The Ankylosaurus, a genus of armored dinosaur known for its formidable appearance, continues to intrigue paleontologists. Named the "stiff lizard," this large, herbivorous dinosaur, specifically the species Ankylosaurus magniventris, roamed western North America during the late Cretaceous period, approximately 66.5 to 65.5 million years ago, just before the cataclysmic extinction event. While a complete fossil skeleton remains elusive, Ankylosaurus is considered the quintessential armored dinosaur, possessing heavy armor and a massive tail club. It was also the largest of its kind.
Despite being a giant compared to most modern land animals, recent studies have proposed a more modest size estimate for the Ankylosaurus. Scientists now believe it measured around 6.25 meters long, 1.5 meters wide, and 1.7 meters tall, with a weight exceeding 6,000 kg. Its body was notably broad and flat. This four-legged creature had hind legs longer than its forelegs and a distinctive, triangular skull that was wider than it was long. Its small, leaf-shaped teeth suggest it didn't chew its food extensively, unlike other contemporary dinosaurs.
The most striking feature of the Ankylosaurus was its armor, a series of bony plates and nodules embedded in its skin, similar to those found on modern crocodiles and armadillos. These osteoderms, covered in a tough, keratinous layer, varied in size. The larger, flat plates were arranged in rows along its neck, back, and hips, with smaller nodules filling the gaps. Notably, the Ankylosaurus's armor was smoother in texture compared to some of its relatives, lacking the pronounced ridges seen in dinosaurs like the Edmontonia. A row of flat, triangular spikes also lined the sides of its tail.
Perhaps the most famous feature of the Ankylosaurus is its heavy tail club. Made from several fused osteoderms and supported by the last seven tail vertebrae, this club was a powerful defensive weapon. Studies have shown that the tail could be swung with enough force to cause significant damage to the bones of an attacker. However, it's still debated whether the tail club was used primarily for defense against predators, in intraspecies combat, or both.
Ankylosaurus lived in a subtropical environment with a humid and warm climate, alongside a diverse array of other dinosaurs, including the Tyrannosaurus, Triceratops, and Edmontosaurus. Its fossils are relatively rare compared to those of its contemporaries. Research suggests that Ankylosaurus, with its broad snout and non-selective feeding habits, likely inhabited upland regions away from the coast, while other armored dinosaurs like the Edmontonia lived in coastal areas.
