Phytosaurs were a widespread and successful group of semi-aquatic, archosaurian reptiles that thrived during the Late Triassic period, approximately 235 to 201 million years ago. They were globally distributed, with fossils found on every modern continent, and were among the top predators in their ecosystems. Ranging in size from 2 to over 12 meters (6 to 40 feet) in length, they bore a remarkable, and classic, example of convergent evolution with much later animals.
Instead of being related to crocodiles, phytosaurs were a distinct lineage of archosaurs, a group that also includes crocodilians, pterosaurs, and dinosaurs. Their most iconic feature was an elongated, heavily armored skull, with nostrils positioned high on a bony crest in front of their eyes, not at the tip of the snout like a crocodile. This adaptation allowed them to breathe while almost completely submerged, much like a modern hippopotamus or crocodile. Their bodies were protected by rows of bony osteoderms (armor plates) embedded in the skin along their back and tail.
Phytosaurs were formidable carnivores, occupying the aquatic apex predator niche that crocodiles would later fill. Different species had different feeding strategies, reflected in their snout morphology: some, like Mystriosuchus, had long, slender, fish-catching snouts filled with numerous conical teeth, while others, like Nicrosaurus, had robust, deep snouts for grappling with larger terrestrial prey that came to the water's edge. They likely spent most of their time in rivers, lakes, and swamps, ambushing prey from beneath the water's surface. The extinction of the phytosaurs at the end of the Triassic period, likely due to widespread volcanic activity and climate change, opened the ecological door for the rise and diversification of the true crocodilians in the Jurassic, which would come to dominate the same semi-aquatic predatory roles for millions of years to come.
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