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Tachiraptor, new theropod from Venezuela + Jurassic sauropod diets (free pdfs)

Ben Creisler

Here are the links and abstracts. Both papers  are in open access.

Max C. Langer, Ascanio D. Rincón, Jahandar Ramezani, Andrés Solórzano
& Oliver W. M. Rauhut (2014)
New dinosaur (Theropoda, stem-Averostra) from the earliest Jurassic of
the La Quinta formation, Venezuelan Andes.
Royal Society Open Access Science 1: 140184
DOI: 10.1098/rsos.140184

Dinosaur skeletal remains are almost unknown from northern South
America. One of the few exceptions comes from a small outcrop in the
northernmost extension of the Andes, along the western border of
Venezuela, where strata of the La Quinta Formation have yielded the
ornithischian Laquintasaura venezuelae and other dinosaur remains.
Here, we report isolated bones (ischium and tibia) of a small new
theropod, Tachiraptor admirabilis gen. et sp. nov., which differs from
all previously known members of the group by an unique suite of
features of its tibial articulations. Comparative/phylogenetic studies
place the new form as the sister taxon to Averostra, a theropod group
that is known primarily from the Middle Jurassic onwards. A new U–Pb
zircon date (isotope dilution thermal-ionization mass spectrometry;
ID-TIMS method) from the bone bed matrix suggests an earliest Jurassic
maximum age for the La Quinta Formation. A dispersal–vicariance
analysis suggests that such a stratigraphic gap is more likely to be
filled by new records from north and central Pangaea than from
southern areas. Indeed, our data show that the sampled summer-wet
equatorial belt, which yielded the new taxon, played a pivotal role in
theropod evolution across the Triassic–Jurassic boundary.


David J. Button, Emily J. Rayfield, and Paul M. Barrett (2014)
Cranial biomechanics underpins high sauropod diversity in
resource-poor environments.
Proceedings of the Royal Society B 281(1795) 20142114
doi: 10.1098/rspb.2014.2114

High megaherbivore species richness is documented in both fossil and
contemporary ecosystems despite their high individual energy
requirements. An extreme example of this is the Late Jurassic Morrison
Formation, which was dominated by sauropod dinosaurs, the largest
known terrestrial vertebrates. High sauropod diversity within the
resource-limited Morrison is paradoxical, but might be explicable
through sophisticated resource partitioning. This hypothesis was
tested through finite-element analysis of the crania of the Morrison
taxa Camarasaurus and Diplodocus. Results demonstrate divergent
specialization, with Camarasaurus capable of exerting and
accommodating greater bite forces than Diplodocus, permitting
consumption of harder food items. Analysis of craniodental
biomechanical characters taken from 35 sauropod taxa demonstrates a
functional dichotomy in terms of bite force, cranial robustness and
occlusal relationships yielding two polyphyletic functional ‘grades’.
Morrison taxa are widely distributed within and between these two
morphotypes, reflecting distinctive foraging specializations that
formed a biomechanical basis for niche partitioning between them. This
partitioning, coupled with benefits associated with large body size,
would have enabled the high sauropod diversities present in the
Morrison Formation. Further, this provides insight into the mechanisms
responsible for supporting the high diversities of large
megaherbivores observed in other Mesozoic and Cenozoic communities,
particularly those occurring in resource-limited environments.

On Tue, Oct 7, 2014 at 7:20 PM, Ben Creisler <bcreisler@gmail.com> wrote:
> Ben Creisler
> bcreisler@gmail.com
> Two papers due out tomorrow are not yet online, but the news stories are out:
> Tachiraptor, new theropod from Venezuela (in Royal Society Open Science)
> http://news.sciencemag.org/latin-america/2014/10/new-meat-eating-dinosaur-lived-wake-mass-extinction
> http://www.livescience.com/48188-predatory-dinosaur-discovered-in-venezuela.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+Livesciencecom+(LiveScience.com+Science+Headline+Feed)
> ******
> Jurassic sauropod diet specialization (in Proceedings of the Royal Society B)
> http://phys.org/news/2014-10-dinosaurs-meals-jurassic-dinner-table.html