Obligate faunivorous megatheropod size class patterns across the Jurassic-Cretaceous Periods

Allosauroidea, Ceratosauria, Megalosauroidea, Megaraptora, and Tyrannosauroidea are five clades containing obligate faunivorous megatheropods. These clades included apex predators from the Early Jurassic until the end of the Cretaceous Period. Studying the timeline of median size class change for ceratosaurians, tyrannosauroids, and megaraptorans compared to the extinction of the incumbent apex predator clades, allosauroids and megalosauroids, is important regarding megatheropod guild structure. This study used the median size classes exhibited by these clades throughout the Jurassic and Cretaceous Periods, along with the relationship of the median number of missing size classes under different apex predatory regimes. We calculated size class medians for each clade during six discrete time bins. Statistical tests on the median size class data were run to identify potential significant differences and test if increases in median size class occurred after the Cretaceous Thermal Maximum (KTM). Statistical tests were run on the number of missing size classes for each type of apex predator regime to determine if previously proposed hypotheses may explain potential differences. Statistical differences were found between four pairs of clades and their respective median size classes. Median size class increased after the Cretaceous Thermal Maximum for tyrannosauroids and potentially megaraptorans, but increased before the Cretaceous Thermal Maximum for ceratosaurians and did not change afterwards. The median number of missing size classes was found to be higher in the abelisauroid, abelisauroid/megaraptoran, and tyrannosauroid ecosystems compared to allosauroid/megalosauroid ecosystems. The median number of missing size classes between allosauroid/megalosauroid environments and tyrannosauroid-dominated environments was found to be significantly different, with a higher median number of missing size classes in tyrannosauroid-dominated environments. The analysis provides support for hypotheses, such as intraclade niche partitioning or niche shifting, to explain the differences in the median number of missing size classes between abelisauroid, abelisauroid/megaraptoran, and tyrannosauroid ecosystems and allosauroid/megalosauroid ecosystems. This study implies a complex history regarding the timing of the increase in the median size class for clades that survived the Cretaceous Thermal Maximum, which requires further study.

peerj.com

(PDF) “HERE, SIZE IS NO ACCIDENT”: A NOVEL FOOD WEB ANALYSIS OF THE DRY MESA DINOSAUR QUARRY AND ECOLOGICAL IMPACT OF MORRISON FORMATION SAUROPOD FAUNA

PDF | The Morrison Formation is a well-preserved Upper Jurassic rock unit with a characteristic terrestrial fauna. Despite over a century of study, the... | Find, read and cite all the research you ne...

researchgate.net

Could T. rex swim? Kinda

Evidence suggests dinosaurs like tyrannosaurs were probably best suited to a version of the doggy paddle.

nationalgeographic.com

Royal Society Open Science - Editor Pick by Shalene Singh-Shepherd

This week's picks in Royal Society Open Science

researchgate.net

How the T. Rex walked from Asia to North America | May 8, 2025

YouTube video by CNN 10

youtu.be

T. rex’s direct ancestor crossed from Asia to North America

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...

eurekalert.org

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

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 ...

royalsocietypublishing.org

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

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 con...

doi.org

T. rex’s direct ancestor crossed from Asia to North America

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...

ucl.ac.uk

Venue — DinoCon

dinocon.co.uk

Theropod dinosaur diversity of the lower English Wealden: analysis of a tooth‐based fauna from the Wadhurst Clay Formation (Lower Cretaceous: Valanginian) via phylogenetic, discriminant and machine learning methods

The Lower Cretaceous Wealden Supergroup of southern England yields a diverse assemblage of theropod dinosaurs, its taxa being represented by fragments in addition to some of the most informative asso...

onlinelibrary.wiley.com