America's Last Dinosaurs
America’s Last Dinosaur Project integrates plant and vertebrate fossils in a stratigraphic context to analyze North American ecosystems leading up to the extinction of the dinosaurs
Earth’s last mass extinction occurred 66 million years ago, when a six-mile-wide meteorite slammed into the Gulf of Mexico causing the extinction of over 75% of species on Earth, including all giant dinosaurs. This was arguably the single worst day for life on Earth and completely changed the course of life—from the Age of the Dinosaurs/Reptiles to the Age of the Mammals. The America’s Last Dinosaur project is a highly collaborative project that includes Kirk Johnson (Smithsonian Institution), Will Clyde (University of New Hampshire), Antoine Bercovici (Smithsonian Institution), Dean Pearson (Pioneer Trails Regional Museum), Gabriella Rossetto Harris (Penn State), Walter Joyce (University of Freiburg), Stephen Chester (Brooklyn College), and Daniel Field (University of Cambridge). The project integrates vertebrates (microsites and macrosites) and plants (leaves and pollen) into a chronostratigraphic framework to analyze North America’s last dinosaur-bearing ecosystems. This includes naming and describing the flora and fauna, which to date has resulted in the description of several new species, including one dinosaur and five turtles. Finally, this project looks at the interplay between changing forest ecology and changes in relative abundance and/or diversity of dinosaurs and the role facies and inferred paleoenvironments might play in this dynamic system, all through the last one million years of the Mesozoic Era.
Relevant Publications
To request PDFs please email Tyler Lyson.
Woodruff, D. C., Goodwin, M. B., Lyson, T. R., & Evans, D. C. 2021. Ontogeny and variation of the pachycephalosaurine dinosaur Sphaerotholus buchholtzae, and its systematics within the genus. Zoological Journal of the Linnean Society, https://doi.org/10.1093/zoolinnean/zlaa179.
Joyce, W. G., T. R. Lyson, and D. Brinkman. 2020. A description of the variation within Axestemys from the Hell Creek Formation. Paleontologia Electronica. https://doi.org/10.26879/949.
Lyson, T. R., J. L. Sayler, and W. G. Joyce. 2019. A new baenid turtle, Saxochelys gilberti, gen. et sp. nov., from the uppermost Cretaceous (Maastrichtian) Hell Creek Formation: sexual dimorphism and spatial niche partitioning within the most speciose group of Late Cretaceous turtles. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2019.1662428.
Rollot, Y., W. G. Joyce, and T. R. Lyson. 2018. A description of the skull of Eubaena cephalica (Hay, 1904) and new insights into the cranial circulation and innervation of baenid turtles. Journal of Vertebrate Paleontology 38(3). DOI: 10.1080/02724634.2018.1474886.
Summary
We CT-scanned new cranial material of the baenid turtle Eubaena cephalica and provide a detailed anatomical description of the skull, particularly the cranial circulation and innervation pattern.
Field, D. J., A. Bercovici, J. S. Berv, R. Dunn, D. Fastovsky, T. R. Lyson, V. Vajda, and J. A. Gauthier. 2018. Early evolution of modern birds structured by global forest collapse at the end-Cretaceous mass extinction. Current Biology 28(11):1825–1831.e2. DOI: 10.1016/j.cub.2018.04.062.
Summary
Please see this article by Ed Yong in The Atlantic for an excellent summary:
The Asteroids that Smote the Dinosaurs Burned the Birds Out of Trees
Joyce, W. G., and T. R. Lyson. 2017. The shell morphology of the latest Cretaceous (Maastrichtian) trionychid turtle Helopanoplia distincta. PeerJ 5:e4169. DOI: 10.7717/peerj.4169.
Summary
We here describe shell material from the enigmatic trionychid turtle Helopanoplia distincta, from the Upper Cretaceous (Maastrichtian) Hell Creek Formation.
Joyce, W. G., T. R. Lyson, and S. Williams. 2016. New cranial material of Gilmoremys lancensis (Testudines, Trionychidae) from the Hell Creek Formation of southeastern Montana, USA. Journal of Vertebrate Paleontology 36(6):e1225748. DOI: 10.1080/02724634.2016.1225748.
Summary
We here describe two large skulls from the Upper Cretaceous (Maastrichtian) Hell Creek Formation of Carter County, Montana, that document the adult morphology of the plastomenid Gilmoremys lancensis.
Bourke, J. M., W. M. R. Porter, R. C. Ridgely, T. R. Lyson, E. R. Schachner, P. R. Bell, and L. M. Witmer. 2014. Breathing life into dinosaurs: tackling challenges of soft-tissue restoration and nasal airflow in extinct species. Anatomical Record 297(11):2148–2186. https://doi.org/10.1002/ar.23046.
Summary
The nasal region plays a key role in sensory, thermal, and respiratory physiology, but exploring its evolution is hampered by a lack of preservation of soft-tissue structures in extinct vertebrates. As a test case, we investigated members of the “bony-headed” ornithischian dinosaur clade Pachycephalosauridae (particularly Stegoceras validum) because of their small body size (which mitigated allometric concerns) and their tendency to preserve nasal soft tissues within their hypermineralized skulls.
Lamanna, M. C., H.-D. Sues, E. R. Schachner, and T. R. Lyson. 2014. A new large-bodied oviraptorosaurian theropod dinosaur from the latest Cretaceous of western North America. PLOS ONE 9(3):e92022 DOI: 10.1371/journal.pone.0092022.
Summary
The oviraptorosaurian theropod dinosaur clade Caenagnathidae has long been enigmatic due to the incomplete nature of nearly all described fossils. Here we describe Anzu wyliei gen. et sp. nov., a new taxon of large-bodied caenagnathid based primarily on three well-preserved partial skeletons. The specimens were recovered from the uppermost Cretaceous (upper Maastrichtian) Hell Creek Formation of North and South Dakota and are therefore among the stratigraphically youngest-known oviraptorosaurian remains. Read more at: Washington Post, Pittsburgh Post-Gazette, Slate, and CNN.
Manning, P. L., R. A. Wogelius, B. E. van Dongen, T. R. Lyson, U. Bergmann, S. Webb, M. Buckley, V. Egerton, and W. I. Sellers. 2014. The role of skin pigment and biochemistry in the exceptional preservation of hadrosaur skin. Pages 600–610 in D. E. Eberth and D. C. Evans, eds. Hadrosaurs. Indiana University Press, Bloomington, IN.
Vajde, V., T. R. Lyson, A. Bercovici, J. H. Doman, and D. A. Pearson. 2013. A snapshot into the terrestrial ecosystem of an exceptionally well-preserved dinosaur (Hadrosauridae) from the Upper Cretaceous of North Dakota, USA. Cretaceous Research 46:114–122. DOI:10.1016/j.cretres.2013.08.010.
Summary
A palynological investigation of sedimentary rocks enclosing an exceptionally well-preserved fossil dinosaur (Hadrosauridae) discovered in the upper part of the Hell Creek Formation in southwestern North Dakota was conducted in order to document the immediate paleoenvironment of this dinosaur. The specimen, an Edmontosaurus annectens, is remarkable in having exceptional three-dimensional preservation of soft tissue around the skeleton, indicating rapid burial.
Joyce, W. G., and T. R. Lyson. 2011. New material of Gilmoremys lancensis Nov. Comb. (Testudines:Trionychidae) from the Hell Creek Formation and the diagnosis of plastomenid turtles. Journal of Paleontology 85(3):444-461. https://doi.org/10.1080/02724634.2016.1225748
Summary
We describe several skulls and abundant shell material from the Upper Cretaceous (Maastrichtian) Hell Creek Formation of Slope County, North Dakota, that document variation with the plastomenid Gilmoremys lancensis.
Knauss, G., W. G. Joyce, T. R. Lyson, and D. Pearson, D. 2011. A new kinosternoid from the Late Cretaceous Hell Creek Formation of North Dakota and the origin of the Dermatemys mawii lineage. Paläontologische Zeitschrift 85(2):125–142. DOI: 10.1007/s12542-010-0081-x
Summary
A nearly complete turtle shell from the Late Cretaceous (Maastrichtian) Hell Creek Formation of Slope County, North Dakota, represents the most complete remains to date of a Mesozoic kinosternoid turtle and a new species, Hoplochelys clark nov. sp. The new taxon is diagnosable from other representatives of Hoplochelys by the plesiomorphic placement of the humeral/femoral sulcus behind the hyo/hypoplastral suture and the autapomorphic development of an interrupted median (neural) keel.
Lyson, T. R., W. G. Joyce, G. Knauss, and D. Pearson. 2011. Boremys (Testudines: Baenidae) from the latest Cretaceous and early Paleocene of North Dakota: an 11 million year range extension and an additional K/T survivor. Journal of Vertebrate Paleontology 31(4):1–9. DOI: 10.1080/0274634.2011.576731.
Also see these articles for excellent summaries:
Tough Turtle Survived What Dinosaurs Couldn't
Lyson, T. R. & Longrich, N. R. 2011. Spatial niche partitioning in dinosaurs from the latest Cretaceous (Maastrichtian) of North America. Proceedings of the Royal Society of London B 278:1158-1164. DOI: 10.1098/rspb.2010.1444.
Summary
We examine patterns of occurrence of associated dinosaur specimens (n = 343) from the North American Upper Cretaceous Hell Creek Formation and equivalent beds, by comparing their relative abundance in sandstone and mudstone.
Lyson, T. R., and W. G. Joyce. 2010. A new baenid turtle from the latest Cretaceous (Maastrichtian) of North Dakota and a revision of the Cretaceous Baenidae alpha taxonomy. Journal of Vertebrate Paleontology 30(2):394–402. DOI: 10.1080/02724631003618389
Summary
A fragmentary skull from the Hell Creek Formation (Maastrichtian) of southwestern North Dakota represents a new taxon of baenid turtle named herein Gamerabaena sonsalla. The length of the frontals, jugal contribution to the labial ridge, and convex contact between the vomer and the pterygoids indicate its affinities with the clade Palatobaena, but the new taxon clearly lacks the great posterior expansion of the triturating surface, complete absence of a lingual ridge, subrectangular skull, and wide angle between the maxillae that diagnose Palatobaena spp.
Lyson, T. R., and W. G. Joyce. 2009a. A new species of Palatobaena (Testudines: Baenidae) and a maximum parsimony and Bayesian phylogenetic analysis of Baenidae. Journal of Paleontology 83(3):457–470. DOI: 10.1666/08-172.1.
Summary
We here describe the skull and shell of a new species of baenid turtle herein named Palatobaena cohen. The paper discusses the geology of the Turtle Graveyard locality, provides a detailed description of the skull and shell, and a phylogenetic analysis of the group of turtle to which Pa. cohen belongs, Baenidae.
Lyson, T. R., and W. G. Joyce. 2009b. A revision of Plesiobaena (Testudines: Baenidae) and an assessment of baenid ecology across the K/T boundary. Journal of Paleontology 83(6):833–853. DOI: 10.1666/09-035.1.
Summary
A new species of baenid turtle is described from the Hell Creek Formation. Material of this new species, Peckemys brinkman, was found at Marmarth Research Foundation's Turtle Graveyard locality. This locality is unusual in that it represents a true snapshot in time (i.e., it is constrained both temporally and spatially). The locality is the most diverse fossil turtle assemblage. Much of the material described in this paper was found by MRF volunteers. The paper discusses the diversity of turtles found at this locality as well as the number of baenid turtles that go extinct at the K/T boundary. Baenid turtles do surprisingly well across the boundary, with seven of nine baenids surviving into the Paleocene. Interestingly, four of the seven survivors are interpreted as having a mollusk and snail type diet.
Manning, P. L., P. M. Morris, A. McMahon, E. Jones, A. Gize, J. H. S. Macquaker, G. Wolff, A. Thompson, J. Marshall, K. G. Taylor, T. R. Lyson, S. Gaskell, O. Reamtong, W. I. Sellers, B. E. van Dongen, M. Buckley, and R. A. Wogelius. 2009. Soft-tissue structure and chemistry in a mummified hadrosaur from the Hell Creek Formation, North Dakota (USA). Proceedings of the Royal Society of London 276(1672):3429–3437.
Summary
This is the first of a series of papers on the mummified dinosaur “Dakota.” This paper was selected by Discover Magazine as one of the top 100 best scientific papers of 2009 (ranking 46). The paper goes through a number of geochemical analyses in search of original biomolecules from “Dakota.” In addition, the paper discusses how “Dakota” was preserved and describes the 3-D preservation of the skin.
Please see this article for an excellent summary: Scientists Flesh Out Fossilized Tissue from Mummified Dinosaur
Sellers, W. I., P. L. Manning, T. R. Lyson, K. Stevens, and L. Margets. 2009. Virtual paleontology: gait reconstruction of extinct vertebrates using high performance computing. Palaeontologica Electronica 4(3):12.3.13A.
Summary
Were hadrosaur dinosaurs running on two or four legs at top speed? This paper uses computer simulations to try and address this question. An 8000 core computer was used to produce mechanically and physiologically plausible gaits and trackway patterns for an Edmontosaurus annectens dinosaur. Galloping was determined to be the most plausible and fastest (16 ms-1) gait, followed by bipedal running (14ms-1).