The taphonomy of a Centrosaurus (Ornithischia : Certopsidae) bone bed fromthe Dinosaur Park Formation (Upper Campanian), Alberta, Canada, with comments on cranial ontogeny

Bone bed 43 is one of at least eight paucispecific Centrosaurus bone beds l ocated in the Dinosaur Park Formation (Upper Campanian) in Dinosaur Provinc ial Park, Alberta, Canada. It long has been used as a case example for evid ence of herding and social behavior in dinosaurs, but a detailed analysis o f the site has not been presented until this study. The bone bed is dominat ed by the disarticulated, mostly fragmentary and slightly abraded remains o f Centrosaurus apertus, with minor occurrences of other taxa, notably teeth from the large tyrannosaurid Albertosaurus libratus. Fossils occur in a st acked to amalgamated succession of lag deposits, deposited and reworked at the erosional base of a paleochannel. The most parsomonious scenerio sugges ts that Centrosaurus material represents part of a large aggregation of ani mals (possibly numbering in the thousands) that died by drowning on the all uvial plain. Disarticulation occurred at a point upriver from the bone-bed site. Scavenging by theropods, primarily Albertosaurus, at or near the orig inal site of death is suggested by the high number of shed theropod teeth. A subsequent event prior to fossilisation moved the material to its present location removing many juvenile-sized and hydrodynamically light elements from the original death assemblage. Evidence for distinct size classes amon gst the preserved elements is not supported by the data, but the size range of elements preserved are representative of living individuals that would have ranged from small juveniles to mature adults. The large data base of s pecimens from bone bed 43 allows for the illustration of the ontogenetic ch anges that occurred in the diagnostic cranial elements of Centrosaurus.