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Dinosaur egg from Spain

From: Ben Creisler

A new published paper in March 2012 Palaeontology:

A new peculiar dinosaur egg, Sankofa pyrenaica oogen. nov. oosp. nov.
from the Upper Cretaceous coastal deposits of the Aren Formation,
south-central Pyrenees, Lleida, Catalonia, Spain.
Palaeontology 55: 325–339.
doi: 10.1111/j.1475-4983.2011.01114.x

A new type of small, ovoid dinosaur egg, Sankofa pyrenaica oogen. nov.
oosp. nov., with a prismatic type eggshell is described from upper
Cretaceous (upper Campanian–Maastrichtian) deposits of the Montsec
area, South Pyrenean Central Unit, Lleida, Catalonia, Spain. This egg
type was sub-vertically laid in only two rich monospecific sites of a
single stratigraphic layer from coastal deposits of the Aren
Formation, interpreted as an emerged beach ridge of a barrier island –
lagoon depositional system. The size and shape of these eggs with
their asymmetric poles are roughly similar to modern hen eggs, which
is unusual in the Cretaceous fossil egg record. Its phylogenetic
position clusters with bird and Troodontid eggs. A morphospace
analysis of egg shapes shows the similarity of the new egg to a
Campanian fossil bird egg from Argentina, both being intermediate
between modern-bird eggs and extinct nonavian theropod eggs. However,
the eggshell microstructure of Sankofa pyrenaica differs from that of
bird eggs in its incipient squamatic texture. It has a peculiar
pattern of interlocking small crystals in the middle of the palisade
layer, instead of the thick squamatic structure commonly present in
modern avian eggshells. This new egg type is attributed to a small
theropod, probably with a single oviduct like birds and whose mosaic
distribution of features is a combination between that of birds and
nonavian theropods. This enhances the arguments supporting the close
phylogenetic relationships between both groups.