Mountain Building Triggered Late Cretaceous North American Megaherbivore Dinosaur Radiation

Abstract

Prior studies of Mesozoic biodiversity document a diversity peak for dinosaur species in the Campanian stage of the Late Cretaceous, yet have failed to provide explicit causal mechanisms. We provide evidence that a marked increase in North American dinosaur biodiversity can be attributed to dynamic orogenic episodes within the Western Interior Basin (WIB). Detailed fossil occurrences document an association between the shift from Sevier-style, latitudinally arrayed basins to smaller Laramide-style, longitudinally arrayed basins and a well substantiated decreased geographic range/increased taxonomic diversity of megaherbivorous dinosaur species. Dispersal-vicariance analysis demonstrates that the nearly identical biogeographic histories of the megaherbivorous dinosaur clades Ceratopsidae and Hadrosauridae are attributable to rapid diversification events within restricted basins and that isolation events are contemporaneous with known tectonic activity in the region. SymmeTREE analysis indicates that megaherbivorous dinosaur clades exhibited significant variation in diversification rates throughout the Late Cretaceous. Phylogenetic divergence estimates of fossil clades offer a new lower boundary on Laramide surficial deformation that precedes estimates based on sedimentological data alone.

Palaeoenvironmental drivers of vertebrate community composition in the Belly River Group (Campanian) of Alberta, Canada, with implications for dinosaur biogeography

“…Environmental changes caused by transgression-regression cycles of the Western Interior Sea have been suggested to drive the high diversity and high faunal turnover rates of non-avian dinosaurs [4, 5, 8–11], along with changes in the vertebrate community structure more generally [12–16]. However, global-scale analyses of dinosaurs, as a whole [17] and at the family level [18], indicate that large-scale changes in sea level may not have had a significant influence on broad patterns of diversity, evolution, or migration.…”

A new clade of Asian Late Cretaceous long-snouted tyrannosaurids

“…Conversely, sauropods were remarkably rare in the Maastrichtian of North America but more diverse in Asia 40 . North America and Asia clearly experienced faunal interchange during the latest Cretaceous, but the presence of the inland Western Interior Sea, extensive mountain building and potential biogeographic provincialism may have uniquely shaped North American dinosaur evolution relative to other regions of the northern hemisphere, and the world, at this time 41 . It appears as if Asian and North American dinosaurs were undergoing distinct biodiversity trajectories during the latest Cretaceous 42,43 , meaning that the well-sampled North American record, which has long been used as a standard to understand dinosaur evolution during the run-up to their extinction, may not be a reasonable proxy for the global record.…”

A new species of troodontid theropod (Dinosauria: Maniraptora) from the Horseshoe Canyon Formation (Maastrichtian) of Alberta, Canada

“…Several researchers (Fiorillo 2008;Fiorillo et al 2009;Larson and Currie 2013;Zanno et al 2011) have noted the unusually wide geographic and stratigraphic distribution of small coelurosaurian theropod species in the Western Interior Basin, and that these ranges are largely defined by the assignment of isolated teeth to form taxa. In other groups, such as large ornithischians, differentiation of species relies on non-dentigerous skeletal elements, and these taxa have small geographic and stratigraphic ranges, and presumably exhibited high evolutionary rates and ecological specialization (Eberth et al 2013;Gates et al 2012;Mallon et al 2012;Ryan and Evans 2005;Sampson and Loewen 2010). Zanno et al (2011) recognized variation in the limited skeletal materials previously referred to Troodon, and hypothesized that the diversity of Late Cretaceous troodontids in North America is underestimated, a conclusion that was supported by a morphometric analysis of small theropod teeth by Larson and Currie (2013).…”