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Mass Estimation in Modern and Fossil Flying Birds

From: Ben Creisler

New in PLoS ONE:

Daniel J. Field, Colton Lynner, Christian Brown & Simon A. F. Darroch (2013)
Skeletal Correlates for Body Mass Estimation in Modern and Fossil Flying Birds.
PLoS ONE 8(11): e82000.

Scaling relationships between skeletal dimensions and body mass in
extant birds are often used to estimate body mass in fossil
crown-group birds, as well as in stem-group avialans. However, useful
statistical measurements for constraining the precision and accuracy
of fossil mass estimates are rarely provided, which prevents the
quantification of robust upper and lower bound body mass estimates for
fossils. Here, we generate thirteen body mass correlations and
associated measures of statistical robustness using a sample of 863
extant flying birds. By providing robust body mass regressions with
upper- and lower-bound prediction intervals for individual skeletal
elements, we address the longstanding problem of body mass estimation
for highly fragmentary fossil birds. We demonstrate that the most
precise proxy for estimating body mass in the overall dataset,
measured both as coefficient determination of ordinary least squares
regression and percent prediction error, is the maximum diameter of
the coracoid’s humeral articulation facet (the glenoid). We further
demonstrate that this result is consistent among the majority of
investigated avian orders (10 out of 18). As a result, we suggest
that, in the majority of cases, this proxy may provide the most
accurate estimates of body mass for volant fossil birds. Additionally,
by presenting statistical measurements of body mass prediction error
for thirteen different body mass regressions, this study provides a
much-needed quantitative framework for the accurate estimation of body
mass and associated ecological correlates in fossil birds. The
application of these regressions will enhance the precision and
robustness of many mass-based inferences in future paleornithological