Dinosaur eggshell morphometric analysis

[Ben Creisler <bcreisler@gmail.com>]

From: Ben Creisler
bcreisler@gmail.com

A new online paper:


Ana María Bravo & Jesús Marugán-Lobón (2012)
Morphometric analysis of dinosaur eggshells: constraints of size on shape.
Historical Biology (advance online publication)
DOI:10.1080/08912963.2012.744989
http://www.tandfonline.com/doi/full/10.1080/08912963.2012.744989



Studies on fossil eggs and eggshells have been traditionally focused
on analysis of microstructure and systematic classification, but few
attempts have been made to examine the variability of eggshell
characters. This work examines the variability of one diagnostic
character, shape of the calcitic units, of some dinosaur eggshells by
using outline shape analysis (elliptic Fourier analysis). The studied
material belongs to five different oospecies of the parafamily
Megaloolithidae Zhao, 1979. To test shape variation within and between
oospecies, an analysis on 129 outlines was carried out and their
variability was summarised by principal component analysis. We then
tested if the shape of megaloolithid units changes according to size
(i.e. allometry). A regression analysis between eggshell unit shape
and two different size measurements (centroid size and eggshell
thickness) showed that the thinnest eggshells (thickness ≤ 1 mm) have
different shapes than thicker ones ( ≥ 2.5 mm). Our results stress
that the variability in the shape of eggshell units in Megaloolithus
oospecies is correlated to size (i.e. eggshell thickness), a
phenomenon that should be then considered carefully when determining
oospecies, since a single oospecies can show both a wide range of
eggshell thickness and combined with different eggshell unit shapes.