The Dinosaur Park Formation of Saskatchewan

The Campanian Belly River Group (BRG) is a nonmarine clastic cycle in the Western Canada Sedimentary Basin. In southern and central Alberta, the BRG has been subdivided in ascending order into the Foremost, Oldman, and Dinosaur Park formations based on distinctive lithologic, petrographic, and geometric characteristics. Regional surface and subsurface correlation of the BRG reveals the three formations are discernable in southwestern Saskatchewan. The BRG and its associated formations are formally recognized for the first time in Saskatchewan with facies, depositional environments, and a stratigraphic framework interpreted to provide a concise treatment of the Group in southwestern Saskatchewan. A new lithostratigraphic unit within the uppermost Dinosaur Park Formation is recognized based on laterally extensive barrier island, lagoon, and estuary basin deposits. The Neekaneet Member is established as a means to aide in discussing the transition from nonmarine clastics of the BRG to marine shales of the overlying Bearpaw Formation.

DOI: 10.18435/vamp29374 Though relatively uncommon, sea turtles (Superfamily Chelonioidae + Family Protosetgidae + Toxochelys) are an intriguing component of western Canada’s Cretaceous marine faunas. Studies of sea turtle diversity patterns within the Late Cretaceous Western Interior Sea suggest, for reasons possibly related to climate, that these animals favoured southern portions of the Western Interior Sea (Nicholls and Russell, 1990), occurring much less frequently in in Canada than in the United States. In Saskatchewan, sea turtles are represented by just two occurrences. The first, representing the northernmost occurrence of a seat turtle in North America, is from the Cenomanian Ashville Formation (erroneously reported as the Santonian Niobrara Formation) along the Manitoba Escarpment (Nicholls et al. 1990). The second occurrence is from the upper Campanian Bearpaw Formation of southwest Saskatchewan (Nicholls et al. 1990). The Ashville Formation specimens, a humerus (RSKM P2077.64) and other fragmentary remains (RSKM P2077.31) were tentatively ascribed to the Protostegidae. The protostegids, which includes the giant sea turtle Archelon, are an extinct basal family of sea turtle that is the sister taxon to the Chelonioidea, which includes all other known sea turtles except the genus Toxochelys (Evers et al., 2019). The Bearpaw Formation specimens, small rib pieces and a badly weathered peripheral fragment (CMN 40660), could not be identified beyond Chelonioidea (Nicholls et al. 1990). Herein is described the first occurrence of a chelonioid sea turtle from marine strata within the Dinosaur Park Formation of Saskatchewan. RSKM P3197.198 is a left costal plate of the carapace, with a maximal length of 150 mm, maximal width of 90 mm in width, and maximal thickness of 16 mm. While broken along its medial margin, the lateral peripheral edge is reasonably well preserved. The costal plate is broad and slightly convex dorsally, with no noticeable suturing or ornamentation. Although more preparation needs to be done on the specimen, it is tentatively ascribed to the Clade Panchelonioidea, nested within the Superfamily Chelonioidea, based on the carapace morphology. The specimen was collected in 2016 from a marine bonebed near the hamlet of Herschel, Saskatchewan. Recent studies have placed the Herschel Marine Bonebed (HMB) within a marine interval of the upper Dinosaur Park Formation, in a shallow-marine barrier-island basin environment (Street et al., 2019). The HMB has yielded a high diversity of marine vertebrates, including ichthyodectids, Enchodus sp., Protosphyraena sp., Ischyodus rayhaasi, hybodontids, odontaspidids and other lamniforms, as well as polycotylid and elasmosaurid plesiosaurs, and mosasaurine and plioplatecarpine mosasaurs. In a review of marine turtles from the Late Cretaceous of Alberta, Brinkman et al. (2015) identified at least three genera of chelonioids from this province; Nichollsemys, Lophochelys and Kimurachelys. Nichollsemys and one specimen of Lophochelys are known from open marine sediments of the Bearpaw Formation (Brinkman et al., 2006). Kimurachelys and a second specimen ascribed to Lophochelys are from the Lethbridge Coal Zone of the uppermost Dinosaur Park Formation (Brinkman et al., 2015). RSM P3197.198 is significantly larger than the Alberta specimens referred to Lophochelys, and both Nichollsemys and Kimurachelys are known only from cranial material. Therefore, more work and more specimens will be required to determine if RSKM P3197.198 can be ascribed to any of these taxa, or if it represents the first occurrence of another taxon in the northern Western Interior Seaway. Comparison of RSKM P3197.198 from the HMB with the Alberta material raises an intriguing question about the possible paleoenvironmental preference of Canadian chelonioids. Although not necessarily directly contemporaneous with the Lethbridge Coal Zone, the HMB represents a similar shallow-marine, nearshore environment. Brinkman et al (2015) suggested that chelonioids may have been brackish-water or even freshwater tolerant. This may also apply to RSKM P3197.198, which was found in a similar paleoenviroment. Although the sample size is small, chelonioid diversity appears to be robust in nearshore, shallow-marine or estuarine deposits. This could be a reflection of sea turtle ecology as, unlike other Cretaceous marine reptiles, these animals needed to come onto land in order to lay eggs. RSM P3197.198 represents the largest and most diagnostic chelonioid specimen known from Saskatchewan. The collection of additional specimens from marine sediments of the Dinosaur Park Formation may reveal important information on the diversity and paleoecology of marine turtles in western Canada. References: Brinkman, D., M. Hart, H. Jamniczky and M. Colbert. 2006. Nichollsemys baieri gen. et sp. nov, a primitive chelonioid turtle from the late Campanian of North America. Paludicola, 5(4), 111-124. Brinkman, D. B., M. Densmore, M. Rabi, M. J. Ryan and D. C. Evans. 2015. Marine turtles from the Late Cretaceous of Alberta, Canada. Canadian Journal of Earth Sciences, 52(8), 581-589. Evers, S. W., P. M. Barrett., R. B. J. Benson. 2019. Anatomy of Rhinochelys pulchriceps (Protostegidae) and marine adaptation during the early evolution of chelonioids. PeerJ, 7: 6811. Nicholls, E.L., and A. P. Russell 1990. Paleobiogeography of the Cretaceous Western Interior Seaway of North America: the vertebrate evidence. Palaeogeography, Palaeoclimatology, Palaeoecology, 79: 149–169. Nicholls, E.L., T. T. Tokaryk, T.T., and L. V. Hills. 1990. Cretaceous marine turtles from the Western Interior Seaway of Canada. Canadian Journal of Earth Sciences, 27(10): 1288–1298. Street, H. P., E. L. Bamforth and M. M. Gilbert. 2019. The formation of a marine bonebed at the Upper Cretaceous Dinosaur Park-Bearpaw transition of west-central Saskatchewan, Canada. Frontiers in Earth Science, 7, 209.

That the province of Saskatchewan contains Late Campanian-aged fossil-bearing deposits coeval with those in Alberta and Montana is not new information. These Saskatchewan deposits had been documented in a number of palaeontological publications (e.g. Eberth et al., 1990, Tokrayk and Harrington 1992), and were referred to generally as the ‘Judith River Formation’. However, these deposits were sometimes more similar, geologically and palaeontologically, to the Dinosaur Park Formation of Alberta. This rendered the designation of Saskatchewan’s Late Campanian rocks as a northern extension of the Judith River Formation somewhat problematic. Would it be more correct to refer to the deposits are an eastern extension of the Dinosaur Park Formation? The fact that outcrops of this aged rock in Saskatchewan are sparse, discontinuous and often difficult to access further complicated the issue. In 2018, the terrestrial-to-marginal marine Late Campanian formation underlying the fully marine Bearpaw Formation in Saskatchewan was formally named the Dinosaur Park Formation (DPF). Based on stratigraphy and biostratigraphy, it was suggested to be coeval with the upper Dinosaur Park Formation of Alberta (Gilbert et al, 2018). However, it was evident from this and more recent studies that the Saskatchewan DPF is unique in and of itself, containing several sedimentological anomalies that differentiate it from both the Albertan Dinosaur Park Formation and the coeval Coal Ridge and Woodhawk members of the Judith River Formation (Gilbert et al., 2019). Saskatchewan’s DPF potentially contains important information about the role of paleolatitide and proximity to the paleocoastline in shaping Late Campanian paleobiodiversity patterns across western North America. Despite this, a lack of quantitative spatial comparative studies has rendered it unclear how Saskatchewan’s DPF paleoecology relates to that in coeval formations external to the province. In this study, we conducted the first large-scale spatial beta (‘among-site’) diversity analysis of Dinosaur Park and Judith River paleocommunities across Alberta, Saskatchewan and Montana. A total of twelve well-sampled DPF/JRF microvertebrate sites from each of the three locations were included in this preliminary study. In these occurrence-based diversity analyses, each microvertebrate assemblage represents a single paleocommunity (‘point’). Non-metric multidimensional scaling was used to ordinate the points, which were then transposed onto a spatial (geographical) plane. Weighted minimum spanning networks were plotted to better identify patterns. Although paleocommunities within Saskatchewan contained many of the same taxa, intra-provincial beta diversity was high, with the Saskatchewan assemblages being more similar to the Alberta or Montana than to one another. Perhaps tellingly, the Saskatchewan site closest to the US boarder was the most similar to the JRF assemblages, while the site furthest to the west was most similar to the Albertan DPF assemblages. The high beta diversity amongst Saskatchewan paleocommunities may be due to the shifting paleoenvironments associated with the Western Interior Sea, as the stratigraphic record demonstrates a prevalence of estuarine environments with frequent marine inundations. Marine influence and by extension, proximity to the paleocoastline, may therefore have been a major driver of this spatial heterogeneity. Future research, including increasing the sample size, will help to elucidate why north-south and east-west spatial heterogeneity exists in the DPF and JRF. References Eberth, D.A., D.R. Braman, and Tokaryk, T.T. 1990. Stratigraphy, sedimentology and vertebrate paleontology of the Judith River Formation (Campanian) near Muddy Lake, west-central Saskatchewan. Bulletin of Canadian Petroleum Geology 38(4): 387-406. Gilbert, M.M., E. L. Bamforth, L.A. Buatois, and R.W. Renaut. 2018. Paleoecology and sedimentology of a vertebrate microfossil assemblage from the easternmost Dinosaur Park Formation (Upper Campanian) Saskatchewan, Canada: Reconstructing diversity in a coastal ecosystem. Palaeogeography Palaeoclimatology Palaeoecology 495: 227-244. Gilbert, M.M., L.A. Buatois, and R.W. Renaut. 2019. Ichnology and depositional environments of the Upper Cretaceous Dinosaur Park–Bearpaw formation transition in the Cypress Hills region of Southwestern Saskatchewan, Canada. Cretaceous Research, In press. Tokaryk, T.T. and C.R. Harington. 1992. Baptornis sp.(Aves: Hesperornithiformes) from the Judith River Formation (Campanian) of Saskatchewan, Canada. Journal of Paleontology 66(6): 1010-1012.

A New Dinosaur Park Formation (Campanian, Late Cretaceous) Microvertebrate Locality From Southwest Saskatchewan The Dinosaur Park Formation has been well-studied in Alberta for decades, particularly in Dinosaur Provincial Park, a UNESCO World Heritage Site, from which the formation gets its name. Although deposits from the same time period have been known in Saskatchewan for nearly as long, it was not until this year (2018) that the Dinosaur Park Formation was described in the province (see Gilbert et al. 2018). Outcrops of the Dinosaur Park Formation are far less common and extensive in Saskatchewan when compared to Alberta but are rich in vertebrate fossils. Studying the floras and faunas of the Dinosaur Park Formation in both provinces can allow for important studies of spatial beta diversity trends, particularly in relation to proximityto the paleocoastline as a biodiversity driver. Herein, we describe a new Dinosaur Park Formation locality in Saskatchewan known as Woodpile Coulee. The site is located in the extreme southwest corner of the province on the southern flank of the Cypress Hills. Outcrops are recorded along two or three small creeks adjacent to the United States/Canada boundary and the Alberta border. The best exposures in this region occur at Woodpile Coulee, where the entirety of the Belly River Group is exposed in roughly inclined strata (dipping ~400 to the south) associated with a Pleistocene thrust structure. Furnival (1946) studied the region and correlated the beds with the Judith River Formation of Montana. In the region, the Dinosaur Park Formation consists of coal dominated muds, silts, and fine-grained sands highly influenced by small-scale transgressive-regressive cycles. The microsite is situated very near the Bearpaw-Dinsosaur Park Formation contact in a silty mudstone dominated by gastropods and bivalves. The Woodpile Coulee microsite contains at least 36 different paleospecies. Fossils were first collected in the late 1980s and early 1990s by the Royal Saskatchewan Museum, which currently curates the collection at the T. rex Discovery Centre in Eastend, SK. One subsequent collection was made in 2014, which included a bulk sample of the fossil-producing layer. The paleocommunity recovered from the Woodpile Coulee microsite is somewhat unusual in Saskatchewan, containing several taxa that are rare or unknown elsewhere in the province. Among the dinosaur species present are nodosaurs (possibly Edmontonia sp. and/or Panoplosaurus sp.), represented only by their distinct teeth, which are known from only one other site (Gilbert et al. 2018). Several teeth from a pachycephalosaur, suggested to be Stegoceras sp., have also been recorded, making it the first occurrence of this genus in Saskatchewan. At least one hadrosaur and one ceratopsian are known from the site, as well as a small hypsolophodont suggested to be Thescelosaurus sp. Tyrannosaurids are present, in addition to several small theropods, including Troodon sp. Crocodile material, attributed to the genus Leidyosuchus sp., and champsosaur material is fairly common. There are at least two families of turtles, including baenids and trionychids, as well as a broad diversity of fish from several different orders, including at least five teleost taxa. Teeth from the ray Myledaphus are also well represented. Intriguingly, the fauna at Woodpile Coulee shares an interesting characteristic with the only other Dinosaur Park Formation assemblage found in Saskatchewan (see Gilbert et al. 2018). The microsite contains a diverse assemblage of both chondrichtians and amphibians. As the sharks present are marine species, and as amphibians are generally known to be intolerant of salinity, the presence of an abundance and diversity of both groups suggests mixing of two different environments. The single occurrence of an ammonite fragment reinforces that the site was deposited under marine influence, while the presence of salamanders, frogs and mammals reinforces the idea of mixing from a terrestrial environment. The Woodpile Coulee site is unique both in terms of biodiversity and depositional environment. Future studies of this locality will provide important insights into our current understanding of the Dinosaur Park Formation in Saskatchewan, and will lead to very interesting and significant discoveries. Literature Cited Furnival, G.M. 1946. Cypress Lake map-area, Saskatchewan. Department of Mines and Resources, Geological Survey of Canada, Memoir, 242. Gilbert, M.M., E.L. Bamforth, L.A. Buatois, and R.W. Renaut. 2018. Paleoecology and sedimentology of a vertebrate microfossil assemblage from the easternmost Dinosaur Park Formation (Late Cretaceous, Upper Campanian) Saskatchewan, Canada: Reconstructing diversity in a coastal ecosystem. Palaeogeography, Palaeoclimatology, Palaeoecology 495:227–244.

A ∼42 m section of Late Cretaceous Upper Campanian sediments in Saskatchewan Landing Provincial Park, southwestern Saskatchewan, Canada, represents the easternmost outcrop of the Dinosaur Park Formation in the Western Interior Basin. Herein we document a new microvertebrate locality from the upper part of this formation that shows high diversity in a mixed coastal and marine assemblage. Palynology, ichnology, sedimentology, and vertebrate palaeontology are integrated to determine paleoenvironmental and paleoecological conditions in the region. The site is interpreted as having been deposited under marginal-marine conditions near a shoreline undergoing transgression by the encroaching Bearpaw Sea. Though well studied and sampled in Alberta, the Dinosaur Park Formation is poorly exposed with little known associated vertebrate assemblages in Saskatchewan. These discoveries from the new microvertebrate site offer new insights into Late Cretaceous ecosystems near paleocoastlines, allowing for future studies of spatial diversity patterns relative to Albertan faunas. Herein is also presented the first published occurrences of several Late Campanian vertebrate taxa in Saskatchewan.

The Campanian-aged Dinosaur Park Formation (DPF) of Alberta, Canada is one of the most productive and well-studied dinosaur bearing units in the world. While the formation is present in Saskatchewan, outcrop is sparser, widely distributed, and difficult to access. As it has been less well studied, Saskatchewan’s DPF is generally less well understood than the DPF in Alberta, despite being highly fossiliferous. The DPF in Saskatchewan represents the northeasternmost occurrence of the formation in Canada, and therefore holds considerable potential for addressing questions about the large-scale spatial diversity patterns in the Late Campanian that cannot be addressed by studying the DPF in Alberta alone. In particular, questions concerning the proximity of the Western Interior Sea, and its influence on diversity could be addressed in a much broader and more temporally expended scale. A ~42 m section of Upper Campanian sediments in Saskatchewan Landing Provincial Park in southwest Saskatchewan represents the easternmost outcrop of the DPF in the Western Interior Basin. Between 2010 and 2015, the Royal Saskatchewan Museum (RSM) and McGill University have collected macrofossil material from several dinosaur taxa, including lambeosaurine hadrosaurs (the first known from Saskatchewan), Chasmosaurine and Centrosaurine ceratopsians, and at least three species of theropod. This locality also contains the first definitive ankylosaur scutes found in the province, as well as fossils of pachycephalosaurs and other small ornthiopods. In addition, hundreds of microvertebrate fossils have been collected, including a diversity of chondrichthyans, osteichthyans, turtles, champsosaurs, crocodiles, salamanders, mammals and rare hesperornithid birds. Palynology, ichnology, sedimentology, and vertebrate paleontology have been integrated to determine the paleoenvironmental and paleoecological conditions of the locality. The site is interpreted as having been deposited under marginal-marine conditions near a shoreline undergoing transgression by the encroaching Western Interior Sea. The vertebrate fossil assemblage found at this locality is highly diverse, and offers new insights into late Cretaceous ecosystems living near paleocoastlines. This ongoing research could provide critical insights into the large-scale alpha (within-site) and beta (amoung-site) diversity patterns, as well as the drivers of that diversity, that were occurring in the Late Campanian of North America.