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Titanosaur embryos from Romania



From: Ben Creisler
bcreisler@gmail.com

A new paper in PLoS ONE:


Grellet-Tinner G, Codrea V, Folie A, Higa A, Smith T (2012)
First Evidence of Reproductive Adaptation to “Island Effect” of a
Dwarf Cretaceous Romanian Titanosaur, with Embryonic Integument In
Ovo.
PLoS ONE 7(3): e32051.
doi:10.1371/journal.pone.0032051
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0032051


Background

The Cretaceous vertebrate assemblages of Romania are famous for
geographically endemic dwarfed dinosaur taxa. We report the first
complete egg clutches of a dwarf lithostrotian titanosaur, from
Totesti, Romania, and its reproductive adaptation to the “island
effect”.

Methodology/Findings

The egg clutches were discovered in sequential sedimentary layers of
the Maastrichtian Sanpetru Formation, Totesti. The occurrence of 11
homogenous clutches in successive strata suggests philopatry by the
same dinosaur species, which laid clutches averaging four ~12 cm
diameters eggs. The eggs and eggshells display numerous characters
shared with the positively identified material from egg-bearing level
4 of the Auca Mahuevo (Patagonia, Argentina) nemegtosaurid
lithostrotian nesting site. Microscopic embryonic integument with
bacterial evidences was recovered in one egg. The millimeter-size
embryonic integument displays micron size dermal papillae implying an
early embryological stage at the time of death, likely corresponding
to early organogenesis before the skeleton formation.

Conclusions/Significance

The shared oological characters between the Hateg specimens and their
mainland relatives suggest a highly conservative reproductive
template, while the nest decrease in egg numbers per clutch may
reflect an adaptive trait to a smaller body size due to the “island
effect”. The combined presence of the lithostrotian egg and its embryo
in the Early Cretaceous Gobi coupled with the oological similarities
between the Hateg and Auca Mahuevo oological material evidence that
several titanosaur species migrated from Gondwana through the Hateg
Island before or during the Aptian/Albian. It also suggests that this
island might have had episodic land bridges with the rest of the
European archipelago and Asia deep into the Cretaceous.