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RE: Erketu ellisoni
Andrew Farke wrote:
The partial citation from the Nature site is Ksepka D. T.& Norell M. A.
2006. AMNH Novitates, 3508.
The full citation is:
Ksepka D.T. and Norell M.A. (2006). _Erketu ellisoni_, a long-necked
sauropod from Bor Guvé (Dornogov Aimag, Mongolia). American Museum
Novitates 3508: 1-16.
Abstract: "The first specimen of the new sauropod _Erketu ellisoni_, from
the Lower Cretaceous of the eastern Gobi of Dornogov, Mongolia, is described
here. The specimen comprises a well-preserved articulated anterior cervical
series, an articulated lower hindlimb, and a sternal plate. This sauropod
displays a unique combination of features including low, bifid neural
spines, elongate cervical centra, and crescent-shaped sternal plates.
Computed tomography imaging reveals the vertebrae were extensively invaded
with pneumatic camellae. The holotype individual of _Erketu_ was of modest
mass relative to other neosauropods, but had an extremely elongate neck.
Phylogenetic analysis indicates _Erketu_ is a member of the Somphospondyli
and may belong to a more exclusive clade therein."
"Holotype: IGM 100/1803: articulated cervical series including complete
first through fifth cervical vertebrae, partial sixth cervical vertebra,
right sternal plate, articulated right tibia, fibula, astragalus, and
Etymology: _Erketu_: In Mongolian shamanistic tradition, there are 99 Tengri
(deities). Erketu Tengri is the Mighty Tengri, a creator-god who called
Yesugei, the father of Chingis Khan, into being. _ellisoni_: In honor of
Mick Ellison, for his contributions to ongoing AMNH dinosaur research.
Diagnosis: Referable to Titanosauriformes based on elongate cervical
vertebrae with camellae and referable within Titanosauriformes to
Somphospondyli based on reduced neural arch lamination. Differentiated from
all other Titanosauriformes in which cervical vertebrae are known by
combination of extremely elongated (EI indices of anterior cervicals
exceeding 5.0) cervical centra and bifurcate anterior cervical neural
Type locality and horizon: Bor Guve: late Early Cretaceous.
Stratigraphically, the beds at this locality lie below the Tsaagan Tsonch
beds (a unit that contains _Iguanodon orientalis_) and above the Khara
Khuutul beds, both believed to be of late Early Cretaceous age (Shuvalov,
2000). The lack of materials suitable for radiometric dating leaves the
exact age of this locality uncertain."
Technically _Erketu_ is not a titanosaur, but a somphospondylian or a
titanosauriform. Further material might show it to be a true titanosaur
(see below). The phylogenetic analysis puts _Erketu_ in one of two
positions: the sister taxon of _Euhelopus_ or the sister taxon of
Titanosauria. Thus, there is a potential for a monophyletic Euhelopodidae
(_Erketu_ + _Euhelopus_). However, although both _Erketu_ and _Euhelopus_
are characterized by having very long necks, in _Euhelopus_ individual
cervical vertebrae show little elongation; instead, the total number of
cervical vertebrae in _Euhelopus_ is increased to 17. In _Erketu_,
individual cervicals are very long, but we don't know the vertebral count
for the neck.
There is more undescribed material from the type locality that may belong to
_Erketu_, including some sauropod teeth. These teeth have cylindrical and
unexpanded crowns, and if they prove to belong to _Erketu_ it may push this
taxon up into the Titanosauria.
The authors also discuss the axial musculature of _Erketu_, with some neat
comments on neural spine bifurcation. Sauropods as a group show no
correlation between the latter character in the cervical series and the
length of the neck relative to the body, in spite of the notion that (as the
authors put it) "[A]s elongation of the neck increases, the functional
benefits of bifurcation should increase concomitantly."