5.8" Fossil Ankylosaurid/Nodosaurid Osteoderm (Scute) - Wyoming

Ankylosaurus was the namesake of the Ankylosaurid family of dinosaurs to which it belonged, and one of the last ones to live before the Cretaceous-Paleogene extinction event 65 million years ago. Residing in western North America, Ankylosaurus was an herbivorous dinosaur with a low, squat body, a short neck with a square head, and a long tail ending with a large, bony club which it likely used for self-defense against predators like T.rex. Perhaps most notably, Ankylosaurus was one of the most heavily armored dinosaurs of all time. Ankylosaurs were known for their heavy bone armor all over the top half of their bodies, as well as bony knobs protruding all over their backs and face. Even their eyelids were protected against potential attack.

At adult size, these impenetrable behemoths measured about 25-30 feet and 4 to 8 tons. At that size, even an adult Tyrannosaurus would have had difficulty getting close enough to try and flip it to get at Ankylosaurus's less armored underbelly. Dinosaurs like Ankylosaurus prove indubitably that herbivores were just as impressive and dangerous as their carnivorous counterparts.

Denversaurus was a panoplosaurin nodosaurid dinosaur from the late Cretaceous, approximately 66 million years ago. Denversaurus was an herbivore like other nodosaurids/ankylosaurids, and measured approximately 20 feet (6 meters) on average. It lived in North America in the midwest alongside more well-known contemporaries such as Tyrannosaurus rex, Triceratops, and Pachycephalosaurus. Like other nodosaurids/ankylosaurids, it had an armored carapace made up of bony scutes all along the dorsal surface of its body.

About The Lance Formation

The Lance Formation of Wyoming, which dates back to the Late Cretaceous period between 66 and 69 million years ago, is home to a wide variety of both dinosaur and assorted small vertebrate fossils. During the Cretaceous, this midwestern formation would have been comprised of streams connected to the large Western Interior Seaway that split continental North America in half down the midwest. As a result of the subtropical climate and frequent rainfall, life flourished both on land and in the sea. These wet environments created perfect scenarios for sediment deposition, making the resulting Lance Formation such a fertile fossil site.

Perhaps the most famous Lance resident would be Tyrannosaurus rex, the largest North American carnivore to ever live. However, other smaller theropods also roamed the American midwest in this subtropical coastal stream system, including the beaked Ornithomimus, a lanky running theropod with a build similar to a modern ostrich, as well as several small predatory troodonts such as Paronychodon and Pectinodon.

Herbivorous dinosaurs also took advantage of the abundance offered by this unique era. Armored ankylosaurs dwelt in herds, their safety assured by their numbers, their heavy bone plating protecting most of their bodies and even their eyelids, and huge bone clubs on the ends of their tails providing them with powerful offensive capabilities. Ceratopsians like the famous Triceratops also formed protective herds, guarding their necks with frills and horns. Their smaller relatives, the dome-headed pachycephalosaurs, were also well represented in the area. Hadrosaurs, duck-billed titans with huge batteries of plant-grinding teeth in elongated snouts, are also well known from the region.

In addition to dinosaurs, a wide variety of fishes, amphibians, lizards, snakes, turtles, champsosaurs, crocodilians, and pterosaurs have been found in the formation.