April 4, 2022 Scott Kraus

Ankylosaurus is a Tank Sized Cretaceous Herbivore

Ankylosaurus is a late cretaceous period herbivore known for its heavy body armor and huge tail club. This tank sized creature may have fed on vegetation but it posed plenty of threat to even the most vicious of carnivores. Below we will take a look at this archetypal armored dinosaur and discover everything you could want to know from physical appearance to fossil discovery.

Quick Facts

What Did Ankylosaurus Look Like?

Ankylosaurus was a Quadrupedal Ornithischian Dinosaur

Ankylosaurus is the largest of the Ankylosaurid family and is approximated to have measured in at 30 feet long and 5 feet wide. Standing at around 5 ½ feet tall, this incredible beast weighed in at around 13,000 lbs. This hefty weight caused by thick bony armor meant that Ankylosaurus could only walk on four legs. The width of the Ankylosaurus’ body made it more than a force to contend with particularly when it began to swing its bony tail club. The body of this Ornithischian dinosaur was low to the ground which gave it the ability to hold fast when swinging its tail in defense.  As an Ornithischian, this Cretaceous period dinosaur had a beak in addition to a birdlike hip structure.

Physical Attributes of Ankylosaurus

The skull of Ankylosaurus is a particularly unique feature, sitting low and much wider than it is long. Of all Ankylosaurus skulls discovered to date the largest measures 23 inches long and 29 inches wide. The bones of these wide skulls were solid and like other bones throughout the body fused which increased their overall strength. There was no area of this dinosaur with the exception of its vulnerable underbelly that was not protected by thick bony armor. Even the eyelids of this wide beast were made of bone.

The Armor of Ankylosaurus

The armor of the Ankylosaurus is the most distinguishing feature of this dinosaur. Made up of bone plates called osteoderms or scutes and knobs of bones that were embedded in the skin, the armor of Ankylosaurus represented an extreme version of today’s armadillos, crocodiles and lizards. Researchers believe that these thick bony plates were covered with a layer of keratin that features small but thick horns adding additional protection to this slow moving herbivore. The skull of this dinosaur also features four longer horns which projected from either side offering protection from predators. The tail of Ankylosaurus is also believed to have featured a number of spikes that not only protected but also provided an incredibly destructive weapon. These spikes ran down the length of the body and the tail beginning at the short neck and ending at the tail club. As if the thick spines along the body weren’t enough to deter predators, the large bony knob at the end acted as a battering club.

The Feeding Habits of the Ankylosaurus

Ankylosaurus had small teeth that were the shape of leaves and designed for cutting off leaves and buds from vegetation. Unlike many of their contemporary dinosaurs, Ankylosaurus did not have tooth batteries for grinding leaves and vegetation. This difference in herbivorous teeth indicates that Ankylosaurus more than likely swallowed vegetation directly with little to no breakdown of the food before it reached the stomach. It is not believed that this dinosaur swallowed gastroliths to grind food in the stomach either. Due to its incredible size, the Ankylosaurus depended upon large amounts of low lying plants to sustain the energy needed to maintain energy levels. With a lack of gastroliths and tooth batteries, this dinosaur more than likely had a large fermentation chamber not unlike much larger herbivores like Supersaurus. These large chambers began to break down plant material before it hit the gut and created large amounts of gas as a byproduct of fermentation.

Locomotion of Ankylosaurus

The low lying body of the hefty Ankylosaurus was supported by four thick columnar legs. The hind limbs were longer than the forelimbs and researchers are still uncertain as to how many digits were on each limb. Most recently it is believed that this Ankylosauridae had five toes on each of its feet. Despite being incredibly heavy, Ankylosaurus is believed to have still been able to move at a decent pace at about six miles per hour. While considered a light jog, six miles per hour was not fast enough to outrun large carnivores like Tyrannosaurus Rex.

Ankylosaurus Predators

Ankylosaurus faced a number of large carnivorous predators but unlike many other herbivores, this armored dinosaur came well protected. The boney armor of this Ankylosaurinae was much more of a challenge than most predators were willing to take on. The fat bony tail club of Ankylosaurus proved another formidable opponent that could easily break bone with direct impact. For large carnivores like Tyrannosaurus Rex, a broken bone could easily mean death by starvation or infection. The large tail club was held up by seven vertebrae and ossified tendons allowed the tail to be swung with incredible force. While larger tail knobs would have easily broken bone there is some question as to whether smaller Ankylosaurids would have been able to exert such force. Some researchers believe that the tail club of Ankylosaurus was used for intraspecies combat as well as for self defense. If a predator managed to avoid the thick armored tail, they would have to have flipped the dinosaur completely to stand a chance at feeding on it. Common predators of this bird hipped dinosaur include: Tyrannosaurus Rex.

The History of Discovering Ankylosaurus

Where Did Ankylosaurus Live?

Ankylosaurus lived around 66.5 to 65.5 million years ago at the end of the Cretaceous Period. The first specimen of this armored dinosaur was discovered in the Hell Creek Formation in Montana. Further specimens of Ankylosaurus have been discovered in the Scollard Formation in Alberta, Canada and the Lance Formation in Wyoming. To date no complete specimen of the Ankylosaurus has been discovered. From discovered remains paleontologists know that this dinosaur was native to the western shore that ran along the shallow sea that bifurcated the North American continent. During the late Cretaceous period this area represented floodplains that were rich in vegetation. The subtropical environment provided the heat and humidity that supported varied plant life on which Ankylosaurus thrived. Contemporaries of this large herbivore include: Triceratops, Torosaurus, Edmontosaurus, Trodon, Pachycephalosaurus and Tyrannosaurus Rex.

Ankylosaurus Specimen Discovery

The first specimen of Ankylosaurus was discovered in 1906 in the Hell Creek Formation in Montana by Barnum Brown. This skeleton consisted of ribs, armor, a section of a shoulder girdle, vertebrae and the top of a skull. Brown named the specimen after the medical term “ankylosis” which results from the fusing of bones in the body that causes stiffness. The full scientific name of this species is Ankylosaurus mangiventris.

The Importance of the Ankylosaurus

Ankylosaurus is an important dinosaur specimen for paleontologists for a number of reasons. As the largest of the armored Ankylosaurids, Ankylosaurus is important because it is one of the periods most formidable prey items. It is also important to study Ankylosaurus because it was one of the last dinosaur species to develop before the great Cretaceous extinction event. As one of the last dinosaurs to develop before the Cretaceous-Paleogene extinction event, this Ankylosaurid provides a number of clues as to how herbivores responded to the giant predators they were forced to contend with over time. It is very possible that Ankylosaurus represented the future of evolutionary developments in herbivorous dinosaurs.