Albertosaurs

Gilmore, C. W. (1946): New carnivorous dinosaur from the Lance formation of Montana. The Smithsonian Institution 106, No. 13: 1-19

@article{doi1015468yhxmzl,
    author = "Gilmore, Charles W.",
    title = "A new carnivorous dinosaur from the Lance Formation of Montana",
    year = "1946",
    journal = "Zenodo (CERN European Organization for Nuclear Research)",
    abstract = "Gilmore, C. W. (1946): New carnivorous dinosaur from the Lance formation of Montana. The Smithsonian Institution 106, No. 13: 1-19",
    url = "https://doi.org/10.15468/yhxmzl",
    doi = "10.15468/yhxmzl",
    openalex = "W2529936223"
}

Molnar, R.E. (1980): An albertosaur from the Hell Creek formation of Montana. Journal of Paleontology 54 (1): 102-108, DOI: 10.5281/zenodo.1039725

@article{doi1015468lnfamn,
    author = "Molnar, Ralph E.",
    title = "An Albertosaur From The Hell Creek Formation Of Montana",
    year = "1980",
    journal = "Global Biodiversity Information Facility",
    abstract = "Molnar, R.E. (1980): An albertosaur from the Hell Creek formation of Montana. Journal of Paleontology 54 (1): 102-108, DOI: 10.5281/zenodo.1039725",
    url = "https://doi.org/10.15468/lnfamn",
    doi = "10.15468/lnfamn",
    openalex = "W2606633890",
    references = "doi101139e72031, doi1015468yhxmzl, doi1023071005355, doi104095101672, doi105281zenodo1040385, doi105281zenodo1040973, doi105281zenodo16692311"
}

Text-fig. 6—Right fibula of Albertosaurus cf. A. lancensis (LACM 23845), in lateral aspect. Diagonal lines indicate broken surfaces. Bar represents 10 cm.

@article{doi105281zenodo3248856,
    author = "Molnar, Ralph E.",
    title = "Text-fig. 6—Right fibula of Albertosaurus cf. A. lancensis (LACM 23845), in lateral aspect. Diagonal lines indicate broken surfaces. Bar represents 10 cm. in An albertosaur from the Hell Creek formation of Montana",
    year = "1980",
    journal = "Figshare",
    abstract = "Text-fig. 6—Right fibula of Albertosaurus cf. A. lancensis (LACM 23845), in lateral aspect. Diagonal lines indicate broken surfaces. Bar represents 10 cm.",
    url = "https://doi.org/10.5281/zenodo.3248856",
    doi = "10.5281/zenodo.3248856",
    openalex = "W3211253641"
}

@article{molnar1980an1,
    author = "Molnar, R. E",
    title = "An albertosaur from the Hell Creek Formation of Montana",
    year = "1980",
    journal = "Journal of Paleontology, v. 54, p. 102-108",
    note = "talkorigins\_source = {true}; raw\_reference = {Molnar, R. E., 1980, An albertosaur from the Hell Creek Formation of Montana: Journal of Paleontology, v. 54, p. 102-108.}"
}

BACKGROUND: A dinosaur census recorded during the Hell Creek Project (1999-2009) incorporates multiple lines of evidence from geography, taphohistory, stratigraphy, phylogeny and ontogeny to investigate the relative abundance of large dinosaurs preserved in the Upper Cretaceous Hell Creek Formation of northeastern Montana, USA. Overall, the dinosaur skeletal assemblages in the Hell Creek Formation (excluding lag-influenced records) consist primarily of subadult or small adult size individuals. Small juveniles and large adults are both extremely rare, whereas subadult individuals are relatively common. We propose that mature individuals of at least some dinosaur taxa either lived in a separate geographic locale analogous to younger individuals inhabiting an upland environment where sedimentation rates were relatively less, or these taxa experienced high mortality before reaching terminal size where late stage and often extreme cranial morphology is expressed. METHODOLOGY/PRINCIPAL FINDINGS: Tyrannosaurus skeletons are as abundant as Edmontosaurus, an herbivore, in the upper Hell Creek Formation and nearly twice as common in the lower third of the formation. Smaller, predatory dinosaurs (e.g., Troodon and dromaeosaurids) are primarily represented by teeth found in microvertebrate localities and their skeletons or identifiable lag specimens were conspicuously absent. This relative abundance suggests Tyrannosaurus was not a typical predator and likely benefited from much wider food choice opportunities than exclusively live prey and/or specific taxa. Tyrannosaurus adults may not have competed with Tyrannosaurus juveniles if the potential for selecting carrion increased with size during ontogeny. CONCLUSIONS/SIGNIFICANCE: Triceratops is the most common dinosaur and isolated skulls contribute to a significant portion of this census. Associated specimens of Triceratops consisting of both cranial and postcranial elements remain relatively rare. This rarity may be explained by a historical collecting bias influenced by facies and taphonomic factors. The limited discovery of postcranial elements may also depend on how extensive a fossil quarry is expanded after a skull is collected.

@article{doi101371journalpone0016574,
    author = "Horner, John R. and Goodwin, Mark B. and Myhrvold, Nathan",
    title = "Dinosaur Census Reveals Abundant Tyrannosaurus and Rare Ontogenetic Stages in the Upper Cretaceous Hell Creek Formation (Maastrichtian), Montana, USA",
    year = "2011",
    journal = "PLoS ONE",
    abstract = "BACKGROUND: A dinosaur census recorded during the Hell Creek Project (1999-2009) incorporates multiple lines of evidence from geography, taphohistory, stratigraphy, phylogeny and ontogeny to investigate the relative abundance of large dinosaurs preserved in the Upper Cretaceous Hell Creek Formation of northeastern Montana, USA. Overall, the dinosaur skeletal assemblages in the Hell Creek Formation (excluding lag-influenced records) consist primarily of subadult or small adult size individuals. Small juveniles and large adults are both extremely rare, whereas subadult individuals are relatively common. We propose that mature individuals of at least some dinosaur taxa either lived in a separate geographic locale analogous to younger individuals inhabiting an upland environment where sedimentation rates were relatively less, or these taxa experienced high mortality before reaching terminal size where late stage and often extreme cranial morphology is expressed. METHODOLOGY/PRINCIPAL FINDINGS: Tyrannosaurus skeletons are as abundant as Edmontosaurus, an herbivore, in the upper Hell Creek Formation and nearly twice as common in the lower third of the formation. Smaller, predatory dinosaurs (e.g., Troodon and dromaeosaurids) are primarily represented by teeth found in microvertebrate localities and their skeletons or identifiable lag specimens were conspicuously absent. This relative abundance suggests Tyrannosaurus was not a typical predator and likely benefited from much wider food choice opportunities than exclusively live prey and/or specific taxa. Tyrannosaurus adults may not have competed with Tyrannosaurus juveniles if the potential for selecting carrion increased with size during ontogeny. CONCLUSIONS/SIGNIFICANCE: Triceratops is the most common dinosaur and isolated skulls contribute to a significant portion of this census. Associated specimens of Triceratops consisting of both cranial and postcranial elements remain relatively rare. This rarity may be explained by a historical collecting bias influenced by facies and taphonomic factors. The limited discovery of postcranial elements may also depend on how extensive a fossil quarry is expanded after a skull is collected.",
    url = "https://doi.org/10.1371/journal.pone.0016574",
    doi = "10.1371/journal.pone.0016574",
    openalex = "W1982210430",
    references = "carr1999craniofacial, doi101038282296a0, doi101073pnas0708903105, doi101080027246342010483632, doi101098rspb20042829, doi101371journalpone0007626, doi1016660094837320010270039coosea20co2, doi1016710272463420000200115lbhoth20co2, doi1023072404970, openalexw1550433756"
}

The placement of over 50 skulls of the well-known horned dinosaur Triceratops within a stratigraphic framework for the Upper Cretaceous Hell Creek Formation (HCF) of Montana reveals the evolutionary transformation of this genus. Specimens referable to the two recognized morphospecies of Triceratops, T. horridus and T. prorsus, are stratigraphically separated within the HCF with the T. prorsus morphology recovered in the upper third of the formation and T. horridus found lower in the formation. Hypotheses that these morphospecies represent sexual or ontogenetic variation within a single species are thus untenable. Stratigraphic placement of specimens appears to reveal ancestor-descendant relationships. Transitional morphologies are found in the middle unit of the formation, a finding that is consistent with the evolution of Triceratops being characterized by anagenesis, the transformation of a lineage over time. Variation among specimens from this critical stratigraphic zone may indicate a branching event in the Triceratops lineage. Purely cladogenetic interpretations of the HCF dataset imply greater diversity within the formation. These findings underscore the critical role of stratigraphic data in deciphering evolutionary patterns in the Dinosauria.

@article{doi101073pnas1313334111,
    author = "Scannella, John B and Fowler, Denver W and Goodwin, Mark B and Horner, John R",
    title = "Evolutionary trends in Triceratops from the Hell Creek Formation, Montana.",
    year = "2014",
    journal = "Proceedings of the National Academy of Sciences of the United States of America",
    abstract = "The placement of over 50 skulls of the well-known horned dinosaur Triceratops within a stratigraphic framework for the Upper Cretaceous Hell Creek Formation (HCF) of Montana reveals the evolutionary transformation of this genus. Specimens referable to the two recognized morphospecies of Triceratops, T. horridus and T. prorsus, are stratigraphically separated within the HCF with the T. prorsus morphology recovered in the upper third of the formation and T. horridus found lower in the formation. Hypotheses that these morphospecies represent sexual or ontogenetic variation within a single species are thus untenable. Stratigraphic placement of specimens appears to reveal ancestor-descendant relationships. Transitional morphologies are found in the middle unit of the formation, a finding that is consistent with the evolution of Triceratops being characterized by anagenesis, the transformation of a lineage over time. Variation among specimens from this critical stratigraphic zone may indicate a branching event in the Triceratops lineage. Purely cladogenetic interpretations of the HCF dataset imply greater diversity within the formation. These findings underscore the critical role of stratigraphic data in deciphering evolutionary patterns in the Dinosauria.",
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC4104892/",
    doi = "10.1073/pnas.1313334111",
    openalex = "W1986799724",
    pmcid = "PMC4104892",
    pmid = "24982159",
    references = "doi10100703064746897, doi101073pnas1313334111, doi10108002724631003763516, doi101093aesa383396, doi101111j109600311995tb00092x, doi101111j155856461951tb02788x, doi101111j155856461985tb00420x, doi101371journalpone0032623, doi10167102724634200828134ooceit20co2, doi1023072405671, doi105860choice333929, doi105962bhltitle5716, doi107312simp93764, openalexw2611511275, openalexw3217097258, openalexw568618627"
}

The small triangular posteriorly oriented nasal crest of Probrachylophosaurus is proposed to represent a transitional nasal morphology between that of a non-crested ancestor such as Acristavus and the large flat posteriorly oriented nasal crest of adult Brachylophosaurus. Because Probrachylophosaurus is stratigraphically and morphologically intermediate between these taxa, Probrachylophosaurus is hypothesized to be an intermediate member of the Acristavus-Brachylophosaurus evolutionary lineage.

@article{doi101371journalpone0141304,
    author = "Fowler, Elizabeth A. Freedman and Horner, John R.",
    title = "A New Brachylophosaurin Hadrosaur (Dinosauria: Ornithischia) with an Intermediate Nasal Crest from the Campanian Judith River Formation of Northcentral Montana",
    year = "2015",
    journal = "PLoS ONE",
    abstract = "The small triangular posteriorly oriented nasal crest of Probrachylophosaurus is proposed to represent a transitional nasal morphology between that of a non-crested ancestor such as Acristavus and the large flat posteriorly oriented nasal crest of adult Brachylophosaurus. Because Probrachylophosaurus is stratigraphically and morphologically intermediate between these taxa, Probrachylophosaurus is hypothesized to be an intermediate member of the Acristavus-Brachylophosaurus evolutionary lineage.",
    url = "https://doi.org/10.1371/journal.pone.0141304",
    doi = "10.1371/journal.pone.0141304",
    openalex = "W2114007970",
    references = "doi101016jgca201006017, doi101016s0009254197001599, doi101016s0195667105800308, doi101017pab201519, doi101038282296a0, doi101038nature11264, doi101073pnas1313334111, doi101080027246342011557116, doi101098rspb20090229, doi101371journalpone0016574, doi101371journalpone0018029, doi101371journalpone0029958, doi1016710272463420000200115lbhoth20co2, doi10167102724634200727373aarolm20co2, doi105860choice435902, doi105860choice514447, doi105962bhltitle101747, doi105962bhltitle115853, horner2011dinosaur, köhler2012seasonal, openalexw2904473752, openalexw3217097258, vanitterbeeck2005stratigraphy"
}

Torosaurus latus is an uncommon and contentious taxon of chasmosaurine ceratopsid known from several upper Maastrichtian units in western North America. We describe a partial parietal of To. latus from the Hell Creek Formation of Montana. Although the specimen's ontogenetic maturity means that it cannot inform the ongoing debate over whether To. latus is the old adult form of the contemporary Triceratops, the specimen is one of the best-preserved To. latus parietals and supplements previous descriptions.

@article{doi101371journalpone0151453,
    author = "McDonald, Andrew T and Campbell, Carl E and Thomas, Brian",
    title = "A New Specimen of the Controversial Chasmosaurine Torosaurus latus (Dinosauria: Ceratopsidae) from the Upper Cretaceous Hell Creek Formation of Montana.",
    year = "2016",
    journal = "PloS one",
    abstract = "Torosaurus latus is an uncommon and contentious taxon of chasmosaurine ceratopsid known from several upper Maastrichtian units in western North America. We describe a partial parietal of To. latus from the Hell Creek Formation of Montana. Although the specimen's ontogenetic maturity means that it cannot inform the ongoing debate over whether To. latus is the old adult form of the contemporary Triceratops, the specimen is one of the best-preserved To. latus parietals and supplements previous descriptions.",
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC4790893/",
    doi = "10.1371/journal.pone.0151453",
    openalex = "W2301233369",
    pmcid = "PMC4790893",
    pmid = "26974149",
    references = "doi101073pnas1313334111, doi101080027246342010483632, doi101111j109636421997tb00340x, doi101371journalpone0012292, doi101371journalpone0016574, doi101371journalpone0032623, doi1016690883135120010160482ttoaco20co2, doi10167102724634200828134ooceit20co2, doi1016710390290119, openalexw597685939"
}

Perinatal specimens of hadrosaurids discovered in the late 1970's by field crews from Princeton University were significant in providing evidence of the early ontogenetic stages in North American dinosaurs. These specimens from the Campanian (Upper Cretaceous) Two Medicine Formation of Montana consist of over a dozen skeletons referable to the saurolophine hadrosaurid Maiasaura peeblesorum, but never fully figured or described. Here, we provide a more complete documentation of the morphology of these specimens, along with an examination of variation during a large span of the development of saurolophine hadrosaurids. Many ontogenetic changes in the available facial and mandibular elements are associated with the progressive elongation of the preorbital region of the skull and mandible. In the postcranium, limb bones change nearly isometrically, with exception of certain elements of the forelimb. Some cranial and postcranial characters commonly used for inferring hadrosaurid phylogenetic relationships remain invariable during the ontogeny of M. peeblesorum. This indicates that early ontogenetic stages may still provide a limited amount of character information useful for systematics and phylogenetic inference.

@article{doi107717peerj4734,
    author = "Prieto‐Márquez, Albert and Guenther, Merrilee F.",
    title = "Perinatal specimens of Maiasaura from the Upper Cretaceous of Montana (USA): insights into the early ontogeny of saurolophine hadrosaurid dinosaurs",
    year = "2018",
    journal = "PeerJ",
    abstract = "Perinatal specimens of hadrosaurids discovered in the late 1970's by field crews from Princeton University were significant in providing evidence of the early ontogenetic stages in North American dinosaurs. These specimens from the Campanian (Upper Cretaceous) Two Medicine Formation of Montana consist of over a dozen skeletons referable to the saurolophine hadrosaurid Maiasaura peeblesorum, but never fully figured or described. Here, we provide a more complete documentation of the morphology of these specimens, along with an examination of variation during a large span of the development of saurolophine hadrosaurids. Many ontogenetic changes in the available facial and mandibular elements are associated with the progressive elongation of the preorbital region of the skull and mandible. In the postcranium, limb bones change nearly isometrically, with exception of certain elements of the forelimb. Some cranial and postcranial characters commonly used for inferring hadrosaurid phylogenetic relationships remain invariable during the ontogeny of M. peeblesorum. This indicates that early ontogenetic stages may still provide a limited amount of character information useful for systematics and phylogenetic inference.",
    url = "https://doi.org/10.7717/peerj.4734",
    doi = "10.7717/peerj.4734",
    openalex = "W2803572907",
    references = "doi101371journalpone0141304"
}

A well-preserved large chasmosaurine ceratopsid premaxilla (MOR 1122 7-22-00-1) collected from the basal sandstone of the Cretaceous Hell Creek Formation (HCF) represents one of the stratigraphically lowest ceratopsid occurrences in the formation. The specimen was discovered in 2000, during the excavation of a large Torosaurus latus skull (MOR 1122) which was later hypothesized to represent an advanced growth stage of the more commonly recovered HCF ceratopsid Triceratops. MOR 1122 7-22-00-1 compares favorably with the incomplete premaxillae of the MOR 1122 skull and reveals details of premaxilla morphology from this stratigraphic zone. It preserves large, closely spaced ventromedial foramina, a narrow triangular process, and a thin septal flange at the base of the narial strut. The nasal process is narrow, caudally inclined and has a forked dorsal surface which appears to represent an intermediate between the morphology expressed in the slightly stratigraphically lower ceratopsid Eotriceratops xerinsularis from the Horseshoe Canyon Formation of Alberta and specimens recovered higher in the HCF. MOR 1122 7-22-00-1 expresses a deep recess extending medial to the strut of the triangular process, a feature shared with other HCF ceratopsid specimens but not Eotriceratops or other earlier occurring triceratopsin taxa. The morphology of MOR 1122 7-22-00-1 is consistent with noted stratigraphic trends in HCF ceratopsids and highlights the increased complexity of the narial region in uppermost Cretaceous triceratopsins.

@article{doi1018435vamp29366,
    author = "Scannella, John B.",
    title = "A chasmosaurine ceratopsid premaxilla from the basal sandstone of the Hell Creek Formation, Montana",
    year = "2020",
    journal = "Vertebrate Anatomy Morphology Palaeontology",
    abstract = "A well-preserved large chasmosaurine ceratopsid premaxilla (MOR 1122 7-22-00-1) collected from the basal sandstone of the Cretaceous Hell Creek Formation (HCF) represents one of the stratigraphically lowest ceratopsid occurrences in the formation. The specimen was discovered in 2000, during the excavation of a large Torosaurus latus skull (MOR 1122) which was later hypothesized to represent an advanced growth stage of the more commonly recovered HCF ceratopsid Triceratops. MOR 1122 7-22-00-1 compares favorably with the incomplete premaxillae of the MOR 1122 skull and reveals details of premaxilla morphology from this stratigraphic zone. It preserves large, closely spaced ventromedial foramina, a narrow triangular process, and a thin septal flange at the base of the narial strut. The nasal process is narrow, caudally inclined and has a forked dorsal surface which appears to represent an intermediate between the morphology expressed in the slightly stratigraphically lower ceratopsid Eotriceratops xerinsularis from the Horseshoe Canyon Formation of Alberta and specimens recovered higher in the HCF. MOR 1122 7-22-00-1 expresses a deep recess extending medial to the strut of the triangular process, a feature shared with other HCF ceratopsid specimens but not Eotriceratops or other earlier occurring triceratopsin taxa. The morphology of MOR 1122 7-22-00-1 is consistent with noted stratigraphic trends in HCF ceratopsids and highlights the increased complexity of the narial region in uppermost Cretaceous triceratopsins.",
    url = "https://doi.org/10.18435/vamp29366",
    doi = "10.18435/vamp29366",
    openalex = "W3101651487",
    references = "doi101016jcretres201012007, doi10108002724631003763516, doi101111j10963642200700349x, doi101126science1062681, doi101139cjes20190019, doi101371journalpone0012292, doi101371journalpone0016574, doi101371journalpone0032623, doi101371journalpone0151453, doi101371journalpone0188426, doi1016710390290119"
}

The Upper Maastrichtian fluvial Hell Creek Formation of the Fort Peck Lake area, Montana (and regional equivalents) is notable for its vertebrate fossils and for the K-Pg mass extinction at or near its upper contact. Despite intense study, internal stratigraphy of the Hell Creek Formation is still poorly constrained, hindering study. This work reviews the stratigraphy of the Hell Creek Formation, as currently understood, and proposes important revisions to the recently proposed type section, particularly concerning complexity of the Hell Creek Formation basal contact. This work also subdivides the Montanan Hell Creek Formation into four 4th order depositional sequences, superimposed over a 3rd order marine transgression. Sequence boundaries are defined by four, laterally continuous disconformities formed by pauses in the creation of accommodation space, marked by overlying amalgamated channel complexes, or less commonly, correlative interfluve paleosols. Cyclicity in Montana may be correlative with similar 4th order cyclicity and marine influence documented in North and South Dakota, Alberta, and Saskatchewan. Magnetostratigraphy and new biostratigraphic data support correlation of the upper Montanan sequence with the North Dakotan Cantapeta tongue (and overlying fines) and Canadian Scollard and Frenchman Formations.

@article{doi103390geosciences10110435,
    author = "Fowler, Denver W.",
    title = "The Hell Creek Formation, Montana: A Stratigraphic Review and Revision Based on a Sequence Stratigraphic Approach",
    year = "2020",
    journal = "Geosciences",
    abstract = "The Upper Maastrichtian fluvial Hell Creek Formation of the Fort Peck Lake area, Montana (and regional equivalents) is notable for its vertebrate fossils and for the K-Pg mass extinction at or near its upper contact. Despite intense study, internal stratigraphy of the Hell Creek Formation is still poorly constrained, hindering study. This work reviews the stratigraphy of the Hell Creek Formation, as currently understood, and proposes important revisions to the recently proposed type section, particularly concerning complexity of the Hell Creek Formation basal contact. This work also subdivides the Montanan Hell Creek Formation into four 4th order depositional sequences, superimposed over a 3rd order marine transgression. Sequence boundaries are defined by four, laterally continuous disconformities formed by pauses in the creation of accommodation space, marked by overlying amalgamated channel complexes, or less commonly, correlative interfluve paleosols. Cyclicity in Montana may be correlative with similar 4th order cyclicity and marine influence documented in North and South Dakota, Alberta, and Saskatchewan. Magnetostratigraphy and new biostratigraphic data support correlation of the upper Montanan sequence with the North Dakotan Cantapeta tongue (and overlying fines) and Canadian Scollard and Frenchman Formations.",
    url = "https://doi.org/10.3390/geosciences10110435",
    doi = "10.3390/geosciences10110435",
    openalex = "W3095792357",
    references = "doi101139cjes20190019, doi107287peerjpreprints2554v2"
}

Five new partial skulls of the hadrosaurid dinosaur Maiasaura peeblesorum from the Linster Quarry bone bed (Two Medicine Formation, Campanian) in Montana, USA, provide the basis for a description of the skull roof and braincase morphology of this taxon. These skulls additionally form an ontogenetic series consisting of one subadult, two small “intermediate adults”, and two larger “mature adults”. The subadult skull is approximately two thirds as wide as the largest adult and lacks a nasofrontal crest, suggesting that the crest formed relatively late in ontogeny compared to some other hadrosaurids. As in closely related taxa, larger skulls of M. peeblesorum have a proportionately wider braincase and a larger, more rugosely ridged nasofrontal contact for supporting a larger crest. In the two largest adults, the skull roof incipiently overhangs the anterior margin of the dorsotemporal fenestrae. In the largest skull examined, the crest is semicircular in anterior view and incorporates flared, anteriorly concave prefrontals in its lateral margins. Intraspecific variation in M. peeblesorum is observed in cranial characters previously discussed as interspecific variation in related taxa, including the prominence of dorsal depressions on the frontal, and the position of the foramen for the facial nerve (CN VII). Although cranial ontogeny in Maiasaura shares some trends with Brachylophosaurus and Probrachylophosaurus, it deviates in other ways from the previous heterochronic model proposed for the evolution of Maiasaurini.

@article{doi104202app006982019,
    author = "McFeeters, Bradley and Evans, David C. and Maddin, Hillary C.",
    title = "Ontogeny and variation in the skull roof and braincase of Maiasaura peeblesorum from the Two Medicine Formation of Montana, U.S.A.",
    year = "2021",
    journal = "Acta Palaeontologica Polonica",
    abstract = "Five new partial skulls of the hadrosaurid dinosaur Maiasaura peeblesorum from the Linster Quarry bone bed (Two Medicine Formation, Campanian) in Montana, USA, provide the basis for a description of the skull roof and braincase morphology of this taxon. These skulls additionally form an ontogenetic series consisting of one subadult, two small “intermediate adults”, and two larger “mature adults”. The subadult skull is approximately two thirds as wide as the largest adult and lacks a nasofrontal crest, suggesting that the crest formed relatively late in ontogeny compared to some other hadrosaurids. As in closely related taxa, larger skulls of M. peeblesorum have a proportionately wider braincase and a larger, more rugosely ridged nasofrontal contact for supporting a larger crest. In the two largest adults, the skull roof incipiently overhangs the anterior margin of the dorsotemporal fenestrae. In the largest skull examined, the crest is semicircular in anterior view and incorporates flared, anteriorly concave prefrontals in its lateral margins. Intraspecific variation in M. peeblesorum is observed in cranial characters previously discussed as interspecific variation in related taxa, including the prominence of dorsal depressions on the frontal, and the position of the foramen for the facial nerve (CN VII). Although cranial ontogeny in Maiasaura shares some trends with Brachylophosaurus and Probrachylophosaurus, it deviates in other ways from the previous heterochronic model proposed for the evolution of Maiasaurini.",
    url = "https://doi.org/10.4202/app.00698.2019",
    doi = "10.4202/app.00698.2019",
    openalex = "W3197264658",
    references = "doi101002ar20982, doi101016jcrpv200905002, doi101016jcub201311008, doi101017pab201519, doi101017pab20202, doi101017s0094837300002165, doi101038282296a0, doi101093biolinneanblaa105, doi101371journalpone0025186, doi101371journalpone0141304, doi1016710272463420000200115lbhoth20co2, doi105860choice380304"
}

Brachylophosaurini is a clade of hadrosaurid dinosaurs from the Campanian of western North America. Although well-known from northern localities in Montana and Alberta, including abundant material of Brachylophosaurus canadensis and Maiasaura peeblesorum and the holotypes of Acristavus gagslarsoni and Probrachylophosaurus bergei, material from southern localities in Utah and Colorado is restricted to a partial skull referred to A. gagslarsoni and several indeterminate specimens. Here we describe Ornatops incantatus gen. et sp. nov., a new brachylophosaurin known from a partial skeleton from the Allison Member of the Menefee Formation in New Mexico. Ornatops is the first brachylophosaurin reported from New Mexico and the southernmost occurrence of the clade. Ornatops shares with Probrachylophosaurus and Brachylophosaurus a caudally expanded nasofrontal suture on the frontals, but also exhibits an autapomorphic nasofrontal suture morphology, with a horizontal rostral region and elevated caudal region with two prominent parasagittal bumps, which is different from other brachylophosaurin specimens, including juvenile and adult Brachylophosaurus. A phylogenetic analysis places Ornatops in a trichotomy with Probrachylophosaurus and Brachylophosaurus, with Maiasaura and Acristavus as successive outgroups.

@article{doi107717peerj11084,
    author = "McDonald, Andrew T. and Wolfe, Douglas G. and Fowler, Elizabeth A. Freedman and Gates, Terry A.",
    title = "A new brachylophosaurin (Dinosauria: Hadrosauridae) from the Upper Cretaceous Menefee Formation of New Mexico",
    year = "2021",
    journal = "PeerJ",
    abstract = "Brachylophosaurini is a clade of hadrosaurid dinosaurs from the Campanian of western North America. Although well-known from northern localities in Montana and Alberta, including abundant material of Brachylophosaurus canadensis and Maiasaura peeblesorum and the holotypes of Acristavus gagslarsoni and Probrachylophosaurus bergei, material from southern localities in Utah and Colorado is restricted to a partial skull referred to A. gagslarsoni and several indeterminate specimens. Here we describe Ornatops incantatus gen. et sp. nov., a new brachylophosaurin known from a partial skeleton from the Allison Member of the Menefee Formation in New Mexico. Ornatops is the first brachylophosaurin reported from New Mexico and the southernmost occurrence of the clade. Ornatops shares with Probrachylophosaurus and Brachylophosaurus a caudally expanded nasofrontal suture on the frontals, but also exhibits an autapomorphic nasofrontal suture morphology, with a horizontal rostral region and elevated caudal region with two prominent parasagittal bumps, which is different from other brachylophosaurin specimens, including juvenile and adult Brachylophosaurus. A phylogenetic analysis places Ornatops in a trichotomy with Probrachylophosaurus and Brachylophosaurus, with Maiasaura and Acristavus as successive outgroups.",
    url = "https://doi.org/10.7717/peerj.11084",
    doi = "10.7717/peerj.11084",
    openalex = "W3142106971",
    references = "doi103133b1940, doi107717peerj5749"
}

Here we describe a new derived tyrannosaurine, Daspletosaurus wilsoni sp. nov., from Judithian strata (~76.5 Ma) intermediate in age between either of the previously described species of this genus. D. wilsoni displays a unique combination of ancestral and derived characteristics, including a cornual process of the lacrimal reduced in height relative to D. torosus and more basal tyrannosaurines, and a prefrontal with a long axis oriented more rostrally than in D. horneri and more derived tyrannosaurines. The description of this taxon provides insight into evolutionary mode in Tyrannosaurinae, lending strength to previous hypotheses of anagenesis within Daspletosaurus and increasing the resolution with which the evolution of this lineage can be reconstructed. Cladistic phylogenetic methods, stratigraphy, and qualitative analysis of the morphology of relevant taxa supports an anagenetic model for the origin of morphological novelty in this genus, highlighting the predominance of anagenetic evolution among contemporary dinosaur lineages.

@article{doi107717peerj14461,
    author = "Warshaw, Elías A. and Fowler, Denver W.",
    title = "A transitional species of Daspletosaurus Russell, 1970 from the Judith River Formation of eastern Montana",
    year = "2022",
    journal = "PeerJ",
    abstract = "Here we describe a new derived tyrannosaurine, Daspletosaurus wilsoni sp. nov., from Judithian strata (\textasciitilde 76.5 Ma) intermediate in age between either of the previously described species of this genus. D. wilsoni displays a unique combination of ancestral and derived characteristics, including a cornual process of the lacrimal reduced in height relative to D. torosus and more basal tyrannosaurines, and a prefrontal with a long axis oriented more rostrally than in D. horneri and more derived tyrannosaurines. The description of this taxon provides insight into evolutionary mode in Tyrannosaurinae, lending strength to previous hypotheses of anagenesis within Daspletosaurus and increasing the resolution with which the evolution of this lineage can be reconstructed. Cladistic phylogenetic methods, stratigraphy, and qualitative analysis of the morphology of relevant taxa supports an anagenetic model for the origin of morphological novelty in this genus, highlighting the predominance of anagenetic evolution among contemporary dinosaur lineages.",
    url = "https://doi.org/10.7717/peerj.14461",
    doi = "10.7717/peerj.14461",
    openalex = "W4310083519",
    references = "doi101139cjes20200185, doi107717peerj5749"
}

AbstractThe posterior portion of a sturgeon skull preserved in a nodule was recovered from the latest Campanian sediments of the Horseshoe Canyon Formation in the city of Edmonton, Alberta, Canada. It is described here as a new genus and species of Acipenseriformes. The skull represents an individual of at least 2 meters in total length. This species is of particular interest because different bones of the skull show a surface ornamentation with different patterns; the clavicle has large pits, the dermal skull bones have smaller pits and radiating ridges, and the subopercle shows fine radiating ridges. The new taxon, here named †Boreiosturion labyrinthicus, can be confidently included in the extant family Acipenseridae but a phylogenetic analysis does not further resolve relationships. This fossil is the first documentation of sturgeon in the latest Campanian of North America, and bridges the gap between the mid-Campanian assemblage of Dinosaur Park and the late Maastrichtian material from the Hell Creek Formation. DATA AVAILABILITY STATEMENTThe data that support the findings of this study are openly available at Morphobank.org, Project number 4720.ACKNOWLEDGMENTSWe thank A. Pavlic and C. Kiejko of Edmonton for finding the specimen and donating it to the UALVP collections. Thanks also to P. Currie (University of Alberta) for arranging to have the specimen scanned and Joel Pumple (Permafrost Archives Lab, University of Alberta) for performing the scan. We are also grateful to an anonymous reviewer, reviewer E. J. Hilton, Phylogenetics Editor P. Godoy, and Associate Editor J. Kriwet for providing suggestions to improve the manuscript. The research was supported by Natural Sciences and Engineering Research Council of Canada Discovery Grant 327448 (AMM).AUTHOR CONTRIBUTIONSAMM and LEN described the specimen, ran the phylogenetic analyses and prepared the figures. DBB analysed distribution data. AMM prepared the first draft of the manuscript and all authors edited and contributed to the final text.LIST OF SUPPLEMENTARY FILESSupplementary File 1: nexus file used in the phylogenetic analysis.Supplementary File 2: the most parsimonious trees resulting from the phylogenetic analysis.Supplementary File 3: the 50% majority rule and strict consensus trees from the phylogenetic analysis.

@article{doi1010800272463420232232846,
    author = "Murray, Alison M. and Nelson, Luke E. and Brinkman, Donald B.",
    title = "A new sturgeon from the Upper Cretaceous Horseshoe Canyon Formation in central Alberta, Canada",
    year = "2023",
    journal = "Journal of Vertebrate Paleontology",
    abstract = "AbstractThe posterior portion of a sturgeon skull preserved in a nodule was recovered from the latest Campanian sediments of the Horseshoe Canyon Formation in the city of Edmonton, Alberta, Canada. It is described here as a new genus and species of Acipenseriformes. The skull represents an individual of at least 2 meters in total length. This species is of particular interest because different bones of the skull show a surface ornamentation with different patterns; the clavicle has large pits, the dermal skull bones have smaller pits and radiating ridges, and the subopercle shows fine radiating ridges. The new taxon, here named †Boreiosturion labyrinthicus, can be confidently included in the extant family Acipenseridae but a phylogenetic analysis does not further resolve relationships. This fossil is the first documentation of sturgeon in the latest Campanian of North America, and bridges the gap between the mid-Campanian assemblage of Dinosaur Park and the late Maastrichtian material from the Hell Creek Formation. DATA AVAILABILITY STATEMENTThe data that support the findings of this study are openly available at Morphobank.org, Project number 4720.ACKNOWLEDGMENTSWe thank A. Pavlic and C. Kiejko of Edmonton for finding the specimen and donating it to the UALVP collections. Thanks also to P. Currie (University of Alberta) for arranging to have the specimen scanned and Joel Pumple (Permafrost Archives Lab, University of Alberta) for performing the scan. We are also grateful to an anonymous reviewer, reviewer E. J. Hilton, Phylogenetics Editor P. Godoy, and Associate Editor J. Kriwet for providing suggestions to improve the manuscript. The research was supported by Natural Sciences and Engineering Research Council of Canada Discovery Grant 327448 (AMM).AUTHOR CONTRIBUTIONSAMM and LEN described the specimen, ran the phylogenetic analyses and prepared the figures. DBB analysed distribution data. AMM prepared the first draft of the manuscript and all authors edited and contributed to the final text.LIST OF SUPPLEMENTARY FILESSupplementary File 1: nexus file used in the phylogenetic analysis.Supplementary File 2: the most parsimonious trees resulting from the phylogenetic analysis.Supplementary File 3: the 50\% majority rule and strict consensus trees from the phylogenetic analysis.",
    url = "https://doi.org/10.1080/02724634.2023.2232846",
    doi = "10.1080/02724634.2023.2232846",
    openalex = "W4385659466",
    references = "doi101139cjes20190019"
}

Abstract Although the Aguja Formation (West Texas, southwestern USA) and its fossil vertebrate fauna have been known for over a century, its basic stratigraphic requisites (type area and type section) have not been formally documented. The formation is herein subdivided into a series of formal members, and a lectostratotype section is proposed. Lithostratigraphic and biostratigraphic subdivisions are documented and integrated with geochronologic data to provide an age model for the formation. Four terrestrial vertebrate biozones are proposed. There are at least four major depositional intervals represented in the Aguja and intertonguing Pen Formations. An initial progradational deltaic succession is recorded by the La Basa Sandstone and lower part of the Abajo Shale Members of the Aguja Formation. A second phase of deposition resulted in a retrogradational shoreface succession that includes the upper part of the Abajo Shale, overlying Rattlesnake Mountain Sandstone Member, and lower part of the McKinney Springs Tongue of the Pen Formation, up to a skeletal phosphate bed interpreted to represent the maximum flooding surface. The third phase of deposition comprises a progradational deltaic succession that includes the upper part of the McKinney Springs Tongue, Terlingua Creek Sandstone Member of the Aguja Formation, and lower part of the Alto Shale Member of the Aguja Formation. This third succession records eastward migration of the strandline and withdrawal of the Western Interior Seaway from the Big Bend region. The fourth phase of deposition comprises a series of aggradational fluvial channel and floodplain successions that form the upper part of the Alto Shale Member and is coincident with redirection of stream flow to the southeast. This interval is much thicker in the central part of the Big Bend region, thins to the southwest and northeast, and likely records initial subsidence in the Laramide Tornillo Basin. The upper part of this succession was also contemporaneous with a series of basaltic pyroclastic eruptions, the westernmost expression of the Balcones igneous province. A dramatic constriction in the southern entrance to the Western Interior Seaway through the Gulf of Mexico occurred during this final phase in deposition of the Aguja Formation and corresponds to a shift of stream flow southeastward and to an outbreak of local pyroclastic eruptions. Regional uplift associated with this episode of magmatism is likely responsible for closing the southern aperture of the Western Interior Seaway.

@article{doi101130ges026621,
    author = "Lehman, Thomas M. and Wick, Steven L. and Macon, Craig Charles and Wagner, Jonathan R. and Waggoner, Karen J. and Brink, Alyson A. and Shiller, Thomas A.",
    title = "Stratigraphy and depositional history of the Aguja Formation (Upper Cretaceous, Campanian) of West Texas, southwestern USA",
    year = "2024",
    journal = "Geosphere",
    abstract = "Abstract Although the Aguja Formation (West Texas, southwestern USA) and its fossil vertebrate fauna have been known for over a century, its basic stratigraphic requisites (type area and type section) have not been formally documented. The formation is herein subdivided into a series of formal members, and a lectostratotype section is proposed. Lithostratigraphic and biostratigraphic subdivisions are documented and integrated with geochronologic data to provide an age model for the formation. Four terrestrial vertebrate biozones are proposed. There are at least four major depositional intervals represented in the Aguja and intertonguing Pen Formations. An initial progradational deltaic succession is recorded by the La Basa Sandstone and lower part of the Abajo Shale Members of the Aguja Formation. A second phase of deposition resulted in a retrogradational shoreface succession that includes the upper part of the Abajo Shale, overlying Rattlesnake Mountain Sandstone Member, and lower part of the McKinney Springs Tongue of the Pen Formation, up to a skeletal phosphate bed interpreted to represent the maximum flooding surface. The third phase of deposition comprises a progradational deltaic succession that includes the upper part of the McKinney Springs Tongue, Terlingua Creek Sandstone Member of the Aguja Formation, and lower part of the Alto Shale Member of the Aguja Formation. This third succession records eastward migration of the strandline and withdrawal of the Western Interior Seaway from the Big Bend region. The fourth phase of deposition comprises a series of aggradational fluvial channel and floodplain successions that form the upper part of the Alto Shale Member and is coincident with redirection of stream flow to the southeast. This interval is much thicker in the central part of the Big Bend region, thins to the southwest and northeast, and likely records initial subsidence in the Laramide Tornillo Basin. The upper part of this succession was also contemporaneous with a series of basaltic pyroclastic eruptions, the westernmost expression of the Balcones igneous province. A dramatic constriction in the southern entrance to the Western Interior Seaway through the Gulf of Mexico occurred during this final phase in deposition of the Aguja Formation and corresponds to a shift of stream flow southeastward and to an outbreak of local pyroclastic eruptions. Regional uplift associated with this episode of magmatism is likely responsible for closing the southern aperture of the Western Interior Seaway.",
    url = "https://doi.org/10.1130/ges02662.1",
    doi = "10.1130/ges02662.1",
    openalex = "W4392977467",
    references = "doi101017s1755691013000261, doi101038s4159802219896w, doi101139cjes20200071"
}

@misc{openalexw7130251455,
    title = "An albertosaur from the Hell Creek formation of Montana",
    year = "2025",
    booktitle = "Open MIND",
    url = "https://openalex.org/W7130251455",
    openalex = "W7130251455"
}

Because teeth can be taxonomically distinct, particularly for non-mammalian carnivores such as non-avian dinosaurs, teeth that have broken off in the bone of another animal during feeding, predation or antagonism can provide direct information on carnivore behaviour. Here, we report on a semi-complete, articulated adult Edmontosaurus skull (MOR 1627) from the Hell Creek Formation with an embedded theropod tooth in the nasal. To ascertain taxonomic identity of the preserved tooth tip, we compare standardized crown and denticle measurements as well as denticle descriptions of the embedded tooth to known non-avian theropods recovered from the Hell Creek Formation. We also use computed tomography (CT) scans to investigate the full extent and orientation of the embedded tooth. The apicobasal, labiolingual and mesiodistal dimensions of the tip as well as measured denticle densities and observed denticle characteristics indicate the embedded tooth is from a medium to large bodied tyrannosaurid. The curvature and ovoid cross-sectional shape of the tooth further suggests that the tooth is a maxillary tooth from a middle or posterior tooth position. The lack of reactive bone in the region surrounding the tooth suggests the animal died around the time the tooth became embedded in the nasal. Combined, this information suggests the tooth broke off when a tyrannosaurid bit the snout of the Edmontosaurus from the front at or near the time of death of the animal. Comparing observations of hunting and feeding behaviors of modern carnivores specializing in large-bodied prey, the scenario captured by MOR 1627 is most consistent with a bite inflicted during an attempt to control the struggling Edmontosaurus or deliver a killing blow followed by carcass consumption.

@article{doi107717peerj20796,
    author = "Wyenberg-Henzler, Taia C A and Scannella, John B",
    title = "Behavioral implications of an embedded tyrannosaurid tooth and associated tooth marks on an articulated skull of Edmontosaurus from the Hell Creek Formation, Montana.",
    year = "2026",
    journal = "PeerJ",
    abstract = "Because teeth can be taxonomically distinct, particularly for non-mammalian carnivores such as non-avian dinosaurs, teeth that have broken off in the bone of another animal during feeding, predation or antagonism can provide direct information on carnivore behaviour. Here, we report on a semi-complete, articulated adult Edmontosaurus skull (MOR 1627) from the Hell Creek Formation with an embedded theropod tooth in the nasal. To ascertain taxonomic identity of the preserved tooth tip, we compare standardized crown and denticle measurements as well as denticle descriptions of the embedded tooth to known non-avian theropods recovered from the Hell Creek Formation. We also use computed tomography (CT) scans to investigate the full extent and orientation of the embedded tooth. The apicobasal, labiolingual and mesiodistal dimensions of the tip as well as measured denticle densities and observed denticle characteristics indicate the embedded tooth is from a medium to large bodied tyrannosaurid. The curvature and ovoid cross-sectional shape of the tooth further suggests that the tooth is a maxillary tooth from a middle or posterior tooth position. The lack of reactive bone in the region surrounding the tooth suggests the animal died around the time the tooth became embedded in the nasal. Combined, this information suggests the tooth broke off when a tyrannosaurid bit the snout of the Edmontosaurus from the front at or near the time of death of the animal. Comparing observations of hunting and feeding behaviors of modern carnivores specializing in large-bodied prey, the scenario captured by MOR 1627 is most consistent with a bite inflicted during an attempt to control the struggling Edmontosaurus or deliver a killing blow followed by carcass consumption.",
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC12922588/",
    doi = "10.7717/peerj.20796",
    openalex = "W7129700407",
    pmcid = "PMC12922588",
    pmid = "41727239",
    references = "doi101007s11692022095731, doi101016s0047248486800021, doi101017cbo9780511608377011, doi101017s0094837300005820, doi101017s0094837300006849, doi101034j16000706200312378x, doi10108002724634199910011161, doi10108002724634200310010947, doi1010802766964520252539638, doi101093icbicm016, doi101111j146979982000tb01076x, doi101515mamm19673111, doi107717peerj5748"
}