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Dakotaraptor holotype is a chimera + first dromaeosaurid from Bayan Gobi Formation



Ben Creisler
bcreisler@gmail.com

New papers in PeerJ:

Victoria M. Arbour, Lindsay E. Zanno, Derek W. Larson, David C. Evans
& Hans-Dieter Sues (2015)
The furculae of the dromaeosaurid dinosaur Dakotaraptor steini are
trionychid turtle entoplastra.
PeerJ PrePrints 3:e1957
doi:  https://doi.org/10.7287/peerj.preprints.1570v1
https://peerj.com/preprints/1570/

Dakotaraptor steini is a recently described dromaeosaurid dinosaur
from the Upper Cretaceous (Maastrichtian) Hell Creek Formation of
South Dakota. Included within the D. steini hypodigm are three
elements originally identified as furculae: one which is part of the
holotype specimen and two referred specimens. We show that the
elements described as D. steini ‘furculae’ are not theropod dinosaur
furculae, but rather trionychid turtle entoplastra. Given that the
holotype 'furcula' is not referable to Dromaeosauridae and that the
specimen is a disarticulated individual based on skeletal remains from
a multitaxic bonebed, the holotype of Dakotaraptor steini is a
chimera.

===


Official version; was a preprint a few months back

Michael Pittman, Rui Pei, Qingwei Tan & Xing Xu (2015)
The first dromaeosaurid (Dinosauria: Theropoda) from the Lower
Cretaceous Bayan Gobi Formation of Nei Mongol, China.
PeerJ 3:e1480
doi: https://doi.org/10.7717/peerj.1480
https://peerj.com/articles/1480/


The first dromaeosaurid theropod from the Lower Cretaceous Bayan Gobi
Formation is identified based on an incompletely preserved
partially-articulated left leg, increasing the known diversity of its
understudied ecosystem. The leg belongs to specimen IVPP V22530 and
includes a typical deinonychosaurian pedal phalanx II-2 with a
distinct constriction between the enlarged proximal end and the distal
condyle as well as a typical deinonychosaurian enlarged pedal phalanx
II-3. It possesses a symmetric metatarsus and a slender and long MT V
that together suggest it is a dromaeosaurid. Two anatomical traits
suggest the leg is microraptorine-like, but a more precise taxonomic
referral was not possible: metatarsals II, III and IV are closely
appressed distally and the ventral margin of the medial ligament pit
of phalanx II-2 is close to the centre of the rounded distal condyle.
This taxonomic status invites future efforts to discover additional
specimens at the study locality because—whether it is a microraptorine
or a close relative—this animal is expected to make important
contributions to our understanding of dromaeosaurid evolution and
biology. IVPP V22530 also comprises of an isolated dromaeosaurid
manual ungual, a proximal portion of a right theropod anterior dorsal
rib and an indeterminate bone mass that includes a collection of ribs.
Neither the rib fragment nor the bone mass can be confidently referred
to Dromaeosauridae, although they may very well belong to the same
individual to whom the left leg belongs.