Trabajos de campo confirman el enorme tamaño del nuevo ejemplar
0 comentarios Publicado por Leonardo Filippi en 8:51
Durante la primera mitad del mes de abril, el MAU (Museo Municipal Argentino Urquiza), Rincón de los Sauces, Neuquén, reanudó los trabajos de campo en Cañadón Mistringa. En este sitio fue hallado durante el 2012 un enorme ejemplar de dinosaurio saurópodo titanosaurio. Durante estos trabajos se recuperaron algunos huesos que dan cuenta del gran tamaño del animal: una escápula incompleta que se estima superaría el 1,50 m de longitud y una enorme vértebra cervical (bochón de la foto) cuyas medidas estimadas superarían el 1,20 m de ancho, 0,90 m de largo y 1 m de alto aproximadamente. Las tareas de recuperación de este gigante recién comienzan, por lo que todavía será necesario remover varios metros cúbicos de roca, para así, extraer nuevas piezas que permitan estimar el tamaño real del ejemplar, el cual se cree, estaría entre los 30 y 35 m de longitud.
Análisis de cáscaras de huevos de dinosaurio de la Formación Allen, Río Negro, Argentina.
0 comentarios Publicado por Leonardo Filippi en 8:31
Mariela S. Fenández
El presente
estudio es una contribución más al conocimiento de la parataxonomía de las
cáscaras de huevos de dinosaurios procedentes del Salitral de Santa Rosa y
Salitral Ojo de Agua de la provincia de Río Negro, Argentina. Para dicho
trabajo fueron estudiados 4469 fragmentos de cáscaras de huevos de la Formación
Allen, Cretácico Superior (Campaniano-Maastrichtiano). Doce de estas cáscaras
fueron sometidas a un Análisis de Componentes Principales, para clasificarlas y
analizar las relaciones entre los caracteres utilizados comúnmente en las
clasificaciones parataxonómicas. Por otra parte se estudiaron 4264 cáscaras con
lupa binocular, 57 cáscaras con microscopio óptico y microscopio de
polarización y por último 14 cáscaras con microscopio electrónico de barrido.
Fueron identificados dos grandes grupos, cáscaras del tipo 1 afines a la
oofamilia Megaloolithidae con cinco subtipos y cáscaras del tipo 2, sin
subtipos. Los caracteres relevantes encontrados con el estudio de ACP fueron:
el espesor de la cáscara, la anchura de las unidades de cáscara, el diámetro de
los nódulos y el diámetro de las mamilas. Los diferentes tipos de cáscaras
registrados fueron comparados con diversos ootaxones de América del Sur y del
resto del mundo.
Fernández, M.S. 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. Ameghiniana 50 (1): 79-97.
Avian eggs from the Late Cretaceous of Patagonia
0 comentarios Publicado por Leonardo Filippi en 8:22
Mariela S. Fernández, Rodolfo
A. García, Lucas Fiorelli, Alejandro Scolaro, Rodrigo B. Salvador, Carlos
N. Cotaro, Gary W. Kaiser y Gareth J. Dyke
We report the
first evidence for a nesting colony of Mesozoic birds on Gondwana: a fossil
accumulation in Late Cretaceous rocks mapped and collected from within the
campus of the National University of Comahue, Neuquén City, Patagonia (Argentina).
Here, Cretaceous ornithothoracine birds, almost certainly Enanthiornithes,
nested in an arid, shallow basinal environment among sand dunes close to an
ephemeral water-course. We mapped and collected 65 complete, nearcomplete, and
broken eggs across an area of more than 55 m2. These eggs were laid either
singly, or occasionally in pairs, onto a sandy substrate. All eggs were found
apparently in, or close to, their original nest site; they all occur within the
same bedding plane and may represent the product of a single nesting season or
a short series of nesting attempts. Although there is no evidence for nesting
structures, all but one of the Comahue eggs were half-buried upright in the
sand with their pointed end downwards, a position that would have exposed the
pole containing the air cell and precluded egg turning. This egg position is
not seen in living birds, with the exception of the basal galliform megapodes
who place their eggs within mounds of vegetation or burrows. This accumulation
reveals a novel nesting behaviour in Mesozoic Aves that was perhaps shared with
the non-avian and phylogenetically more basal troodontid theropods.
Fernández MS, García RA, Fiorelli
L, Scolaro A, Salvador RB, et al. (2013) A Large Accumulation of Avian Eggs
from the Late Cretaceous of Patagonia (Argentina) Reveals a Novel Nesting
Strategy in Mesozoic Birds. PLoS ONE 8(4): e61030.
doi:10.1371/journal.pone.0061030
Morfología e histología de los osteodermo de un nuevo crocodyliforme de Rincón de los Sauces, Neuquén.
0 comentarios Publicado por Leonardo Filippi en 14:50
Filippi L. S., Cerda I. A. y Garrido, A. C.
Resumen. Se describen
osteodermos de un nuevo ejemplar de crocodyliforme hallado en un afloramiento
correspondiente a niveles de la Formación Plottier (Coniaciano tardío) de la
localidad de Puesto Hernández, en inmediaciones de la localidad de Rincón de los
Sauces, Provincia del Neuquén. Los osteodermos estudiados, que son parte del
material hallado, están integrados por: región dorso-sacra, osteodermos
apendiculares asociados al fémur derecho, región proximoventral de osteodermos
caudales articulados y osteodermos aislados. La histología de los osteodermos
permitió determinar que están constituidos por una corteza compacta que
circunda una región interna más porosa. Fue posible reconocer marcas de
crecimiento (annuli) en prácticamente todo el tejido compacto, pudiendo
determinarse una edad mínima de 18 años para el espécimen estudiado. Los
osteodermos exhiben caracteres que permiten preliminarmente asignar al ejemplar, como un Mesoeucrocodylia cercanamente relacionado con
Peirosauridae.
Abstract. Osteoderms of a new crocodyliform
specimen recovered from the Puesto Hernández locality are described here, found
in sediments of the Plottier Formation (late Coniacian), near Rincón de los
Sauces city, Neuquén Province. The studied osteoderms, that are part of the
associated material, include: dorso-sacral region, appendicular osteoderms
associated to the right femur, proximoventral region of articulated caudal
osteoderms, and isolated osteoderms. The histology of the osteoderms allowed
determining they have a compact cortex that surrounds a more cancellous
internal region. It was possible to recognize growth marks (annuli) in the
entire compact tissue, indicating a minimum age of 18 years for the studied
specimen. The osteoderms have characters that allow preliminarily assigning the
specimen to Mesoeucrocodylia closely related to Peirosauridae.
Filippi, L.S., Cerda, I.A. y Garrido, A. C.
2013 Morfología e histología de los osteodermos de un peirosauridae de la
Cuenca Neuquina. Ameghiniana 50 (1):3-13.
Early basicranial evolution and the origins of Crocodyliformes
0 comentarios Publicado por Leonardo Filippi en 15:06
Diego Pol, Oliver W. M.
Rauhut, Agustina Lecuona, Juan M. Leardi, Xing Xu and James M. Clark
Extant crocodylians
have a limited taxonomic and ecological diversity but they belong to a lineage
(Crocodylomorpha) that includes basal and rather generalized species and a
highly diverse clade, Crocodyliformes. The latter was among the most successful
groups of Mesozoic tetrapods, both in terms of taxonomic and ecological
diversity. Crocodyliforms thrived in terrestrial, semiaquatic, and marine
environments, and their fossil diversity includes carnivorous, piscivorous,
insectivorous, and herbivorous species. This remarkable ecological and trophic
diversity is thought only to occur in forms with a completely akinetic skull,
characterized by a functionally integrated and tightly sutured
braincase-quadrate-palate complex. However, the patterns of evolutionary change
that led to the highly modified skull of crocodyliforms and that likely enabled
their diversification remain poorly understood. Herein, a new basal
crocodylomorph from the Late Jurassic of Patagonia is described, Almadasuchus
figarii gen. et sp. nov. The new taxon is known from a well-preserved posterior
region of the skull as well as other craniomandibular and postcranial remains.
Almadasuchus figarii differs from all other crocodylomorphs in the presence of
six autapomorphic features, including the presence of a large lateral notch on
the upper temporal bar, an otic shelf of the squamosal that is wider than long,
a deep subtriangular concavity on the posterolateral surface of the squamosal,
and an elongated pneumatopore on the ventral surface of the quadrate.
Phylogenetic analysis focused on the origin of Crocodyliformes places
Almadasuchus as the sister group of Crocodyliformes, supported by synapomorphic
features of the skull (e.g. subtriangular basisphenoid, absence of
basipterygoid process, absence of a sagittal ridge on the frontal, and a flat
anterior skull roof with an ornamented dorsal surface). New braincase
information provided by Almadasuchus and other crocodylomorphs indicates that
most of the modifications on the posterior region of the skull of
crocodyliforms, including the strongly sutured braincase, quadrate, and the
extensive secondary palate appeared in a stepwise manner, and pre-dated the
evolutionary changes in the snout, jaws, and dentition. This indicates that the
progressively increased rigidity of the skull provided the structural framework
that allowed the great ecological diversification of crocodyliforms during the
course of the Mesozoic. The phylogenetic pattern of character acquisition
inferred for the strongly sutured (akinetic) skull and the appearance of more
diverse feeding behaviours that create high mechanical loads on the skull
provides another interesting parallel between the evolution of Mesozoic
crocodyliforms and the evolutionary origins of mammals.
Pol, D., Rauhut, O.W.M., Lecuona, A., Leardi, J. M., Xu. X. and Clark, J.M. 2013
A new fossil from the Jurassic of
Patagonia reveals the early basicranial evolution and the origins of
Crocodyliformes. Biological Reviews.
doi: 10.1111/brv.12030
Philip J. Currie y Ariana Paulina Carabajal
There were considerable
differences in Late Cretaceous faunas of the Northern and Southern Hemispheres,
although the differences were breaking down during Campanian and Maastrichtian
times with the appearance of hadrosaurids in Antarctica and South America, and titanosaurids
in North America. However, theropods continued to be separated into northern
and southern faunas until paravians were discovered in the Southern Hemisphere
(Novas and Puerta, 1997; Forster et al. 1998; Calvo et al. 2004; Makovicky et
al. 2005; Novas and Pol, 2005; Novas et al. 2008). During the 2008 field
season, a joint expedition to the Bajo de Santa Rosa (Río Negro, Argentina)
recovered a second, slightly smaller specimen of Austroraptor cabazai Novas,
Pol, Canale, Porfiri and Calvo, 2008 (Novas et al. 2008; Paulina Carabajal et
al., 2009). The specimen was identified on the basis of the morphology of the
humerus, metatarsal III and pedal phalanx IV-2 (originally identified as IV-1
in the holotype, MML 195). Although the skeleton is incomplete, it preserves
bones (radius, ulna, and elements of the metacarpus, metatarsus and pes) that
were not recovered with the holotype of this large dromaeosaurid. The
description of this second specimen is intended to complement the description
of the holotype (Novas et al., 2008), adding information about the limb
morphology, particularly the forelimb and foot of this dinosaur.
Currie, P.J. y Paulina Carabajal, A. 2012.
A new specimen of
Austroraptor cabazai Novas, Pol, Canale, Porfiri and Calvo, 2008 (Dinosauria,
Theropoda, Unenlagiidae) from the Latest Cretaceous (Maastrichtian) of Río
Negro, Ameghiniana 49(4): 662-667.
Primer registro de Pterosauria en la Fm. Bajo Barreal, Patagonia central, Argentina
0 comentarios Publicado por Leonardo Filippi en 8:25
The fossil record of
pterosaurs is relatively abundant in South America. Remains of this group have
been primarily found in Early Cretaceous rocks exposed in two different areas, i.e.,
in Northeastern Brazil (Kellner and Tomida, 2000) and in San Luis Province,
Central Argentina (Bonaparte, 1970). Excepting the records in Neuquén Province,
the fossil record of pterosaurs in Patagonia (i.e., Golfo San Jorge and Austral
basins) is poor and incomplete (Codorniú and Gasparini, 2007). Continental
deposits of the Bajo Barreal Formation (Cenomanian–Turonian) exposed in Central
Patagonia, Argentina (Golfo San Jorge Basin), preserve an important record of
South American Late Cretaceous vertebrates, particularly dinosaurs (Martínez
et al., 2004; Martínez and Novas, 2006; Casal et al., 2007; Ibiricu et al.,
2010). This record has been significantly increased over the past decade. The
best known assemblages from Bajo Barreal come from the localities known as
Estancia Ocho Hermanos and Estancia Laguna Palacios. Herein we report recently
identified pterosaur material from rocks of the Bajo Barreal Formation exposed
at Estancia Ocho Hermanos and discuss the implications of this material for the
Patagonian fossil record of Pterosauria. The fossil is significant because it
adds to the generally sparse global record of Cretaceous (especially Late
Cretaceous) pterosaurs and constitutes the second most southern occurrence of Pterosauria
worldwide. This material confirms the presence of pterosaurs in the Bajo
Barreal Formation, increasing the number of taxa in the known fossil fauna from
this unit and thus our knowledge of the early Late Cretaceous vertebrate assemblages
of Central Patagonia.
Ibicuru,L. M., Martínez, R. D. y Casal, G. A. 2012. The first record of
Pterosauria in the Bajo Barreal Formation (Upper Cretaceous), central
Patagonia, Argentina. Ameghiniana 49(4): 657-661
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