Egg shape changes at the theropod–bird transition, and a morphometric study of amniote eggs

Deeming, D. Charles and Ruta, Marcello (2014) Egg shape changes at the theropod–bird transition, and a morphometric study of amniote eggs. Royal Society Open Science . ISSN 2054-5703

Full content URL: http://dx.doi.org/10.1098/rsos.140311

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Abstract

The eggs of amniotes exhibit a remarkable variety of shapes,
from spherical to elongate and from symmetrical to asymmetrical.
We examine eggshell geometry in a diverse sample of fossil
and living amniotes using geometric morphometrics and linear
measurements. Our goal is to quantify patterns of morphospace
occupation and shape variation in the eggs of recent through to
Mesozoic birds (neornithe plus non-neornithe avialans), as well
as in eggs attributed to non-avialan theropods. In most amniotes,
eggs show significant deviation from sphericity, but departure
from symmetry around the equatorial axis is mostly confined
to theropods and birds. Mesozoic bird eggs differ significantly
from extant bird eggs, but extinct Cenozoic bird eggs do not. This
suggests that the range of egg shapes in extant birds had already
been attained in the Cenozoic. We conclude with a discussion
of possible biological factors imparting variation to egg shapes
during their formation in the oviduct.

Keywords:birds, Cenozoic, eggshell outline, Mesozoic, morphospace, theropods, NotOAChecked
Subjects:C Biological Sciences > C142 Reproductive Biology
C Biological Sciences > C182 Evolution
C Biological Sciences > C300 Zoology
F Physical Sciences > F641 Palaeontology
C Biological Sciences > C100 Biology
Divisions:College of Science > School of Life Sciences
ID Code:15967
Deposited On:11 Nov 2014 12:08

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