Anklyosaurus (“fused lizard”) may have been a tank, in more ways than one. The wide-bodied, armor-plated dinosaur of the Cretaceous period (70 million to 65 million years ago) may have moved around like a military tank, with a body mass of between 4,000 kilograms (kg) and 7,000 kilograms—roughly the weight of a small dump truck. Plant-eating Ankylosaurus, though, may also have had an enormous gut that provided plenty of room for plant matter to sit and ferment, like a brewer’s tank.
This low-browsing dinosaur may have been the largest armored dinosaur. Estimates of its length vary from six to 11 meters in length and up to 2.5 meters in height. With a body width of some two meters, Ankylosaur evolved to stay firmly on the ground. The armoring of Ankylosaurus (pronounced ahn-KEE-low-sore-us) even extended to its eyelids, with thick horny plates covering most of its body from snout to tail. The tail ended in a large bony mass, which Ankylosaur probably swung like a club for defense or territorial battles with other Ankylosaurs.
For all its tough exterior, this dinosaur was primarily a placid plant eater, probably spending most of its time foraging in low, thick undercover for food, using its shearing teeth to tear off leaves of the woody and fibrous plants of the Late Cretaceous. It did not have grinding teeth, and due to its size, Ankylosaur would have needed huge quantities of plant matter, which it swallowed whole. Without grinders, the animal would have depended on its digestive system to slowly turn the intact leafy food into fermented pulp. Such a process probably produced enormous amounts of digestive gas.
In an odd twist of evolution, considering the methane Ankylosaur undoubtedly produced, the dinosaur may have had a keen sense of smell. This is theorized from the shape of the two fossil skulls found by paleontologists, and suggests that it depended more on smell than vision to detect predators. Since Ankylosaur shared territory with Tyrannosaurus, it needed every defense possible. With its wide, low body, if Ankylosaur could stay upright, it may have been too challenging for most predators. Its underbelly was not armored, but any predator trying to flip the creature would have needed to push over three to four tons of armored muscle moving about on four stubby legs. Its armored tail, though probably limited in its swing, probably also helped the animal to defend itself. Even its tiny head was protected, with four large horns, discouraging Tyrannosaurus and other carnivores from trying to take the entire head in its mouth. Ankylosaur’s tiny head also reveals a tiny brain for its body; it was not an intelligent creature, a trait it shared with all of the ankylosaurids.
From the two fossil skulls and three partial fossil skeletons, scientists know Ankylosaur roamed the area of North America in what is now Montana and western Canada, but in 1996 its tracks were found in Bolivia, South America. From these tracks, paleontologists calculate that the dinosaur could move quickly if needed, despite its mass and short (four feet or less) legs. First named by Barnum Brown in 1908, Ankylosaur is the last in the evolution of armored dinosaurs, arriving shortly before the mass extinction 65 million years ago, in the Cretaceous-Tertiary period.
Ankylosaurus is one of the most popular and best-known dinosaurs, not least for its improbably massive, low body and its heavy armoring. The taxonomy of Ankylosaur is Animalia, Chordata, Archosauria, Ornithischia, Thyreophora, (Enoplosauria), Ankylosauria, Ankylosauridae, Ankylosaurus. The species is Ankylosaurus magniventris.