New material of Chirostenotes pergracilis (Theropoda, Oviraptorosauria) from the Campanian Dinosaur Park Formation of Alberta, Canada

ABSTRACT

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.

KEYWORDS:

• Caenagnathidae
• Oviraptorosauria
• late Cretaceous
• osteohistology
• Dinosaur Park Formation

Acknowledgments

We thank the anonymous reviewer, whose insightful, constructive comments greatly improved the quality of the manuscript. We thank E. Bamforth, who initially discovered UALVP 59400 in 2016. The specimen was prepared by the lead author and C. Coy, who greatly improved the quality of the preparation. CT scanning of the blocks was conducted by E. Sonnex at the Alberta Cardiovascular and Stroke Research Centre (ABACUS) CT Facility in the University of Alberta Hospitals Mazankowski Centre. We thank K. Shepherd for collections access at the CMN; B. Strilisky, D. Brinkman, R. Russell, and T. Courtenay (all TMP) for access at the TMP; and C. Coy and H. Gibbins for assistance at the UALVP. We thank M. Rhodes for providing measurements of the specimen. GFF is funded by The Royal Society, NSERC and Vanier Canada. PJC is funded by NSERC Grant # RGPIN-2017-04715.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Natural Sciences and Engineering Research Council of Canada [RGPIN-2017-04715].