Agathaumas (AG-ah-THAW-mus; “Great Wonder”) is a genus of large ceratopsian dinosaur from the Late Cretaceous Period, living approximately 66 million years ago in what is now Wyoming, USA. The name was given by paleontologist Edward Drinker Cope in 1872, based on very large but incomplete fossil remains discovered earlier that year by Fielding Bradford Meek and Henry Martyn Bannister. While historically significant as one of the first ceratopsians to be named, Agathaumas is now generally considered a nomen dubium (a doubtful name) because the original fossils are not distinctive enough to confidently assign other specimens to the genus or differentiate it clearly from other ceratopsians like Triceratops.
Description and Classification
Agathaumas is known only from postcranial remains, meaning bones from behind the skull. These fossils include parts of the hip (pelvis, including a large sacrum), several vertebrae (backbones), and ribs. No skull material was found with the original specimen. Based on the size of these bones, Agathaumas was clearly a very large animal, comparable in size to other large ceratopsians such as Triceratops. Estimates suggest it could have been around 9 meters (30 feet) long and weighed several tons.
Edward Drinker Cope, who named Agathaumas, later commissioned artist Charles R. Knight to create a famous painting of the dinosaur in 1897. This illustration depicted Agathaumas with a prominent nasal horn, smaller brow horns, and a short, spiked frill. However, this appearance was highly speculative and combined features from other ceratopsian dinosaurs known at the time or discovered later, as no skull of Agathaumas was ever found. Agathaumas belongs to the family Ceratopsidae, a group of large, horned, and frilled dinosaurs. Due to its fragmentary nature, its exact position within this family is uncertain, though some have suggested it might be a chasmosaurine ceratopsid.
Distinguishing Features
Because Agathaumas is based on incomplete and non-diagnostic fossils, defining its unique distinguishing features is difficult. What is known includes:
- Extremely large body size, indicated by the massive hip bones and vertebrae.
- Fossils consist solely of postcranial elements (parts of the hip, vertebrae, and ribs).
- Lack of associated skull material, making it impossible to determine its specific horn or frill structure.
- Considered a nomen dubium because the known fossils do not show unique characteristics to distinguish it from other large ceratopsians from the same time and region, like Triceratops or Torosaurus.
Paleoenvironment and Diet
The fossils of Agathaumas were discovered in southwestern Wyoming, in rocks dating to the Maastrichtian age of the Late Cretaceous. This environment was likely a warm, humid coastal plain with forests, rivers, and swamps. Agathaumas would have shared this ecosystem with many other dinosaurs, including the famous Tyrannosaurus rex, hadrosaurs like Edmontosaurus, and other ceratopsians such as Triceratops. Like all ceratopsians, Agathaumas was a herbivore. It would have used its powerful beak to snip off tough plant material, such as ferns, cycads, and early flowering plants, which it then processed with its batteries of shearing teeth.
Significance and Ongoing Research
Agathaumas holds a significant place in the history of paleontology. It was one of the very first horned dinosaurs to be scientifically described, offering an early glimpse into this diverse group of dinosaurs. Its discovery also played a role in the “Bone Wars,” a period of intense fossil hunting and scientific rivalry between Edward Drinker Cope and Othniel Charles Marsh in the late 19th century.
Despite the limited fossil evidence, Agathaumas gained public recognition largely due to Charles R. Knight’s dramatic and widely reproduced painting. This artwork helped shape early public perceptions of horned dinosaurs, even though the reconstruction was speculative. Today, because Agathaumas is considered a nomen dubium, there is little direct ongoing research focused on the genus itself. Scientific attention has shifted to more complete and diagnostic ceratopsian specimens from the Late Cretaceous. However, Agathaumas remains an important historical footnote, illustrating the early stages of dinosaur discovery and the challenges of interpreting fragmentary fossil remains.