Finding a dinosaur bone is good. A skeleton? Even better. And a bonebed? That can keep palaeontologists enraptured for decades. Even if the site is a jumble of disarticulated bones, a bonebed can offer an incredibly rich amount of detail about prehistoric lives and environments. And one of the latest to start yielding secrets is a spot near Edmonton, Alberta called the Danek Bonebed.
The 71 million year old site was discovered by amateur fossil hunter Danek Mozdzenski in 1989. Alberta’s Royal Tyrrell Museum of Palaeontology went out to collect some of the bones that summer and in 1991, bringing 80 specimens back to the museum. But excavations since 2006 by University of Alberta palaeontologists has increased the number of fossils from the Danek Bonebed more than tenfold, now totalling close to 900 specimens. That collection is the basis for an entire volume of the Canadian Journal of Earth Sciences in which collaborating teams of researchers have started to tell the tales extracted from the Cretaceous fossils.
Most of the bones at Danek are from Edmontosaurus regalis. This is a classic hadrosaur, with a long snout tipped with a shovel-shaped beak, and one of the most abundant dinosaurs from the Late Cretaceous. At least 12 of them were buried at the Danek Bonebed, which represents part of an ancient floodplain.
What killed these Edmontosaurus is a mystery. The state of preservation of the bones, Phil Bell and Nicolás Campione write, suggests that all the Edmontosaurus died around the same time rather than piecemeal over the course of many seasons. Yet the Edmontosaurus were not buried immediately. Over 30% of their bones have bite marks on them from scavengers, and some of the carnivores – such as the little, feathery Troodon and the tyrannosaur Albertosaurus – left broken teeth behind.
However they came to be entombed at the site, though, the Edmontosaurus are offering palaeontologists new details about the well-known hadrosaur. For starters, the occurrence of Edmontosaurus in central Alberta links these dinosaurs with contemporary members of the same species found in southern Alberta and even older specimens found in the northwestern part of the province. Plotting out these finds will help palaeontologists better understand what sort of habitat Edmontosaurus preferred and how populations of the dinosaur spread through North America.
And the interiors of the Edmontosaurus bones are also offering more details of the dinosaur. By looking at growth patterns in the bones, Evan Vanderven and colleagues found that Edmontosaurus reached adulthood between 10 and 15 years of age. And by comparing cycles of growth inside the Danek Bonebed fossils with those of Edmontosaurus found much further north, Vanderven and coauthors found that the Danek dinosaurs don’t show the same regular stoppage of growth as those that lived in the Arctic. This is a clue that the Arctic Edmontosaurus really did remain in the harsh northern environments year round, temporarily ceasing their growth during the cold, dark winters. More simply, the finds at one site help put others in context.
Of course, Edmontosaurus wasn’t the only dinosaur found at the site. In addition to the theropod teeth, the researchers also found some skull bones from an Albertosaurus that died close in time to the hadrosaurs. These bones, Bell and Phil Currie write, represent the northernmost occurrence of Albertosaurus yet found and adds to the picture that as the herbivorous dinosaurs of Cretaceous Alberta came and went, Albertosaurus remained a top predator for a longer span of time than any individual prey species.
There was even a scrap of a horned dinosaur in the Danek Bonebed. Tentatively assigned to Anchiceratops by Currie and Eva Koppelhus, the fossil is a single brow horncore measuring about a foot and a half long. This isn’t the only time a horned dinosaur has been found in a hadrosaur-dominanted bonebed, but here’s the thing – where palaeontologists find lots of hadrosaur bones, horned dinosaur bones are rare. What this means isn’t entirely clear. The horned dinosaurs may have been rarer on the landscape, but, then again, Currie and Koppelhus suggest that there were so many hadrosaurs that the horned dinosaurs were left to seek out other Cretaceous pastures.
These are just some of the initial findings. As Michael Burns and many of the other issue coauthors explain in their introduction, fieldwork and study of the Danek Bonebed is going to continue into the future, and is likely to be just one of an increasing number of finds in the Edmonton area. There are literally dinosaurs beneath the city, some of which have been uncovered by construction crews digging through the rock. Along with the Danek Bonebed, such finds will give us an ever-clearer picture of what it was like to walk through Cretaceous Canada.
To learn more about the Danek Bonebed, check out the special issue of the Canadian Journal of Earth Sciences.
Bell, P., Campione, N. 2014. Taphonomy of the Danek Bonebed: a monodominant Edmontosaurus (Hadrosauridae) bonebed from the Horseshoe Canyon Formation, Alberta. Canadian Journal of Earth Sciences. 51 (11): 992-1006. doi: 10.1139/cjes-2014-0062
Bell, P., Currie, P. 2014. Albertosaurus (Dinosauria: Theropoda) material from an Edmontosaurus bonebed (Horseshoe Canyon Formation) near Edmonton: clarification of palaeogeographic distribution. Canadian Journal of Earth Sciences. 51: 11: 1052-1057. doi: 10.1139/cjes-2014-0050
Currie, P., Koppelhus, E. 2014. Implications of finding a ceratopsian horncore in the Danek bonebed. Canadian Journal of Earth Sciences. 51 (11): 1034-1038. coi: 10.1139/cjes/2014-0065
Davies, J., Wotzlaw, J., Wolfe, A., Heaman, L. 2014. Assessing the age of the Late Cretaceous Danek Bonebed with U-Pb geochronology. Canadian Journal of Earth Sciences. 51 (11): 982-986. doi: 10.1139/cjes-2014-0136
Vanderven, E., Burns, M., Currie, P. 2014. Histologic growth dynamic study of Edmontosaurus regalis (Dinosauria: Hadrosauridae) from a bonebed assemblage of the Upper Cretaceous Horseshoe Canyon Formation, Edmonton, Alberta, Canada. Canadian Journal of Earth Sciences. 51 (11): 1023-1033. doi: 10.1139/cjes-2014-0064