Dinosaurs from the Santonian–Campanian Atlantic coastline substantiate phylogenetic signatures of vicariance in Cretaceous North America

Abstract

During the Cretaceous, diversifications and turnovers affected terrestrial vertebrates experiencing the effects of global geographical change. However, the poor fossil record from the early Late Cretaceous has concealed how dinosaurs and other terrestrial vertebrates responded to these events. I describe two dinosaurs from the Santonian to Early Campanian of the obscure North American paleolandmass Appalachia. A revised look at a large, potentially novel theropod shows that it likely belongs to a new clade of tyrannosauroids solely from Appalachia. Another partial skeleton belongs to an early member of the Hadrosauridae, a highly successful clade of herbivorous dinosaurs. This skeleton is associated with the first small juvenile dinosaur specimens from the Atlantic Coastal Plain. The tyrannosauroid and hadrosaurid substantiate one of the only Late Santonian dinosaur faunas and help pinpoint the timing of important anatomical innovations in two widespread dinosaur lineages. The phylogenetic positions of the tyrannosauroid and hadrosaurid show Santonian Appalachian dinosaur faunas are comparable to coeval Eurasian ones, and the presence of clades formed only by Appalachian dinosaur taxa establishes a degree of endemism in Appalachian dinosaur assemblages attributable to episodes of vicariance.

A reappraisal of tyrannosauroid fossils from the Iren Dabasu Formation (Coniacian–Campanian), Inner Mongolia, People’s Republic of China

“…other workers; and Tyrannosaurus bataar and T. rex are equivalent to Tarbosaurus and Tyrannosaurus, respectively, of other workers. The purpose of this approach is to maximize the information content of the taxonomy by aligning it with sister group relationships as recovered by phylogenetic analyses (Brusatte & Carr, 2016;Carr et al, 2017;Brownstein, 2021).…”

Large-bodied ornithomimosaurs inhabited Appalachia during the Late Cretaceous of North America

“…From these often-isolated elements, researchers have been able to piece together a diverse Appalachian vertebrate fauna represented by hadrosauroids, ceratopsids, and theropods [11][12][13][14][15][16][17]. These discoveries have greatly strengthened our understanding of the evolution, biodiversity, and paleoecology of the Appalachian dinosaur fauna [3,10,11,13,[17][18][19][20][21][22]. Yet much remains to be learned.…”

“…Nonetheless, knowledge of the Mesozoic terrestrial fauna of eastern North America is rapidly growing. From these often-isolated elements, researchers have been able to piece together a diverse Appalachian vertebrate fauna represented by hadrosauroids, ceratopsids, and theropods [11][12][13][14][15][16][17]. These discoveries have greatly strengthened our understanding of the evolution, biodiversity, and paleoecology of the Appalachian dinosaur fauna [3,10,11,13,[17][18][19][20][21][22].…”

Large-bodied ornithomimosaurs inhabited Appalachia during the Late Cretaceous of North America

“…Nonetheless, knowledge of the Mesozoic terrestrial fauna of eastern North America is rapidly growing. From these often-isolated elements, researchers have been able to piece together a diverse Appalachian vertebrate fauna represented by hadrosauroids, ceratopsids, and theropods [11][12][13][14][15][16][17]. These discoveries have greatly strengthened our understanding of the evolution, biodiversity, and paleoecology of the Appalachian dinosaur fauna [3,10,11,13,[17][18][19][20][21][22].…”

“…From these often-isolated elements, researchers have been able to piece together a diverse Appalachian vertebrate fauna represented by hadrosauroids, ceratopsids, and theropods [11][12][13][14][15][16][17]. These discoveries have greatly strengthened our understanding of the evolution, biodiversity, and paleoecology of the Appalachian dinosaur fauna [3,10,11,13,[17][18][19][20][21][22]. Yet much remains to be learned.…”