INVESTIGADORES
POL Diego
congresos y reuniones científicas
Título:
Jurassic sauropods from Patagonia and sauropod faunal replacement in the Jurassic.
Autor/es:
POL, D.; RAUHUT, O.W.; CARBALLIDO, J.L.
Lugar:
Mendoza
Reunión:
Congreso; 4th International Paleontological Congress; 2014
Resumen:
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The main diversification
of sauropod lineages dinosaurs happened during the Jurassic, but especially the
pre-Late Jurassic sauropod record is still rather poor. Thus, the origin of the
Late Jurassic and Cretaceous sauropod faunas is still poorly understood. In
South America, pre-Cretaceous sauropod dinosaurs are mainly known from the
Cañadón Asfalto Basin of Central Patagonia. Within this basin, two geological
units have yielded sauropod remains, the Cañadón Asfalto Formation and the
Cañadón Calcáreo Formation. From the latest Early to early Middle Jurassic
Cañadón Asfalto Formation, two sauropod taxa have been described so far, the
basal eusauropods Patagosaurus and Volkheimeria. Two further taxa
of sauropods are represented by so far undescribed material. Phylogenetic
analysis demonstrates that all of these taxa are basal, non-neosauropod
sauropods, representing at least three distinct lineages. The Late Jurassic
(Oxfordian-Kimmeridgian) Cañadón Calcáreo Formation has yielded two taxa of
sauropods, the basal macronarian Tehuelchesaurus and the dicraeosaurid Brachytrachelopan.
Furthermore, fragmentary remains indicate the presence of a brachiosaurid
titanosauriform and a diplodocid. Thus, the taxonomic composition of the
sauropod fauna from the Cañadón Calcáreo Formation is markedly different from
that of the Cañadón Asfalto Formation, but remarkably similar to roughly
contemporaneous faunas from the Morrison Formation of North America, various
units in Europe, and the Tendaguru Formation of Tanzania. These records show
that a sauropod assemblage formed by basal macronarians, basal
titanosauriforms, and diplodocids had been established by the Kimmeridgian at
the latest both in Gondwana and western Laurasia. The Middle Jurassic sauropod
fossil record indicates that up to the Bathonian sauropod assemblages were
dominated by basal eusauropods (non-neosauropodan sauropods), this indicates a
rapid sauropod faunal turnover from the Middle to the Late Jurassic. Taking
into account palaeogeographical reconstructions, this faunal replacement
probably happened between the Bathonian and the beginning of the Oxfordian, in a
geologically short period of less than five million years.