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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_.