SVP 2015

Posté par Croc en stock il y a 9 ans

Les résumés des découvertes qui seront présentées lors du prochain congrès de la Society of Vertebrate Paleontology, en Octobre prochain, sont déjà en ligne. Encore pas mal de découvertes passionnantes en perspective.

Parmi les sujets abordés il y a ces trois là qui m'interpelle :

Le sauropode de Damparis va enfin avoir la description qu'il mérite, et ce plus de 80 ans après sa découverte, et plus de 70 ans après l'attribution de ce spécimen à l'espèce Bothriospondylus madagascariensis par Lapparent (un genre aujourd'hui invalide). Comme on pouvait s'y attendre, il représente un nouveau taxon de Brachiosauridae. Espérons que l'on n'ait pas à attendre aussi longtemps pour la description du squelette presque complet du titanosaure Eva.

THE EARLIEST KNOWN TITANOSAURIFORM SAUROPOD DINOSAUR AND
THE EVOLUTION OF BRACHIOSAURIDAE
MANNION, Philip, Imperial College London, London, United Kingdom; ALLAIN,
Ronan, Muséum National d'Histoire Naturelle, Paris, France; MOINE, Olivier, Laboratoire de Géographie Physique, Paris, France

Brachiosauridae is a clade of titanosauriform sauropods that includes the wellknown
Late Jurassic taxa Brachiosaurus and Giraffatitan. However, there is
disagreement over the brachiosaurid affinities of other taxa, and little consensus
regarding the clade's composition or inter-relationships. An unnamed partial skeleton
from the Oxfordian (Upper Jurassic) of France potentially represents the earliest known
titanosauriform and has been known as the 'French Bothriospondylus' or 'Damparis
sauropod' in the literature. Full preparation and description of this individual (comprising
teeth, vertebrae, and most appendicular elements) recognizes it as a distinct brachiosaurid
taxon. Along with all putative brachiosaurids, the Damparis sauropod was incorporated
into a revised phylogenetic analysis comprising 69 taxa, scored for 407 characters,
several of which are novel to this study. After pruning of several unstable and highly
incomplete taxa, analysis in TNT produces 18 MPTs of length 1482 steps, and we
recover a nearly fully resolved Brachiosauridae, with good stratigraphic fit. The
Damparis sauropod and other Late Jurassic European forms are recovered as a
paraphyletic array of basal brachiosaurids, with Brachiosaurus, Giraffatitan, and
Cretaceous North American taxa successively more nested within Brachiosauridae. The
putative Middle Jurassic brachiosaurid Atlasaurus is a non-neosauropod eusauropod that
shows some convergence with brachiosaurids, including forelimb elongation. The Late
Jurassic dwarf sauropod Europasaurus has been recovered either as a nontitanosauriform
macronarian or basal brachiosaurid in previous studies. Although the
latter placement seems secure, the effects of alternative treatment of scoring
paedomorphic character states impacts upon tree resolution. Scoring these as missing
data, rather than autapomorphic reversals to the plesiomorphic basal eusauropod
condition, produces a well resolved tree congruent with that recovered with
Europasaurus excluded a priori. Currently, Brachiosauridae is only definitely known
from the Late Jurassic of East Africa, western Europe, and the USA (along with a
possible South American occurrence), and was seemingly restricted to the USA in the
Early Cretaceous. Regardless of whether their absence from the Cretaceous of Africa and
Europe, as well as other regions in general, reflects regional extinctions and genuine
absences, respectively, or sampling artefacts, brachiosaurids appear to have become
globally extinct by the earliest Late Cretaceous.

Posté par Croc en stock il y a 9 ans

Un autre papier à venir sur un nouveau spécimen canadien d'Ornithomimus avec empreinte de peau et de plumes. Un spécimen qui révèle de nouvelles informations sur la microstructure, la distribution, et la taille des plumes sur certaines parties du corps de ces dinosaures. Ainsi, les plumes présentes sur la surface dorsale de la queue sont plus grandes que celles recouvrant le reste du corps. La face ventrale de la queue ne porterait pas de plumes, de même que la plus grande partie des pattes postérieures (les plumes étant seulement présentes sur le haut de la cuisse). Finalement ces bestiaux devaient vraiment beaucoup ressembler à nos autruches (ou plutôt ce sont ces dernières qui ressemblent à des ornithomimosaures, question de priorité).

A NEW SPECIMEN OF ORNITHOMIMID (THEROPODA) FROM DINOSAUR
PROVINCIAL PARK PROVIDES UNPRECEDENTED DETAILS OF
DINOSAUR PLUMAGE AND FEATHER EVOLUTION
VAN DER REEST, Aaron J., University of Alberta, Edmonton, AB, Canada, T6G 2H6;
WOLFE, Alex, University of Alberta, Edmonton, AB, Canada; CURRIE, Philip J.,
University of Alberta, Edmonton, AB, Canada

A newly discovered articulated partial skeleton of cf. Ornithomimus preserves body
outlines, skin (preserved as thin carbonaceous film), and feathers. The skin represents an
anterior femoral web similar to skin webs in extant birds; however, this is the first report
for non-avian theropods. The specimen also shows signs of a body outline around the left
leg preserved by differentiation in matrix. The new specimen is the first of this taxon to
preserve a relatively complete tail that possesses feathers. Visible plumage indicates
plumaceous feathers along the dorsal surface of the tail are longer than those on the
remainder of the body. Plumage is absent on the ventrum of the tail. Feathers are also
found on the proximal half of the femur, indicating the remainder of the leg was also
devoid of plumage. This plumage pattern is similar to the pattern in Struthio camelus
(ostrich), indicating that the plumage may have served a similar thermoregulatory
function.

Feather macro-structure and micro-structure are preserved in extraordinary detail,
allowing unprecedented understanding of the evolution of feathers. The feathers are
simple branching structures composed of a fully developed rachis and ramus, with no
indication of barbules. Using electron microscopy the internal structure of the feathers
was compared to that of several extant birds. Internal structural components, such as the
pith, cortex, and melanosomes are identifiable. These components indicate that primitive
feathers (prior to the development of barbules, and thus flight) were light and durable,
and flight feathers were exapted based on these properties. This discovery pushes back
the origin of organized interior feather structures to Maniraptoriformes. Both macro- and
micro structure indicate that feathers were functioning similarly those found on Dromaius
novaehollandiae (Emu) and Rhea pennata (Darwin's Rhea).


Un nouveau croco géant du Cénomanien du Maroc et du Niger (crâne mesurant près de 2 m) montrant une convergence de morphologie avec les spinosaures (forme du museau et dents disposées en rosette).

NEW GIANT LATE CRETACEOUS CROCODYLIFORM WITH FEEDING
ADAPTATIONS CONVERGENT ON SPINOSAURIDS
LARSSON, Hans C., McGill University, Montreal, QC, Canada, H3A 0C4; SERENO,
Paul C., University of Chicago, Chicago, IL, United States of America; EVANS, David
C., Royal Ontario Museum, Toronto, ON, Canada

A new giant crocodyliform was discovered in two localities in the Sahara of
Cenomanian age, the Kem Kem beds in Morocco and the Echkar Formation in Niger.
The new taxon represents a late-surviving relative of the longirostrine crocodyliform
Stolokrosuchus from mid-Cretaceous rocks in Niger. Features shared by these presumed
sebecids include unique modifications to the narial region and anterior tooth occlusion.
The incisive foramen is greatly expanded and the chamber dorsal to the foramen opens
anteriorly through a midline foramen between the anterior premaxillary midline suture.
This morphology presumably housed a vomeronasal organ, a sensory organ absent in
extant crocodylians. A hypertrophied tusk-like first dentary tooth occludes into a deep
recess on the premaxilla. The remaining premaxillary and anterior dentary teeth interlock
to create a unique tight fitting anterior tooth rosette.

The new taxon converges with the contemporary theropod Spinosaurus in size and
in several features of the snout. Convergences include the presence of a terminal rosette
of teeth, elongate, laterally compressed, and gently down-sloping snout, recurved
concical teeth, and gigantic skull size. Total skull length approached two meters and
makes this crocodyliform one of the largest to have existed. Skull length is comparable to
or even exceeds that of the giant piscivorous Spinosaurus. The presence of two gigantic,
presumably piscovorous taxa is explained by the diverse fish fauna of these formations.

Posté par Red Dear il y a 9 ans

Je suis tombé sur ce PDF du programme de SVP il y a un mois ou deux et j'avoue que parmi toutes les présentations, beaucoup sont en fait très très intéressantes et il me tarde de les voir publiées !!!

Parmi celles qui ont titillé mon intérêt, il y a la description d'un squelette assez complet de Saurornitholestes qui lève le voile sur l'apparence de son crâne, visiblement différent de celui de Velociraptor sur lequel les précédentes reconstitutions se basaient.

On a aussi je crois la description des specimens multiples d'Utahraptor et de Pantidraco (pourra-t-on enfin voir les nouvelles proportions étranges de ce grand dromaeosauridé ?).

Et enfin, une redescription des nodules sur le bras de Concavenator qui, selon cette nouvelle études, pourraient effectivement être des "quill nobs" contrairement à la controverse qui jusque là les interprétait comme des ancrages musculaires.

Il y en a bien d'autres très intéressants et j'ai hâte d'en savoir plus.

Posté par Webmaster il y a 9 ans

Citation de Red Dear:

Et enfin, une redescription des nodules sur le bras de Concavenator qui, selon cette nouvelle études, pourraient effectivement être des "quill nobs" contrairement à la controverse qui jusque là les interprétait comme des ancrages musculaires.

L'interprétation de ces nodules chez Concavenator n'était pas forcément en faveur des ancrages musculaires. Mais ça fait bien de le dire dans un article. Reste à voir si cette redescription apporte de nouveaux éléments.

Depuis sa description, on a privilégié ici l'hypothèse des insertions de plumes:
Concavenator, le dinosaure-requin/chameau
Description sur le PaleoWiki