecology
Based on fossil evidence and the environment in which it was found, *Mesosaurus* likely inhabited shallow, brackish (mixed saltwater and freshwater) environments along ancient river systems that drained into seas during the Triassic period. It’s believed to have been a predator, feeding on invertebrates and small fish.