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| Suskityrannus hazelae
Nesbitt, Denton, Loewen, Brusatte, Smith, et al., 2019
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Abstract
Late Cretaceous dinosaur assemblages of North America—characterized by gigantic tyrannosaurid predators, and large-bodied herbivorous ceratopsids and hadrosaurids—were highly successful from around 80 million years ago (Ma) until the end of the ‘Age of Dinosaurs’ 66 Ma. However, the origin of these iconic faunas remains poorly understood because of a large, global sampling gap in the mid-Cretaceous, associated with an extreme sea-level rise. We describe the most complete skeleton of a predatory dinosaur from this gap, which belongs to a new tyrannosauroid theropod from the Middle Turonian (~92 Ma) of southern Laramidia (western North America). This taxon, Suskityrannus hazelae gen. et sp. nov., is a small-bodied species phylogenetically intermediate between the oldest, smallest tyrannosauroids and the gigantic, last-surviving tyrannosaurids. The species already possesses many key features of the tyrannosaurid bauplan, including the phylogenetically earliest record of an arctometatarsalian foot in tyrannosauroids, indicating that the group developed enhanced cursorial abilities at a small body size. Suskityrannus is part of a transitional Moreno Hill (that is, Zuni) dinosaur assemblage that includes dinosaur groups that became rare or were completely absent in North America around the final 15 Myr of the North American Cretaceous before the end-Cretaceous mass extinction, as well as small-bodied forebears of the large-bodied clades that dominated at this time.
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| Skeletal element of both specimens of Suskityrannus hazelae gen. et sp. nov. and reconstruction. |
Systematic palaeontology
Dinosauria Owen, 1842
Theropoda Marsh, 1881
Coelurosauria
Tyrannosauroidea
Suskityrannus hazelae gen. et sp. nov.
Etymology. Genus: from the Zuni ‘Suski’ (coyote) and the Latin ‘tyrannus’ (king). The specific name is for Hazel Wolfe, whose tireless efforts, support and sacrifices made possible much of the success at the Moreno Hill fossil localities.
Sterling J. Nesbitt, Robert K. Denton Jr, Mark A. Loewen, Stephen L. Brusatte, Nathan D. Smith, Alan H. Turner, James I. Kirkland, Andrew T. McDonald and Douglas G. Wolfe. 2019. A mid-Cretaceous Tyrannosauroid and The Origin of North American end-Cretaceous Dinosaur Assemblages. Nature Ecology & Evolution. DOI: 10.1038/s41559-019-0888-0
New three-foot-tall relative of Tyrannosaurus rex
