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Extreme Cranial Ontogeny in the Upper Cretaceous Dinosaur Pachycephalosaurus
Background Extended neoteny and late stage allometric growth increase morphological disparity between growth stages in at least some dinosaurs. Coupled with relatively low dinosaur density in theExpand
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Major cranial changes during Triceratops ontogeny
  • J. Horner, M. Goodwin
  • Biology, Medicine
  • Proceedings of the Royal Society B: Biological…
  • 7 November 2006
This is the first cranial ontogenetic assessment of Triceratops, the well-known Late Cretaceous dinosaur distinguished by three horns and a massive parietal–squamosal frill. Our analysis is based onExpand
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Cranial histology of pachycephalosaurs (Ornithischia: Marginocephalia) reveals transitory structures inconsistent with head-butting behavior
Abstract Modern histological techniques allow paleontologists to investigate the internal microstructure of bone tissue. We apply high resolution images of histological thin sections from anExpand
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The first radiometric ages from the Judith River Formation (Upper Cretaceous), Hill County, Montana
A new isotopic age of ca. 78 Ma was obtained by the conventional K–Ar method and by laser-fusion 40Ar/39Ar analysis of biotite and sanidine crystals from two bentonites in the Judith River FormationExpand
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THE SMALLEST KNOWN TRICERATOPS SKULL: NEW OBSERVATIONS ON CERATOPSID CRANIAL ANATOMY AND ONTOGENY
Abstract The discovery of the smallest Triceratops skull (UCMP 154452) provides a new ontogenetic end member for the earliest stage of ceratopsid (Centrosaurinae plus Chasmosaurinae) cranialExpand
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Marine transgressions and the evolution of Cretaceous dinosaurs
FLUCTUATIONS (transgressions and regressions) of intercon-tinental sea-ways during the Mesozoic Era affected the habitat area of coastal plains by alternately restricting the space duringExpand
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Cranial Ontogeny in Stegoceras validum (Dinosauria: Pachycephalosauria): A Quantitative Model of Pachycephalosaur Dome Growth and Variation
Historically, studies of pachycephalosaurs have recognized plesiomorphically flat-headed taxa and apomorphically domed taxa. More recently, it has been suggested that the expression of theExpand
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Mesozoic continental vertebrates with associated palynostratigraphic dates from the northwestern Ethiopian plateau
The East African Rift separates the northwestern and southeastern Ethiopian high plateaus, which are capped by massive Cenozoic volcanics overlying thick deposits of marine and nonmarine MesozoicExpand
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Dinosaur Census Reveals Abundant Tyrannosaurus and Rare Ontogenetic Stages in the Upper Cretaceous Hell Creek Formation (Maastrichtian), Montana, USA
BACKGROUND A dinosaur census recorded during the Hell Creek Project (1999-2009) incorporates multiple lines of evidence from geography, taphohistory, stratigraphy, phylogeny and ontogeny toExpand
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Evolutionary trends in Triceratops from the Hell Creek Formation, Montana
Significance The deciphering of evolutionary trends in nonavian dinosaurs can be impeded by a combination of small sample sizes, low stratigraphic resolution, and lack of ontogenetic (developmental)Expand
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