[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

JVP 32 (3): Argentinean neosauropods and a Chinese enantiornithean



Salgado, L., J.I. Canudo, A.C. Garrido & J.C. Carballido, 2012. Evidence of 
gregariousness in rebbachisaurids (Dinosauria, Sauropoda, Diplodocoidea) from 
the Early Cretaceous of Neuquén (Rayoso Formation), Patagonia, Argentina. 
 Journal of Vertebrate Paleontology 32 (3):603-613.

Abstract:  For the first time an association of adult and juvenile 
rebbachisaurid sauropods is described. The material comes from the Early 
Cretaceous locality of Agrio del Medio (Neuquén, Argentina). The three 
specimens apparently formed a single group, and their death seems to have been 
almost simultaneous. The two juvenile specimens are represented by axial and 
appendicular bones. They show a close relationship with *Zapalasaurus 
bonapartei*, which comes from a different sector of the same basin, but which 
is approximately the same age. The discovery at Agrio del Medio suggests that 
rebbachisaurid sauropods displayed gregarious behavior. The paleoenvironments 
in which rebbachisaurids are normally recorded implies a greater tolerance 
toward extremely arid environments than that shown by macronarian sauropods.



Mannion, P.D. & A. Otero, 2012. A reappraisal of the Late Cretaceous 
Argentinean sauropod dinosaur *Argyrosaurus superbus*, with a description of a 
new titanosaur genus.  Journal of Vertebrate Paleontology 32 (3): 614-638.

Abstract:  *Argyrosaurus superbus* is one of the earliest-named Argentinean 
dinosaurs. The holotype comprises a complete forelimb, probably from the upper 
member of the Bajo Barreal Formation (Late Cretaceous), Chubut Province. 
Numerous remains have been referred to *Argyrosaurus* from Argentina and 
Uruguay; however, the type specimen has not been adequately diagnosed and 
referrals have predominantly been based upon their large size. Here we 
redescribe *Argyrosaurus*, demonstrating it to be a valid titanosaur genus 
based on five autapomorphies, as well as an unique character combination. The 
exact placement of *Argyrosaurus* within Titanosauria is uncertain, although 
the probable presence of carpal bones, otherwise unknown in titanosaurs, may 
indicate a basal position. None of the referred remains can be attributed to 
*Argyrosaurus*, and most should be regarded as indeterminate titanosauriforms. 
The exception to this is a partial skeleton from the lower member of the Bajo 
Barreal Formation (early Late Cretaceous), Chubut Province, comprising dorsal 
and caudal vertebrae, as well as numerous appendicular elements. This specimen 
is distinct from *Argyrosaurus* and can also be differentiated from other 
sauropods based on an unusual character combination (including plesiomorphic 
tarsus), plus one autapomorphy. *Elaltitan lilloi*, gen. et sp. nov., displays 
numerous titanosaur characters and shares several features with derived taxa 
such as *Neuquensaurus*, *Opisthocoelicaudia*, *Rapetosaurus*, *Saltasaurus*, 
and *Trigonosaurus*. *Elaltitan* can be referred to Lithostrotia; however, its 
precise position within this clade must await future phylogenetic analysis. The 
revision and description of the titanosaurs *Argyrosaurus* and 
*Elaltitan* provides new information on this diverse but still poorly 
understood clade.




Hu, D., X. Xu, L. Hou & C. Sullivan, 2012.  A new enantiornithine bird from the 
Lower Cretaceous of Western Liaoning, China, and its implications for early 
avian evolution.  Journal of Vertebrate Paleontology 32 (3): 639-645.

Abstract:  Recent studies have blurred the distinctness of two major avian 
groups: the Enantiornithes, a major radiation of early birds in the Cretaceous, 
and the Ornithuromorpha, the clade including extant birds. Here we describe a 
new enantiornithine bird from the Lower Cretaceous Jiufotang Formation of 
western Liaoning, China, *Xiangornis shenmi*, gen. et sp. nov., which further 
reduces the morphological gap between the two groups. *Xiangornis shenmi* has 
several enantiornithine features, including a furcula with a significantly 
elongated hypocleidium, a coracoid with a convex lateral margin, and a minor 
metacarpal that extends further distally than the major metacarpal. However, it 
also possesses some derived ornithurine features, such as a short alular 
metacarpal (about one-sixth as long as the major metacarpal) that is completely 
fused to the major metacarpal, a large extensor process on the alular 
metacarpal, proximal and distal fusion between the minor and major metacarpals, 
and an intermetacarpal space positioned significantly distal to the alular 
metacarpal. This new find indicates that a carpometacarpal morphology similar 
to that seen in modern birds probably evolved independently in enantiornithines 
and appeared earlier than in Ornithuromorpha, and demonstrates that character 
evolution in early birds was more complex than previously believed.