The Chubut Monster is officially named!

Posted by Nima On Thursday, August 10, 2017 26 comments

Today the Chubut Monster, possibly the largest dinosaur known, has been published.

There are apparently six specimens from the same site. The largest of them may have exceeded 120 feet in length, and though the paper proposed a maximum mass of 82 tons, I suspect that when restored with the correct rib curvature and soft tissue levels, this animal may have exceeded 110 tons.


The AMNH mount, which is entirely made of fiberglass replicas, appears to be based on the holotype and a few similar-sized specimens. These are still smaller than the individual represented by the gigantic femur on the forklift pallets.


Patagotitan mayorum is build like something between Argentinosaurus and a lognkosaur, with traces of Malawisaurus-like features as well. Though the cladistic analysis in the paper is odd to say the least (taking Rinconsaurus and most other aeolosaurs out of Saltasauridae and making them sister-group to lognkosauria, and throwing Argentinosaurus into lognkosauria, while throwing Malawisaurus into a derived lithostrotian cluster!) it does make two very interesting points; not only is the new Chubut Monster Patagotitan related to Argentinosaurus, but Ruyangosaurus is classed as a titanosaur more derived than Andesaurus.



It seems ironic that the paper does not draw a closer relation between Patagotitan and Ruyangosaurus, because the morphology of their posterior dorsal vertebrae appears almost identical. The oddly leaf-shaped neural spines, the many shallow and thin laminae, and V-shaped prezygapophyses so recently having lost the hypantrum, are very similar to those of Patagotitan, which still retains a small hypantrum in a few of the mid-dorsals. The slender neural spines of the caudal vertebrae recall Mendozasaurus. The centra of the dorsals resemble Malawisaurus to some extent, and Argentinosaurus from certain angles. It's looking like Patagotitan occupies a node on the titanosaur family tree somewhat more derived than Argentinosaurus, a direct descendant of the fork in the road between the "Malawisaurs" (Malawisaurus and Savannasaurus) and more derived groups such as the true lognkosaurs.



The biggest specimen of Patagotitan is known from a femur that both has the unusual proximal curvature of that of Ruyangosaurus, and a size exceeding the (reconstructed) length of the Argentinosaurus femur.




A terrible skeletal of Patagotitan. In reality the neck and back would have been steeper, and the tail likely less kinked downward.