Redescription of Bonatitan reigi, Sauropoda Titanosauria from Rio Negro, Argentina
0 comentarios Publicado por Leonardo Filippi en 15:15
L.
Salgadoa, P.A. Gallina and A. Paulina Carabajal
The titanosaur sauropod
Bonatitan reigi is redescribed. The material collected, originally interpreted
as pertaining to two different individuals, is reorganised in five individuals,
and the original type specimen is separated into three different individuals.
One of the braincases is designated as a new type specimen. Some materials are
described by the first time (sacral ribs, distal caudal, chevrons, metacarpals,
astragalus and metatarsals), others reinterpreted as different bones (‘ulna’
and ‘radius’). The diagnosis of B. reigi is emended, removing some of the
original characters (longitudinal groove located on the suture between the
parietals that continues posteriorly over the supraoccipital to the foramen
magnum) and adding some new (small paired pits on the frontals and posterior
ridge of the metacarpal IV). The phylogenetic analysis does not support B.
reigi as a member of the Saltasaurinae, but rather as a basal member of a broad
clade of sauropods that in turn is recovered as the sister group of the
Saltasauridae.
L. Salgado, P.A.
Gallina & A. Paulina Carabajal (2014): Redescription of Bonatitan reigi (Sauropoda: Titanosauria),
from the Campanian–Maastrichtian of the Río Negro Province (Argentina), Historical
Biology: An International Journal of Paleobiology, DOI:
10.1080/08912963.2014.894038
Osteology of the Middle Triassic archosaur Lewisuchus admixtus Romer, Chañares Formation, Argentina
0 comentarios Publicado por Leonardo Filippi en 8:14
Jonathas S. Bittencourt, Andrea B.
Arcucci, Claudia A. Marsicano and Max C. Langer
Lewisuchus admixtus is an enigmatic
early dinosauriform from the Chañares Formation, Ladinian of Argentina, which
has been recently considered a member of Silesauridae. Yet, it differs markedly
from Late Triassic silesaurids in dental and vertebral anatomy. Indeed, a
detailed redescription of its holotype allowed the identification of several
features of the skeleton previously unrecognized amongst silesaurids. These
include pterygoid teeth, a dorsomedial posttemporal opening on the otoccipital,
foramina associated with cranial nerves X–XII on the caudal region of the
prootic–otoccipital, and postaxial neck/trunk vertebrae with craniocaudally
expanded neural spines. The presence of a single row of presacral scutes was
also confirmed. Some elements previously referred to, or found associated with,
the holotype, including a lower jaw, pedal elements and an astragalus, more
probably correspond to proterochampsid remains. The anatomical information
available for the holotype of L. admixtus
was rescored into a new phylogenetic dataset for dinosauromorphs, mostly
based on previous works. Lewisuchus
admixtus and Pseudolagosuchus major
are treated as distinct OTUs because their preserved skeletons mostly lack
overlapping parts. The parsimony analysis supports the basal position of L. admixtus within dinosauriforms, prior
to the silesaurid–dinosaur split, rather than at the base of Silesauridae. This
suggests that a higher number of early dinosauriform clades branched in the
Middle and Late Triassic than previously suggested.
Jonathas S. Bittencourt, Andrea
B. Arcucci, Claudia A. Marsicano & Max C. Langer (2014): Osteology of the
Middle Triassic archosaur Lewisuchus admixtus Romer (Chañares Formation,
Argentina), its inclusivity, and relationships amongst early dinosauromorphs,
Journal of Systematic Palaeontology, DOI: 10.1080/14772019.2013.878758
The caudal vertebral series in abelisaurid dinosaurs
0 comentarios Publicado por Leonardo Filippi en 5:18
Ariel H. Méndez
The caudal
vertebrae of abelisaurid theropods show notable variations in the shape of the
transverse process, among other characters, and these distinguish the two
subclases Brachyrostra and Carnotaurini. The vertebrae in the proximal third of
the tail in abelisaurids, especially derived taxa, show adaptations that
provide considerable rigidity, when compared to other theropod dinosaurs,
especially Maniraptora, which have highly flexible tails. This continues the
considerable rigidity in the neck, trunk, and sacral region in abelisaurids,
and is consistent with the hypothesis that South American abelisaurids evolved
in isolation from those that inhabited India and Madagascar.
Parataxonomic review of the Upper Cretaceous dinosaur eggshells
1 comentarios Publicado por Leonardo Filippi en 14:03
Mariela
S. Fernández and Ashu Khosla
The eggshell
oospecies from India and Argentina are compared and reviewed in detail. These
eggshells resemble each other in having a nodular outer surface ornamentation
and clearly arched growth lines of the shell units. Microstructurally, the eggshell
oospecies belonging to the oofamily Megaloolithidae shows fan-like shell units,
which are sharply separated from each other throughout the thickness of the
eggshell and can be traced up to the surface of the eggshell. Comparisons
between four oospecies from India and Argentina reveal three groupings, which
show similarities between megaloolithids of both countries: (1) Megaloolithus
jabalpurensis, M. matleyi and M. patagonicus; (2) M. cylindricus, M.
rahioliensis and Tipo 1d; and (3) M. megadermus and Tipo 1e. The other two
types of eggshell oospecies from India and Argentina show partially fused
external nodes and shell units. As a result, growth lines enter into the
adjacent shell units with a marked concavity. A new oogenus Fusioolithus have
been erected due to fusion between shell units and tubospherulitic morphotype,
which include two new oospecies F. baghensis and F. berthei. Till date,
morphostructurally, a total of 15 eggshell oospecies belonging to different
oofamilies have been recorded from India and seven oospecies from Argentina.
Mariela S.
Fernández & Ashu Khosla, Historical Biology (2014): Parataxonomic review of
the Upper Cretaceous dinosaur eggshells belonging to the oofamily
Megaloolithidae from India and Argentina, Historical Biology: An International
Journal of Paleobiology, DOI: 10.1080/08912963.2013.871718.
A new titanosaur from Neuquén Basin of Mendoza Province
0 comentarios Publicado por Leonardo Filippi en 12:23
Bernardo
González Riga y Leonardo Ortíz David
Quetecsaurus
rusconii gen. et sp. nov. is a new titanosaur (Dinosauria,
Sauropoda) from the Neuquén Basin of Mendoza Province, Argentina. The specimen
comes from red mudstones of the Cerro Lisandro Formation (middle-late Turonian,
Upper Cretaceous), and is the first sauropod with well-preserved remains to be
discovered in this formation. The holotype includes a postorbital, teeth, the
atlas, a posterior cervical vertebra, an incomplete dorsal vertebra, a
posterior caudal centrum, dorsal ribs, a coracoid, fragments of a humerus,
radius and ulna, and five metacarpals. It is characterized by the following
combination of autapomorphies: (1) intercentrum of atlas with a prominent anteroventral
border and expanded posteroventral processes; (2) posterior cervical neural
spines with incipient lateral expansions; and (3) humerus with strongly sigmoid
proximal border, rounded proximomedial border, and angular proximolateral
corner. A preliminary cladistic analysis placed Quetecsaurus as a sister taxon
of Lognkosauria (Mendozasaurus + Futalognkosaurus). Quetecsaurus shares with
the lognkosaurs the presence of cervical neural spines with ‘lateral laminae’,
but relatively reduced in comparison with those taxa. This discovery provides
new information on the diagnosis of Lognkosauria within South American
titanosaurs.
González Riga, B. y
Ortíz David, L. 2014.A New titanosaur (Dinosauria, Sauropoda) from the Upper
Cretaceous (Cerro Lisandro Formation) of Mendoza Province, Argentina.
Ameghiniana 51(1):3-25.
Tafonomía del sitio de nidificación de Neosaurópodos de Sanagasta La Rioja, Argentina
0 comentarios Publicado por Leonardo Filippi en 3:36
Lucas
Ernesto Fiorelli, Gerald Grellet-Tinner, Eloisa Argañaraz y Leonardo Salgado
El sitio de
nidificación de Sanagasta (Cretácico), La Rioja, Argentina, resolvió aspectos
sobre la reproducción de los neosaurópodos, evidenciando comportamientos
coloniales, filopatría, y su reproducción oportunista dependiente de su
paleoambiente termal. Aquí describimos la tafonomía del sitio determinando sus
patrones bioestratinómicos y diagenéticos. El agrupamiento oológico 3D está
bien preservado, sugiriendo asociaciones autóctonas representadas por
oviposiciones in situ, sin estructura de nido. El nivel portador
presenta una biofábrica matriz-soportada y una clasificación genética de
acumulación biogénica “intrínseca”; esto implica comportamiento gregario y colonización
preferencial del sitio. La biocenosis corresponde a la producción biogénica
(huevos), con la cáscara diagenizada por hidrotermalismo y microorganismos
extremófilos. La tanatocenosis y el tiempo promedio fueron nulos por el
inmediato enterramiento de los huevos luego de la oviposición indicando que no
existió una etapa bioestratinómica. La tafocenosis representa el carácter
tafonómico más significativo. Las cáscaras presentan alteraciones por
soluciones hidrotermales, mientras la recalcificación y silicificación
representan las mineralizaciones más frecuentes. La presencia de microchert,
calcedonia, microesferas de ópalo-A, agregados de epidoto y minerales de
arcilla reemplazando sectores de la cáscara y las membranas del huevo,
confirman una alteración hidrotermal bajo condiciones excepcionales. La
presencia de microorganismos fósiles (estromatolitos, cianobacterias y
diatomeas), numerosas macro-estructuras, microfacies y microfábricas
hidrotermales, y los atributos tafonómicos oológicos, sugiere que el sitio de
nidificación de Sanagasta representa un particular ejemplo de tafocenosis y un Lagerstätte.
El sitio de nidificación de neosaurópodos de Sanagasta es el primer caso fósil
documentado sobre la reproducción de un grupo de
dinosaurios dependiente de su ambiente.
Fiorelli, L. E., Grellet-Tinner, G., Argañaraz, E. y
Salgado, L. 2013. Tafonomía
del sitio de nidificación de Neosaurópodos de Sanagasta (La Rioja, Argentina):
Ejemplo de preservación excepcional en un paleoambiente hidrotermal del
Cretácico. Ameghiniana 50 (4): 389 – 406.
Silvina
de Valais, Sebastián Apesteguía, Alberto C. Garrido
Ecological
relationships among fossil vertebrate groups are interpreted based on evidence
of modification features and paleopathologies on fossil bones. Here we describe
an ichnological assemblage composed of trace fossils on reptile bones, mainly
sphenodontids, crocodyliforms and maniraptoran theropods. They all come from La
Buitrera, an early Late Cretaceous locality in the Candeleros Formation of
northwestern Patagonia, Argentina. This locality is significant because of the
abundance of small to medium-sized vertebrates. The abundant ichnological
record includes traces on bones, most of them attributable to tetrapods. These
latter traces include tooth marks that provide evidence of feeding activities
made during the sub-aerial exposure of tetrapod carcasses. Other traces are
attributable to arthropods or roots. The totality of evidence provides an
uncommon insight into paleoecological aspects of a Late Cretaceous southern
ecosystem.
de Valais S, Apesteguía S,
Garrido AC (2012) Cretaceous Small Scavengers: Feeding Traces in Tetrapod Bones
from Patagonia, Argentina. PLoS ONE 7(1): e29841. doi:10.1371/journal.pone.0029841
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