En
la Antártida, paleontólogos argentinos descubrieron fósiles de un pingüino de
unos 2 metros de altura, el más grande encontrado hasta el momento, con una
antigüedad de 34 millones de años. La paleontóloga Carolina Acosta,
investigadora del Museo de La Plata, explicó que "los cálculos realizados
indican que se trata del pingüino más grande que se conoce hasta el momento, en
cuanto a altura y masa corporal". En la actualidad, la especie de mayor tamaño es el Pingüino
emperador, que alcanza los 1,20 metros. El descubrimiento, realizado por
Marcelo Reguero, director de la campaña paleontológica del Instituto Antártico
Argentino, fue posible debido al hallazgo, por primera vez en la Antártida, de
un esqueleto articulado del animal, lo que permitió obtener mayor información
sobre su anatomía y cómo se movía. Los restos permitieron a Acosta reconstruir
parte de la musculatura del pingüino gigante, que "debía emplear más
fuerza para impulsarse en el agua y tenía una musculatura más desarrollada".
La reconstrucción no proporcionó elementos para definir a qué género perteneció
el pingüino gigante, aunque la especialista adelantó que el objetivo de la
campaña antártica del próximo verano será "buscar nuevos esqueletos"
para continuar con la investigación.
Fuente:
colectivosalas.blogspot.com.ar
Aerotitan el mas grande de los pterosaurios Sudamericanos
0 comentarios Publicado por Leonardo Filippi en 6:55
Fernando
E. Novas, Martin Kundrat, Federico L. Agnolín,
Martín D. Ezcurra, Per Erik Ahlberg, Marcelo P. Isasi, Alberto Arriagada, y Pablo Chafrat
Here, we expand the meager record
of Late Cretaceous South American pterosaurs with the description of a partial
rostrum belonging to a large azhdarchid pterodactyloid. The specimen was collected
close to the Bajo de Arriagada locality, corresponding to the uppermost
Cretaceous Allen Formation of Argentina, around 80 km northwest of the
well-sampled Bajo de Santa Rosa locality (Martinelli and Forasiepi, 2004). The Azhdarchidae were the most abundant pterosaurs during latest Cretaceous
times (Company et al., 1999; Butler et al., 2009). This clade comprises several
species of long-necked pterosaurs ranging from 2.5 to 10 m in wing span, thus
including the largest known flying vertebrates, such as the gigantic
Quetzalcoatlus and Hatzegopteryx (Kellner and Langston, 1996; Buffetaut et al.,
2002; Witton and Naish, 2008; Witton and Habib, 2010). Azhdarchid remains have been
documented from almost all continental landmasses, includ-ing Europe, North
America, Africa, Asia, and probably Oceania (Bennett and Long, 1991; Company et
al., 1999; Averianov et al., 2005; Barrett et al., 2008; Kear et al., 2010;
˝Osi et al., 2011). In South America, probable azhdarchid remains consist of a
fragmentary postcranial skeleton from the Aptian of Brazil (Martill and Frey,
1998, 1999) and partial long bones from the Turonian–Coniacian of Argentina (Kellner
et al., 2006; Codorniú and Gasparini, 2007). However, recent reassessments of
this material suggested that the Brazilian specimen is more closely related to
tapejarids than to azhdarchids and that the Argentinean records are dubious
(Kellner, 2004; Kellner et al., 2006; Unwin and Martill, 2007). As a result,
the specimen reported here represents the first unambiguous evidence of an
azhdarchid pterosaur from South America. This specimen represents a new genus
and species, Aerotitan sudamericanus, which is diagnosed based on a unique
combination of characters, including one autapomorphy, and represents one of the
largest known South American pterosaurs. The fossil here described resulted
from a joint Argentine-Swedish paleontological expedition to Patagonia.
Novas, F. E., Kundrat, M., Agnolín, F. L., Ezcurra, M. D., Ahlberg, P. E., Isasi, M. P., Arriagada, A. y Chafrat, P. 2012.
A New Large
Pterosaur From The Late Cretaceous Of Patagonia.
Journal
of Vertebrate Paleontology 32(6):1447–1452
Dinosaur tracksites in Early Cretaceous deposits in Patagonia
0 comentarios Publicado por Leonardo Filippi en 17:46
P.J. Pazos, D. G. Lazo, M. A. Tunik, C. A. Marsicano, D.E. Fernández, M. B. Aguierre-Urreta
The study of the
uppermost section of the Early Cretaceous Agrio
Formation in northern Patagonia (Neuquén Basin)
where dinosaur tracks assigned to cf. Therangospodus pandemicus are exposed
(tracksites I and II) evidence mixed marginal marine siliciclastic-carbonate
deposits. The succession was divided in two intervals. A lower one containing
theropod tracks, recorded on top of subtidal oolithic limestones with tiny wave
ripples suggesting shoreline fluctuations and subaerial exposure. Tidal influence
is recognised by fining upward and prograding cycles starting with subtidal
carbonates and ending with fine-grained siliciclastic deposits at the top, or rarely
laminites. Dolomitization affects subtidal deposits generated in an alkaline
media stressful for tracemakers. Intertidal facies include abundant
heterolithic deposits, coquinas composed of gastropods encrusted by
multilayered bryozoans and muddy levels with incipient mud cracking.
Invertebrate ichnofossils recognized from tidally dominated deposits include Arenicolites, Kouphichnium, and Rhizocorallium. The upper interval is a transgressive–regressive
cycle that starts with dark shales, deficiently oxygenated, and covered by
prograding sandstones and finally sand flat deposits. This interval contains Gyrochorte, Hillichnus, and Ophiomorpha
documented in wave-influenced sandstones. Dinosaur tracks as well as Hillichnus, attributed to tellinoid
bivalves, and Kouphichnium assigned to
xiphosurans, imply the activity of producers rarely recorded previously as body
fossils in marginal marine deposits of southern South America. Previous
paleogeographic schemes are questioned by our analysis, which shows evidence of
extremely shallow and tide-controlled sedimentation, sometimes with subaerial
exposure, with high cyclicity related to a marginal marine depositional setting
and lack of significant erosion by the overlying unit, as traditionally was
suggested.
P.J. Pazos, D. G. Lazo, M. A. Tunik, C. A. Marsicano, D.E. Fernández, M. B. Aguirre-Urreta 2012.Paleoenvironmental framework of dinosaur tracksites and other ichnofossils in Early Cretaceous mixed siliciclastic-carbonate deposits in the Neuquén Basin, northern Patagonia (Argentina).Gondwana Research 22: 1125-1140.
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