Mesozoic bird body masses

[Ben Creisler <bcreisler@gmail.com>]

Ben Creisler
bcreisler@gmail.com

A new online paper:

Francisco José Serrano, Paul Palmqvist and José Luis Sanz (2015)
Multivariate analysis of neognath skeletal measurements: implications
for body mass estimation in Mesozoic birds.
Zoological Journal of the Linnean Society  (advance online publication)
DOI: 10.1111/zoj.12215
http://onlinelibrary.wiley.com/doi/10.1111/zoj.12215/abstract



The abundant fossils of avian stem taxa unearthed during the last
years make it necessary to review and improve the models for
estimating body mass used in palaeoecological studies. In this
article, single and multiple regression functions based on
osteological measurements were obtained from a large data set of
extant flying birds for estimating the body mass of 42 Mesozoic
specimens from stem taxa Archaeopterygidae, Jeholornithidae,
Sapeornithidae, Confuciusornithidae, and Enantiornithes, and basal
members of Ornithuromorpha. Traditionally, body mass has been
estimated in fossil vertebrates using univariate scaling functions. In
contrast, multiple regression functions have been used less
frequently. Both predictive methods can be affected by different
sources of error from statistics, phylogenetic relationships,
ecological adaptations, and bone preservation; however, although some
studies have addressed these biases, few have tested them within the
context of a single data set. In our data set, we find that the models
with greater predictive strength and applicability for new specimens,
especially for stem taxa, are those derived from multiple regression
analyses. For this reason, we suggest that multiple regression
analyses may provide improved predictive strength for stem group
specimens. Moreover, the methodology used for selecting variables
allowed us to obtain specific sets of predictors for each fossil stem
group that presumably minimized the variation resulting from
historical contingency (i.e. differences in skeletal morphology
arising from phylogeny), locomotor adaptations, and diagenetic
compaction. The loss of generalizability in the multiple regression
models resulting from collinearity effects was negligible on the body
mass estimates derived from our data set. Therefore, the body mass
values obtained for Mesozoic specimens are accurate and can be used in
future studies in a number of palaeobiological and evolutionary
aspects of extinct birds, particularly the first stages of avian
flight.