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THE MOST ANCIENT ORNITHOMIMOSAUR (THEROPODA, DINOSAURIA)

www.walkdinosaur.comwhich was included in the superfamily Megalosauroi
dea (Carnosauria sensu lato). Its relationship with
ornithomimosaurs was first recognized by Rozh
destvensky (1970) and supported by other authors
(Paul, 1988; Alifanov, 2012c). However, Makovicky
et al. (2004) cast doubt on the reliability of ornithomi
mosaur hypothesis until more complete specimens are
found. Some researchers (for example, Norman,
1990; Currie, 2000) preferred to identify D. mirificus as
Theropoda incertae sedis.
A recent publication on new skeletal finds of
Deinocheirus mirificus in southern Mongolia has
shown that this species undoubtedly belongs to ornith
omimosaurs (Lee et al., 2014). It turned out that this
taxon displays an unusual complex of advanced and
archaic characters. The first include a low and trans
versely wide rostral part of the upper jaw, which is
atypical for theropods and makes this species exter
nally similarity to duckbilled dinosaurs; closed lower
temporal fenestra; short frontals; massive lower jaw;
large mandibular fenestrae; absence of jaw teeth; high
neural spines of the dorsal and sacral vertebrae; fusion
between the most terminal caudal vertebrae (indirectly
suggesting that D. mirificus was feathered); Ushaped
clavicles (which have not been recorded in ornithomi
mosaurs); extensive ilium and long ischium; the fem
ora longer than the tibia and fibula; and noncompact
metatarsal region. In the new description, D. mirificus
is considered to belong to the family Deinocheiridae,
along with  Garudimimus brevipes and  Beishanlong
grandis. The diagnosis of the last taxon only includes a
few characters, i.e., loose contact between the ulna
and humus, a proximal position of the flexor tubercle
on the ungual phalanges of the forelimb, and antero
dorsal orientation of the cnemial crest of the tibia.
In the last decades, it has been shown that ornitho
mimosaurs were common in the Early Cretaceous
time. Their remains have been recorded in the Berria
sian–Valanginian of Africa (Nqwebasaurus thwazi de
Klerk et al., 2000), Barremian of Spain (Pelecanimi
mus polyodon PerezMoreno et al., 1994), Barre
mian–Aptian of China (Shenzhousaurus orientalis Ji
et al., 2003), and Aptian–Albian of China (Beishan
long grandis Makovicky et al., 2010) and Mongolia
(Harpymimus okladnikovi Barsbold et Perle, 1984).
Excluding from consideration the specimens difficult
to identity from the Lower Cretaceous of Australia
(Timimus hermani Rich et VickersRich, 1994, nomen
dubium), the geography of other finds indicates that
ornithomimosaurs initially occurred of in the territory
of three northern continents and Africa. This distribu
tion of records agrees with the reconstruction Jurassic
landmass of Afrolaurasia (Kalandadze and Rautian,
1992, 1997).
The material considered in the present study
enable the most ancient ornithomimosaur,  Lepido
cheirosaurus natatilis gen. et sp. nov. to be character
ized. These remains come from Transbaikalia of Rus
sia (3 km west of the village of Novoil’inskoe in the
Chernyshevskii District, northeastern slope of the
Kulinda Fold). In this area, the bone beds are confined
to the Ukureiskaya Formation of lacustrine genesis
and presumably Tithonian age. The history of discov
ery and characteristics of the locality are provided in
the previous studies (Alifanov and Saveliev, 2011; Ali
fanov, 2012a, 2014; Alifanov and Sinitsa, 2013).
In Kulinda, dinosaur remains belong to relatively
small forms. Specimens are usually imprinted on the
rock of isolated postcranial bones, frequently limbs
and their girdles. Two points at a distance about 100 m
from each other had bone beds; one is in the middle
part of the slope, in a layer gray silty tufa sandstone up
to 10 cm thick; the second is in the lower part, in a
layer yellow–gray and gray–brown sandy tufa siltstone
about 5–10 cm thick.
Most of the records in Kulinda belong to ornithis
chian dinosaurs (Ornithischia), including two Orni
thopoda species (Alifanov and Saveliev, 2014),
Kulindapteryx ukureica (Jeholosauridae) and Dauro
saurus olovus (Hypsilophodontidae). One more taxon,
Kulindadromeus zabaicalicus (family is not estab
lished) was described (Godefroit et al., 2014) in paral
lel, presuming that the locality contains the only spe
cies. The holotype of this species is a specimen with
bone imprints of a squeezed skull, which precludes
unequivocal interpretation to the majority of signifi
cant morphological structures. In particular, one of
the diagnostic characters is a low rostral “process” of
the maxilla compared to the “caudal process” of this
bone. These structures are actually the rostral and
occipital margins of the dorsal process, in place of
which ornithischian dinosaurs frequently have a pre
orbital fossa structurally connected with a foramen at
the boundary of the lachrymal and maxilla (absent in
Ankylosauria, Hadrosauridae, Psittacosauridae, Cer
atopidae). The doubtfulness of the diagnosis is con
cerned not only with the ambiguous recognition of
the above features, but also with speculative determi
nation of connections between the lachrymal and lat
eral process of the premaxilla (Godefroit et al., 2014,
textfig. 1c). The connection is figured in the position
of the lost part of the dorsal process of the maxilla and
simultaneously borders the preorbital depression.
Such a reconstruction requires a distinct substantia
tion, but most likely follows from a mistaken interpre
tation. The quality of description of “K. zabaicalicus”
is also determined by introduction in it of the data on
theropods.
Remains of carnivorous dinosaurs from Kulinda
(Theropoda fam. indet.: Alifanov, 2012a, 2014) belong
to the same group. It is determined based on the distal
caudal vertebrae, short articulated series of these ver
tebrae, and a manus fragment. The last specimen, as
most of theropod specimens, comes from the lower
point. This is just the specimen which has provided
necessary taxonomic definitions, including the diag
nosis of the new genus and species.
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