Centrosaurus apertus was an herbivorous ceratopsian dinosaur. It was relatively small compared to its larger relatives, only reaching a length of approximately 6 m (1). C. apertus lived in the Late Cretaceous, 76.5 to 75.5 million years ago (2). Like its relative Triceratops, C. apertus had a bony frill protecting its neck and a large nose horn (1). Its name refers to this nose horn, meaning “sharp-point reptile (3).” It has another two large horns on its frill, curving forward distinctively.
C. apertus is known from numerous specimens. Thousands of individuals have been discovered in bonebeds at Dinosaur Provincial Park in Alberta, ranging from juveniles to old adults. The vast numbers of C. apertus at this location has led paleontologists to conclude that C. apertus traveled in large herds (1).
Like all other certopsids, Centrosaurus apertus ate only plant material. C. apertus fossils have been found in massive bonebeds, with thousands of individuals of all different ages. These findings have led paleontologists to conclude that C. apertus traveled in large herds (1). One of the sites where large numbers of C. apertus have been found is the Dinosaur Park Formation of Alberta, Canada. The environment represented by this site was a coastal plain river system, flowing east towards the large inland sea that covered much of North America during the time period. This was a lush location with high diversity among vertebrates, invertebrates, and plants. High seasonal variation in rainfall led to periodic droughts that could have caused mass mortality among the dinosaurian residents (2).
C. apertus fossils are found in a very limited range of sites. This is strange, considering that they are among the most abundant fossils found at those locations. C. apertus appears to have had a very small geographic range, even though their large body sizes would have allowed them great mobility (3).
Centrosaurus apertus is the only member of the Centrosaurus genus, though this has not always been the case. Coronosaurus brinkmani was originally classified as Centrosaurus brinkmani, due to the similarities between it and C. apertus (1). It has since been reclassified, but recent analysis suggests that it is the closest known relative to C. apertus. Both Centrosaurus and Coronosaurus are members of the Ceratopsidae species group, along with the famous Triceratops (2).
This is not the only taxonomic debate surrounding C. apertus. Previously, paleontologists wondered whether species within the generaStyracosaurusand Monoclonius might in fact be the same species as C. apertus (3). This question was answered with the discovery of hornlike growths that protrude from the back of the frill of C. apertus. These growths are only found in C. apertus and not the other species (4). These sorts of questions are not uncommon in the study of Ceratopsidae, as it can be difficult to tell whether a specimen represents a new species or simply an older or younger version of a species already discovered (5).
Massive bonebeds have been found containing thousands of Centrosaurus apertus individuals. One of these is the Hilda mega-bonebed, an area near Hilda, Alberta. Paleontologists think that this bonebed represents a massive herd of C. apertus killed by a flood. The flood could have drowned C. apertus directly, or induced outbreaks of flood-related diseases. There is no way to tell which of these happened based on the evidence found thus far. These floods were caused by tropical storms, or possibly hurricanes such as those sometimes seen in the Gulf of Mexico today (1).
A similar case can be seen in the Dinosaur Park Formation. The skeletons found here were disarticulated bones jumbled into one large assemblage. Carnivorous theropod dinosaur teeth were found, as well as C. apertus bones marked by theropod bites. Theropods likely scavenged dead C. apertus individuals after death. The number of specimens found at this site provides ways for paleontologists to answer longstanding questions about C. apertus (2). For a long time, paleontologists have wondered whether there might be sexual dimorphism in ceratopsids, differences between the males and females of the species (3). However, no evidence was seen for sexual dimorphism among the numerous specimens found at the Dinosaur Park Formation, which undoubtedly included both males and females (2).
Ceratopsid dinosaurs are famous for their distinctive frills and facial horns. Ever since these dinosaurs were discovered, there has been debate as to what the function of these features may have been. Commonly, these features are thought to either function in defense, combat, or display. While Triceratops had solid and thick frills, the frills of Centrosaurus apertus were too thin to have provided much defense against predators. A recent study of ceratopsid skulls, including C. apertus, found bone injuries caused by intraspecific combat. To cause these injuries, C. apertus individuals must have fought with members of their own species. This behavior is similar to stags butting heads during mating season (1).