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28th Argentine Congress of Vertebrate Paleontology abstracts and other Argentine items



Ben Creisler
bcreisler@gmail.com

This posting is mainly about dinosaur and related finds in Argentina.
Again, apologies for typing "Western Hemisphere" instead of "Southern
Hemisphere" (what I intended to type) in the last news posting. Force
of habit I guess....


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More information on the discovery of pterosaur fossils from the
Triassic in San Juan Province in Argentina. This article appeared in a
university magazine [Revista La Universidad] for Universidad Nacional
de San Juan back in June it seems (I missed it then). It indicates the
discovery of a new fossil site thought to be Norian in age (215 to 220
million years old). The pterosaurs are the oldest known from the
Southern Hemisphere (some fossils in Brazil thought to be from
Triassic pterosaurs have been questioned). Of particular interest is
that the pterosaurs were found in a continental context--other
Triassic pterosaurs from Europe are in marine deposits.  Other remains
include crocodile-like animals, turtles, synapsids, and sauropodomorph
dinosaurs. Basal dinosaurs were also found, although the article
refers to "of the euroraptor type, which lived in Ischisgualasto" so I
assume they meant "Eoraptor type" instead.

http://www.revista.unsj.edu.ar/?p=811


*****

Abstracts from  XXVIII Jornadas Argentinas de Paleontología de
Vertebrados (28th Argentine Congress of Vertebrate Paleontology) from
May 2014

http://www.28japv.com.ar/resumenes_28japv.pdf

A number of dinosaur discoveries are mentioned in both English and
Spanish, including the following abstracts in English:


NEW SPECIMEN OF VELOCISAURUS UNICUS (THEROPODA, ABELISAUROIDEA) FROM
THE PASO CÓRDOVA LOCALITY (SANTONIAN), RÍO NEGRO

F. BRISSÓN EGLI, F.L. AGNOLÍN and F.E. NOVAS

Abelisauroids are the most diverse and abundant theropods of Gondwana.
They include the medium to large sized Abelisauridae, and a wide array
of smaller taxa mainly included in Noasauridae. Velocisaurus unicus
Bonaparte, 1991 is a small abelisauroid theropod from the Bajo de la
Carpa formation. The holotype and only known specimen is represented
by an incomplete hind limb with peculiar morphology. Here we describe
a of Velocisaurus (MPCN-PV-370) that includes a partial left hind limb
and offers new information about this poorly known species. The
specimen comes from Paso Córdova, Río Negro Province, from the same
beds bearing the holotype material. The femur is short and strongly
bowed anteriorly, and has a remarkably triangular cross-section. The
tibia is coelurosaur-like, being long and slender. It distal end is
anteriorly flat and has a large surface to accommodate a tall and wide
ascending process of the astragalus. The metatarsals are
“antarctometatarsal” with rod-like outer metatarsals, thus differing
from Noasaurus and Masiakasaurus, which have laminar metatarsals II
and IV. Phalanx IV-1 is short and medially curved, a feature also
present in some indeterminate Indian abelisauroids. The proximal
articular surface is undivided and remarkably deep, a feature unknown
in other theropods. The ungual phalanx shows the typical abelisauroid
morphology. The new material differs from the holotype in its
robustness, having pronunced muscular and ligament attachments.
Presence of “gracile” and “robust” morphs is also reported in
Masiakasaurus and coelophysoids. The morphology of Velocisaurus
indicates an adaptive type that is not matched by any known
abelisauroid.

*****
A NEW SAUROPOD DINOSAUR FROM THE EARLY CRETACEOUS OF COLOMBIA AND THE
YOUNGEST BRACHIOSAURID RECORD FOR GONDWANA

J.L. CARBALLIDO, D. POL, M.E. PÁRAMO-FONSECA, F. ETAYO-SERNA, M.L.
PARRA RUGE, and S. PADILLA BERNAL

Brachiosaurid sauropods first appeared during the Late Jurassic and
achieved a broad distribution during that time. Nevertheless, their
Cretaceous record was restricted to the Aptian-Albian of North
America, possibly reflecting differential extinction. Here we present
a new titanosauriform dinosaur from Colombia, including caudal
vertebrae that indicate brachiosaurid affinities. The specimen was
recovered from the middle member of the marine Paja Formation
(Barremian), close to locality of Villa de Leiva, Colombia and is
currently housed in the Junta de Acción Comunal Vereda Monquira Museum
(JACVM 0001). The new sauropod is represented by an isolated posterior
dorsal centrum, partially preserved sacrum, and the first eight caudal
vertebrae preserved in articulation. The combination of several
characters indicate the basal titanosauriform affinities of the
specimen, which include: opisthocoelous dorsal centrum with large
pleurocoels that opens into a polycamerate system and presence of
accessory posterior centrodiapophyseal lamina;
platycoelous/distoplatyan anterior caudal vertebrae with anteriorly
placed neural arches, long centroprezygapophyseal laminae, and
posteriorly directed transverse processes with a ventral bulge on
them. Among titanosauriforms, the presence of ablind fossa in anterior
caudal vertebrae is a character solely present in Giraffatitan,
Venenosaurus, Cedarosaurus and Abydosaurus, indicating the
brachiosaurid affinities of this sauropod. The weakly laterally
expanded and divided transverse processes of the anteriormost caudal
vertebrae allow the recognition of a new sauropod species. Although
more evidence is needed to test more thoroughly the brachiosaurid
affinities of this new taxon, available evidence indicates this clade
could have survived at lower latitudes of Gondwana into the Early
Cretaceous.
***

A NEW DERIVED ABELISAURID TAXON FROM THE BAJO DE LA CARPA FORMATION,
LATE CRETACEOUS OF THE NEUQUÉN BASIN, NEUQUÉN

L.S. FILIPPI, R.D. JUAREZ VALIERI & C.A. GARRIDO

We report a new abelisaurid theropod specimen, which represent the
most complete abelisaurid theropod skeleton yet reported from the Bajo
de La Carpa Formation. It comes from the La Invernada area, located 50
kilometers south from Rincón de los Sauces, Neuquén Province. The
partially excavated material is well preserved and display scarce
signs of deformation. The pieces recovered comprises a partial skull
with complete basicranium, both frontals, postorbitals and squamosals,
four cervical vertebrae including atlas, eight dorsals and eigth
caudals, cervical and dorsal ribs, an haemal arch, and indeterminate
pieces. The frontals are flat, opposite to the condition present in
Abelisaurus, Aucasaurus and Carnotaurus. The postorbitals present
slightly convex and ornamented dorsal margins, in contrast to
Ekrixinatosaurus and Skorpiovenator. The jugal process of the
postorbitals is anteriorly recurved thus enclosing the orbit, a
character proposed as autapomorphic of Brachyrostra. The cervical
vertebrae show anterior processes on the epipophysis and reduced
neural spines as in Carnotaurus. The anterior and middle caudal
vertebrae are tipical of derived abelisaurids, with strong
centrodiapophyseal laminae and with laterodorsally projected and
distally expanded transverse processes. Is evident the presence of
hyposphene-hypantrum in the anterior caudals as in Aucasaurus and
Carnotaurus, but it appear absent in the preserved middle caudals,
similar to Ilokelesia. This new specimen is relevant both anatomically
and phylogenetically, contributing to the knowledge of the abelisaurid
theropods, and increasing the diversity of the Cretaceous vertebrates
from the Bajo de la Carpa Formation.

*****

THE SAUROPOD FAUNA OF THE BAJADA COLORADA FORMATION
(BERRIASIAN-VALANGINIAN), NEUQUÉN PROVINCE, ARGENTINA

P. A. GALLINA, S. APESTEGUÍA, A. HALUZA, J. I. CANALE and A. OTERO

The terrestrial tetrapod record of the lowermost Cretaceous
(pre-Barremian) of South America is quite scarce, biased both by a
reduced area of outcrops (restricted to southeastern Neuquén Basin)
and a lack of systematic exploration on it. Successive fieldworks
carried out since 2010 in Bajada Colorada locality, near Picún Leufú
town, Neuquén, Argentina, allowed the recognition of a rich dinosaur
fauna that include sauropod and theropod representatives. The
sauropods are well-represented by abundant skeletal remains of two
specimens: a diplodocid and a dicraeosaurid, as well as several teeth.
On one hand, the diplodocid remains (MMCH-Pv 63-1/8), which include
three cervical, one dorsal and four caudal vertebrae represent the
first Diplodocidae in South America, and the youngest record of the
clade anywhere. On the other hand, the dicraeosaurid specimen includes
not only partially articulated vertebral elements but a slightly
disarticuled skull. The latter is composed by the skull roof and
braincase, left postorbital, left squamosal, left jugal, left
quadratojugal, the edentulous part of the left maxilla and the nearly
complete lower jaw with more than twenty teeth in position. All these
new records will substantially contribute to a better understanding of
the early evolution and diversification of the dinosaur faunas,
providing for the first time a link between the Jurassic fauna of
Chubut Province and the quite well-known post-Barremian faunal
assemblages from southern continents. In addition, these new findings
augment the list of sauropod clades in southern South America, thus
turning this area into an extremely rich portrait of sauropod
evolution.
****
NEW SAUROPOD REMAINS FROM THE LATE CRETACEOUS OF LOS LLANOS FORMATION,
LA RIOJA, ARGENTINA

E.M. HECHENLEITNER, L.E. FIORELLI and G. GRELLET-TINNER

To date, the fossil record of Cretaceous sauropod dinosaurs in La
Rioja Province (Argentina) is from the Cienaga del Río Huaco and Los
Llanos formations. Recent field works conducted by the Geosciences
Group from CRILAR in the exposures of the Los Llanos Formation,
located near the village of Tama (Dpto. V.A. Peñaloza) led to the
discovery of new titanosaur poscraneal materials. The partially
remains were discovered in the lower levels of the Upper Member of
this formation. The skeletal material consists of axial (a dorsal
vertebra, at least 8 caudal vertebrae, and several ribs) and
appendicular elements (a humerus, ulna, ilium, pubis and at least 3
femora) from several individuals of different age groups. These
remains are found mostly disarticulated (excluding the caudal
vertebrae) displaying various diagenetic and taphonomic grades (e.g.,
recrystalization, biogenic alteration, and weathering). The best
preserved material exhibits features typically known for titanosaurs,
such as an ubiquitous pleurocoel in the first dorsal vertebra, and
procoelous caudal vertebrae. In addition, other squeletal elements are
remarkably similar to those from derived titanosaur genera, namely
Rapetosaurus, Bonitasaura and Mendozasaurus. This new record, coupled
with the recent discovery of an Upper Cretaceous microfossils
association and cranial material of a notosuchian crocodyliform,
strengthens previous interpretations of a Late Cretaceous age for the
Los Llanos Formation. Finally, given the significant paleolatitudinal
distinction between the Los Llanos fauna and those of Brazil and
Patagonia, these new fossils are pivotal for the understanding of the
paleobiogeographical relationships of the South American titanosaurs.

*****

REINTERPRETATION OF THE ROSTRAL SKULL SHAPE OF MALAWISAURUS DIXEYI
(HAUGHTON, 1928) (SAUROPODA, TITANOSAURIA)

R. JUÁREZ VALIERI and  S.D. RÍOS DÍAZ

Among titanosaur sauropods, only a few species are known from skull
remains, with the snout and rostrum being especially poorly
represented in the fossil record. Among then, cranial remains were
reported for Malawisaurus dixeyi (Haughton, 1928) from the Early
Cretaceous (Aptian) of Africa, and a structure reminiscent of basal
macronarians was proposed for its rostrum. Here we reinterpret the
identification of some of the cranial bones, and discuss their
significance. The principal subject is the assignment of the supposed
vertical jugal as an inverted structure comprising most of the jugal
with the maxillary and lacrimal process articulated with the complete
lacrimal. The morphology of the jugal proposed here implies the
presence of a long and thin articulation facet for the maxilla, which
obligatory has to display a long jugal process separate from the
principal body, as present in Rapetosaurus and Tapuiasaurus, and could
be considered a derived character respect to the morphology of
Nemegtosaurus, Giraffatitan and other basal titanosauriforms. The
lacrimal present a foramen as in other titanosaurians and a
dorsoanterior projection for the articulation with the maxilla, which
is strongly developed as in Rapetosaurus and Bonitasaura. The lacrimal
is constricted in the point of contact with the jugal, a character
only present in Rapetosaurus. The resulting skull shape represent a
clearly differs from the original reconstruction of the Malawisaurus
skull, with an extensive anteroposterior maxillojugal articulation
developing a long snouted rostrum, suggesting a derived morphology
similar to other gondwanan titanosaurians.

****
FIRST BIOMECHANICAL ANALYSIS ON THE SKULL OF THE ORNITHOSUCHID
RIOJASUCHUS TENUISCEPS BONAPARTE 1967 FROM THE LOS COLORADOS
FORMATION, LATE TRIASSIC OF ARGENTINA

M.B. von BACZKO, J.R.A. TABORDA and J.B. DESOJO

Riojasuchus tenuisceps Bonaparte 1967 is a terrestrial quadrupedal
archosaur from the Late Triassic. It has a triangular-shaped skull
with a ventrally curved snout, and posteriorly curved serrated teeth.
Although it has been assumed that ornithosuchids had animalivorous
feeding habits based on morphological features, no functional study
has been carried out to test its type of animalivory (carnivorous or
scavenging). R. tenuisceps has a very well anteroventrally expanded
and laterally constricted snout; the holotype (PVL 3827) comprises a
complete skull that allowed us to study the problematic of its feeding
habits. We developed a virtual 3D model of the skull of the holotype
using CT scan, and generated a Finite Elements Model of it, applying
anteroposterior and lateral forces on the weird snout of R.
tenuisceps, simulating some basic efforts during its feeding. We
tested the response of the modeled skull using Finite Elements
Analysis, obtaining that the snout of R. tenuisceps had a high
resistance to anteroposterior dragging (around 75kg), but when
applying lateral forces to the snout it was much weaker and would
endure approximately 25kg. Considering the resistance of this
structure, we propose that R. tenuisceps could have been carnivorous,
hunting small to medium size live preys, and even drag larger
carcasses. We conclude that R. tenuisceps could have had both
carnivore and scavenging habits depending on the size of the chosen
prey, needing a different strategy to overthrow its larger victims
avoiding strong lateral stresses that may occur when a prey tries to
escape.
*****

CARCHARODONTOSAURID TEETH ASSOCIATED WITH TITANOSAUR CARCASSES FROM
THE EARLY CRETACEOUS (ALBIAN) OF THE CHUBUT GROUP, CHUBUT PROVINCE,
PATAGONIA, ARGENTINA

J.I. CANALE, J.L CARBALLIDO, A. OTERO, J.I. CANUDO and A. GARRIDO

The finding of theropod teeth together with sauropod carcasses has
been often documented, but usually with equivocal information
regarding prey/predator preferences due the lack of accurate taxonomic
and taphonomic determinations. This study reports the finding of 57
theropod teeth associated with at least six titanosaur disarticulated
carcasses, all from the same locality of the Cerro Barcino Formation
(Albian). Fifty-five teeth can be assigned to the
Carcharodontosauridae, based on their large size, not recurved crowns,
strong enamel wrinkles, mesial carina terminating well beneath the
cervix and sigmoid distal carinae. Carcharodontosaurids are
represented in this unit by Tyrannotitan chubutensis, which has almost
identical teeth to those here described. The remaining two teeth can
be assigned to Abelisauridae? (not recurved crown, hooked distal
denticles) and Dromaeosauridae? (strongly recurved crown, absence of
mesial denticles, base outline 8-shaped) respectively. Moreover, the
carcharodontosaurid teeth present the following peculiarities: about
90% belong to the rostral sector of the skull (suggested by the
displacement of both carinae), they are only represented by the crown,
and have wear facets at the tip of the mesial carinae. Such evidence
suggests some kind of predation/scavenging behaviour, in which the
predator might lose their anterior teeth by scratching meat from the
titanosaur bones. Also, given the slow energy paleonvironment inferred
for the locality, and the huge-sized bones (some of them surpassing
widely 2 meters long) we postulate that part of the disarticulation of
the carcasses could be done by the carcharodontosaurids while feeding
on them.

****
OTHER ITEMS


New issue of Ameghiniana 51(4) is out:

http://www.ameghiniana.org.ar/index.php/ameghiniana

Pliosaurus patagonicus is now valid.

********
New July issues of Paleo

Paleo, Revista de Paleontología numbers 105, 106, 107, 108 - Julio de
2014 are now available for free downloads as pdfs. The text is in
Spanish, written for a more general reader.  Lots of dinosaur-related
news.


http://www.grupopaleo.com.ar/paleoboletin/principal.htm



http://www.grupopaleo.com.ar/web/descargas/paleorevista105.pdf
http://www.grupopaleo.com.ar/web/descargas/paleorevista106.pdf
http://www.grupopaleo.com.ar/web/descargas/paleorevista107.pdf
http://www.grupopaleo.com.ar/web/descargas/paleorevista108.pdf

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