Abstract
The ability to accurately and reliably estimate body mass of extinct taxa is a vital tool for interpreting the physiology and even behavior of long-dead animals. For this reason, paleontologists have developed many possible methods of estimating the body mass of extinct animals, with varying degrees of success. These methods can be divided into two main categories: volumetric mass estimation and extant scaling methods. Each has advantages and disadvantages, which is why, when possible, it is best to perform both, and compare the results to determine what is most plausible within reason. Here we employ volumetric mass estimation (VME) to calculate an approximate body mass for previously described specimens of Anzu wyliei from the Carnegie Museum of Natural History. We also use extant scaling methods to try to obtain a reliable mass estimate for this taxon. In addition, we present the first digital life restoration and convex hull of the dinosaur Anzu wyliei used for mass estimation purposes. We found that the volumetric mass estimation using our digital model was 216-280kg, which falls within the range predicted by extant scaling techniques, while the mass estimate using minimum convex hulls was below the predicted range, between 159-199 kg . The VME method for Anzu wyliei strongly affirms the predictive utility of extant-based scaling. However, volumetric mass estimates are likely more precise because the models are based on comprehensive specimen anatomy rather than regressions of a phylogenetically comprehensive but disparate sample.
Highlights
Body mass is an important characteristic of organisms, as it relates to many important life functions such as metabolic rate (Strotz et al 2018), relative maturity, and biomechanics (Hutchinson et al 2011; Sander et al 2011; SchmidtNielsen 1984)
We wanted to determine whether volumetric mass estimation could create a narrower range of body mass estimates than extant scaling for a taxon such as Anzu wyliei based on known specimens, using a class of techniques known
Minimum convex hulling yielded a volume of 0.199 m3 (Tab. 1), with a mass estimate between 159 and 199 kg, depending on which body density value was applied
Summary
Body mass is an important characteristic of organisms, as it relates to many important life functions such as metabolic rate (Strotz et al 2018), relative maturity, and biomechanics (Hutchinson et al 2011; Sander et al 2011; SchmidtNielsen 1984). A wide range of techniques have been developed to try to solve this conundrum, reviewed comprehensively by Brassey (2017) and Campione and Evans (2020). There are two major categories into which mass estimation techniques fall - volumetric mass estimates, that use various ways of estimating body volume and density, and extant scaling methods, which use relationships between measured osteological characters and body mass in modern taxa, and attempt to reconcile these relationships with extinct organisms. Each method has advantages and drawbacks, which is why using both can be informative (Campione and Evans 2020) for identifying potential errors in one method or the other and to provide what may be a more realistic range of values, and for tradeoffs of comparative sample size versus time investment. We wanted to determine whether volumetric mass estimation could create a narrower range of body mass estimates than extant scaling for a taxon such as Anzu wyliei based on known specimens, using a class of techniques known
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