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New Upper Cretaceous titanosaur nesting site from Argentina



Ben Creisler
bcreisler@gmail.com

A new paper:

E. Martín Hechenleitner, Lucas E. Fiorelli, Gerald Grellet-Tinner, Léa
Leuzinger, Giorgio Basilici, Jeremías R. A. Taborda, Sergio R. de la
Vega and Carlos A. Bustamante (2016)
A new Upper Cretaceous titanosaur nesting site from La Rioja (NW
Argentina), with implications for titanosaur nesting strategies.
Palaeontology (advance online publication)
DOI: 10.1111/pala.12234
http: // onlinelibrary.wiley.com/doi/10.1111/pala.12234/abstract


Cretaceous titanosaur nesting sites are currently known only from
Europe, Asia and South America. In the latter, only the Auca Mahuevo
and Sanagasta nesting sites have been confidently assigned to this
clade of sauropod dinosaurs. Here we report the discovery of the first
eggs and egg clutches found at Tama, a new Upper Cretaceous
fossiliferous locality in the Los Llanos Formation, Sierra de Los
Llanos (La Rioja, NW Argentina). At least five egg clutches, several
partially preserved, isolated eggs and many eggshell fragments were
discovered in a single outcrop of a sandstone horizon which represents
a cumulative palaeosol profile. Although the mechanical and digital
preparation of eggs did not reveal any embryonic remains in ovo, the
morphology of the eggs and eggshells closely matches that of
titanosaur eggs and eggshells found worldwide. The morphology and
spatial grouping of the titanosaur eggs from Tama, along with
geological observations support a burrow-nesting strategy for these
dinosaurs. Although the Sanagasta and Tama eggs were found in the same
stratigraphical unit and share several morphological characters, they
clearly differ in shell thickness and egg size. This, coupled with the
interpretation of different sedimentary contexts for these nesting
sites, strongly suggests that at least two different titanosaur
species nested in La Rioja during the Late Cretaceous, using different
nesting strategies. The occurrence of this new titanosaur nesting site
in a semiarid palaeoenvironment represents an interesting case study
for the reproductive biology of the titanosaur dinosaurs, particularly
their labile nesting behaviour.