Abstract
The giant tyrannosaurids were the apex predators of western North America and Asia during the close of the Cretaceous Period. Although many tyrannosaurid species are known from numerous skeletons representing multiple growth stages, the early evolution of Tyrannosauridae remains poorly known, with the well-known species temporally restricted to the middle Campanian-latest Maastrichtian (∼77–66 Ma). The recent discovery of a new tyrannosaurid, Lythronax argestes, from the Wahweap Formation of Utah provided new data on early Campanian (∼80 Ma) tyrannosaurids. Nevertheless, the early evolution of Tyrannosauridae is still largely unsampled. We report a new tyrannosaurid represented by an associated skeleton from the lower Campanian Allison Member of the Menefee Formation of New Mexico. Despite fragmentation of much of the axial and appendicular skeleton prior to discovery, the frontals, a metacarpal, and two pedal phalanges are well-preserved. The frontals exhibit an unambiguous autapomorphy and a second potential autapomorphy that distinguish this specimen from all other tyrannosaurids. Therefore, the specimen is made the holotype of the new genus and species Dynamoterror dynastes. A phylogenetic analysis places Dynamoterror dynastes in the tyrannosaurid subclade Tyrannosaurinae. Laser-scanning the frontals and creation of a composite 3-D digital model allows the frontal region of the skull roof of Dynamoterror to be reconstructed.
Highlights
During most of the Late Cretaceous Epoch, the interior of North America was inundated by a shallow epicontinental seaway, with two landmasses on either side remaining as dry land: Appalachia in the east and Laramidia in the west (Fig. 1 in Sampson et al (2010))
The electronic version of this article in portable document format will represent a published work according to the International Commission on Zoological Nomenclature (ICZN), and the new names contained in the electronic version are effectively
Locality: UMNH VP 28348 was collected in San Juan County, New Mexico, on land administered by the US Bureau of Land Management (BLM)
Summary
During most of the Late Cretaceous Epoch, the interior of North America was inundated by a shallow epicontinental seaway, with two landmasses on either side remaining as dry land: Appalachia in the east and Laramidia in the west (Fig. 1 in Sampson et al (2010)). Tyrannosauroid theropods were the largest dinosaurian predators in Appalachia, Laramidia, and Asia during the Campanian and Maastrichtian ages (Loewen et al, 2013; Brusatte & Carr, 2016), approximately the final 15 million years of the Late Cretaceous before the K–Pg mass extinction (Cohen et al, 2013; Renne et al, 2013). The Asian record of Tyrannosauridae includes the unusual, small-bodied, longirostrine alioramins (Alioramus remotus (Kurzanov, 1976), Alioramus altai (Brusatte et al, 2009), and Qianzhousaurus sinensis (Lü et al, 2014)), numerous skeletons of the immense Tarbosaurus bataar (Hurum & Sabath, 2003; Tsuihiji et al, 2011), and the recently named large-bodied tyrannosaurid Zhuchengtyrannus magnus (Hone et al, 2011)
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