Significant crocodyliform specimens from the Paleocene Estevan Coalfield of south-east Saskatchewan, Canada

The Souris River Valley in the south-east corner of Saskatchewan, Canada hosts rich fossil assemblages of mammals, fish, and reptiles of mid-late Paleocene (~ 59 Ma) age termed the ‘Roche Percée local fauna’. These are located within the upper strata of the Ravenscrag Formation, equated to the upper Tongue River Member (formerly “Bullion Creek Formation”) of Montana and North Dakota, and Paskapoo Formation of Alberta. We present two notable crocodyliform specimens from this region; the first (CMNFV 2758/RSKM P3437) is from a Ravenscrag Formation outcrop of similar age to the ‘Roche Percée local fauna’ located east of the village of Roche Percée. This specimen is referred to Borealosuchus based upon relatively large, keelless dorsal osteoderms and an enlarged foramen on the medial jugal surface. It is preserved within an interbedded siltstone-mudstone and interpreted to represent a distal overbank depositional setting. CMNFV 2758/RSKM P3437 represents the first occurrence of Borealosuchus from the middle-late Paleocene of Saskatchewan and may represent the first documented specimen of Borealosuchus formidabilis in Canada. A second notable specimen (RSKM P2243.1), an isolated nearly complete frontal found near Boundary Dam, possibly from the lower early Paleocene portion of the Ravenscrag Formation, shows alligatorid affinities. While RSKM P2243.1 cannot be assigned a precise stratigraphic placement at this time, it represents the first alligatorid-like specimen from this corner of the province. These fossil specimens highlight the need for detailed examination of the distribution and disconformable nature of the two informal units of the Ravenscrag Formation.