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Late Jurassic brachiosaurid from Argentina




A new paper from a journal I haven't heard of before...

Rauhut, O.W.M. (2006). A brachiosaurid sauropod from the Late Jurassic Canadon Calcareo Formation of Chubut, Argentina. Fossil Record 9: 226-237.

Abstract: "Fragmentary sauropod remains from the Late Jurassic (Tithonian) Canadon Calcareo Formation of Chubut, Argentinean Patagonia, are derived from a taxon of large size, but with very slender forelimbs. The characters of the caudal vertebrae, such as anteriorly placed neural arches, slender forelimbs, and large deltopectoral crest of the humerus indicate that this material represents the first brachiosaurid sauropod reported from South America. This occurrence confirms an almost global distribution of brachiosaurids in the Late Jurassic and thus indicates a rapid diversification and dispersal of this group after its origin, presumable in the late Middle Jurassic."

This new Patagonian brachiosaurid isn't named, due to the fragmentary nature of the material. What is known suggests an animal very similar to _Brachiosaurus_, suggesting that it may actually be referrable to this genus (pending further material). It wasn't as big as the largest _Brachiosaurus_ specimens, although it was still an impressive size (humerus: >160cm long).

Rauhut notes that brachiosaurids have been found in the Late Jurassic of every landmass for which Late Jurassic dinosaurs are known, except for Asia (China). Given that Asia, Antarctica and Australia each comprise a large slab of real estate, perhaps "almost global distribution" is a mild overstatement; but it is clear that brachiosaurids were widespread in the Late Jurassic (and I would add in the Early Cretaceous as well).

Rauhut uses the more recent concept of Brachiosauridae, so _Lusotitan_ is considered a true brachiosaurid, but _Lapparentosaurus_ and _Volkheimeria_ are not. He gives _Ornithopsis leedsi_ (Callovian) as the oldest confirmed brachiosaurid. Rauhut reaffirms _Tehuelchesaurus_ as a titanosauriform, not an omeisaurid as found by certain other studies. For _Lapparentosaurus_ , he also suggests that "the very primitive dorsal neural arches of this taxon indicate that its affinities might even lie outside Neosauropoda." This is interesting, given that in the _Europasaurus_ paper, Sander et al. (2006) recovered _Lapparentosaurus_ as more derived than _Brachiosaurus_.

Cheers

Tim