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Late Campanian terrestrial communities of western Canada are best known from the fluvial–paralic deposits of the Dinosaur Park Formation (DPF) in Dinosaur Provincial Park (DPP), Alberta. However, a growing list of localities from isolated DPF outcrops, outside of the DPP area, offers a glimpse into palaeocommunities that evolved isochronously with DPP biotas in greater proximity to the Western Interior Seaway. Over the past decade, one such locality was explored along Lake Diefenbaker in Saskatchewan Landing Provincial Park. The initial palaeoecological analysis of this marginal marine community was based on palynomorph and vertebrate microfossil diversity and has laid a foundation for the current study of its monodominant ceratopsian bonebed. The latter has resulted in new occurrences of Centrosaurus apertus and of the elmisaurine Citipes elegans for Saskatchewan based on incomplete yet diagnostic specimens. Centrosaurus apertus is unequivocally identified by a parietal bar bearing two prominent P1 and P2 hooks, which expands the geographical and habitat range of this species to the most coastal environment known from the DPF. Furthermore, the presence of Centrosaurus apertus suggests that the DPF in this region of Saskatchewan is closer in age to the lower DPF than to the uppermost DPF in DPP, which is at odds with a previous palynostratigraphic interpretation. The faunal composition of this bonebed also supports the presence of a widely distributed metacommunity across these deposits. This contribution demonstrates how evidence from multiple localities in the DPF along a spatial gradient, beyond the temporal gradient available within DPP alone, expands the picture of this metacommunity as a potential model system for biotic turnover in response to sea level rise at a geological temporal scale. [ABSTRACT FROM AUTHOR]

CMN 8917 is a small, partial skull of a duck-billed dinosaur from the upper Campanian Dinosaur Park Formation in what is now Dinosaur Provincial Park, Alberta. It represents one of the few nestling-sized juvenile hadrosaurines known to date. Support for this phylogenetic placement includes a narial vestibule not enclosed within the premaxillary dorsal and lateral processes, the presence of an anterodorsal maxillary process, and a maxillary dorsal process that is longer anteroposteriorly than dorsoventrally. The skull also possesses tooth traits traditionally associated with lambeosaurines, such as secondary ridges on some maxillary and dentary tooth crowns, and denticulation on some maxillary tooth crowns. The occurrence of these features in a juvenile hadrosaurine suggests that they were modified during ontogeny, calling into question their taxonomic utility for identifying juvenile specimens. The dentary teeth of CMN 8917 are similar to those of many adult hadrosaurids in that they possess a concave occlusal surface with steeper lingual and shallower buccal wear zones. This differs from the occlusal surface morphology present in some other juvenile hadrosaurids, which suggests interspecific differences in dental battery development—possibly reflective of dietary differences—occurred during early ontogeny in some taxa.

Here we report two new small‐bodied pachycephalosaurines: one from the Dinosaur Park Formation of Alberta and the other from the Hell Creek Formation of Montana, each represented by an isolated squamosal. These two new specimens are approximately the same size as squamosals of Sphaerotholus buchholtzae, and possess several overlapping morphologies with the genus (such as a strongly posteroventrally projecting and laterally tapering parietosquamosal bar). Therefore, these two new specimens are identified as belonging to the genus Sphaerotholus. However, a suite of characters and combinations differentiate these two new specimens from the other three Sphaerotholus species. Most notably, they possess multiple posterior and lateral node rows on the squamosal, and lack a parietosquamosal node (a single row and a parietosquamosal node define these other species in the genus). Specifically, the Alberta specimen possesses two posterior and two lateral node rows, whereas the Montana specimen has three of each. This analysis provides phylogenetic support for the evolutionary hypothesis that a single‐rowed and parietosquamosal node‐less taxon underwent a cladogenetic event that gave rise to a single‐rowed and parietosquamosal node‐bearing lineage and a multi‐rowed, parietosquamosal node‐less lineage (the two taxa described herein). In turn, these two Sphaerotholus lineages possibly underwent anagenetic change throughout the latest Maastrichtian. Additionally, these new taxa suggest that while large‐bodied taxa from well sampled formations are to be found with decreasing frequency, the inverse holds true for small‐bodied taxa and that pachycephalosaurines were more diverse than previously recognized, and continued to diversify up until the very end of the Cretaceous. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Elasmosaurid plesiosaurian remains have been documented from non-marine to paralic (fluvial to estuarine) sediments of the upper Campanian Dinosaur Park Formation (DPF) of southern Alberta since 1898. Despite this long collection history, this material has received relatively little research attention, largely due to the highly fragmentary nature of most recovered specimens. However, this assemblage is significant, as it constitutes a rare occurrence of plesiosaurian remains in a non-marine depositional environment. This study reports on a recently collected and prepared specimen, which represents the most complete elasmosaurid yet collected from the DPF. This specimen preserves the trunk region, the base of the neck and tail, a partial fore and hind limb, and tooth, and is sufficiently complete to be assigned as the holotype of a new genus and species. This new taxon is diagnosed by a distinctive character state combination including a boomerang-shaped clavicular arch with acute anterior process, convex anterolateral margin, deeply embayed posterior margin, and pronounced ventral keel, together with the presence of 22 dorsal vertebrae, and the anterior dorsal centra bearing a ventral notch. The DPF plesiosaurian fossils were recovered from both estuarine/bay and fluvial palaeochannel sediments. The holotype skeleton represents an osteologically mature individual with an estimated body length of around 5 m, although the largest referred DPF elasmosaurid might have been closer to 7 m, which is considerably larger than other plesiosaurians reported from non-marine deposits. This suggests small-body lengths relative to typical elasmosaurids from marine settings, but is consistent with other plesiosaurians recovered from non-marine sediments. The identification of a distinct elasmosaurid taxon in the DPF might be evidence of niche-partitioning among the predominantly oceanic members of the ubiquitous plesiosaurian clade.

Elasmosaurid plesiosaurian remains have been documented from non-marine to paralic (fluvial to estuarine) sediments of the upper Campanian Dinosaur Park Formation (DPF) of southern Alberta since 1898. Despite this long collection history, this material has received relatively little research attention, largely due to the highly fragmentary nature of most recovered specimens. However, this assemblage is significant, as it constitutes a rare occurrence of plesiosaurian remains in a non-marine depositional environment. This study reports on a recently collected and prepared specimen, which represents the most complete elasmosaurid yet collected from the DPF. This specimen preserves the trunk region, the base of the neck and tail, a partial fore and hind limb, and tooth, and is sufficiently complete to be assigned as the holotype of a new genus and species. This new taxon is diagnosed by a distinctive character state combination including a boomerang-shaped clavicular arch with acute anterior process, convex anterolateral margin, deeply embayed posterior margin, and pronounced ventral keel, together with the presence of 22 dorsal vertebrae, and the anterior dorsal centra bearing a ventral notch. The DPF plesiosaurian fossils were recovered from both estuarine/bay and fluvial palaeochannel sediments. The holotype skeleton represents an osteologically mature individual with an estimated body length of around 5 m, although the largest referred DPF elasmosaurid might have been closer to 7 m, which is considerably larger than other plesiosaurians reported from non-marine deposits. This suggests small-body lengths relative to typical elasmosaurids from marine settings, but is consistent with other plesiosaurians recovered from non-marine sediments. The identification of a distinct elasmosaurid taxon in the DPF might be evidence of niche-partitioning among the predominantly oceanic members of the ubiquitous plesiosaurian clade. [ABSTRACT FROM AUTHOR]

Our understanding of caenagnathid anatomy, diversity, and ecology has improved considerably in the past twenty years, but numerous issues still remain. Among these, the diversity and taxonomy of caenagnathids from the Dinosaur Park Formation of Alberta, Canada, have remained problematic. Whereas some authors recognize three genera, others suggest only two were present, and there is considerable disagreement about which specimens are referable to which genus. This study aims to resolve this issue by reviewing the known specimens and using osteohistology, to establish a testable taxonomic framework of Dinosaur Park Formation caenagnathids. Numerous new specimens from all regions of the skeleton provide insight into morphological variation in caenagnathids, and three morphotypes are recognized based on a combination of morphological features and body size. Osteohistology shows that representatives in each body size class are at skeletal maturity, and therefore supports the delineation of three taxa: the smaller Citipes elegans gen. nov., the intermediate Chirostenotes pergracilis, and the larger Caenagnathus collinsi, new material of which shows it rivalled Anzu wyliei in size. However, these analyses also raise concerns about the referral of isolated material to each taxon in the absence of skeletal overlap between specimens or osteohistological analysis. Caenagnathids are consistently recovered throughout the Dinosaur Park Formation interval, and two geographic clusters of increased abundance probably reflect collection and taphonomic biases. The coexistence of three taxa was apparently facilitated by differences in both adult body size and functional morphology of the dentary and pes, which suggests that caenagnathids minimized niche overlap rather than subdividing niche space. Regardless, little is known of the exact roles caenagnathids played in Late Cretaceous ecosystems. Incorporation of the new material and taxonomic framework into a phylogenetic analysis drastically improves our understanding of the relationships between caenagnathines, and sheds light on the evolution of body size in caenagnathids and its role in their diversification.

A partial pterosaur pelvis from the Campanian Dinosaur Park Formation of Canada adds to our knowledge of Late Cretaceous pterosaurs. The pelvis is tentatively referred to Azhdarchidae and represents the first pelvic material from a North American azhdarchid. The morphology of the ilium is bizarre compared with other pterosaurs: it is highly pneumatized, the preacetabular process tapers anteriorly, and muscle scars show that it would have anchored strong adductor musculature for the hindlimb. The acetabulum is deep and faces ventrolaterally, allowing the limb to be positioned underneath the body. These features support previous suggestions that azhdarchids were well adapted to terrestrial locomotion.

Ornithomimid material from the Belly River Group (Campanian) of Alberta, Canada is described as sharing characters with Qiupalong henanensis from the Qiupa Formation of Henan Province, China. Derived characters and character combinations of the pubis and astragalocalcaneum were previously used to diagnose Q. henanensis and support the referral of this material to Qiupalong sp., representing the first known occurrences of Qiupalong outside of China. Qiupalong is the sixth ornithomimid taxon to be reported from the Dinosaur Park Formation and the first ornithomimid genus with a transcontinental distribution. The Alberta material represents the oldest known occurrences of Qiupalong, and a reconsideration of character evidence suggests that this genus is phylogenetically nested within other North American ornithomimids. A North American origin for Qiupalong and subsequent dispersal to Asia is proposed.

The Dinosaur Park Formation (DPF) has a diverse assemblage of chasmosaurines currently represented by Chasmosaurus belli, C. russelli, Vagaceratops irvinensis, and Mercuriceratops gemini, and may also include remains possibly referable to Spiclypeus shipporum. Two skulls, YPM 2016 and AMNH 5402, previously referred to C. belli, both have a straight posterior parietal bar with five epiparietals present (YPM 2016) or inferred (AMNH 5402) on each side – the combination of which is unique to V. irvinensis. Based on our new morphological observations and interpretations of these two skulls, we recover V. irvinensis as a species of Chasmosaurus (C. irvinensis), although the interrelationships between C. irvinensis, C. belli, and C. russelli remain unclear. We refrain from formerly assigning YPM 2016 and AMNH 5402 to C. irvinensis, however, as their parietal fenestrae are significantly larger and their epiparietals are significantly shorter than those of C. irvinensis; instead, we reassign these two skulls to Chasmosaurus sp. Given the low stratigraphic position of YPM 2016 (unknown in AMNH 5402) relative to C. irvinensis, we believe this specimen to represent a basal member of the lineage leading to C. irvinensis. If our assessment is correct, this would indicate that the C. irvinensis lineage has a large degree of stratigraphic overlap with that of C. belli and C. russelli. The close phylogenetic relationship and supposed stratigraphic separation for these three taxa reported in previous studies were used to suggest that they may represent an anagenetic lineage, whereby C. russelli evolved into C. belli, and C. belli evolved into, and was entirely replaced by, the latter. However, the lack of stratigraphic separation between these three taxa indicates that they instead arose via cladogenesis.

Chasmosaurine ceratopsids are well documented from the Upper Cretaceous (Campanian) Dinosaur Park Formation (DPF) of southern Alberta and Saskatchewan, and include Chasmosaurus belli, Chasmosaurus russelli, Mercuriceratops gemini, Vagaceratops irvinensis, and material possibly referable to Spiclypeus shipporum. In this study, we describe three recently prepared chasmosaurine skulls (CMN 8802, CMN 34829, and TMP 2011.053.0046) from the DPF, and age-equivalent sediments, of Alberta. CMN 8802 and CMN 34829 are both referred to Chasmosaurus sp. based on the size and shape of the preserved parietal fenestrae. TMP 2011.053.0046 is referred to Vagaceratops sp. based on the position and orientation of its preserved epiparietals. Each skull is characterized by the presence of an accessory fenestra in either the squamosal (CMN 8802 and TMP 2011.053.0046) or parietal (CMN 34829). Such fenestrae are common occurrences in chasmosaurine squamosals, but are rare in the parietal portion of the frill. The origin of the fenestrae in these three specimens is unknown, but they do not appear to exhibit evidence of pathology, as has been previously interpreted for the accessory fenestrae in most other chasmosaurine frills. These three skulls contribute to a better understanding of the morphological variation, and geographic and stratigraphic distribution, of chasmosaurines within the DPF and age-equivalent sediments in Western Canada.

Chasmosaurine ceratopsids are well documented from the Upper Cretaceous (Campanian) Dinosaur Park Formation (DPF) of southern Alberta and Saskatchewan, and include Chasmosaurus belli, Chasmosaurus russelli, Mercuriceratops gemini, Vagaceratops irvinensis, and material possibly referable to Spiclypeus shipporum. In this study, we describe three recently prepared chasmosaurine skulls (CMN 8802, CMN 34829, and TMP 2011.053.0046) from the DPF, and age-equivalent sediments, of Alberta. CMN 8802 and CMN 34829 are both referred to Chasmosaurus sp. based on the size and shape of the preserved parietal fenestrae. TMP 2011.053.0046 is referred to Vagaceratops sp. based on the position and orientation of its preserved epiparietals. Each skull is characterized by the presence of an accessory fenestra in either the squamosal (CMN 8802 and TMP 2011.053.0046) or parietal (CMN 34829). Such fenestrae are common occurrences in chasmosaurine squamosals, but are rare in the parietal portion of the frill. The origin of the fenestrae in these three specimens is unknown, but they do not appear to exhibit evidence of pathology, as has been previously interpreted for the accessory fenestrae in most other chasmosaurine frills. These three skulls contribute to a better understanding of the morphological variation, and geographic and stratigraphic distribution, of chasmosaurines within the DPF and age-equivalent sediments in Western Canada. [ABSTRACT FROM AUTHOR]

A Corythosaurus skull (UALVP 13) was collected in 1920 from what is now Dinosaur Provincial Park in southern Alberta, Canada and was designated the holotype of Corythosaurus excavatus , a new hadrosaur species by Gilmore (1923). In 1992, a previously uncovered, weathered, headless skeleton was found. This was collected in 2012 by the University of Alberta as there was potential it could belong to the holotype skull. In addition, an isolated hadrosaur dentary had been found in 1992 close to the articulated postcranial skeleton and may be one of the missing jaws of Corythosaurus excavatus . The hypothesis that it may be the skeleton of the holotype of Corythosaurus excavatus is tested using anatomical information and statistical analyses. Statistical comparisons suggest it is possible that the skull and dentary belong to the same specimen. Furthermore, bivariate plots and percentage prediction errors also indicate that the postcranial material could belong to the UALVP 13 skull. Because many large vertebrate fossil specimens (even types) are not always collected in their entirety, this method may be used as a line of evidence to determine whether independently collected specimens potentially belong to the same individual. The problems described herein highlight the need to collect specimens in their entirety, and for good field documentation, including the spatial and stratigraphic context of all finds. [ABSTRACT FROM AUTHOR]

In June 2016, the remains of an articulated fish was discovered during field work in Dinosaur Provincial Park, in southern Alberta, Canada. Articulated remains of fishes are very rare in the park, so this specimen was carefully collected and prepared. The new specimen represents a new species of sturgeon that differs from those previously reported from the Cretaceous of North America by the ornamentation patterns of the dermal skull elements. We believe that the radiating ridges forming the ornamentation on the dermal skull bones of the new Dinosaur Park specimen is indicative of it being a different species from that represented by any of the scutes or other articulated material previously named.

The horned dinosaur Chasmosaurus from the late Campanian Dinosaur Park Formation of Alberta, is known from numerous skulls and skeletons, but over a century after its description, the taxonomy of the genus is controversial. Two species, Chasmosaurus belli and C. russelli, are currently recognized, with a third species, C. irvinensis, recently placed in a new genus, Vagaceratops. Here, the Yale Chasmosaurus skull is described, and implications for Chasmosaurus systematics are explored. The Yale skull is intermediate between typical C. belli and C. irvinensis. C. belli-like features include large, triangular lateral epiparietals, large parietal fenestrae, and an emarginate parietal. Yet the skull also exhibits derived features of C. irvinensis, including a posteriorly inclined narial strut, brow horns replaced by rugose bosses, reduced parietal emargination, five pairs of epiparietals, and epiparietals that fuse at their bases and hook forward over the frill. Specimen-level phylogenetic analysis provides a hypothesis of relationships upon which to base the taxonomy of Chasmosaurus. C. belli is paraphyletic with respect to C. irvinensis, and the Peabody skull is closer to C. irvinensis than to other C. belli. The holotype of C. russelli clusters with C. belli, making C. russelli a junior synonym of C. belli. Accordingly, Chasmosaurus can be divided into three species: C. belli, C. irvinensis, and C. priscus sp. nov, including specimens previously referred to C. russelli. The systematics of Chasmosaurus show how specimen level phylogeny can provide an evolutionary framework upon which to establish taxonomies. However, the resulting phylogenies may lead to paraphyletic species and genera.

We confirm the presence of pigmented keratinized integumentary structures attributable to feathers in the Late Cretaceous Ornithomimus specimen UALVP 52531. We falsify the hypothesis that these features represent collagen fibers and address additional criticisms of our paper made by Lingham-Soliar (2016). [ABSTRACT FROM AUTHOR]

A reexamination of large caenagnathid material from the Upper Cretaceous (Campanian) Dinosaur Park Formation of Alberta, Canada, reveals undescribed material referable to Caenagnathus collinsi. A femur, two astragalocalcanei, two metatarsals, two unguals, and a caudal vertebra provide anatomical information on Caenagnathus collinsi. Estimates of femoral length based on the proportions of other oviraptorids suggest that the non-femoral material represents a taxon intermediate in size between Chirostenotes pergracilis from the Dinosaur Park Formation and Anzu wyliei from the Maastrichtian Hell Creek Formation. The femur is within the range of predictions, and confirms the body size estimates based on the other material. The large size of the material and a number of morphological characters distinguish the material from Chirostenotes pergracilis and suggest that it is referable to Caenagnathus collinsi. The relative diversity of caenagnathids in the Dinosaur Park Formation is likely underestimated. [ABSTRACT FROM AUTHOR]

The upper Campanian of the American Southwest has produced dinosaurs that are unknown from the northern Great Plains and vice versa. This has led to the idea that North America's Campanian dinosaur fauna was characterized by high levels of endemism and distinct faunal provinces. Here, two horned dinosaurs known from the Southwest, Pentaceratops and Kosmoceratops, are described from southern Canada. Pentaceratops aquilonius sp. nov. is represented by two frill fragments from the uppermost Dinosaur Park Formation near Manyberries, southeast Alberta. Features shared with Pentaceratops include large, triangular epiparietals, an M-shaped parietal posterior bar, and an epiparietal P1 that curls up and twists laterally. The Manyberries specimens differ from Pentaceratops sternbergii and Utahceratops gettyi in that the posterior bar is broader, emargination is weakly developed, and P1 is directed dorsally, rather than anteriorly. Phylogenetic analysis places P. aquilonius as sister to a clade comprising P. sternbergii and Utahceratops. Kosmoceratops is documented by a partial skull from Dinosaur Provincial Park. Previously referred to Chasmosaurus, the skull exhibits derived features inconsistent with this referral, including a reduced septal flange, a caudally inclined narial strut, a triangular narial process, a reduced frontal fontanelle, a weakly hooked rostral, and a narrow, caudally inclined internal naris. Phylogenetic analysis recovers the animal as sister to Kosmoceratops richardsoni, but differences in the shape of the naris and nasal horn suggest that it likely represents a distinct species. The presence of Pentaceratops and Kosmoceratops in Canada argues against the idea of distinct northern and southern faunal provinces, but the fact that they differ from their southern relatives confirms that endemism was high in the Campanian. The ability of dinosaur lineages to disperse long distances across North America suggests that dinosaur distribution was not constrained by geographic barriers, climate, or flora. Instead, dinosaur endemism may result from competitive exclusion of immigrants by established populations adapted to local environmental conditions. [ABSTRACT FROM AUTHOR]

A new taxon of chasmosaurine ceratopsid demonstrates unexpected disparity in parietosquamosal frill shape among ceratopsid dinosaurs early in their evolutionary radiation. The new taxon is described based on two apomorphic squamosals collected from approximately time equivalent (approximately 77 million years old) sections of the upper Judith River Formation, Montana, and the lower Dinosaur Park Formation of Dinosaur Provincial Park, Alberta. It is referred to Chasmosaurinae based on the inferred elongate morphology. The typical chasmosaurine squamosal forms an obtuse triangle in dorsal view that tapers towards the posterolateral corner of the frill. In the dorsal view of the new taxon, the lateral margin of the squamosal is hatchet-shaped with the posterior portion modified into a constricted narrow bar that would have supported the lateral margin of a robust parietal. The new taxon represents the oldest chasmosaurine from Canada, and the first pre-Maastrichtian ceratopsid to have been collected on both sides of the Canada-US border, with a minimum north-south range of 380 km. This squamosal morphology would have given the frill of the new taxon a unique dorsal profile that represents evolutionary experimentation in frill signalling near the origin of chasmosaurine ceratopsids and reinforces biogeographic differences between northern and southern faunal provinces in the Campanian of North America. [ABSTRACT FROM AUTHOR]

Abstract: Using the megaherbivorous dinosaur assemblage from the Dinosaur Park Formation as a model, linear and geometric morphometrics are applied to examine the degree to which different feeding styles—as reflected by beak morphology—facilitated the coexistence of these animals on the Late Cretaceous island continent of Laramidia. Our findings indicate that megaherbivorous dinosaurs occupied a spectrum of feeding habits. The wide, square beaks of the ankylosaurs suggest that these animals were bulk-feeders that consumed more fibrous herbage than traditionally assumed. Conversely, the narrow, square beaks of the ceratopsids evoke concentrate feeders, although the large body sizes and sophisticated dental batteries of these animals suggest a diet of forbs and low-growing scrub, akin to the feeding strategy of the black rhinoceros (Diceros bicornis). Both nodosaurids and hadrosaurids had beaks of intermediate size and shape, suggesting that these were mixed feeders that consumed a diversity of plant types of variable nutritional quality. Contrary to previous suggestions, there is little evidence for different feeding styles within the aforementioned families. Feeding styles were evolutionarily stable, and lend further support to the contention that the fossil assemblage of the Belly River Group constitutes a chronofauna. [Copyright &y& Elsevier]

Background: Herbivore coexistence on the Late Cretaceous island continent of Laramidia has been a topic of great interest, stemming from the paradoxically high diversity and biomass of these animals in relation to the relatively small landmass available to them. Various hypotheses have been advanced to account for these facts, of which niche partitioning is among the most frequently invoked. However, despite its wide acceptance, this hypothesis has not been rigorously tested. This study uses the fossil assemblage from the Dinosaur Park Formation of Alberta as a model to investigate whether niche partitioning facilitated herbivorous dinosaur coexistence on Laramidia. Specifically, the question of feeding height stratification is examined in light of the role it plays in facilitating modern ungulate coexistence. Results: Most herbivorous dinosaur species from the Dinosaur Park Formation were restricted to feeding no higher than approximately 1 m above the ground. There is minimal evidence for feeding height partitioning at this level, with ceratopsids capable of feeding slightly higher than ankylosaurs, but the ecological significance of this is ambiguous. Hadrosaurids were uniquely capable of feeding up to 2 m quadrupedally, or up to 5 m bipedally. There is no evidence for either feeding height stratification within any of these clades, or for change in these ecological relationships through the approximately 1.5 Ma record of the Dinosaur Park Formation. Conclusions: Although we cannot reject the possibility, we find no good evidence that feeding height stratification, as revealed by reconstructed maximum feeding heights, played an important role in facilitating niche partitioning among the herbivorous dinosaurs of Laramidia. Most browsing pressure was concentrated in the herb layer, although hadrosaurids were capable of reaching shrubs and low-growing trees that were out of reach from ceratopsids, ankylosaurs, and other small herbivores, effectively dividing the herbivores in terms of relative abundance. Sympatric hadrosaurids may have avoided competing with one another by feeding differentially using bipedal and quadrupedal postures. These ecological relationships evidently proved to be evolutionarily stable because they characterize the herbivore assemblage of the Dinosaur Park Formation through time. If niche partitioning served to facilitate the rich diversity of these animals, it may have been achieved by other means in addition to feeding height stratification. Consideration of other feeding height proxies, including dental microwear and skull morphology, may help to alleviate problems of underdetermination identified here. [ABSTRACT FROM AUTHOR]

Abstract: Ongoing research into the biostratigraphy of the upper Campanian Dinosaur Park Formation (DPF) of Alberta has demonstrated that megaherbivorous dinosaur taxa (ankylosaurs, ceratopsids, hadrosaurids) are not homogeneously distributed throughout the unit. This has compelled proposals of different, informal assemblage zone schemes, and the hypothesis that faunal turnover was driven by environmental change associated with marine transgression. The current study tests previous zonation schemes in addition to the hypothesis of turnover pulses in the DPF. Clustering and ordination methods are used to demonstrate the existence of two broad assemblage zones within the DPF, each of which lasted ~600Ka: a lower zone characterized by the presence of the ceratopsid Centrosaurus apertus and the hadrosaurids Corythosaurus, and an upper zone characterized by the presence of the ceratopsid Styracosaurus albertensis and the hadrosaurid Prosaurolophus maximus. These zones can be further sub-divided, based on the distributions of rarer or shorter-lived ankylosaur, ceratopsid, and hadrosaurid species, into ~300Ka sub-zones. Canonical correspondence analysis is used to explore the association between the turnover of the megaherbivorous dinosaurs and various palaeoevironmental proxies. Megaherbivorous dinosaur turnover most closely corresponds to that of fossil palynomorphs. However, none of the palaeoenvironmental proxies explains dinosaur distribution better than a simple time gradient, suggesting that dinosaur turnover was not inextricably linked to environmental change as predicted by the turnover pulse hypothesis. [Copyright &y& Elsevier]

In 1916, a centrosaurine dinosaur bonebed was excavated within the Campanian-aged deposits of what is now Dinosaur Provincial Park, Alberta, Canada. Specimens from this now-lost quarry, including two parietals, a squamosal, a skull missing the frill, and an incomplete dentary, were purchased by The Natural HistoryMuseum, London. The material was recently reprepared and identified herein as a previously unknown taxon, Spinops sternbergorum gen. et sp. nov. Based upon the available locality data and paleopalynology, the quarry lies in either the upper part of the Oldman Formation or the lower part of the Dinosaur Park Formation. The facial region of the partial skull is similar to putative mature specimens of Centrosaurus spp. and Styracosaurus albertensis, with short, rounded postorbital horncores and a large, erect nasal horncore. Parietal ornamentation is consistent on both known parietals and is unique among ceratopsids. Bilateral, procurved parietal hooks occupy the P1 (medial-most) position on the dorsal surface of the parietal and are very similar to those seen in Centrosaurus apertus. Epiparietals in the P2 or possibly P3 position (lateral to P1) manifest as extremely elongate, caudally directed spikes, unlike the condition in C. apertus, S. albertensis, or any other "derived" centrosaurine. Cladistic analysis suggests that S. sternbergorum is closely related to Centrosaurus and Styracosaurus. Historically, based upon the condition in Styracosaurus and related centrosaurines, it was assumed that the medial-most elongated spikes on centrosaurine parietals correspond to the P3 epiparietal position. The exception illustrated in the newtaxon suggests that homologies of epiparietals among basal centrosaurines (e.g., Albertaceratops and Diabloceratops) and derived centrosaurines (e.g., Styracosaurus and "pachyrhinosaurs") should be reconsidered. The medially-placed, caudally-directed "P3" process of basal centrosaurines may, in fact, be homologous with P2. [ABSTRACT FROM AUTHOR]

We describe bones from the Late Cretaceous of Alberta – including bones of large dinosaurs, a femur from the aquatic reptile Champsosaurus, and a dentary from the marsupial Eodelphis– that bear tooth marks made by animals with opposing pairs of teeth. Of the animals known from the Late Cretaceous of North America, only mammals are capable of making such tooth marks. In particular, multituberculates, which have paired upper and lower incisors, are the most likely candidates for the makers of these traces. The traces described here represent the oldest known mammalian tooth marks. Although it is possible that some of these tooth marks represent feeding traces, the tooth marks often penetrate deep into the dense cortices of the bone. This raises the possibility that, much as extant mammals gnaw bone and antler, some Cretaceous mammals may have consumed the bones of dinosaurs and other vertebrates as a source of minerals. However, none of the tooth marks described here resemble the extensive gnaw traces produced by Cenozoic multituberculates or rodents. This suggests that specialized gnawing forms may have been rare or absent in the Late Cretaceous of North America. [ABSTRACT FROM AUTHOR]

The fossil assemblages of the Late Cretaceous of North America are dominated by large-bodied dinosaur species. Associated skeletons of small dinosaurs are exceedingly rare, and small (<10 kg) carnivorous theropods have not previously been reported from these beds. Here, we describe a small dromaeosaurid from the 75-million-year-old Dinosaur Park Formation of Alberta, Canada. Hesperonychus eiizabethae gen. et sp. nov. is represented by a pelvic girdle from an animal weighing ≈1,900 g. Despite its size, the pubes and ilia are coossified, indicating that the animal was somatically mature. This is the smallest carnivorous, nonavian dinosaur known from North America. Phylogenetic analysis of Hesperonychus reveals that it is not closely related to previously described North American dromaeosaurids. Instead, Hesperonychus is a member of the dromaeosaurid dade Microraptorinae, a group containing the 4-winged Microraptor and the feathered Sinornithosaurus, both from the Lower Cretaceous Jehol Group of China. Hesperonychus is the youngest known member of this lineage, extending the temporal range of the dade by 45 million years. and it is the first microraptorine known from North America, providing further evidence for an affinity between the dinosaur faunas of North America and Asia. Study of fossil collections from the Dinosaur Park and Oldman formations of Alberta has revealed numerous isolated bones of small, basal dromaeosaurids, which are tentatively referred to Hesperonychus. These fossils suggest that small dromaeosaurids were a significant component of the carnivore community in this Late Cretaceous biota. [ABSTRACT FROM AUTHOR]

Abstract: Relatively little is known the diversity of Late Cretaceous ornithurines, and it has generally been assumed that the ornithurine sister taxon, the Enantiornithes, were the dominant birds in Late Cretaceous continental ecosystems. Here, an ornithurine-dominated avifauna is described from the terrestrial Belly River Group (Campanian, Upper Cretaceous) of southern Alberta. On the basis of the most common element, the coracoid, eight species can be identified; all represent ornithurines. More precise identifications are hindered by the fragmentary nature of the material, but some of the forms described here resemble Cretaceous birds known from elsewhere in North America and Asia. The Judithian birds show considerable size disparity; a coracoid from the Irvine mammal locality belongs to a sparrow-sized bird, making it one of the smallest known Cretaceous birds, while the peacock-sized Palintropus is among the largest birds known from the Cretaceous. Surprisingly, no enantiornithine fossils were identified. These fossils show that the Ornithurae had diversified considerably by the end of the Campanian, and that they were the dominant birds in some North American ecosystems. The diversification of the Ornithurae towards the end of the Cretaceous could help explain how this clade managed to survive the end Cretaceous mass extinction. [Copyright &y& Elsevier]

The sexual dimorphism attributed to Chasmosaurus belli by Sternberg (1927) is revisited and reevaluated. A reexamination of the two specimens originally considered by Sternberg reveals that they are less complete than first suggested, with only a moderate amount of overlapping material between them. Only a few of the postcranial elements (humeri, sternal plates, and presacral vertebrae) show evidence of dimorphism, the significance of which is either doubtful or equivocal. Instead of representing sexual dimorphs, it is likely that the two specimens belong to separate species, C. belli and C. russelli, as evidenced by their distinct frill morphologies and by their stratigraphic segregation within the Dinosaur Park Formation of Alberta. These findings emphasize the need to remain sceptical about claims advocating sexual dimorphism in the fossil record in the absence of statistical significance or stratigraphic control. [ABSTRACT FROM AUTHOR]

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 tyrannosaurids been more like ectotherms than endotherms in their metabolic rates. Distribution of different large theropod species across different, and surprisingly small (for the size of the animals) portions of Mesozoic landscapes may also account for the remarkably high diversity of morphologically similar large theropods in other dinosaur faunas. [ABSTRACT FROM AUTHOR]