Dinosaur eggs from Argentina (two new papers)

[Ben Creisler <bcreisler@gmail.com>]

From: Ben Creisler
bcreisler@gmail.com

Two recent papers not yet mentioned on the DML:



Eloísa Argañaraz, Gerald Grellet-Tinner, Lucas E. Fiorelli, Marcelo
Krause & Oliver W. H. Rauhut.
HUEVOS DE SAURÓPODOS DEL APTIANO–ALBIANO, FORMACIÓN CERRO BARCINO
(PATAGONIA, ARGENTINA): UN ENIGMA PALEOAMBIENTAL Y PALEOBIOLÓGICO.
[SAUROPOD EGGS FROM THE APTIAN–ALBIAN CERRO BARCINO FORMATION, CHUBUT
(PATAGONIA, ARGENTINA): A PALEOENVIRONMENTAL AND PALEOBIOLOGICAL
ENIGMA.]
Ameghiniana 50(1): 33--50
http://www.ameghiniana.org.ar/index.php/ameghiniana/article/view/551

The Upper Cretaceous has yielded several important nesting sites and
isolated sauropod dinosaur eggs and eggshells in South America.
However, the Lower Cretaceous dinosaur egg record is still poorly
known on this continent, an exception being the Hauterivian–Aptian
nesting site at Sanagasta in La Rioja Province, Argentina. Herein we
report the oldest Cretaceous sauropod eggs from Patagonia. The two
eggs are from Chubut Province (Patagonia) and were discovered in the
Cerro Castaño Member of the Aptian–Albian Cerro Barcino Formation
exposed in the Huanimán area. The specimens were preserved in a fine,
pedogenized, and tuffaceous sandstone in proximal floodplain facies
related to multi-episodic sinuous channel facies. The eggshell
morphology is similar to that of megaloolithid eggs (a paraphyletic
group in egg parataxonomy) known from Patagonia at (1) Auca Mahuevo,
Neuquen, positively identified as sauropod titanosaurs on the bais of
in ovo embryos, and (2) Salitral Moreno, Rio Negro. However, the new
specimens from Chubut exhibit structural features of the eggshell not
previously reported such as a horizontal network of pore canals
clearly visible near and beneath the outer nodular eggshell surface,
similar in morphology but differently placed than in the Auca Mahuevo
eggs —where it overlays the membrana testacea. This morphological
feature and the 1.5 mm thick eggshell may illustrate a novel
adaptation to this specific nesting environment. Although only two
isolated eggs were found in Huanimán, this discovery suggests a high
likelihood for the existence of a more substantial nesting site with
several eggs clutches.

==

Mariela Soledad Fernández (2013)
ANÁLISIS DE CÁSCARAS DE HUEVOS DE DINOSAURIOS DE LA FORMACIÓN ALLEN,
CRETÁCICO SUPERIOR DE RÍO NEGRO (CAMPANIANO–MAASTRICHTIANO): UTILIDAD
DE LOS MACROCARACTERES DE INTERÉS PARATAXONÓMICO.
[ANALYSIS OF DINOSAUR EGGSSHELLS OF ALLEN FORMATION, UPPER CRETACEOUS
OF THE RIO NEGRO PROVINCE (CAMPANIAN-MAASTRICHTIAN): USEFULNESS OF
MACROCHARACTERS OF PARATAXONOMIC INTEREST.]
Ameghiniana 50(1): 79 – 97
http://www.ameghiniana.org.ar/index.php/ameghiniana/article/view/586


The present study is a further contribution to the parataxonomy
knowledge of dinosaur eggshells from Salitral de Santa Rosa and
Salitral Ojo de Agua, Río Negro province, Argentina. We studied 4469
fragments of dinosaur eggshells Allen Formation, Upper Cretaceous
(Campanian-Maastrichtian). Twelve of these shells were subject to a
principal component analysis (PCA) to classify and establish the
relationships between characters commonly used in parataxonomic
classifications. We studied under binocular scope 4264 eggshells (BL),
57 eggshells under transmitted light microscope (TLM) and polarized
light microscope (PLM), 14 eggshells under scanning electron
microscope (SEM). We identified two main groups, type 1 eggshells
related to the oofamily Megaloolithidae with five subtypes and type 2
eggshells, with no subtypes assigned. Relevant traits found with the
ACP study were: shell thickness, the width of the shell units, the
diameter of the nodules, and the diameter of the mamila. Different
types of eggshells found were compared with various ootaxa from South
America and other regions of the world.