Park Formation Research Articles

Методика формирования парка транспортно-технологических машин с использованием лизинга и кредита

Методика формирования парка транспортно-технологических машин с использованием лизинга и кредита

Effects of oxidation on residual shear strength of shales within Lea Park Formation

The residual shear strength of Cretaceous Lea Park Formation shale near Lloydminster, Saskatchewan, was evaluated to determine its suitability for road construction. Exposure of these shales results in oxidation, leaching, and other geochemical changes, which may affect the physicochemical forces that control the shear strength behaviour. A laboratory geotechnical testing program was complemented with geochemical testing and modelling. In situ pore-water chemistry and cation-exchange site composition were determined from soil-water extracts using an equilibrium geochemical model. It was found that leaching by low ionic strength recharge removes dissolved and adsorbed sodium from surficial deposits. Sulfur oxidation overprinted the effects of leaching by releasing acidity and sulfate, increasing stored gypsum, and increasing dissolved and adsorbed magnesium. Shear testing indicated higher apparent residual friction angles for surficial samples with lower exchangeable sodium; however, this relationship is obfuscated by the impact of increased sand contents on increased strength. Samples at depth exhibited lower apparent residual friction angles with higher clay fractions and greater exchangeable sodium. Fully assessing the long-term stability of the material would require further laboratory testing, and a theoretical basis to link the geochemical model results to the calculation of physicochemical forces in multi-ion, multi-mineral systems. Qualitatively, it can be concluded that near-surface oxidized and leached shales have greater shear strength, with less risk of this strength changing as a result of post-construction weathering.

Palaeoenvironmental drivers of vertebrate community composition in the Belly River Group (Campanian) of Alberta, Canada, with implications for dinosaur biogeography.

BackgroundThe Belly River Group of southern Alberta is one of the best-sampled Late Cretaceous terrestrial faunal assemblages in the world. This system provides a high-resolution biostratigraphic record of terrestrial vertebrate diversity and faunal turnover, and it has considerable potential to be a model system for testing hypotheses of dinosaur palaeoecological dynamics, including important aspects of palaeoecommunity structure, trophic interactions, and responses to environmental change. Vertebrate fossil microsites (assemblages of small bones and teeth concentrated together over a relatively short time and thought to be representative of community composition) offer an unparalleled dataset to better test these hypotheses by ameliorating problems of sample size, geography, and chronostratigraphic control that hamper other palaeoecological analyses. Here, we assembled a comprehensive relative abundance dataset of microsites sampled from the entire Belly River Group and performed a series of analyses to test the influence of environmental factors on site and taxon clustering, and assess the stability of faunal assemblages both temporally and spatially. We also test the long-held idea that populations of large dinosaur taxa were particularly sensitive to small-scale environmental gradients, such as the paralic (coastal) to alluvial (inland) regimes present within the time-equivalent depositional basin of the upper Oldman and lower Dinosaur Park Formations.ResultsPalaeoenvironment (i.e. reconstructed environmental conditions, related to relative amount of alluvial, fluvial, and coastal influence in associated sedimentary strata) was found to be strongly associated with clustering of sites by relative-abundance faunal assemblages, particularly in relation to changes in faunal assemblage composition and marine-terrestrial environmental transitions. Palaeogeography/palaeolandscape were moderately associated to site relative abundance assemblage clustering, with depositional setting and time (i.e. vertical position within stratigraphic unit) more weakly associated. Interestingly, while vertebrate relative abundance assemblages as a whole were strongly correlated with these marine-terrestrial transitions, the dinosaur fauna does not appear to be particularly sensitive to them.ConclusionsThis analysis confirms that depositional setting (i.e. the sediment type/sorting and associated characteristics) has little effect on faunal assemblage composition, in contrast to the effect of changes in the broader palaeoenvironment (e.g. upper vs. lower coastal plain, etc.), with marine-terrestrial transitions driving temporal faunal dynamics within the Belly River Group. The similarity of the dinosaur faunal assemblages between the time-equivalent portions of the Dinosaur Park Formation and Oldman Formation suggests that either these palaeoenvironments are more similar than characterized in the literature, or that the dinosaurs are less sensitive to variation in palaeoenvironment than has often been suggested. A lack of sensitivity to subtle environmental gradients casts doubt on these forces acting as a driver of putative endemism of dinosaur populations in the Late Cretaceous of North America.Electronic supplementary materialThe online version of this article (doi:10.1186/s12898-016-0106-8) contains supplementary material, which is available to authorized users.

A new ornithomimid theropod from the Dinosaur Park Formation of Alberta, Canada

ABSTRACTA partial ornithomimid skeleton, ROM 1790, from the lower Dinosaur Park Formation (upper Campanian) of Alberta was previously referred to Struthiomimus altus, but lacks diagnostic characters of that species. It is here described as the holotype of a new species, Rativates evadens, gen. et sp. nov., diagnosed by the form of the maxilla-jugal contact, the reduction of the mid-caudal neural spines, the convex fusion of the left and right ischial shafts, the straight-edged distal end of the third metatarsal, and possibly the relatively enlarged medial condyle of the tibia. A histological section of the femur confirms that the type specimen is not a juvenile, despite its relatively small size (approximately 50% the size of large individuals of Struthiomimus altus). Phylogenetic analysis recovers Rativates as a member of a derived ornithomimid clade that includes Ornithomimus, Struthiomimus, and the Asian taxa Anserimimus and Qiupalong. Fusion of the proximal tarsals to the tibia in some ornithomimid specimens was observed to be more complete than previously recognized, increasing the suite of features that these non-avian dinosaurs share homoplastically with birds.http://zoobank.org/urn:lsid:zoobank.org:pub:E0163526-7C26-4E8C-90C9-C72A3E90ED2DSUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: McFeeters, B., M. J. Ryan, C. Schröder-Adams, and T. M. Cullen. 2016. A new ornithomimid theropod from the Dinosaur Park Formation of Alberta, Canada. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1221415.

Reply to comment on: “A densely feathered ornithomimid (Dinosauria: Theropoda) from the Upper Cretaceous Dinosaur Park Formation, Alberta, Canada”

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).

A flowing material balance equation for two-phase flowback analysis

Abstract Flowback data from wells completed in shale gas reservoirs usually show a surprising behavior of immediate two-phase flow. This is especially the case in wells with an extended shut-in period. This paper seeks to understand the fundamental reasons behind this early-time behavior by identifying trends in water/gas field production data. Diagnostic Gas–Water Ratio plots of 8 multi-fractured horizontal wells from the Muskwa and Otter Park formations show a unique v-shaped trend. Based on this early-time production signature, we hypothesize that the early gas production is linked to the initial free gas in the complex fracture network of the shale reservoir. We test this hypothesis by numerical simulation of the shut-in and flowback processes, and observe a similar v-shaped trend caused by a gradual build-up of free gas saturation in the fracture network during the shut-in period. This conclusion is also backed by extensive imbibition experiments conducted on the corresponding shale samples and by the presence of gas-saturated natural fractures. We also develop a simple mathematical model to describe gas and water production during the early hours of flowback. Based on the observations from field and simulated data, the primary drive mechanism is assumed to be the expansion of free gas built up in the fractures during the shut-in period. Other drive mechanisms considered include fracture closure and water expansion. The driving forces are modeled by an effective compressibility term analogous to the total compressibility in conventional multi-phase flow formulations. This model gives an easy method for the quick interpretation of early-time two-phase flowback data in a manner similar to conventional well testing methods. It can be applied to estimate the effective fracture volume and a dimensionless fracture parameter, which measures the flow capacity of the fracture network. Finally, we demonstrate the application of this model by analyzing flowback data from 2 fractured horizontal wells completed in the Horn River Basin.

A juvenile chasmosaurine ceratopsid (Dinosauria, Ornithischia) from the Dinosaur Park Formation, Alberta, Canada

ABSTRACTAn articulated, 1.5 m long skeleton of a juvenile Chasmosaurus, lacking only the front limbs, pectoral girdles, and terminal caudal vertebrae, was collected from the Dinosaur Park Formation in Dinosaur Provincial Park, Alberta. The short, tall skull has a narrow frill that lacks a posterior embayment. Many of the cranial bones are co-ossified in spite of the small size of the specimen. The nasals form an incipient horncore, and the short, knob-like postorbital horncore lacks sinuses. The palpebral is not fused to the rest of the skull. The frontal fontanelle is keyhole-shaped. The triangular squamosal extends to the back of the parietals. Epiossifications are lacking, although the squamosal margin is thick and scalloped. The parietal has a pronounced midline sagittal crest. Parietal fenestrae, if present, would have been narrow and elongate. There are only 18 maxillary tooth positions. The syncervical comprises three co-ossified, but distinct vertebrae. Anterior caudal vertebrae support unfused caudal ribs. Ossified tendons in the neck, trunk, and sacrum do not extend into the tail. Hind limb proportions are comparable to those of adult ceratopsids. The pedal unguals are distally acute. Skin impressions are similar to those of mature chasmosaurines. Phylogenetic analysis, if all characters are coded as they are seen, suggests that the specimen is a basal chasmosaurine. When size or age dependent characters are recoded as ‘?,’ the specimen groups with other Chasmosaurus. These characters should only be used in phylogenetic analyses when all specimens are mature.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Currie, P. J., R. B. Holmes, M. J. Ryan, and C. Coy. 2016. A juvenile chasmosaurine ceratopsid (Dinosauria, Ornithischia) from the Dinosaur Park Formation, Alberta, Canada. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2015.1048348.

A Re-Evaluation of the Chasmosaurine Ceratopsid Genus Chasmosaurus (Dinosauria: Ornithischia) from the Upper Cretaceous (Campanian) Dinosaur Park Formation of Western Canada.

BackgroundThe chasmosaurine ceratopsid Chasmosaurus is known from the Upper Cretaceous (Campanian) Dinosaur Park Formation of southern Alberta and Saskatchewan. Two valid species, Chasmosaurus belli and C. russelli, have been diagnosed by differences in cranial ornamentation. Their validity has been supported, in part, by the reported stratigraphic segregation of chasmosaurines in the Dinosaur Park Formation, with C. belli and C. russelli occurring in discrete, successive zones within the formation.Results/ConclusionsAn analysis of every potentially taxonomically informative chasmosaurine specimen from the Dinosaur Park Formation indicates that C. belli and C. russelli have indistinguishable ontogenetic histories and overlapping stratigraphic intervals. Neither taxon exhibits autapomorphies, nor a unique set of apomorphies, but they can be separated and diagnosed by a single phylogenetically informative character—the embayment angle formed by the posterior parietal bars relative to the parietal midline. Although relatively deeply embayed specimens (C. russelli) generally have relatively longer postorbital horncores than specimens with more shallow embayments (C. belli), neither this horncore character nor epiparietal morphology can be used to consistently distinguish every specimen of C. belli from C. russelli.Status of Kosmoceratops in the Dinosaur Park FormationKosmoceratops is purportedly represented in the Dinosaur Park Formation by a specimen previously referred to Chasmosaurus. The reassignment of this specimen to Kosmoceratops is unsupported here, as it is based on features that are either influenced by taphonomy or within the realm of individual variation for Chasmosaurus. Therefore, we conclude that Kosmoceratops is not present in the Dinosaur Park Formation, but is instead restricted to southern Laramidia, as originally posited.

A vertebrate microsite from a marine-terrestrial transition in the Foremost Formation (Campanian) of Alberta, Canada, and the use of faunal assemblage data as a paleoenvironmental indicator

Vertebrate microfossil assemblages contain abundant fossil material of small and large bodied animals recruited from the local paleocommunity that can provide important information for reconstructing regional paleoecology. The Foremost Formation is the oldest unit of the Belly River Group, and records the transition from the fully marine shales of the Pakowki Formation to the non-marine strata of the relatively well-sampled Oldman and Dinosaur Park formations. Although the Foremost Formation has relatively limited exposure and vertebrate fossil material is not abundant, it does contain some important early records of major vertebrate clades from Laramidia (e.g. ceratopsids, pachycephalosaurids).Here we document a new microfossil locality from the upper part of the formation that shows a transitional assemblage containing an abundance of terrestrial forms such as dinosaurs and other sauropsids, while still showing considerable marine influence. The proportion of marine taxa at this site is reduced relative to most sites known from the Foremost Formation, though much higher than more terrestrial sites of the overlying Oldman Formation. In addition to filling a gap in our understanding of this paleoenvironmental transition, this new site preserves two particularly significant specimens: a large, complete, cephalic spine of the hybodont shark Hybodus, and jaw fragments from the ratfish Elasmodus. This represents the first known complete cephalic spine of a hybodont shark from the Cretaceous of Alberta. The ratfish jaw fragments represent the first published record of this group from the Foremost Formation, further increasing our knowledge of chondrichthyan diversity in the Western Interior Seaway. Comparisons of this site to other microsites from the Campanian of Alberta demonstrate the utility of certain key groups, such as lissamphibians and chondrichthyans, in determining paleoenvironments from Mesozoic and Cenozoic vertebrate microsite assemblage data.

Systematics of Chasmosaurus - new information from the Peabody Museum skull, and the use of phylogenetic analysis for dinosaur alpha taxonomy

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.

Baenid turtles of the Kaiparowits Formation (Upper Cretaceous: Campanian) of southern Utah, USA

I describe the assemblage of baenid turtles found in the Campanian Kaiparowits Formation of southern Utah and compare it with baenids from other basins across Laramidia. Baenids were one of the most diverse and abundant freshwater turtle clades during the Late Cretaceous. They were restricted to North America, with all except the basal-most taxon (Arundelemys) restricted to Laramidia. During the Campanian, baenids were conspicuous parts of the turtle assemblages of Alberta, Montana and New Mexico. The baenids of the Kaiparowits Formation are critical in that they provide an assemblage from southern Laramidia that is correlative with those from northern Laramidia, allowing for more accurate testing of Campanian palaeobiogeographical hypotheses. In this paper, two new baenid species, Neurankylus hutchisoni sp. nov. and Neurankylus utahensis sp. nov., are described. Additionally, the first description of cranial material from Denazinemys nodosa is provided. A comprehensive survey of collected material indicates that at least six baenid taxa are present in the formation, including Neurankylus hutchisoni, Neurankylus utahensis, Thescelus sp., Arvinachelys goldeni, Denazinemys nodosa and Boremys grandis. Arvinachelys, Neurankylus hutchisoni and Neurankylus utahensis have not been identified outside of the Kaiparowits Basin, but Denazinemys nodosa and Boremys grandis both are known from younger sediments of the San Juan Basin of New Mexico. Members of the genus Thescelus are known from the Campanian of New Mexico and the Maastrichtian of Wyoming, Montana and Saskatchewan, but are conspicuously absent in the Campanian of Alberta and Montana. The baenid assemblage in the Kaiparowits Formation provides support for both basin-scale endemism and north–south provincialism across Laramidia during the Campanian. There is also evidence for a latitudinal gradient in diversity, as only three baenid species have been reported from the temporally correlated Dinosaur Park Formation in Alberta.http://zoobank.org/urn:lsid:zoobank.org:pub:75DF6CFF-3E87-4729-9798-975C0157514F

A densely feathered ornithomimid (Dinosauria: Theropoda) from the Upper Cretaceous Dinosaur Park Formation, Alberta, Canada

A recently discovered articulated partial skeleton of Ornithomimus from the Upper Cretaceous Dinosaur Park Formation of Alberta, Canada is remarkable in the extent and quality of preservation of integumentary structures including feathers. It is the first ornithomimid to preserve a tail bearing extensive plumaceous feathers that are slightly more elongate in comparison to those present on the remainder of the body. However, the underside of the tail and the hind limb distal to the middle of the femur appear devoid of plumage. Overall, the plumage pattern in Ornithomimus is similar to that of Struthio camelus (ostrich) and other large palaeognaths, indicating a probable function in thermoregulation. The specimen also preserves the body outline around the legs, including a skin contour anterior to the femur, analogous to skin webs in extant birds. Whereas the knee web of birds bridges the knee to the abdomen, in Ornithomimus it spans from the mid-femoral shaft to the abdomen, and is herein referred to as an anterior femoral web. This is the first report of such soft tissue structures in non-avian theropods. It may indicate that the resting position of the femur was positioned more anteroventrally in ornithomimids than in most theropods, and in that sense may have been transitional to the situation in modern birds.

TAPHONOMY OF A MONODOMINANTCENTROSAURUS APERTUS(DINOSAURIA: CERATOPSIA) BONEBED FROM THE UPPER OLDMAN FORMATION OF SOUTHEASTERN ALBERTA

Abstract The horned dinosaur Centrosaurus apertus from the Belly River Group (Campanian) is represented by multiple articulated skulls and skeletons, and is particularly notable for its occurrence in dozens of large-scale monodominant bonebeds, which have been found in the Dinosaur Park Formation across southern Alberta and Saskatchewan. Here we present a detailed taphonomic analysis of the first large-scale Centrosaurus apertus bonebed (McPheeters bonebed) from the Oldman Formation of southeastern Alberta. The McPheeters bonebed rivals the richest bonebeds in the Dinosaur Park Formation in terms of bone density and size, and the complete disarticulation of elements. The bonebed occurs in an overbank facies and is dominated by small bone clasts, suggesting that only low energy water current contributed to the formation of the bonebed before its final burial event. Patterns of taphonomic modification suggest that bones experienced little weathering, breakage, or scavenging. In turn, these conclusions are c...

Redescription of UALVP 40, an unusual specimen ofChasmosaurusLambe, 1914 (Ceratopsidae: Chasmosaurinae) bearing long postorbital horns, and its implications for ontogeny and alpha taxonomy of the genus

UALVP 40, an articulated and reasonably complete skull of a small chasmosaurine dinosaur collected in 1920 by George F. Sternberg from the lower unit of the Dinosaur Park Formation, Dinosaur Provincial Park, Alberta, Canada, is here redescribed. The focus of the study is on the newly prepared right side of the skull and the hitherto undescribed mandible. There are substantial differences between the right and the left side of the skull, most notably the right postorbital horncore exhibits a greater angle of inclination at 60° from horizontal, which is approximately 15° greater than that of the left. The right side of the skull also shows many unfused cranial sutures that are obliterated on the left side. These unfused sutures and the short predentary lacking an anterior elongation, indicate that UALVP 40 likely represents a subadult individual. UALVP 40 is diagnosed to the genus Chasmosaurus by its possession of the following: (i) premaxillary flange along entire anterior margin of external naris; (ii) supraorbital horns curving posteriorly along their length; and (iii) squamosal dorsal border laterally adjacent to supratemporal fenestra straight in profile, sloping posteroventrally at a shallow angle before ascending farther posteriorly to form lateral border of parietal fenestra. The last character is newly proposed. A bivariate correlation in UALVP 40 and other Canadian specimens of Chasmosaurus bearing long postorbital horncores (>150 mm long) reveals a near isometric relationship between interorbital width and horn length. This may indicate those specimens represent an ontogenetic series of a single species diagnosed by long postorbital horncores.

Origins of dinosaur bonebeds in the Cretaceous of Alberta, Canada

Upper Cretaceous dinosaur bonebeds are common in Alberta, Canada, and have attracted continuous scientific attention since the 1960s. Since its inception, the Royal Tyrrell Museum of Palaeontology has documented the presence of hundreds of these sites and has been involved directly in the scientific study of many tens. Because many of these bonebeds have been used to address questions about the paleobiology and paleoecology of dinosaurs, questions have arisen about bonebed origins and preservation in the Cretaceous of Alberta. This study of 260 bonebeds delineates broad paleoenvironmental settings and associations, and taphonomic signatures of assemblages as a first step in assessing patterns of dinosaur bonebed origins in the Upper Cretaceous of Alberta. Bonebeds are known predominantly from the Belly River Group and the Horseshoe Canyon, lower St. Mary River, Wapiti, and Scollard formations. In these units, bonebeds are mostly associated with river channel and alluvial wetland settings that were influenced by a subtropical to warm-temperate, monsoonal climate. Most bonebeds formed in response to flooding events capable of killing dinosaurs, reworking and modifying skeletal remains, and burying taphocoenoses. The “coastal-plain-flooding hypothesis,” proposed in 2005, suggested that many bonebeds in the Dinosaur Park Formation formed in response to the effects of recurring coastal-plain floods that submerged vast areas of ancient southern Alberta on a seasonal basis. It remains the best mechanism to explain how many of the bonebeds were formed and preserved at Dinosaur Provincial Park, and here, is proposed as the mechanism that best explains bonebed origins in other Upper Cretaceous formations across central and southern Alberta.

Marine turtles from the Late Cretaceous of Alberta, Canada

Previously reported and new specimens of marine turtles from the late Campanian of Alberta, Canada, provide additional information on the diversity and distribution of chelonioid turtles at this time. An articulated carapace from the Bearpaw Formation previously interpreted as Lophochelys niobrarae is considered to be a juvenile of a specifically indeterminate chelonioid and is referred to Lophochelys sp. Isolated neurals and a hyoplastron from nonmarine estuarine deposits in the uppermost beds of the Dinosaur Park Formation are tentatively referred to Lophochelys sp. These specimens suggest that this chelonioid could enter freshwater environments. A new chelonioid, Kimurachelys slobodae gen. et sp. nov., is recognized on the basis of two mandibles and a maxilla from the uppermost beds of the Dinosaur Park Formation of southeastern Alberta. A partial postcranial skeleton of an indeterminate chelonioid from the Bearpaw Formation provides additional evidence that chelonioids of this formation included taxa that were phylogenetically intermediate between chelonioids of the late Santonian and members of the crown group.

Dinosaur trackways from the Upper Cretaceous Oldman and Dinosaur Park formations (Belly River Group) of southern Alberta, Canada, reveal novel ichnofossil preservation style

Dinosaur tracksites recently discovered in exposures of the Belly River Group in the Milk River Natural Area (MRNA) and Dinosaur Provincial Park (DPP) of southern Alberta represent a novel type of ichnofossils. The tracks, all referable to hadrosaurs, occur as sideritic or calcareous concretions protruding above fine-grained deposits and are here termed concretionary tracks. Detailed sedimentological, petrographic, and geochemical analyses reveal that, although the MRNA and DPP tracks are of different mineralogical compositions (calcium carbonate versus siderite, respectively), they display similar internal structures (microscopic convoluted laminations) and occur in depositional settings indicative of wet paleoenvironments, where the ground was soft and water saturated. These characteristics suggest that concretionary tracks are footprint casts that formed as groundwater rich in dissolved carbonates flooded depressions left in the soft substrate. As the ponded water evaporated, minerals began to precipitate and mix with clastic material transported into the depressions, settling as finely laminated mud within the tracks and filling them either completely or partially. The geochemical composition of the precipitate would depend on the prevalent groundwater conditions (e.g., pH, dissolved carbonate and sulphate concrentrations). Cementation of the tracks occurred relatively soon after burial (<100 years), possibly in response to microbial activity and saturation by mineral-rich groundwater, and modern erosion exposed the concretionary tracks by removing the softer host unit. Recognition of this novel type of ichnofossils suggests dinosaur tracks may be more common than previously thought. Unfortunately, concretionary tracks tend to break apart rapidly when the encasing and underlying substrate erodes away, altering their diagnostic shape and rendering them indistinguishable from nonichnogenic concretions. As such, concretionary tracks may be transient ichnofossils in the badlands, explaining why they are rarely recognized.

An edentulous frog (Lissamphibia; Anura) from the Upper Cretaceous (Campanian) Dinosaur Park Formation of southeastern Alberta, Canada

The frog Tyrrellbatrachus brinkmani, gen. et sp. nov., is described on the basis of seven incomplete maxillae from vertebrate microfossil localities in the Upper Cretaceous (Campanian) Dinosaur Park Formation, in the Dinosaur Provincial Park area, southeastern Alberta, Canada. The maxillae are distinctive in a unique suite of features related to size, shape, and proportions of the bone, texture of the labial surface, form of the surface for inferred contact with the squamosal, form of the lamina horizontalis and the processus pterygoideus, relative depth of the crista dentalis, and in being edentulous (i.e., lacking teeth). The higher level affinities of Tyrrellbatrachus are uncertain, although certain features exclude it from several known families; for example, the presence of a processus pterygoideus excludes it from Gobiatidae (Late Cretaceous, Asia), whereas the presence of a crista dentalis and of a relatively unreduced pars facialis exclude it from Pipidae (Cretaceous–Recent, Africa and South America). The lack of teeth in Tyrrellbatrachus is notable because although tooth loss is widespread among extant anurans and has arisen independently multiple times, it has rarely been documented among Mesozoic anurans. Comparisons with the only other edentulous anuran from the Mesozoic of the Northern Hemisphere, namely Theatonius (late Campanian – late Maastrichtian, western USA), reveal no compelling similarities to support a close relationship between the two genera. Those taxa represent an early (Campanian) instance of independent tooth loss in anurans and, potentially, the oldest record of tooth loss in nonpipid anurans.

Jaw mechanics and evolutionary paleoecology of the megaherbivorous dinosaurs from the Dinosaur Park Formation (upper Campanian) of Alberta, Canada

ABSTRACTThe question of what role differential jaw mechanics may have played in facilitating dietary niche partitioning among Late Cretaceous megaherbivorous dinosaurs from Laramidia is examined, using the fossil assemblage of the Dinosaur Park Formation as a test case. We use phylogenetic inference to reconstruct the mandibular adductor musculature of these animals, which we then apply to the construction of biomechanical lever models of the mandible to estimate relative bite forces. Our findings reveal predictably weak bite forces in ankylosaurs, and comparatively high bite forces in ceratopsids and hadrosaurids, both of which possessed a mechanical advantage that produced bite forces 2–3 times higher than those forces exerted by the adductor musculature. The impressive jaw mechanism shared by the last two taxa evolved in a stepwise fashion, independently in each lineage. There is tentative evidence to suggest that nodosaurids had more powerful bites than ankylosaurids, but the overall mechanical diversity among megaherbivores from the Dinosaur Park Formation is low, suggesting that differential jaw mechanics could have played only a subsidiary role in niche partitioning. Such mechanical conservatism may have may have been selected for, or it may simply reflect the limits imposed by evolutionary constraints. Regardless, mechanical disparity patterns remained stable throughout the ∼1.5 Ma evolution of the Dinosaur Park Formation megaherbivore chronofauna.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

New material of the large-bodied caenagnathid Caenagnathus collinsi from the Dinosaur Park Formation of Alberta, Canada

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.