Wednesday, April 21, 2021

[Paleontology • 2021] Absolute Abundance and Preservation Rate of Tyrannosaurus rex

 Tyrannosaurus rex

in Marshall, Latorre, Wilson, ... et Poust, 2021. 
Illustration: JuliusCsotonyi 

Although much can be deduced from fossils alone, estimating abundance and preservation rates of extinct species requires data from living species. Here, we use the relationship between population density and body mass among living species combined with our substantial knowledge of Tyrannosaurus rex to calculate population variables and preservation rates for postjuvenile T. rex. We estimate that its abundance at any one time was ~20,000 individuals, that it persisted for ~127,000 generations, and that the total number of T. rex that ever lived was ~2.5 billion individuals, with a fossil recovery rate of 1 per ~80 million individuals or 1 per 16,000 individuals where its fossils are most abundant. The uncertainties in these values span more than two orders of magnitude, largely because of the variance in the density–body mass relationship rather than variance in the paleobiological input variables.

 Charles R. Marshall, Daniel V. Latorre, Connor J. Wilson, Tanner M. Frank, Katherine M. Magoulick, Joshua B. Zimmt and Ashley W. Poust. 2021. Absolute Abundance and Preservation Rate of Tyrannosaurus rexScience. 372, 6539; 284-287. DOI: 10.1126/science.abc8300 

COVER: Tyrannosaurus rex prowl a Cretaceous coast. 
By using the rich fossil record of T. rex, including its body mass, growth and survivorship curves, geographic range, and geologic longevity, together with the relationship between population density and body mass among living animals, it is possible to ascertain how many T. rex ever roamed the planet and to estimate the fossil recovery rate for this species.
 Illustration: Julius Csotonyi

Estimating dinosaur abundance
Estimating the abundance of a species is a common practice for extant species and can reveal many aspects of its ecology, evolution, and threat level. Estimating abundance for species that are extinct, especially those long extinct, is a much trickier endeavor. Marshall et al. used a relationship established between body size and population density in extant species to estimate traits such as density, distribution, total biomass, and species persistence for one of the best-known dinosaurs, Tyrannosaurus rex, revealing previously hidden aspects of its population ecology.