Saturday, November 23, 2013

[Paleontology • 2013] Siats meekerorum • Neovenatorid theropods are Apex Predators in the Late Cretaceous of North America

Siats meekerorum 
Zanno & Makovicky 2013

Allosauroid theropods were a diverse and widespread radiation of Jurassic–Cretaceous megapredators. Achieving some of the largest body sizes among theropod dinosaurs, these colossal hunters dominated terrestrial ecosystems until a faunal turnover redefined apex predator guild occupancy during the final 20 million years of the Cretaceous. Here we describe a giant new species of allosauroid – Siats meekerorum gen. et sp. nov. – providing the first evidence for the cosmopolitan clade Neovenatoridae in North America. Siats is the youngest allosauroid yet discovered from the continent and demonstrates that the clade endured there into the Late Cretaceous. The discovery provides new evidence for ecologic sympatry of large allosauroids and small-bodied tyrannosauroids. These data support the hypothesis that extinction of Allosauroidea in terrestrial ecosystems of North America permitted ecological release of tyrannosauroids, which went on to dominate end-Cretaceous food webs.

This illustration shows Siats within its ecosystem,
eating an Eolambia and intimidating early, small-bodied tyrannosauroids.
Illustration: Julio Lacerda

Siats meekerorum
Illustration: Jorge Gonzales

Zanno, L. E.; Makovicky, P. J. 2013. Neovenatorid theropods are Apex Predators in the Late Cretaceous of North America. Nature Communications. 4. doi:

Colossal new predatory dino terrorized early tyrannosaurs
A new species of carnivorous dinosaur – one of the three largest ever discovered in North America – lived alongside and competed with small-bodied tyrannosaurs 98 million years ago. This newly discovered species, Siats meekerorum, (pronounced see-atch) was the apex predator of its time, and kept tyrannosaurs from assuming top predator roles for millions of years.