How Do Modern Day Crocodilians Differ from Their Ancestors like Sarcosuchus and Deinosuchus?

Modern crocodilians, including crocodiles, alligators, and gharials, have come a long way from their prehistoric ancestors like Sarcosuchus and Deinosuchus. These ancient creatures had a completely different set of characteristics and behaviors compared to their modern counterparts.

Postosuchus: A Transitional Species

One of the most fascinating prehistoric ancestors of modern crocodilians is Postosuchus. This extinct species had longer legs positioned more vertically beneath its body, unlike the sprawling legs of its crocodilian descendants. Instead of spending most of its time in the water, Postosuchus likely spent more time on land, running after prey in a fashion similar to modern lizards.

Unlike its modern relatives, Postosuchus was not well-adapted for swimming, and its diet consisted more of terrestrial animals than aquatic ones. This creature appears to be a transitional species, bridging the gap between terrestrial and aquatic lifestyles.

Modern Crocodilians: Specialized Adaptations

Modern crocodilians have evolved to become highly specialized creatures, particularly in their extraordinary bite force, which is the strongest among living animals. They are primarily semi-aquatic, spending much of their time in the water. They have a variety of adaptations that facilitate their aquatic lifestyle:

Vertebral Musculature: Strong muscles close their ears and nose off from water, preventing water from entering these organs. Mouth Flap: A flap at the back of their mouth keeps water from entering their throats when their mouths are open. Salinity-Excreting Glands: Species that live in salt water have glands in their tongues that excrete salt collected from their body fluids. Sensory Receptors: Heads are covered with sensory receptors that detect movements in the water.

One of the most noticeable features of their skulls is the flatness and the strong suture of the braincase bones to the bones that suspend the lower jaw. This is absent in their Triassic ancestors, whose skulls were not sutured in the same way.

Evolution from Terrestrial to Aquatic

Contrary to the common belief that crocodilians are “living fossils” from the ancestral archosaurs that gave rise to dinosaurs, their evolutionary journey has been quite complex. Late Triassic Rauisuchids, which held their limbs directly under their bodies, were the ancestors of modern crocodilians, not the large and formidable Sarcosuchus or Deinosuchus.

For many years, crocodilians were thought to have no significant changes from their ancestors, but recent studies show that their evolution goes beyond simple size and shape changes. Unlike their modern relatives, the Triassic ancestors of crocodilians had much less contact between the quadrate bone and the braincase, which is a significant difference from modern crocodilians.

Conclusion

The evolution of modern crocodilians from their prehistoric ancestors like Sarcosuchus and Deinosuchus has been a remarkable journey filled with significant changes in their physical and behavioral characteristics. These adaptations have allowed crocodilians to thrive in aquatic and terrestrial environments, becoming the resilient and powerful predators they are today.