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Eggs and eggshell are generally rare in the Upper Cretaceous rocks of Alberta, despite being relatively abundant nearby in Montana. Palaeontologists and other people have been prospecting the Horseshoe Canyon Formation for more than a 130 years, but eggshell fragments have only just been recovered. The fragments are unornamented with angusticanaliculate pores and three structural layers. Numerous features support their referral to Prismatoolithus levis, and they confirm the presence of a bird-like external layer in this ootaxon. The fragments, which likely belonged to Albertavenator curriei, are from a site with abundant troodontid teeth and perinate material from hadrosaurs, ceratopsians, and theropods. The discovery of eggshell challenges the notion that the Horseshoe Canyon Formation is too heavily sideritized to preserve eggshell. [ABSTRACT FROM AUTHOR]

Troodontid material from the Maastrichtian of North America is extremely rare, beyond isolated teeth from microvertebrate sites. Here we describe troodontid frontals from the early Maastrichtian Horseshoe Canyon Formation (Horsethief Member). The most complete specimen, TMP 1993.105.0001, is notably foreshortened and robust when compared with numerous specimens referred to Troodon from the Dinosaur Park Formation, and exhibits several characteristics that distinguish it from other Late Cretaceous troodontids. Morphometric analyses reinforce shape differences between TMP 1993.105.0001 and other North American troodontids, and show that proportional differences are independent of size. We therefore erect a new taxon, Albertavenator curriei gen. et sp. nov., which is diagnosed by the following autapomorphies: (1) primary supraciliary foramen is truncated anteriorly by the lacrimal contact; (2) superficial (ectocranial) surface of the frontal proportionally shorter than all known troodontids, with a length to width ratio under 1.3; and (3) frontoparietal contact in which an enlarged lappet of the frontal extends medially to extensively overlap the lateral region of the anteromedial process of the parietal. Interestingly, tooth and jaw morphology from the single relatively complete dentary recovered from the Horseshoe Canyon cannot be distinguished from dentaries and teeth from the Dinosaur Park Formation. If the dentary and teeth from the Horsethief Member of the Horseshoe Canyon Formation prove to belong to A. curriei, extensive overlap in tooth morphology between the Dinosaur Park and Horseshoe Canyon formations reinforces the notion that tooth morphotypes do not exhibit strong correspondence to species alpha diversity, and may encompass multiple closely related taxa. [ABSTRACT FROM AUTHOR]

Eighty-nine samples from three boreholes penetrating the Horseshoe Canyon Formation (Late Campanian) in south-central Alberta (Canada) were investigated for megaspore content. The samples were found to contain 49 species belonging to the genera Azolla, Bacutriletes, Costatheca, Dictyothylakos, Echitriletes, Erlansonisporites, Ghoshispora, Glomerisporites, Minerisporites, Molaspora, Monophyllosporites, Paxillitriletes, Spermatites, Striatriletes and Trileites, including one new species of Spermatites (S. reticulatus). Deposits representing low-lying coastal plains with widespread peat swamps, meandering channels and back swamp environments yielded the highest numbers of megaspores. An analysis of characteristics of the 22 species of Costatheca and 18 species and one subspecies of Spermatites leads to the proposal of a system of shape classes. Dichotomous keys to species were prepared. The geographical and stratigraphical distributions of the genera were also reviewed to elucidate their potential use in biostratigraphic and palaeoecological studies. [ABSTRACT FROM AUTHOR]

In connection with the excavation of the Danek Bonebed in 2011, a half-metre long, well preserved right ceratopsian orbital horncore was recovered. The horncore belongs to the taphonomic group of larger, heavier elements from the bonebed. So far, no other ceratopsian elements have been identified from the bonebed. Ceratopsids from the Horseshoe Canyon Formation of southern Alberta include Anchiceratops, Arrhinoceratops, Eotriceratops, and Pachyrhinosaurus. The size, proportions, and gently anterolaterally procurving morphology of the horncore indicates that it is from a chasmosaurine ceratopsid. There is weak morphological information to suggest that it may represent Anchiceratops ornatus, which is the most common chasmosaurine at this stratigraphic level. The base of the specimen has been hollowed out by a sinus system, which in conjunction with its large size indicates it is probably from a mature animal. The rarity of ceratopsian remains in this and other hadrosaur bonebeds suggests horned dinosaurs were excluded from anywhere that was occupied by herds of large numbers of Edmontosaurus. [ABSTRACT FROM AUTHOR]

The Danek Bonebed (Edmonton, Alberta, Canada) is a monodominant Edmontosaurus regalis assemblage of the upper Campanian (Upper Cretaceous) Horseshoe Canyon Formation. Bone histology of humeri and femora are used in this paper to test hypotheses about the growth dynamics and palaeobiology of Edmontosaurus. The high number of elements collected from the Danek Bonebed allow for an expansion of the multi-element histological record for hadrosaurs. Results indicate that Edmontosaurus had a growth trajectory similar to other large-bodied dinosaurs and reached the onset of somatic maturity at about 10-15 years of age; however, even the largest elements to preserve lines of arrested growth do not have external fundamental systems. This timing of the onset of somatic maturity agrees with the estimated body size of Edmontosaurus relative to other dinosaurs for which life-history data are available. Vascularity patterns support the hypothesis that edmontosaurs preserved at the Danek Bonebed were not subject to the same extreme seasonal environmental shifts as congenerics preserved at higher latitudes, further supporting overwintering behaviour in the latter. [ABSTRACT FROM AUTHOR]

Although considerable work has been conducted on the stratigraphy and dinosaur assemblages of the Horseshoe Canyon Formation of southern Alberta, equivalent strata and assemblages in central Alberta remain poorly understood. Data from the Danek Bonebed (Edmonton, Alberta) are beginning to fill this gap. The bonebed occurs 4 m above the #9 Big Island Coal Seam. This stratigraphic position lies just below the middle of the Horseshoe Canyon Formation in the Edmonton region, and also lies below a thick, stratigraphically significant non-coaly interval that is expressed throughout central and southern Alberta. The stratigraphic position of the Danek Bonebed equates best with the uppermost Horsethief Member of the Horseshoe Canyon Formation in the Drumheller region and the upper part of Unit 4 of the Wapiti Formation in the Grande Prairie region. In both Drumheller and Grande Prairie, the correlated position of the bonebed underlies a zone of marine transgression (Drumheller Marine Tongue), which, in turn, includes the Campanian-Maastrichtian boundary. In the context of Geologic Time Scale 2004, we infer a late Campanian age of 71.0-71.3 Ma for the bonebed. The Danek's dinosaurian assemblage is limited taxonomically, but compares well with the Edmontosaurus regalis - Pachyrhinosaurus canadensis fossil assemblage zone in the Drumheller region. We propose that a mega-herbivore faunal assemblage, characterized by Edmontosaurus and Pachyrhinosaurus, extended continuously across the climatically wet coastal plain of latest Campanian southern and central Alberta, and likely extended northwest into the North Slope of Alaska, where it persisted into the early Maastrichtian. [ABSTRACT FROM AUTHOR]

The Danek Bonebed is a monodominant Edmontosaurus bonebed preserving predominantly disarticulated material from the Upper Campanian Horseshoe Canyon Formation within the city limits of Edmonton, Alberta, Canada. To date, at least six dinosaur taxa have been identified at the site: Albertosaurus sarcophagus, Chasmosaurinae indet., Dromaeosauridae indet., Edmontosaurus regalis, Ornithomimidae indet., and Troodontidae indet. This bonebed has been used as a case study for creating a digital, searchable bonebed map using a geographic information system (GIS) platform. The original quarry maps produced on site are refined when digitized with new anatomical information gathered during preparation of collected specimens. Each specimen is labeled with the known specimen identification, quarry coordinates, and catalogue number. Creating a digital map of the bonebed allows easier interpretation of data and the ability to share maps to compare specific elements within the bonebed. [ABSTRACT FROM AUTHOR]

For fossil assemblages, quantitative size and shape studies are often complicated by diagenetic distortion. Different vertebrate elements, although subjected to similar burial stresses, exhibit deformations based upon their original shapes; this hypothesis is tested here by quantitatively comparing deformed humeri and femora from the Danek Bonebed (a monodominant Edmontosaurus regalis bonebed from the upper Campanian Horseshoe Canyon Formation in Edmonton, Alberta, Canada) with samples of undeformed humeri and femora from modern and fossil assemblages. Analyses suggest that at the Danek Bonebed a strong relationship exists between element length and circumference despite being distorted by crushing deformation. Major and minor axes of the midshaft cross section, however, were not uniformly distorted. Although their anatomical position did not change, the major axis became longer relative to the minor axis in distorted specimens. A regression based on the undeformed humeri was not able to accurately predict circumference in the Danek humeri. Further study might quantify the deformation of other bones in the Danek Bonebed and could be extended to other assemblages and genera. Caution should be taken when conducting studies in which diagenetic crushing may have altered morphological features of fossil vertebrate remains. [ABSTRACT FROM AUTHOR]

Tyrannosaurid cranial bones - including a maxilla, dentary, and pterygoid - were collected from a monodominant Edmontosaurus bonebed in the Horseshoe Canyon Formation exposed near the city of Edmonton, Alberta, Canada. The maxilla can be identified as Albertosaurus sarcophagus based on the narrow interfenestral strut and relatively deep dental pits along the length of the palatal shelf. Cranial bones are interpreted to have come from a single large individual that was incorporated into the site during, or temporally close to, the formation of the final taphocoenosis. This discovery constitutes the northernmost record of A. sarcophagus, and helps to narrow the geographic gap of latest Cretaceous tyrannosaurs between Alberta and Alaska. The geographic distribution of A. sarcophagus - eclipsed only in areal extent by Tyrannosaurus rex in North America - attests to the adaptability of this species, which endured regional changes in climate that forced extirpation of many ornithischian taxa during deposition of the Horseshoe Canyon Formation. [ABSTRACT FROM AUTHOR]

An ash-rich volcaniclastic sandstone immediately underlying dinosaur-rich material from the Danek Bonebed in the Horseshoe Canyon Formation (HCF), Edmonton, Alberta, Canada, contains accessory zircon, which have been dated employing U-Pb geochronology. Both laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and chemical abrasion isotope dilution thermal ionization mass spectrometry (ID-TIMS) U-Pb analyses have been conducted. The zircon age distributions are complex with U-Pb dates ranging from Precambrian to Cretaceous. We consider the youngest ID-TIMS 206Pb/238U date of 71.923 ± 0.068 Ma as the maximum deposition age of the ash-rich sandstone, placing the overlying Danek bonebed in the early Maastrichtian. This age is compatible with the paleontological assemblage from the Danek Bonebed and the regional stratigraphy. The zircon age distribution also implies that the HCF had a complex provenance of the detritus with some Archean and Proterozoic zircons, a group of Mesozoic, and a large compliment of Cretaceous grains. The results highlight the importance of high precision geochronology in constraining the age of important fossil deposits such as the Danek Bonebed. [ABSTRACT FROM AUTHOR]

A significant number of fossil remains of the hadrosaurid Edmontosaurus have been recovered from the Danek Bonebed (Horseshoe Canyon Formation, Upper Cretaceous, Alberta). Bones from theropod dinosaurs are scarce in this hadrosaur-dominated bonebed, but more than 60 tyrannosaurid theropod teeth have been found. The isolated tyrannosaurid teeth include juvenile and adult specimens, although the precise ontogenetic stage has not been determined. The use of multivariate analyses helps determine the variance of the sample and verifies the initial taxonomic affinities given to these teeth, showing their high potential as a useful tool to better discriminate tyrannosaurid teeth. It also provides an insight into the tyrannosaurid intraspecific variability in the Horseshoe Canyon Formation. [ABSTRACT FROM AUTHOR]

The Danek Bonebed (Horsethief Member, Horseshoe Canyon Formation, Late Campanian) is dominated by the remains of at least 12 Edmontosaurus regalis. Skeletal remains of a tyrannosaurid and ceratopsid are also known. The predominantly disarticulated remains were interred on a periodically inundated floodplain and, although the cause of death is unknown, a sudden, catastrophic death explains the demographic spread, faunal diversity, rare greenstick fractures, and homogeneous weathering/abrasion categories of the assemblage. The Danek Bonebed shares a similar taphonomic signature to the Liscomb Bonebed (Prince Creek Formation, Alaska), but it is unique among all other described hadrosaurid bonebeds in the unusually high proportion of bite-marked bones (∼30%), suggesting scavenging played a major role in the reworking of the assemblage. The highest frequency of bite marks is found on small, often unidentifiable (and commonly ignored) bone fragments, underscoring the role that such fragments can play in taphonomic interpretation. Finally, the recognition of E. regalis from central Alberta is an important datum linking contemporaneous occurrences in southern Alberta with slightly older records of this species from the Wapiti Formation in northwestern Alberta. [ABSTRACT FROM AUTHOR]

We describe a new species of nanhsiungchelyid turtle, Basilemys morrinensis, based on a nearly complete shell from the Horsethief Member (lower Maastrichtian) of the Horseshoe Canyon Formation of Alberta. The species is intermediate in age between the Campanian forms B. variolosa and B. gaffneyi and the upper Maastrichtian forms B. sinuosa and B. praeclara. It is also intermediate in its morphology, possessing a unique suite of both plesiomorphic (e.g., divided extragulars) and derived (e.g., square epiplastral beak, pygal wider than long) traits. It is further characterized by an autapomorphic square cervical scale. Phylogenetic analysis assuming parsimony recovers B. morrinensis in a polytomy with B. variolosa and B. gaffneyi, outside the clade formed by the upper Maastrichtian forms B. sinuosa and B. praeclara. The holotype of Basilemys morrinensis provides the first evidence that this genus reached large size (∼1 m long) in the Horseshoe Canyon Formation and was not diminutive as previously thought based on less complete shell material. Although Basilemys is usually regarded as terrestrial in habit based on its skull and limb morphology, we note that the low profile of its shell is a derived feature usually indicative of an aquatic mode of life. This suggests that there is yet much to learn about the life habits of this interesting turtle. https://zoobank.org/urn:lsid:zoobank.org:pub:F1F61F25-C441-4D7D-99B0-D460ABCC7918 SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Mallon, J. C., and D. B. Brinkman. 2018. Basilemys morrinensis, a new species of nanhsiungchelyid turtle from the Horseshoe Canyon Formation (Upper Cretaceous) of Alberta, Canada. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1431922. [ABSTRACT FROM AUTHOR]