Tyrannosaurids and Other Big Ancient Predators

[zorkan]

Yes but the tourist trade in North Scotland relies on that one image.

[billy rubin]

certainly not on the weather

[Recusant]

Investigation of the origin of the tyrannosaurids. 

"T. rex's direct ancestor crossed from Asia to North America, new study finds" | Phys.org

Tyrannosaurus rex evolved in North America, but its direct ancestor came from Asia, crossing a land bridge connecting the continents more than 70 million years ago, according to a new study led by UCL researchers.

The study, published in Royal Society Open Science, also found that the rapid growth in size of tyrannosaurids (the group that included the T. rex) as well as a closely related group called megaraptors coincided with a cooling of the global climate following a peak in temperatures 92 million years ago.

This suggests T. rex and its cousins might have been better suited to cooler climates than other dinosaur groups at the time, perhaps due to having feathers or a more warm-blooded physiology.

The international team involved researchers from the universities of Oxford, Pittsburgh, Aberdeen, Arizona, Anglia Ruskin, Oklahoma and Wyoming.

Lead author Cassius Morrison, a Ph.D. student at UCL Earth Sciences, said, "The geographic origin of T. rex is the subject of fierce debate. Paleontologists have been divided over whether its ancestor came from Asia or North America.

"Our modeling suggests the 'grandparents' of T. rex likely came to North America from Asia, crossing the Bering Strait between what is now Siberia and Alaska.

"This is in line with past research finding that the T. rex was more closely related to Asian cousins such as the Tarbosaurus than to North American relatives such as Daspletosaurus.

[Continues . . .]

The paper is open access:

"Rise of the king: Gondwanan origins and evolution of megaraptoran dinosaurs" | Royal Society Open Science

Abstract:

Late Cretaceous Earth was dominated by theropods such as tyrannosauroids and megaraptorans; however, it is unclear how these clades diversified and grew to massive proportions. This study aimed to conduct a biogeographical analysis and test climate as a potential mechanism for the increase in size.

We used published phylogenetic matrices with the R package BioGeoBears to test different biogeographical hypotheses for both clades. We mapped body mass (BM) and body length against known climate data to test this potential hypothesis.

Continental-scale variance did not drive tyrannosauroid biogeography and instead widespread ancestral populations, sympatric speciation and localized extinctions throughout these clades constricted geographic range. Both patterns were supported by statistical analyses. This biogeographical model also indicates the ancestor of the clade Tarbosaurus and Tyrannosaurus was present in both Asia and Laramidia, and therefore the ancestor of Tyrannosaurus came from Asia.

Statistical data illustrated no correlation between Mean Annual Temperature (MAT) and BM but potential climatic shifts may be associated with gigantism in derived megaraptorids and eutyrannosaurians. This biogeographical model implies megaraptorans may have had a cosmopolitan distribution prior to the splitting of Laurasia and Gondwana. Also, gigantism in these clades may be associated with climatic shifts in the Late Cretaceous.