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Re: [dinosaur] New Nemegtosaurus material from Mongolia (Opisthocoelicaudia likely junior synonym) + giant sauropod track




I knew it. Ever since Opisthocoelicaudia was realized to be a titanosaur I figured it was the same as Nemegtosaurus. So it was always amusing to see cladograms in which the two taxa were at different parts of the results. What remains frustrating is the lack of cervicals, so the length of the neck is still unknown drats. Hopefully that will change at some point. 

Interesting the Nemegtosaurus is known only from just below and above the lower boundary of the Nemegt, not higher in the formation. Will be interesting to see the distribution of dinosaurs in the rest of the Nemegt. 

GSPaul

-----Original Message-----
From: Ben Creisler <bcreisler@gmail.com>
To: dinosaur-l <dinosaur-l@usc.edu>
Sent: Sat, Nov 4, 2017 12:02 am
Subject: [dinosaur] New Nemegtosaurus material from Mongolia (Opisthocoelicaudia likely junior synonym) + giant sauropod track




Ben Creisler


Two new papers:

Philip J. Currie, Jeffrey A. Wilson, Federico Fanti, Buuvei Mainbayar &, Khishigjav Tsogtbaatar (2017)
Rediscovery of the type localities of the Late Cretaceous Mongolian sauropods Nemegtosaurus mongoliensis and Opisthocoelicaudia skarzynskii: Stratigraphic and taxonomic implications.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance omline publication)

Highlights

Relocation of quarries for two sauropod holotypes
Description of new material of Nemegtosaurus
Discussion of probability that Opisthocoelicaudia is a junior synonym of Nemegtosaurus
New data showing sauropods more prevalent in Nemegt Formation ecosystem than previously thought

Abstract

In 1965, the Polish-Mongolian Palaeontological Expeditions recovered two sauropods from the Nemegt Formation of the Nemegt Basin, Mongolia (Kielan-Jaworowska and Dovchin 1968). One specimen, a nicely preserved, complete skull that in 1971 became the holotype of Nemegtosaurus mongoliensis, was found in Central Sayr at the Nemegt Locality. The other was found at Altan Uul IV and is a nearly complete postcranial skeleton lacking only the skull and neck. In 1977, this skeleton became the holotype of Opisthocoelicaudia skarzynskii. Nemegtosaurus and Opisthocoelicaudia were initially assigned to different sauropod higher taxa, Dicraeosaurinae and Camarasauridae respectively. However, since the late 1990s, both genera have been recognized as members of Titanosauria. Their coincident spatiotemporal distribution and non-overlapping skeletal parts have led to the persistent suspicion that they belong to the same species. Rediscovery of the original quarries and discovery of the postcranial remains attributable to the Nemegtosaurus holotype provides the first opportunity to directly compare these two taxa. Seven additional sites at the Nemegt locality preserve sauropod remains (including vertebrae, humeri, femora, pelvic elements, pedal phalanges, and unguals), and more than 20 sauropod footprint sites have been mapped. None of this material suggests that there is more than one sauropod taxon present in the Nemegt Formation. All localities occur within a discrete stratigraphic interval encompassing the uppermost Baruungoyot (footprints), Baruungoyot-Nemegt interfingering interval (Nemegtosaurus type), and lowermost Nemegt formations. Stratigraphic comparisons indicate the Opisthocoelicaudia locality at Altan Uul IV is within the lower beds of the Nemegt Formation. As sauropod remains are now documented for a total of 34 sites in the Nemegt Formation, a more refined stratigraphic framework may shed new light on the taxonomic inclusiveness of the sample.


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Brennan Stettner, W. Scott Persons IV &  Philip J. Currie (2017)
A giant sauropod footprint from the Nemegt Formation (Upper Cretaceous) of Mongolia.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance omline publication)

Highlights

New dinosaur footprints from the Nemegt Formation of Mongolia are described.
A single track from a sauropod (long-neck dinosaur) measures over 75 cm in length.
This track indicates the presence of a Mongolian sauropod 64â120% larger than any previously known from skeletal material.

Abstract

An expedition to the Nemegt Formation in 2007 discovered new footprint sites at the Nemegt Locality. The sites contained natural-cast tracks identifiable as those of hadrosaurs, tyrannosaurs, and sauropods. Among the sauropod tracks was the best-preserved pes print yet described from the Late Cretaceous of Mongolia. The footprint is referred to Brontopodus sp. on the basis of footprint morphology, age, and potential trackmakers from the same formation. Size estimations based on the track indicate the trackmaker had an acetabular height of approximately 3.0â3.5 m. As such, the size of the trackmaker exceeds that of any Mongolian dinosaur yet reported from skeletal material.