Tyrannosaurus rex mais para hiena do que para leão

quinta-feira, fevereiro 24, 2011

T. Rex More Hyena Than Lion: Tyrannosaurus Rex Was Opportunistic Feeder, Not Top Predator, Paleontologists Say

ScienceDaily (Feb. 22, 2011) — The ferocious Tyrannosaurus rex has been depicted as the top dog of the Cretaceous, ruthlessly stalking herds of duck-billed dinosaurs and claiming the role of apex predator, much as the lion reigns supreme in the African veld.

This cast of a Tyrannosaurus rex is on display in UC Berkeley's Valley Life Sciences Building. The original fossil skeleton from Montana's Hell Creek Formation is in the Museum of the Rockies in Bozeman, Mont. (Credit: Randy Irmis)

But a new census of all dinosaur skeletons unearthed over a large area of eastern Montana shows that Tyrannosaurus was too numerous to have subsisted solely on the dinosaurs it tracked and killed with its scythe-like teeth.
Instead, argue paleontologists John "Jack" Horner from the Museum of the Rockies and Mark B. Goodwin from the University of California, Berkeley, T. rex was probably an opportunistic predator, like the hyena in Africa today, subsisting on both carrion and fresh-killed prey and exploiting a variety of animals, not just large grazers.
"In our census, T. rex came out very high, equivalent in numbers to Edmontosaurus, which many people had thought was its primary prey," said Horner, curator of paleontology at the Museum of the Rockies in Bozeman, Mont., and Regents Professor at Montana State University. "This says that T. rex is not a cheetah, it's not a lion. It's more like a hyena."
"This putative apex predator is as abundant in the upper layers of the Hell Creek Formation as the herbivores, its reputed primary food source," added Goodwin, a curator in UC Berkeley's Museum of Paleontology and assistant director of the museum. "And it's even more plentiful in the other two-thirds of the formation. This supports the view that T. rex benefited from a much wider variety of food sources than live prey."

Read more here/Leia mais aqui: Science Daily

Dinosaur Census Reveals Abundant Tyrannosaurus and Rare Ontogenetic Stages in the Upper Cretaceous Hell Creek Formation (Maastrichtian), Montana, USA

John R. Horner1*, Mark B. Goodwin2, Nathan Myhrvold3

1 Museum of the Rockies, Montana State University, Bozeman, Montana, United States of America, 2 Museum of Paleontology, University of California, Berkeley, California, United States of America, 3 Intellectual Ventures, Bellevue, Washington, United States of America



A dinosaur census recorded during the Hell Creek Project (1999–2009) incorporates multiple lines of evidence from geography, taphohistory, stratigraphy, phylogeny and ontogeny to investigate the relative abundance of large dinosaurs preserved in the Upper Cretaceous Hell Creek Formation of northeastern Montana, USA. Overall, the dinosaur skeletal assemblages in the Hell Creek Formation (excluding lag-influenced records) consist primarily of subadult or small adult size individuals. Small juveniles and large adults are both extremely rare, whereas subadult individuals are relatively common. We propose that mature individuals of at least some dinosaur taxa either lived in a separate geographic locale analogous to younger individuals inhabiting an upland environment where sedimentation rates were relatively less, or these taxa experienced high mortality before reaching terminal size where late stage and often extreme cranial morphology is expressed.

Methodology/Principal Findings

Tyrannosaurus skeletons are as abundant as Edmontosaurus, an herbivore, in the upper Hell Creek Formation and nearly twice as common in the lower third of the formation. Smaller, predatory dinosaurs (e.g., Troodon and dromaeosaurids) are primarily represented by teeth found in microvertebrate localities and their skeletons or identifiable lag specimens were conspicuously absent. This relative abundance suggests Tyrannosaurus was not a typical predator and likely benefited from much wider food choice opportunities than exclusively live prey and/or specific taxa.Tyrannosaurus adults may not have competed with Tyrannosaurus juveniles if the potential for selecting carrion increased with size during ontogeny.


Triceratops is the most common dinosaur and isolated skulls contribute to a significant portion of this census. Associated specimens of Triceratops consisting of both cranial and postcranial elements remain relatively rare. This rarity may be explained by a historical collecting bias influenced by facies and taphonomic factors. The limited discovery of postcranial elements may also depend on how extensive a fossil quarry is expanded after a skull is collected.

Citation: Horner JR, Goodwin MB, Myhrvold N (2011) Dinosaur Census Reveals Abundant Tyrannosaurusand Rare Ontogenetic Stages in the Upper Cretaceous Hell Creek Formation (Maastrichtian), Montana, USA. PLoS ONE 6(2): e16574. doi:10.1371/journal.pone.0016574

Editor: Peter Roopnarine, California Academy of Sciences, United States of America

Received: July 29, 2010; Accepted: January 4, 2011; Published: February 9, 2011

Copyright: © 2011 Horner et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: This work was supported with funding by the following individuals: James Kinsey, Catherine B. Reynolds, and Homer Hickam. Intellectual Ventures, the Windway Foundation, and the Smithsonian Institution provided additional funding. The University of California Museum of Paleontology provided funding to MBG. NM is the founder and CEO of Intellectual Ventures and contributed to the study design. Homer Hickham participated as a Hell Creek Project volunteer in the field in Montana. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: Nathan Myhrvold contributed financially to the Hell Creek Project and intellectually to the design of the study.