The question of the most common dinosaur refers not to the largest population that once roamed the Earth, but rather the species for which the largest quantity of fossil material has been discovered. Paleontology relies on preserved remains, and a species’ visibility in the fossil record is heavily influenced by how easily its remains were preserved and found. A dinosaur’s “commonality” is primarily a measure of how frequently its bones were buried and fossilized in accessible locations. The answer is rooted in the sheer volume of recovered bones.
Identifying the Most Frequent Find
The dinosaur most abundantly represented in the fossil record belongs to the Hadrosauridae family, often called duck-billed dinosaurs. Specifically, the genus Edmontosaurus stands out as one of the most frequently found dinosaurs in North America. This massive herbivore lived during the Late Cretaceous period and is known from numerous immense bonebeds across the western United States and Canada. These sites contain countless skeletal elements, sometimes representing hundreds of individual animals buried together in a single mass death event.
One notable example is the Danek Bonebed in Alberta, Canada, where the remains of at least a dozen Edmontosaurus regalis individuals were found. Another significant concentration is the Hanson Ranch bonebed, which has yielded over 13,000 skeletal elements corresponding to dozens of Edmontosaurus annectens individuals. The sheer volume of recovered material from these mass burial sites far surpasses the fossil evidence for many other dinosaur species, providing a detailed record of their anatomy, growth, and group behavior.
Factors Behind its Widespread Existence
The widespread existence of Hadrosaurs like Edmontosaurus in the fossil record reflects their successful life strategy. As large herbivores, they occupied the base of the food chain, allowing them to exist in much greater numbers than predatory dinosaurs, such as Tyrannosaurus rex. Their broad, duck-like snouts and specialized dental batteries contained hundreds of tightly packed teeth, enabling them to process tough, fibrous vegetation efficiently. This dietary advantage supported enormous population sizes within their ecosystem.
Evidence suggests that Edmontosaurus was a gregarious animal that lived in vast herds. This social behavior contributed significantly to their high count in bonebeds, as mass deaths of large groups led to the simultaneous preservation of many individuals. Furthermore, related hadrosaurs, such as Maiasaura, exhibited communal nesting behavior, laying clutches of 30 to 40 eggs in closely packed colonies. This social reproductive strategy, which may have included parental care, boosted their reproductive success and contributed to maintaining a high population density across their wide geographical range.
The Science of Counting Fossil Remains
Paleontologists use specific methodologies to quantify dinosaur finds, acknowledging that the fossil record is inherently biased toward certain types of organisms and preservation environments. The concept of the “bonebed” is central to these discoveries, referring to a localized geological layer containing a dense concentration of bones from multiple individuals. These accumulations are often the result of catastrophic events, such as droughts, floods, or volcanic ash falls, which rapidly buried entire herds, leading to excellent preservation conditions.
The study of taphonomy, which is the process of how organisms decay, are buried, and become fossilized, helps explain why some species are more common than others. Organisms that live in environments prone to rapid sedimentation, like floodplains and river deltas, have a much higher chance of fossilizing than those in dry uplands. Therefore, the “common” hadrosaur is also the “commonly preserved” hadrosaur, due to its preference for coastal and floodplain environments where mass burial was more likely.
To estimate the number of animals in a bonebed, scientists use a statistical method called the Minimum Number of Individuals (MNI). This technique involves counting the most frequently occurring or unique skeletal element from one side of the body, such as the left femur, to determine the fewest possible individuals present in a mixed assemblage of bones. For example, if a bonebed yields 110 left femurs of Edmontosaurus, the MNI is at least 110 individuals, regardless of the total number of bone fragments recovered. This rigorous calculation method confirms that the high number of Edmontosaurus fossils genuinely represents a massive quantity of ancient animals.