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



IMHO it's exciting that the _Nemegtosaurus_ / _Opisthocoelicaudia_
issue might finally be resolved.  Whether _Opisthocoelicaudia_ might
be a junior synonym of _Nemegtosaurus_ has been the subject of debate
for several decades.  There were positive signs in 2003, when isolated
teeth referred to _Nemegtosaurus_ were reported from the same Nemegt
site as a partial tail (MPD 100/406) referred to _Opisthocoelicaudia_
(Currie et al. 2003 dx.doi.org/10.1080/10420940390235071).  The fact
that this new material referred to _Nemegtosaurus_ includes an
opisthocoelous caudal is highly significant - though it should be
noted that opisthocoelous caudals are found in certain other
titanosaurs (e.g., _Rinconsaurus_, _Borealosaurus_), though not
necessarily as proximally/anteriorly in the tail as the opisthocoelous
caudals of _Nemegtosaurus_ / _Opisthocoelicaudia_.

Although both _Nemegtosaurus_ and _Opisthocoelicaudia_ have long been
recognized as derived titanosaurs, the two genera had very different
taxonomic beginnings: _Nemegtosaurus_ was initially described as a
member of the Dicraeosaurinae (family "Atlantosauridae"_) by Nowinski
(1971), whereas _Opisthocoelicaudia_ was originally assigned to the
Camarasauridae by Borsuk-Bialynicka (1977).  Nemegtosauridae Upchurch,
1995 began as a family of diplodocoids, whereas Opisthocoelicaudinae
McIntosh, 1990 (subsequently emended to Opisthocoelicaudiinae) began
as a subfamily of camarasaurids.  So although _Nemegtosaurus_ was
named before _Opisthocoelicaudia_, Nemegtosauridae was named later
than Opisthocoelicaudiidae (as Opisthocoelicaudiinae).  This may have
ramifications for the phylogenetic taxonomy of titanosaurs insofar as
coordinated family-level taxa are concerned.

Several authors have also flagged _Quaesitosaurus_ from the underlying
Baruun Goyot Formation as possibly congeneric with _Nemegtosaurus_.

Another potential synonymy is mentioned by Currie et al. (2017), this
time for two Nemegt hadrosaur genera: "there could be as few as one
species of hadrosaurid (_Saurolophus angustirostris_, which may be the
senior synonym of _Barsboldia sicinskii_)."  This is a curious aside,
because although Prieto-MÃrquez (2011 doi.org/10.1666/10-106.1) found
_Barsboldia_ to be a saurolophine, they upheld it as a valid genus,
and specifically rebutted the hypothesis that _Barsboldia_ was a large
(and aged) individual of _Saurolophus_.  That's not to say that this
is the last word on _Barsboldia_, but any suggestion that _Barsboldia_
is a junior synonym of _Saurolophus_ needs to take this into account.

Regarding the Nemegt Formation, Currie et al. (2017) make the point
that "Much of the diversity of large herbivores is composed of large
herbivorous theropods like _Deinocheirus_ and _Therizinosaurus_".
Elsewhere in Mongolia, there was also _Gigantoraptor_ (Iren Dabasu)
and the related MPC-D 107/17 (Bayn Shire).  When it comes to the large
herbivore stakes, in Late Cretaceous Mongolia (including Nei Mongol)
theropods certainly punched above their weight.


On Sat, Nov 4, 2017 at 3:01 PM, Ben Creisler <bcreisler@gmail.com> wrote:
>
>
>
> Ben Creisler
> bcreisler@gmail.com
>
>
> 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)
> doi: 
> https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1016_j.palaeo.2017.10.035&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=SHOaH6a2Nqg6xLKMy_THbKmDh0fo2jdTZQ7im3pAzcU&s=6louJv-n0xwJaEFXUR0t5gx_sgi8ZIyuGOi-MxMiQ-s&e=
> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.sciencedirect.com_science_article_pii_S0031018217306909&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=SHOaH6a2Nqg6xLKMy_THbKmDh0fo2jdTZQ7im3pAzcU&s=pAi2wWAQUlpp1cBw7JvXmwdEld9_7psVSpA8SZUMj3E&e=
>
> 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.
>
>
> ============
>
>
>
> 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)
> doi: 
> https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1016_j.palaeo.2017.10.027&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=SHOaH6a2Nqg6xLKMy_THbKmDh0fo2jdTZQ7im3pAzcU&s=DXURfRc9CwU5MdGZjAOut5TFwLiBVPKxnnCs-VYzsz0&e=
> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.sciencedirect.com_science_article_pii_S0031018217306892&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=SHOaH6a2Nqg6xLKMy_THbKmDh0fo2jdTZQ7im3pAzcU&s=C5_abPcT-lF14qICvPCsJnc1MOAiBa8DldxNV_r7aDQ&e=
>
> 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.
>
>
>