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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
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.