Taphonomy of Three Dinosaur Bone Beds in the Upper Cretaceous Two Medicine Formation of Northwestern Montana: Evidence for Drought-Related Mortality

Palaios ◽  
1990 ◽  
Vol 5 (5) ◽  
pp. 394 ◽  
Author(s):  
Raymond R. Rogers
Keyword(s):  
Upper Cretaceous ◽  
Northwestern Montana ◽  
Related Mortality ◽  
Bone Beds

Hadrosaurid and lambeosaurid bone beds from the Upper Cretaceous Two Medicine Formation of Montana: taphonomic and biologic implications

1993 ◽  
Vol 30 (5) ◽  
pp. 997-1006 ◽  
Author(s):  
David J. Varricchio ◽  
John R. Horner
Keyword(s):  
Growth Rates ◽  
Upper Cretaceous ◽  
Mass Mortality ◽  
Common Mechanism ◽  
Adult Size ◽  
Juvenile Growth ◽  
Total Length ◽  
Size Frequency ◽  
Related Mortality ◽  
Bone Beds

Numerous dinosaur bone beds have been found in the Upper Cretaceous Two Medicine Formation. Taphonomy and size-frequency profiles for the most common skeletal elements of six predominantly hadrosaurid and (or) lambeosaurid assemblages were compared. All six localities are single, highly concentrated bone horizons within silty mudstones. Most are monospecific with some degree of skeletal association, parautochthonous, and likely the result of mass mortality. Four are associated with small lacustrine or waterhole environments and may be the result of drought-related mortality. Within the Two Medicine Formation drought was apparently a common mechanism for generating fossil assemblages.Both hadrosaurids and lambeosaurids appear to have been gregarious. Lack of association between small (total length < 3 m) and larger individuals suggests either that juvenile growth rates were as rapid as large ungulates or less likely, that juveniles had a period of noninteraction with adults, perhaps dwelling in strictly juvenile groups. In Maiasaura peeblesorum, reproduction appears to have been synchronous among herd members and seasonal. Additionally, mortality was high for juveniles and dropped off rapidly as animals approached adult size.

scholarly journals A new, transitional centrosaurine ceratopsid from the Upper Cretaceous Two Medicine Formation of Montana and the evolution of the ‘ Styracosaurus -line' dinosaurs

2020 ◽  
Vol 7 (4) ◽  
pp. 200284 ◽  
Author(s):  
John P. Wilson ◽  
Michael J. Ryan ◽  
David C. Evans
Keyword(s):  
North America ◽  
Late Cretaceous ◽  
Upper Cretaceous ◽  
Frames Of Reference ◽  
Unique Combination ◽  
Holotype Specimen ◽  
Intermediate Morphology ◽  
Northwestern Montana ◽  
Phylogenetic Framework ◽  
Stratigraphic Succession

Ceratopsids are among the most ubiquitous dinosaur taxa from the Late Cretaceous terrestrial formations of the Western Interior of North America, comprising two subfamilies, Chasmosaurinae and Centrosaurinae. The Two Medicine Formation of northwestern Montana has produced numerous remains of centrosaurine dinosaurs, which represent three taxa previously considered valid: Rubeosaurus ovatus , Einiosaurus procurvicornis and Achelousaurus horneri . Here, we reassess the previous referral of specimens to Rubeousaurus ovatus and demonstrate that this taxon is represented solely by its holotype specimen, which was first diagnosed as Styracosaurus ovatus . One of the specimens previously referred to ‘ Rubeosaurus ’ ovatus instead represents a new eucentrosauran centrosaurine taxon diagnosed here, Stellasaurus ancellae gen. et sp. nov. Stellasaurus expresses a unique combination of eucentrosauran centrosaurine characters, including an elongate nasal horncore, diminutive supraorbital horncores, and a parietal bearing straight, elongate P3 processes, semi-elongate P4 processes and non-elongate P5, P6 and P7 processes. Within the stratigraphic succession of Eucentrosaura, Stellasaurus occurs intermediate to Styracosaurus albertensis and Einiosaurus , and likewise reflects intermediate morphology. Assessed within the stratigraphic, geographical, taphonomic, ontogenetic and phylogenetic framework of Unified Frames of Reference, we fail to reject the hypothesis that Stellasaurus ancellae represents a transitional taxon within an anagenetic lineage of eucentrosauran centrosaurines.

Correlation of the Upper Cretaceous Montana Group between southern Alberta and Montana

1970 ◽  
Vol 7 (4) ◽  
pp. 1099-1108 ◽  
Author(s):  
Loris S. Russell
Keyword(s):  
Upper Cretaceous ◽  
Southern Alberta ◽  
Northwestern Montana ◽  
Judith River Formation ◽  
East West

Critical comparisons of Montanan sequences in southern Alberta and various parts of Montana permit some conclusions on north–south, as well as east–west, correlation. The Lower Milk River sandstone of Alberta is the equivalent of the Lower Eagle sandstone of northwestern Montana but both differ from the type Virgelle Sandstone, with which they have been equated. The Pakowki Formation of Alberta represents the Claggett of Montana plus lower parts of the Judith River Formation. The remainder of the Judith River Formation is equivalent to the Foremost and Oldman Formations of Alberta. The Bearpaw Formation thins markedly from east to west, and uppermost shales pass into marine sandstones and these in turn into non-marine formations. Of the various formational boundaries, the top of the Lower Milk River and Lower Eagle sandstone, the base of the Pakowki and Claggett Shale, and the top of the Oldman and Judith River Formations, are also time boundaries throughout large parts of the region.

Composition and provenance of the Upper Cretaceous to Eocene sandstones in Central Palawan, Philippines: Constraints on the tectonic development of Palawan

Island Arc ◽  
2000 ◽  
Vol 9 (4) ◽  
pp. 611-626 ◽  
Author(s):  
Shigeyuki Suzuki ◽  
Shizuo Takemura ◽  
Graciano P. Yumul ◽  
Sevillo D. David ◽  
Daniel K. Asiedu
Keyword(s):  
Upper Cretaceous ◽  
Tectonic Development

Upper Cretaceous and Cenozoic Geology of the Southeastern Atlantic Coastal Plain: Atlanta, Georgia to Chesapeake, Virginia July 1-9, 1989

10.1029/ft172 ◽  
1989 ◽  
Author(s):  
W. Burleigh Harris ◽  
Vernon J. Hurst ◽  
Paul G. Nystrom ◽  
Lauck W. Ward ◽  
Charles W. Hoffman ◽  
...  
Keyword(s):  
Coastal Plain ◽  
Upper Cretaceous ◽  
Atlantic Coastal Plain ◽  
Atlantic Coastal ◽  
Southeastern Atlantic
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