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The taxonomy of caenagnathids from the Dinosaur Park Formation of Alberta, Canada, has remained problematic because of incomplete, partial skeletons that do not overlap anatomically. This is particularly problematic for referring mandibular remains, which are the most abundant caenagnathid fossils recovered, but cannot be confidently tied to taxa known from postcranial remains. A new, partial skeleton of Chirostenotes pergracilis preserves the mandibles, cervical and caudal vertebrae, and parts of the hindlimb. Importantly, this is the first specimen with associated mandibles and postcrania of a caenagnathid from the Dinosaur Park Formation, allowing for unambiguous referral of mandibles to this taxon. The mandibles are remarkably similar to those previously suggested to pertain to Chirostenotes pergracilis, and support its distinction from Caenagnathus collinsi. An unfused distal tarsal IV distinguishes the skeleton from Leptorhynchos elegans and supports the referral of small, upturned mandibles to this taxon. Osteohistological analysis indicates that the individual was approaching maximum body size, and provides information on the growth patterns and size of Chirostenotes pergracilis. Accordingly, this supports the division of Dinosaur Park Formation caenagnathids into three taxa of varying body sizes.

Ecological studies of extant tetrapod predators indicate that morphologically similar species which coexist in the same habitats routinely reduce interspecific competition for food by regular spacing of body size. The biggest predator species in the assemblage often differ more from one another in size than the smallest species. When coexisting carnivore species do not differ greatly in size, they commonly show morphological differences related to prey handling that may reduce dietary overlap. If carnivore species are very similar in both size and morphology, competition is avoided by habitat partitioning. Two tyrannosaurid species from the late Campanian Dinosaur Park Formation of western Canada are similar in both size and morphology, suggesting that they were segregated on the basis of habitat and/or biogeographic province. However; consideration of the living-space requirements of predator species of such large body size suggests that this kind of spatial separation would only have been possible had t...

Ecological and behavioral aspects of dinosaur research are receiving increasing attention. Tooth‐marked bones have been studied for many years, and have provided important information on the feeding behaviour of mammalian carnivores. Similarly, theropod tooth marks on dinosaur bones can provide clues to feeding behaviour and predator/prey interaction in ancient ecosystems. A study of 1000 dinosaur bones from the Dinosaur Park Formation (Judith River Group, Upper Cretaceous) in Alberta, Canada showed a relatively high percentage of tooth‐marked hadrosaurid bones (14%), whereas only 5% of the ceratopsid bones showed tooth marks, and 2% of the tyrannosaurid bones.