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An Early Ostrich Dinosaur and Implications for Ornithomimosaur Phylogeny


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A new ornithomimosaur from the Yixian Formation of Liaoning Province People's Republic of China is described. These beds are near the Jurassic-Cretaceous boundary. This specimen is interesting because it has several primitive characters for ornithomimosaurs such as teeth and a short first metacarpal. This taxon is placed in a phylogenetic analysis of Coelurosauria and shown to be near the base of the ornithomimosaur clade. Using this phylogeny we comment on the biogeographic history of this group.
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American Museum of Natural History 2003 ISSN 0003-0082
Number 3420, 19 pp., 12 figures, 1 table October 29, 2003
An Early Ostrich Dinosaur and Implications for
Ornithomimosaur Phylogeny
A new ornithomimosaur from the Yixian Formation of Liaoning Province People’s Republic
of China is described. These beds are near the Jurassic-Cretaceous boundary. This specimen
is interesting because it has several primitive characters for ornithomimosaurs such as teeth
and a short first metacarpal. This taxon is placed in a phylogenetic analysis of Coelurosauria
and shown to be near the base of the ornithomimosaur clade. Using this phylogeny we com-
ment on the biogeographic history of this group.
Spectacular fossils from China’s Liaoning
Province have become commonplace in the
last few years (Ji and Ji, 1996; Ji et al., 1999;
Hou, 1997; Gao et al., 2000). However, most
of these are nearly two-dimensional fossils
found in paper shales that represent ancient
pond and lake deposits. Although beautiful
Department of Earth Sciences, Nanjing University, 22 Hankou Road, Nanjing 210093, and Institute of Geology,
Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, Beijing 100037 China. e-mail:
Division of Paleontology, American Museum of Natural History. e-mail:
The Field Museum, 1400 S. Lake Shore Drive, Chicago IL, 60660. e-mail:
School of Earth and Space Sciences, Peking University, Beijing 100871, China. e-mail: kqgao@geoms.geo.pku.
China University of Geosciences, Beijing 100083, China.
and often preserving soft-part anatomy, these
fossils can be frustrating because of a lack of
three-dimensional preservation. Furthermore,
theropod remains from Liaoning only in-
clude the maniraptoran groups Dromaeosaur-
idae (Xu et al., 1999b, 2000), Oviraptorosau-
ria (Ji et al., 1998, Xu et al., 2002a), Troo-
dontidae (Xu et al., 2002b), and Segnosaur-
idae (Xu et al., 1999a) and the more
primitive compsognathid Sinosauropteryx
(Chen et al., 1998). Here we describe a new
ornithomimid dinosaur, the first from the
Liaoning beds, and comment on its relation-
ships to other ornithomimids.
Ornithomimid dinosaurs were the first
toothless nonavian dinosaurs to be described
(Marsh, 1890). Consequently, much has been
written concerning their relationships and
diet (Gauthier, 1986; Holtz, 1994; Sereno,
1997, Kobayashi et al., 1999; Norell et al.,
2001b). Although toothed forms have been
recovered (Pe´rez-Moreno et al., 1994; Bars-
bold and Perle, 1984), these are either diffi-
cult to place phylogenetically or are extreme-
ly fragmentary.
Local farmers collected the specimen, and
some of the elements were clearly lost during
the excavation process. It is apparent that
both the tail and the forelimbs were present
in adjoining blocks (fig. 1). When the spec-
imen was collected it was cracked into two
blocks, shattering many bones and leaving
parts of the skeleton in each block. During
the preparation process parts of the counter
block were glued to the main slab, and the
sediment surrounding the bones was re-
moved. In other cases individual elements
were prepared completely free of the counter
slab and affixed to the main slab. This prep-
aration process resulted in a single block
with the specimen preserved in bas-relief
(fig. 2).
AMNH American Museum of Natural History
IGM Institute of Geology Mongolia
NGMC National Geological Museum of China
ROM Royal Ontario Museum
Shenzhousaurus orientalis, new taxon
: NGMC (National Geolog-
ical Museum of China) 97-4-002.
: A partial skeleton preserved on
a sandstone block in a death pose with its
head above the torso. The distal hindlimbs,
distal tail, and the forelimbs (except for part
of the right hand) and the pectoral girdle are
missing. The head is crushed, exposing the
left side obliquely.
:Shenzhou is the ancient name
of China, orientalis refers to the east.
: Sihetun fossil site, Bei-
piao, Western Liaoning, China (fig. 3).
: The holotype
comes from the lowermost, fluvial part of the
Early Cretaceous Yixian Formation. These
rocks are older than 128 mybp and younger
than 139 mybp (Swisher et al., 2002); older
dates have been reported (Lo et al., 1999).
: an ornithomimosaur distin-
guishable from all others except Harpymimus
in having teeth restricted to the anterior den-
tary. Shenzhousaurus orientalis shows prim-
itive characters not found in advanced orni-
thomimosaurs, like a straight ischium and a
postacetabular process that is gently curved
rather than truncated. Shenzhousaurus orien-
talis is distinguishable from Pelecanimimus
by the tooth distribution pattern and the
primitive configuration of the hand where
digit I is shorter than digits II and III.
The left side of the snout is well pre-
served, whereas the right side is crushed and
displaced postmortem (fig. 4). The orbital
and braincase regions are flattened and the
left frontal and parietal are flipped under the
right. The left squamosal is isolated and lies
adjacent to the caudal end of the lower jaw.
The left mandible appears to be intact and
well preserved.
The premaxilla has a relatively short body,
and the premaxillary buccal margin is only
as long as the external naris. The internarial
bar is dorsoventrally flat and is formed main-
ly by the premaxillae, with only a minor con-
tribution from the nasals. The posterodorsal
process of the premaxilla is elongate as in
other ornithomimids, and it overlaps the na-
somaxillary suture well posterior to the cau-
dal end of the naris. It is broadest at its base
but tapers caudally. Although incomplete dis-
tally, it does not appear to have reached the
level of the antorbital fossa. The labial sur-
Fig. 1. NGMC 97-4-002 before preparation.
Fig. 2. The holotype skeleton of Shenzhousaurus orientalis as preserved on the main block, with
parts in counterblock reattached. Abbreviations: g, gastralia; ga, gastroliths; lf, left femur; li, left ilium;
lis, left ischium; lp, left pubis; lu, ungual of left hand; pb, pubic boot; r-dI, right digit I; r-dII, right digit
II; r-dIII, right digit III; rf, right femur; rp, right pubis.
Fig. 3. The fossil locality.
Fig. 4. Close-up of the left side of the skull of Shenzhousaurus orientalis. Abbreviations: ch, choana;
fr, frontal; ld, left dentary; ll, left lacrimal; lmx, left maxilla; ln, left nasal; lpmx, left premaxilla; lsq,
left squamosal; mxf, maxillary fenestra; plr, palatine recess; rn, right nasal.
face of the subnarial part of the premaxilla
is marked by a few neurovascular foramina,
the largest of which is located at the base of
the internarial bar.
The maxilla is very elongate and bears a
large antorbital fossa that is perforated by a
larger antorbital and a smaller accessory fe-
nestra. The rostral 40% of the maxilla lies
anterior to the antorbital fenestra and has a
flat lateral surface marked only by a few fo-
ramina, presumably for neurovascular trans-
mission. The buccal margin is slightly sinu-
ous in this region and rises gently toward the
front. The buccal margin of the maxilla is
very shallow beneath the antorbital fossa. A
large maxillary palatal shelf is visible along
the anterior two-thirds of the antorbital fossa.
The fossa appears to be bordered by the nasal
for a short stretch dorsal to the antorbital fe-
nestra, although the maxilla is not complete
in this region. Posterior to this the dorsal
edge of the antorbital fenestra is bordered by
the elongate anterior ramus of the lacrimal.
The accessory fenestra perforates a de-
pressed medial lamina of the maxilla that
walls off the anterior third of the antorbital
fossa medially. The posterior part of this
lamina, which forms the interfenestral bar,
bears dorsal and ventral embayments along
the posterior border, perhaps indicating some
type of interfenestral connection as in troo-
dontids (Norell et al., 2000; Makovicky et
al., 2003).
The jugal is poorly preserved, and articu-
lar contacts with the maxilla and lacrimal
cannot be traced. The orbital portion of the
jugal is very slender, and the anteroventral
corner of the orbit appears to have had a
right-angled rather than a rounded shape.
Posteriorly, the jugal is obscured by other el-
The lacrimal bears an elongate anterior
process that borders the caudal half of the
antorbital fenestra dorsally. A short, pointed
posterior process is present on the lacrimal.
It may have inserted into a notch on the dor-
sal surface of the prefrontal as in Gallimi-
mus, but the prefrontal cannot be identified.
Neither large fossae nor hornlike structures
are present on the lacrimal.
A short section of the right postorbital is
exposed in dorsal view, and it forms the an-
terior part of the intertemporal bar. It is rel-
atively massive compared to the postorbital
contribution to the intertemporal bar in other
ornithomimid taxa. The postorbital of Shen-
zhousaurus orientalis does not reveal the
characteristic anterodorsal curvature seen in
The right frontal is exposed in dorsal view
(fig. 5). A coronally directed crack extending
through the frontal just anterior to the artic-
ulation of the postorbital may be the result
of dorsoventral crushing of a strongly flexed
part of the frontal. The frontals of other or-
nithomimid taxa are domed near the poste-
rior part of the orbit, forming a flexure be-
tween the flat parts of the frontal and parie-
tals. Anterior to the extensive orbital rim, the
lateral edge of the frontal is sinuous and the
medially inflected portion may mark a de-
pression for the reception of a prefrontal.
The parietals appear paired and unfused.
The dorsal surface of the parietal is flat and
lacks a sagittal crest. A laterally concave
flexure marks the medial edge of the supra-
temporal fenestra and separates the dorsal
surface of the parietal from the lateral surface
that forms parts of the adductor chamber. The
frontoparietal suture is sinuous in dorsal
view, as in Gallimimus (Osmo´lska et al.,
The left squamosal is disarticulated and
lies adjacent to the caudal end of the left
mandible. It is exposed in lateral view, and
the proximal end of the quadrate is preserved
in articulation with the squamosal. The squa-
mosal is tetraradiate, with two processes ex-
tending anteriorly around the caudal end of
the supratemporal fenestra, a rostroventrally
directed quadrate process that adheres to the
anterior edge of the quadrate shaft, and a
short lateral process. The intertemporal pro-
cess of the squamosal is longer than the me-
dial supratemporal process. The dorsal sur-
face of the squamosal between these two pro-
cesses is incised by a caudal extension of the
supratemporal fenestra, bordered by a sharp
rim, as in Gallimimus (IGM 100/1133). The
quadrate process of the squamosal is trian-
gular. The posterolateral process extends pos-
terior to the quadrate articulation, but its
length cannot be determined because it is
overlapped by a disarticulated piece of the
braincase. The articulation with the quadrate
is not exposed in lateral view in Shenzhou-
saurus orientalis,asitisinGallimimus
(IGM 100/1133) and Ornithomimus.
Parts of the palate, including parts of both
palatines and possibly the left pterygoid, are
exposed. The palatine bears two anteriorly
elongate processes that almost enclose the in-
ternal choana. The medial, interchoanal pro-
cess is longer than the lateral one, in contrast
to Allosaurus (Madsen, 1976), but similar to
Sinraptor (Currie and Zhao, 1993) and Dei-
nonychus (Witmer, 1997), and it extends at
least as far rostrally as the interfenestral bar.
The interchoanal process of the left side rises
dorsomedially to meet its counterpart on the
right side and form the interchoanal bar, pos-
sibly with participation of the pterygoids.
The interchoanal bar is unlike the large, lo-
bate structure of Allosaurus (Madsen, 1976),
but is more slender and curves anteriorly
from the posterior end of the choana as in
Velociraptor (Barsbold and Osmo´lska,
1999). The dorsal surface of the palatine
bears a deep fossa, the palatine recess (Wit-
mer, 1995), near the base of the maxillary
process just rostral to the level of the lacrimal
(fig. 5). The palatine recess in Shenzhousau-
rus orientalis is in a similar position to pal-
atine recesses observed in dromaeosaurs
such as Deinonychus (Witmer, 1995: fig. 32)
and Velociraptor (IGM 100/982). The recess
invades the palatine body mediodorsally in
Shenzhousaurus orientalis rather than poster-
odorsally as in the two dromaeosaurid taxa.
Part of the pterygoid process of the palatine
Fig. 5. Closeup of braincase. Abbreviations: dv, dorsal vertebra; f, frontal; lp, left prootic, ls?, left
laterosphenoid, lsa, left surangular, lsq, left squamosal; r, rib.
is exposed within the orbit, posterior to the
The hooked jugal process is the only vis-
ible part of the ectopterygoid and is exposed
within the orbit slightly posterior to the pter-
ygoid process of the palatine. A narrow sliv-
er of bone dorsal to the jugal process of the
ectopterygoid to this may represent a part of
the pterygoid.
A large, crushed bone that overlaps the
posterior part of the mandible may be a la-
terosphenoid. We interpret a large broken el-
ement posterior to the right parietal as the left
prootic with its anterior surface (laterosphen-
Fig. 6. The dentition of Shenzhousaurus orientalis as preserved in the left dentary.
oid articulation) facing upward (fig. 5). A
well-delimited depression on the lateral sur-
face appears to be the dorsal tympanic recess.
Medial to it, the posterior border of the floc-
cular recess is visible. Part of the border of
a large foramen, which is surrounded by a
wide fossa on the lateral surface of the brain-
case, is visible anteroventral to the floccular
recess and is here interpreted as the exit for
the trigeminal nerve.
The complete left mandible is preserved,
but much of the postdentary region is cov-
ered by the unidentifiable braincase element.
The dentary is elongate but shallow and
spans about two-thirds the length of the jaw.
The dentary is deepest below the middle of
the antorbital fenestra. It tapers gently rostral
to this point, up to a point just posterior to
the toothrow, where it deflects rostroventral-
ly. The buccal margin is deflected anteroven-
trally at the symphysis, as in other ornithom-
imosaurs except Pelecanimimus (Pe´rez-Mo-
reno et al., 1994). The lateral surface of the
dentary is pocked by three roughly linear
rows of neurovascular foramina (fig. 6).
These extend posteriorly to the end of the
abbreviated toothrow. Farther caudally, a
shallow groove follows the dorsal margin of
the dentary until it reaches the rostrodorsal
process of the surangular.
As in other ornithomimosaurs, the external
mandibular fenestra is reduced. It is bordered
dorsally by the surangular that has a long,
splintlike process overlapping the dentary.
Fragments of the angular are exposed along
the ventral border of the external mandibular
fenestra. The glenoid and retroarticular pro-
cess are exposed. A flattened area just rostral
to the glenoid may correspond to the dorsal
trough or sulcus seen on the surangular of
many theropods, including Velociraptor,Ty-
rannosaurus, and Ornitholestes. As in other
ornithomimids, an everted tab forms the an-
terolateral margin of the glenoid. In these
taxa, such as Gallimimus, this tab articulates
with an elongate, curved extension of the lat-
eral quadrate condyle. The retroarticular pro-
cess is crushed, but it appears to be expanded
Six minute tooth crowns and a broken root
are preserved at the deflected anterior tip of
the left dentary. Gaps between the preserved
teeth suggest the presence of one or two ad-
ditional tooth positions. The teeth are conical
and project slightly anteriorly. They do not
have a constriction between the root and
crown. A thin layer of enamel is preserved
on the teeth. There is no trace of either ca-
rinae or serrations.
No cervical vertebrae can be identified on
the specimen.
Fig. 7. Dorsal vertebrae of Shenzhousaurus
An articulated series of the last eight dor-
sal vertebrae are preserved in articulation
with the sacrum. The centra are elongate and
spool-shaped and are devoid of pneumatic
foramina (fig. 7). The anteriormost centrum,
which is broken anteriorly, bears a faint keel
ventrally. Neural arches bear large pneumatic
infraprezygapophyseal, infradiapophyseal,
and infrapostzygapophyseal fossae below the
transverse processes. The infraprezygapo-
physeal fossae are especially large and ap-
pear to extend into the prezygapophyses. The
neural spines are long, tall anteroposteriorly
expanded distally. The neurocentral sutures
are fused but not obliterated. In no case is a
neural arch separated from its corresponding
Parts of 10 dorsal ribs are preserved on the
block, but none is complete. Two left ribs,
which probably articulated with the fourth
and fifth dorsals in the preserved series, have
anteroposteriorly flared shafts as in other or-
nithomimids (Barsbold and Osmo´lska,
Parts of five sacral vertebrae are exposed
but are partly obscured by the pelvic ele-
ments and the left femur. The centra appear
to be fused, but the sutural lines are still ev-
ident. A constricted pit is visible on the ex-
posed lateral surface of both the third and
fourth sacrals. Such noninvasive depressions
are also present on the sacral vertebrae of
other ornithomimid taxa, including Orni-
thomimus (Makovicky, 1995), Gallimimus
(Osmo´lska et al., 1972), Struthiomimus, and
Archaeornithomimus (Makovicky, 1995).
The ilium appears to be slightly displaced
from the sacrum, thus exposing the trans-
verse processes of the last sacral in lateral
view. As in other ornithomimosaurs, the
transverse processes of this element flare
widely distally where they meet the medial
border of the brevis fossa, and they may have
contributed to the insertion area of the cau-
difemoralis brevis musculature. The neural
spine of the last sacral appears to have been
freestanding, but it cannot be determined
whether the neural spines of the remaining
sacrals formed a lamina as in some other or-
nithomimosaurian specimens.
A section of the tail comprising 15 artic-
ulated caudal vertebrae is preserved, curving
posterodorsally from the sacrum (fig. 8). All
the preserved caudals possess transverse pro-
cesses or traces thereof, indicating that the
transition point lies distal to the preserved
section of the tail. Centrum length increases
distally in the preserved section, whereas
centrum height decreases distally.
The transverse processes are distally ex-
panded and backswept. Their distal ends are
rounded. In the second and third caudal ver-
tebrae, a thin lamina extends anteriorly from
the transverse process on to the lateral face
of the prezygapophysis, where it forms a dis-
tinct ridge bounding a shallow fossa. This
connection between the transverse process
and prezygapophysis is also present in Or-
nithomimus. The neural spines of the first 12
vertebrae are obscured by transverse pro-
cesses. Those of the remaining three caudals
are parallelogram-shaped and lean posteri-
orly, extending beyond the caudal end of
their respective centra.
The first chevron is situated between the
first and second caudals. It is rod-shaped, but
its length is indeterminate, as the second
chevron covers it distally. The second to
fifths chevron are very elongate, slender, and
rod-shaped with a slight posterior curvature
that becomes more pronounced in more dis-
Fig. 8. Anterior caudal vertebrae of Shenzhousaurus orientalis.
tal elements. Posterior to this, the chevrons
become progressively wider, mediolaterally
compressed, shorter, and more hooked. The
last two chevrons are strongly hooked and
end in a point distally.
Parts of eight gastral arches from the right
side are preserved, but only one preserves
both the complete medial and lateral seg-
ments (fig. 9). The medial segment has an
expanded and dorsoventrally compressed
midline end. It tapers distally and is over-
lapped anteriorly by the lateral element. The
two elements are approximately equal in
length, unlike those of higher ornithomimids,
in which the medial elements are longer. The
dorsal ends of the rodlike lateral elements are
slightly expanded and curve dorsally. The
last gastral element is three times wider than
the preceding segments. The last gastral arch
may have only comprised this medial ele-
The pelvis is present in semiarticulation
although some elements were shattered when
the slab was split. The ilium is about equal
in length to the pubis, and the ischium is only
slightly shorter (see table 1).
Most of the exposed dorsal surface of the
ilium is shattered, as it lay on the contact
between the slab and counterslab (fig. 10).
Nevertheless, it can be determined that the
anterior and posterior blades are roughly
equivalent in length and that the iliac blade
was dorsoventrally low. The ilia covered six
vertebrae, less than in Gallimimus and Or-
nithomimus (Barsbold and Osmo´lska, 1990).
Apparently the ilia met at the midline as in
other ornithomimids (Makovicky et al., in
Fig. 9. Gastroliths of Shenzhousaurus orientalis. ga, gastroliths; ldIIIu, left digit 3 ungual; lf, left
femur; li, left ilium; rdI, right digit 3, rdII; right digit 2; rdIII, right digit 3.
press; Barsbold and Osmo´lska, 1990). Both
anterior and posterior blades also are round-
ed similar to the oviraptorosaur Khaan
mckennai (personal obs.). This is unlike the
condition in other ornithomimids where the
ilium is dolichoiliac and the posterior blade
is truncated rather than tapering to a point
(Barsbold and Osmo´lska 1990). Although the
anterior blade is hooked as in other orni-
thomimids, the hook is small as in Khaan
mckennai (personal obs.), Ornitholestes her-
manni (Osborn, 1903), and Velociraptor
mongoliensis (Norell and Makovicky, 1997,
1999). Posterior to the acetabulum the lateral
border of the brevis fossa is concave ven-
trally, giving it a slightly hooked appearance.
This is unlike the condition in other orni-
thomimids where the lateral margin of the
brevis fossa is straight (Barsbold and Os-
mo´lska 1990). The preacetabular apron is
slightly concave and is separated from the
main body of the ilium by a sharp ridge that
continues anteriorly to form the lateral bor-
der of the deep cupedicus fossa. The acetab-
ulum is marked by a large supra-acetabular
crest that overhangs the acetabulum. As is
typical of ornithomimosaurs, the supracetab-
ular crest formed a hood or cap over the en-
tire proximal femur. The ischiac peduncle is
not wide, but is formed as a ventral conical
process, as in other ornithomimids and tyran-
nosaurs, which inserts into a slot in the is-
chium. A large antitrochanter is present. The
postacetabular apron is large and like the
preacetabular apron is separated from the il-
iac blade by a large ridge that continues pos-
Measurements of Holotype of Shenzhousaurus orientalis (all measurements in millimeters)
teriorly to define the lateral edge of the brev-
is fossa. The brevis fossa is large and deep
and expands posteriorly as a deep trough to
the posterior limit of the ilium.
The left ischium is preserved in near ar-
ticulation with the ilium and can be observed
in lateral view. The iliac process is long and
is angled posterodorsally from the shaft. On
its posteroproximal lateral surface is a large
triangular scar as in other ornithomimosaurs
and tyrannosaurs (Buffetaut et al., 1996). The
surface of the acetabulum that lies in be-
tween the iliac and pubic processes is smooth
and crescent-shaped. The pubic process is
short, relatively shorter than in other orni-
thomimids. In fact, the pubic contact lies
along the same axis as the shaft of the ischi-
um. Just ventral to the pubic contact lies a
large hook-shaped obturator process. It is
possible that this process may have com-
pletely enclosed a foramen; however, break-
age in this area prevents confirmation. Dis-
tally the ischium tapers and then expands on
its distal end into a small triangular boot that
projects anteriorly.
The left pubis and part of the right are ex-
posed laterally and are in near articulation
with the ilia and ischia. The overlying femur
obscures most of its proximal features. How-
ever, the articulation with the ilium indicates
that it was propubic. Near the iliac contact
the pubis is flat, becoming thin and rodlike
distally. It is slightly anteriorly convex, and
laterally it is marked by a small sinuous lon-
gitudinal ridge or crest which extends nearly
half the length of the shaft. This crest divides
Fig. 10. Pelvis of Shenzhousaurus orientalis. Abbreviations: ct, ectocondylar tuber; ft, fourth tro-
chanter; gp, gastrocnemius process; gt, greater trochanter; lc, lateral crest; lf, left femur; lp, left pubis;
li, left ilium; lis, left ischium; lt, lesser trochanter; mc, medial crest; o, obturator foramen; pb, pubic
boot; rf, right femur, rp, right pubis; sac, sacrum.
Fig. 11. Manus of Shenzhousaurus orientalis. ga, gastroliths; ldIIIu, left digit 3 ungual; rmcII, right
metacarpal 2; rmcIII, right metacarpal 3; rpII-1, right digit 2 first phalanx; rpII-2, right digit 2 second
phalanx; rpIII-1, right digit 3 first phalanx; rpIII-2, right digit 3 second phalanx; rpIII-3, right digit 3
third phalanx, rdIu, right digit 1 ungual; rdIIu, right digit 2 ungual; rdIIIu, right digit 3 ungual.
the pubis into anterior, and posterior-facing
surfaces. Medially the pubic moietes meet to
form the pubic apron, which is extensive,
forming nearly two-thirds the length of the
pubis. The pubic apron is posteriorly concave
and is formed from crests that emanate from
the anterior of the pubic shafts. Distally the
pubes form a large pubic boot. At the ter-
minus of the pubes the pubic boot appears to
be transversally expanded. This boot is mod-
erately expanded anteriorly, where it forms a
pronounced point. Posteriorly the pubic boot
is much more extensive. Ventrally the pubic
boot is deeply convex, as opposed to the con-
dition in Gallimimus, where the ventral edge
of the boot is nearly straight.
Only parts of the right hand, including all
of digits II and III, and a single ungual of
the left hand are preserved (fig. 11). The pre-
served elements of the right hand are in ar-
ticulation, but the hand is situated at the edge
of the block, and the missing parts were ob-
viously lost during collection when the block
was trimmed. The ungual and a partial im-
pression of the penultimate phalanx are the
only preserved parts of digit I. The ungual is
slightly curved, not trenchant, and has a
small flexor tubercle situated distal to the
proximal articulation. A deep groove extends
along the medial surface of the ungual, to the
distal end of the ungual. The preserved un-
gual of digit I of the left manus shows a sim-
ilar groove on the lateral surface, and these
two grooves are parallel along the ungual,
unlike the offset grooves on the unguals of
dromaeosaurs. As preserved, the ungual of
digit I does not reach the level of the prox-
imal end of the unguals of digits II and III.
Because the hand is articulated, the pre-
served position of ungual I-2 reflects the ac-
tual proportions of the digits in life and in-
dicates that digit I is proportionately shorter
than digits II or III, which is the primitive
condition for Tetanurae (Gauthier, 1986; Ser-
eno, 1997). Among ornithomimosaurs, the
condition in Shenzhousaurus appears most
like that of Harpymimus (Barsbold and Perle,
1984), in which digit I is short. The unguals
are slightly curved, not trenchant, and bear
small flexor tubercles distal to the proximal
articulations as in other ornithomimosaurs
(Osmo´lska, 1997; Sereno, 2001). In Galli-
mimus (Osmo´lska et al., 1972), Struthiomi-
mus (Osborn, 1917; Nicholls and Russell,
1985; AMNH 5339), Anserimimus (IGM
100/300), Pelecanimimus (Pe´rez-Moreno et
al., 1994), and Ornithomimus (Sternberg,
1933) the ungual of digit I reaches to at least
the base of the unguals of digits II and III.
Only the distal part of metacarpal II is pre-
served, and it is exposed in ventral and me-
dial views. The distal articulation is divided
into two distinct tubercles ventrally. A pro-
nounced flexor pit separates the two tuber-
cles. Phalanx II-1 has a transversely flat ven-
tral surface, with a pronounced arch in lateral
view. The proximal articulation is extensive,
and a small posteromedial lappet forms a
small heel extending ventral to the distal end
of the metacarpal. The distal articulation is
divided into two widely separated tubercles
in ventral view, and the articulation appears
ginglymous, although it is poorly preserved.
Phalanx II-2 is elongate, slender, and has
a nearly straight shaft that is oval in cross
section. The proximal articulation is formed
as a deep arc in lateral view, with dorsal and
ventral parts of the articulation projecting far
posteriorly. In contrast to Gallimimus, the
ventral end of the articulation extends farther
proximally than the dorsal tip. A small, mid-
line process or tuber is present on the ventral
surface of the phalanx II-2, adjacent to prox-
imal articulation. The apparently ginglymous
distal articulation describes an arc of approx-
imately 180
and has a small, elliptical col-
lateral ligament pit. The ungual of digit II is
similar to that of digit I, except that is slight-
ly longer.
Metacarpal III is almost complete. It ap-
pears to be almost as thick as the preserved
part of metacarpal II, as in Harpymimus
(Barsbold and Osmo´lska, 1990). The proxi-
mal end is triangular in proximal view, with
a slightly concave area where it was apressed
against the shaft of metacarpal II. The shaft
of metacarpal III appears to curve slightly
laterally. The distal articulation divides into
two tubera ventrally.
Phalanx III-1 is short and blocky, with flat
medial and ventral faces that are set perpen-
dicular to each other. As in phalanx II-1, the
medioventral end of the proximal articulation
extends for a short distance below the end of
metacarpal III. Distally, the medial collateral
ligament pit is very weak. The distal articu-
lation is apparently ginglymoid. Phalanx III-
2 is almost identical to phalanx III-1, except
for being more slender and lacking the short
heel on the proximal articulation. Phalanx
III-3 is longer than the combined lengths of
digits III-1 and III-2, as in derive ornithom-
imids (Barsbold and Osmo´lska, 1990). Prox-
imally, phalanx III-3 is similar to II-2, in-
cluding the presence of a small tubercle just
ventral to the proximal articulation. The shaft
thins distally and is thinnest just adjacent to
the distal articulation, which is offset ven-
trally from the shaft. The medial collateral
ligament fossa is deep but not displaced dor-
sally as in many other theropods. The ungual
is similar to those of digits I and II and is
roughly as long as that of digit II. It appears
to have a more pronounced groove for the
claw sheath than do the other unguals.
Both right and left femora are preserved;
however, the right is severely damaged (fig.
10). The left femur lies in articulation with
the acetabulum, and proximal lateral and dis-
tal proximal surfaces are exposed. Hindlimb
elements distal to the femur are not pre-
As in other ornithomimids, the femur is
Fig. 12. Strict consensus of 432 most parsimonious trees depicting relationships among ornithomi-
mosaur species derived from parsimony analysis of 220 characters in 50 coelurosaurian species (see Tree statistics for shortest trees are (TL
586, CI
45, and RI
75). Continental distributions are listed after taxon names.
slightly bowed (contra Barsbold and Osmo´l-
ska, 1990), but not to the level of Manirap-
tora. The proximal end is exposed in lateral
view. The greater trochanter is higher than
the lesser trochanter. The lesser trochanter is
alariform and is separated from the greater
trochanter by a deep cleft that extends ap-
proximately 28 mm down the femoral shaft.
This cleft ends in the bump, which appar-
ently does not continue down the femoral
shaft as the lateral ridge as in maniraptori-
forms like Velociraptor (Norell and Makov-
icky, 1997, 1999). A small ridge divides the
lesser trochanter into anterior and posteriorly
oriented surfaces. A weakly developed fourth
trochanter lies distal and medial to the pos-
terior trochanter. Distally the femur istwisted
to expose the posterior surface. The medial
condyle is much larger than the lateral one,
is bulbous, and extends medial to the axis of
the femoral shaft. A thin crest, or buttress,
extends proximally up the shaft of the femur
from the medial condyle. The medial and lat-
eral condyles are separated by a deep wide
popliteal fossa that is not closed distally by
lateral or medial expansions. The gastrocne-
mius process that lies posterior to the lateral
condyle is unusual in that it is thin and its
lateral surface is nearly flat. It contacts the
shaft of the femur nearly at a right angle and
borders a flat, triangular surface on the fem-
oral shaft that extends to the edge of the lat-
eral condylar surface. A very low ectocon-
dylar tuber is also present at the lateral apex
of the lateral condyle.
The thoracic cavity of Shenzhousaurus or-
ientalis contains numerous pebbles, which
are best interpreted as gastroliths. The uni-
form matrix surrounding the skeleton is de-
void of lithic clasts of a comparative size.
The pebbles are distributed unevenly in the
thoracic cavity, with a concentration just an-
terior to the preserved part of the gastral bas-
ket. Less concentrated amounts of gastroliths
occur throughout the rest of the thoracic cav-
ity, and some are dispersed posteriorlyacross
the femur and proximal end of the left ischi-
um and sacrum. The gastroliths are hetero-
geneous in size, shape, and composition.
Whereas some are smooth and rounded, oth-
ers are highly angular and/or pockmarked.
Gastroliths have been previously reported in
ornithomimosaurs (Kobayashi et al., 1999).
Phylogenetic analysis posits Shenzhousau-
rus near the base of Ornithomimosauria (Ma-
kovicky et al., in press), being more ad-
vanced than the Barremian Pelecanimimus
(fig. 12). Ornithomimosaurs are monophylet-
ic and are the sister group to a clade com-
posed of Maniraptora (including Ornitholes-
tes) (Gauthier, 1986; Sereno, 1997; Xu et al.,
2002b). No support was found for a close
relationship between ornithomimosaurs and
troodontids (Holtz, 1994). Alvarezsaurids,
which have been postulated as close orni-
thomimosaur relatives (Sereno, 2001), are
found to be the sister group of all other Man-
iraptora except Ornitholestes.Shenzhousau-
rus and other ornithomimosaurs are more de-
rived than Pelecanimimus in the progressive
loss of teeth from the upper jaws and all but
the tip of the dentary (Shenzhousaurus,Har-
pymimus) or complete loss of teeth (higher
ornithomimosaurs). Harpymimus and Shen-
zhousaurus are similar in having primitive
manual proportions in which metacarpal I is
much shorter than either II or III, but Har-
pymimus shares a derived curvature of the
ischium with higher ornithomimids.
Except for the Spanish taxon Pelecanimi-
mus, most ornithomimids are known from
Central Asia and western North America.
Examining distributions within the context of
the phylogeny (fig. 12) demonstrates that ear-
ly ornithomimids have an extensive evolu-
tionary history in eastern Asia, yet the center
of origin is ambiguous because of the Euro-
pean range of Pelecanimimus. Several other
dinosaur clades, including tyrannosaurs (Hutt
et al., 2001) and pachycephalosaurs (Sereno,
1999), whose derived members are mainly
known from Asia and North America, also
have basal taxa from the Early Cretaceous of
Europe predating the formation of the Turgai
Straits. Among higher ornithomimosaurs, a
single dispersal across Beringia is required to
account for the distribution of taxa between
North America and Asia if North American
ornithomimids form a monophyletic taxon.
Otherwise, two dispersals are required to ex-
plain the known geographic diversity of this
Advanced ornithomimosaurs lack teeth
and had beaks (Osborn, 1917, Norell et al.,
2001b). The edentulous nature of their beaks
has been used along with gastroliths (Kobay-
ashi et al., 1999) to suggest that the diet was
highly specialized. According to our phylo-
genetic analysis, the advanced ornithomimid
condition progressed through stages of loss
of the upper and posterior dentary teeth ini-
tially as seen in the reduced maxillary tooth-
row in the basal form Pelecanimimus.Shen-
zhousaurus and Harpymimus illustrate a
more progressive state in which maxillary
teeth are absent and the dentary only bears
teeth near the symphysis.
Although tooth loss is common among
coelurosaurs (Chiappe et al., 1999), the pat-
tern is disparate among groups. Therizino-
sauroids and hesperornithiformes have eden-
tulous premaxillae, but retain maxillary and
dentary teeth. Although advanced ovirapto-
rosaurs are edentulous, the basal Caudipteryx
has teeth restricted to the premaxilla. Nev-
ertheless, the ornithomimosaur pattern where
the lower jaw is toothed anteriorly and the
entire upper jaw is edentulous appears
unique as a phylogenetic precursor to tooth-
lessness among theropod dinosaurs, with the
possible exception of the basal avialan Shen-
zhouraptor (Ji et al., 2002b and 2003, Zhou
and Zhang, 2002).
We thank the National Geological Muse-
um of China. Mick Ellison prepared the il-
lustrations, and Brian Roach prepared the
specimen with the consultation of Marilyn
Fox. The Division of Paleontology at the
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aThis paper meets the requirements of ANSI/NISO Z39.48-1992 (Permanence of Paper).
... The sacrum consists of five sacral vertebrae, which are sandwiched between the ilia. Among ornithomimosaurs in which the sacrum is known, only Shenzhousaurus orientalis, Archaeornithomimus asiaticus and Gallimimus bullatus possess five sacral vertebrae (Osm olska et al., 1972;Smith and Galton, 1990;Ji et al., 2003), rather than the typical number of six (Makovicky et al., 2004;Kobayashi and Barsbold, 2005a;Lee et al., 2014;McFeeters et al., 2016;Sues and Averianov, 2016a). The sacral centra are elongated and spool-shaped, having a constriction in the middle but expanding at their anterior and posterior ends. ...
... On the lateral surface, the first sacral centrum bears a distinct, anteroposteriorly aligned groove; the fourth bears an oblong depression; and the fifth appears to lack a groove or depression, but bears an irregular pit, probably resulting from damage. Lateral non-invasive depressions comparable to those on the first and fourth sacrals also occur in the sacral vertebrae of Shenzhousaurus orientalis and other ornithomimid taxa, including Archaeornithomimus asiaticus, Sinornithomimus dongi, Gallimimus bullatus, Ornithomimus velox, Struthiomimus altus and Rativates evadens (Osm olska et al., 1972;Smith and Galton, 1990;Ji et al., 2003;Kobayashi and Lü, 2003;Makovicky et al., 2004;McFeeters et al., 2016). The lateral surfaces of the second and third sacrals are concealed by the ilia. ...
... The ischial peduncle is narrower and slightly longer than the pubic peduncle, and is convex ventrally, inserting into a concavity on the iliac peduncle of the ischium as in other ornithomimosaurs (Makovicky et al., 2004). The left ilium has a squared off posterior end as in other ornithomimosaurs, with the exception of Shenzhousaurus orientalis (Ji et al., 2003). The right brevis fossa is broad, and is formed by an arched shelf that extends across the medial surface of the ilium from the base of the ischial peduncle to the posterior end of the ilium. ...
Full-text available
A newly identified ornithomimosaurian pelvis and sacrum from the Upper Cretaceous Erlian Formation of Nei Mongol, China is described in detail in this paper. This specimen is distinguished from previously described taxa by the presence of a combination of features that is unique among Ornithomimosauria: sacrum comprising five vertebrae with neural spines fused into a continuous plate, iliac posterior end rectangular, pubic shaft distally straight, ischial boot not broadened transversely, and ischial shaft proximally straight, distally curved, and 80 percent as long as the pubis. This specimen differs from at least some material assigned to the sympatric Archaeornithomimus asiaticus, showing that two distinct ornithomimosaurian taxa are present in this Late Cretaceous fossiliferous rock unit. A phylogenetic analysis places LH-02-01 in a relatively early-diverging position within Ornithomimosauria, outside the two major clades Deinocheiridae and Ornithomimidae, but its relationships with other early-diverging ornithomimosaurs remain unresolved. The primitive nature of LH-02-01 adds to the evidence from fossil vertebrates that the Erlian Formation correlates with the Turonian Bissekty Formation of Uzebekistan, while the biostratigraphic evidence from non-vertebrates instead indicates a Campanian to Maastrichtian age for the Erlian Formation. This apparent contradiction remains unresolved, pending future research aimed at reconciling the seemingly incompatible lines of evidence.
... The coexistence of two ornithomimosaur genera is relatively common in Cretaceous ecosystems of Laurasia [15,[125][126][127][128]. Typically, co-occurrences include taxa of similar body size (small or medium-bodied) [125,126]. ...
... The coexistence of two ornithomimosaur genera is relatively common in Cretaceous ecosystems of Laurasia [15,[125][126][127][128]. Typically, co-occurrences include taxa of similar body size (small or medium-bodied) [125,126]. However, co-occurrences of both small/medium and large-bodied ornithomimosaur genera are rare. ...
Full-text available
Reconstructing the evolution, diversity, and paleobiogeography of North America's Late Cretaceous dinosaur assemblages require spatiotemporally contiguous data; however, there remains a spatial and temporal disparity in dinosaur data on the continent. The rarity of vertebrate-bearing sedimentary deposits representing Turonian-Santonian ecosystems, and the relatively sparse record of dinosaurs from the eastern portion of the continent, present persistent challenges for studies of North American dinosaur evolution. Here we describe an assemblage of ornithomimosaurian materials from the Santonian Eutaw Formation of Mississippi. Morphological data coupled with osteohistological growth markers suggest the presence of two taxa of different body sizes, including one of the largest ornithomimosaurians known worldwide. The regression predicts a femoral circumference and a body mass of the Eutaw individuals similar to or greater than that of large-bodied ornithomimosaurs, Beishanlong grandis, and Gallimimus bullatus. The paleoosteohistology of MMNS VP-6332 demonstrates that the individual was at least ten years of age (similar to B. grandis [~375 kg, 13-14 years old at death]). Additional pedal elements share some intriguing features with ornithomimosaurs, yet suggest a larger-body size closer to Deino-cheirus mirificus. The presence of a large-bodied ornithomimosaur in this region during this time is consistent with the relatively recent discoveries of early-diverging, large-bodied ornithomimosaurs from mid-Cretaceous strata of Laurasia (Arkansaurus fridayi and B. grandis). The smaller Eutaw taxon is represented by a tibia preserving seven growth cycles, with osteohistological indicators of decreasing growth, yet belongs to an individual approaching somatic maturity, suggesting the coexistence of medium-and large-bodied ornithomimosaur taxa during the Late Cretaceous Santonian of North America. The Eutaw ornithomimosaur materials provide key information on the diversity and distribution of North American ornithomimosaurs and Appalachian dinosaurs and fit with broader evidence of PLOS ONE PLOS ONE |
... 6). ZIN PH 1/13 is slightly bowed as in the Ornithomimosauria while in the Maniraptora the bowing of the femur is more pronounced (Ji et al., 2003). Thus, the previous referral of ZIN PH 1/13 to the Ornithomimosauria (Nesov, 1992(Nesov, , 1995Averianov et al., 2003b) is followed here. ...
... The Early Cretaceous Ornithomimosauria in Asia are represented by Harpymimus okladnikovi from the Albian Khuren Dukh Formation of Mongolia (Barsbold and Perle, 1984;Kobayashi and Barsbold, 2005), A.O. Averianov, A.V. Sizov, D.V. Grigoriev et al. Cretaceous Research 138 (2022) 105287 Shenzhousaurus orientalis from the Barremian Yixian Formation of Liaoning Province, China (Ji et al., 2003), Beishanlong grandis from the Aptian-Albian Xinminpu Group of Gansu Province, China (Makovicky et al., 2010), and Kinnareemimus khonkaenensis from the Barremian (?) Sao Khua Formation of Thailand (Buffetaut et al., 2009). The femur is unknown for Harpymimus and Kinnareemimus. ...
The revised dinosaur assemblage from the Lower Cretaceous Murtoi Formation at Mogoito locality in Transbaikalia, Russia, includes lithostrotian titanosaur Tengrisaurus starkovi known from caudal vertebrae, Sauropoda indet. represented by isolated teeth and metatarsal IV, theropods Ornithomimosauria, Therizinosauria, Dromaeosauridae, Theropoda indet. and ornithopods Jeholosauridae known from isolated teeth and bones. Isolated teeth with sculptured enamel attributed previously to Psittacosaurus sp. are referred here to Jeholosauridae indet. The Mogoito vertebrate assemblage is most similar to that from the Early Cretaceous locality Khuren Dukh in Mongolia by sharing a turtle Kirgizemys, a choristodere Khurendukhosaurus, and a similar ornithomimosaur.
... The coexistence of two ornithomimosaur genera is relatively common in Cretaceous ecosystems of Laurasia [15,[125][126][127][128]. Typically, co-occurrences include taxa of similar body size (small or medium-bodied) [125,126]. ...
... The coexistence of two ornithomimosaur genera is relatively common in Cretaceous ecosystems of Laurasia [15,[125][126][127][128]. Typically, co-occurrences include taxa of similar body size (small or medium-bodied) [125,126]. However, co-occurrences of both small/medium and large-bodied ornithomimosaur genera are rare. ...
Full-text available
Reconstructing the evolution, diversity, and paleobiogeography of North America’s Late Cretaceous dinosaur assemblages requires spatiotemporally contiguous data; however, there remains a spatial and temporal disparity in dinosaur data on the continent. The rarity of vertebrate-bearing sedimentary deposits representing Turonian–Santonian ecosystems, and the relatively sparse record of dinosaurs from the eastern portion of the continent, present persistent challenges for studies of North American dinosaur evolution. Here we describe an assemblage of ornithomimosaurian materials from the Santonian Eutaw Formation of Mississippi. Morphological data coupled with osteohistological growth markers suggest the presence of two taxa of different body sizes, including one of the largest ornithomimosaurians known worldwide. The regression predicts a femoral circumference and a body mass of the Eutaw individuals similar to or greater than that of large-bodied ornithomimosaurs, Beishanlong grandis and Gallimimus bullatus . The paleohistology of MMNS VP-6332 demonstrates that the individual was at least 11 years of age (similar to B. grandis [~375 kg, 13–14 years old at death]). Additional pedal elements share some intriguing features with ornithomimosaurs yet suggest a larger-body size closer to Deinocheirus mirificus . The presence of a large-bodied ornithomimosaur in this region during this time is consistent with the relatively recent discoveries of early-diverging, large-bodied ornithomimosaurs from mid-Cretaceous strata of Laurasia ( Arkansaurus fridayi and B. grandis ). The smaller Eutaw taxon is represented by a tibia preserving seven growth cycles, with osteohistological indicators of decreasing growth, yet belongs to an individual with near reaching somatic maturity of the larger taxon, suggesting the co-existence of medium- and large-bodied ornithomimosaur taxa during the Late Cretaceous Santonian of North America. The Eutaw ornithomimosaur materials provide key information on the diversity and distribution of North American ornithomimosaurs and Appalachian dinosaurs and fit with broader evidence of multiple cohabiting species of ornithomimosaurian dinosaurs in Late Cretaceous ecosystems of Laurasia.
... In compsognathids such as Beipiaognathus jii (Hu et al. 2016) and Sinocalliopteryx gigas ), manual phalanx III-3 is shorter than phalanges III-1 and III-2 combined and the flexor tubercles are weakly developed, but phalanx III-3 is longer than phalanges III-1 and III-2 combined and the flexor tubercles are well developed in SDUST-V1042. In ornithomimosaurians such as Shenzhousaurus orientalis (Ji et al. 2003) and therizinosauroids such as Beipiaosaurus inexpectus (Xu et al. 1999a), Jianchangosaurus yixianensis (Pu et al. 2013) and Lingyuanosaurus sihedangensis (Yao et al. 2019), flexor tubercles of these groups are small, and not as high as that of the proximal articular facet, but in SDUST-V1042, the flexor tubercles are well developed and the height is similar to that of the proximal articular facet. In oviraptorosaurians, the manus is well preserved in Caudipteryx spp. ...
A well-preserved paravian manus was described from the Jehol Biota of western Liaoning, China. This specimen was inferred as an early-diverging troodontid and reveals new morphological details of the troodontid clade, such as both ends of phalanx II-1 and phalanx II-2 asymmetrical, phalanx II-1 and phalanx III-3 twisted medially, the ventral side of the distal end of phalanx II-2 flat, and the proximal articular surface of phalanx III-1 non-trochoid. The range of motion of this manus was examined based on the CT data of the bones, showing that the range of flexion of this troodontid manus is relatively large while the range of extension is relatively limited, which is consistent with the tendency of the decrease in the manual extension capabilities from early-diverging theropods to maniraptoriforms.
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Ornithomimosauria consists of the ostrich-mimic dinosaurs, most of which showing cursorial adaptations, that often exhibit features indicative of herbivory. Recent discoveries have greatly improved our knowledge of their evolutionary history, including the divergence into Ornithomimidae and Deinocheiridae in the Early Cretaceous, but the early part of their history remains obscured because their fossil remains are scarce in the Aptian–Albian sediments. In recent years, many isolated ornithomimosaur remains have been recovered from the Aptian Kitadani Formation of Fukui, central Japan. These remains represent multiple individuals that share some morphological features common to them but unknown in other ornithomimosaurs, suggesting a monospecific accumulation of a new taxon. As a result of the description and phylogenetic analysis, the Kitadani ornithomimosaur is recovered as a new genus and species Tyrannomimus fukuiensis, the earliest definitive deinocheirid that complements our knowledge to understand the early evolutionary history of Ornithomimosauria. Due to its osteological similarity to Tyrannomimus, a taxon previously considered an early tyrannosauroid based on fragmentary specimens, namely Aviatyrannis jurassica, may represent the earliest ornithomimosaur from the Upper Jurassic of Europe, significantly expanding the temporal and biogeographic range of Ornithomimosauria. This finding fills a 20-million-year ghost lineage of Ornithomimosauria implied by the presence of the oldest fossil record of Maniraptora from the Middle Jurassic and is consistent with the hypothesis that their biogeographic range was widespread before the Pangaean breakup in the Kimmeridgian.
A new small-bodied theropod dinosaur, Migmanychion laiyang gen. et sp. nov., is erected based on appendicular skeletal material from the Lower Cretaceous of the Pigeon Hill locality, Inner Mongolia, China. This theropod shows a peculiar combination of features in the hand, in part shared with therizinosauroids, oviraptorosaurs and with the enigmatic Fukuivenator paradoxus from Japan. Phylogenetic analysis supports the closest affinity of Migmanychion with Fukuivenator, yet alternative placements among Oviraptorosauria or among the non-avialan paravians result suboptimal descriptions of the character distribution. Although this new taxon is confidently referred to Maniraptora, this result is based uniquely on derived features of the hand: only additional material could substantiate its precise placement among the bird-like theropods. Fragmentary appendicular material from the same locality cannot be unambiguously referred to Migmanychion. One specimen, including associated partial pelvis and hindlimbs, is tentatively referred to a paravian maniraptoran.
This Doctoral Thesis presents an exhaustive review of the Patagonian alvarezsaurids (Dinosauria, Theropoda). It includes a detailed osteological description of specimens of Patagonykus puertai (Holotype, MCF-PVPH-37), cf. Patagonykus puertai (MCF-PVPH-38), Patagonykinae indet. (MCF-PVPH-102), Alvarezsaurus calvoi (Holotype, MUCPv-54), Achillesaurus manazzonei (Holotype, MACN-PV-RN 1116), Bonapartenykus ultimus (Holotype, MPCA 1290), and cf. Bonapartenykus ultimus (MPCN-PV 738). A phylogenetic analysis and a discussion about the taxonomic validity of the recognized species and the taxonomic assignment of the materials MCF-PVPH-38, MCF-PVPH-102 and MPCN-PV 738 are presented. Different evolutionary and paleobiological studies were carried out in order to elucidate functional and behavioral aspects. Alvarezsaurus calvoi (MUCPv-54), Achillesaurus manazzonei (MACN-PV-RN 1116), Patagonykus puertai (MCF-PVPH-37) and Bonapartenykus ultimus (MPCA 1290) are valid species due to the presence of many autapomorphies. In this sense, the hypothesis proposed by P. Makovicky and collaborators that Achillesaurus manazzonei is a junior synonym of Alvarezsaurus calvoi is rejected. Likewise, certain morphological evidence allows hypothesizing that Alvarezsaurus calvoi represents a growth stage earlier than skeletal maturity. Specimen MCF-PVPH-38 is referable as cf. Patagonykus puertai, while MCF-PVPH-102 is considered an indeterminate Patagonykinae. In turn, MPCN-PV 738 is assigned as cf. Bonapartenykus ultimus based on the little overlapping material with the Bonapartenykus ultimus holotype. The results obtained from the mineralogical characterization through the X-ray diffraction method of specimens MPCN-PV 738 and the holotype of Bonapartenykus ultimus (MPCA 1290), allow to suggest that both specimens come from the same geographical area and stratigraphic level. The phylogenetic analysis, which is based upon the matrix of Gianechini and collaborators of 2018 with the inclusion of proper characters, and the database of Xu and collaborators of 2018, recovered the South American members of Alvarezsauria, such as Alnashetri cerropoliciensis (Candeleros Formation; Cenomanian), Patagonykus puertai (Portezuelo Formation, Turonian-Coniacian), Alvarezsaurus calvoi and Achillesaurus manazzonei (Bajo de La Carpa Formation, Coniacian-Santonian), and Bonapartenykus ultimus (Allen Formation, Campanian-Maastrichtian), nesting within the family Alvarezsauridae. In this sense, the forms that come from the Bajo de La Carpa Formation (Coniacian-Santonian) are recovered at the base of the Alvarezsauridae clade, while Alnashetri cerropoliciensis nests as a non-Patagonykinae alvarezsaurid. Regarding the type specimens of Patagonykus puertai and Bonapartenykus ultimus, they are recovered as members of the Patagonykinae subclade, a group that is recovered as a sister taxon of Parvicursorinae, both nested within the Alvarezsauridae. In addition, the topology obtained allows discerning the pattern, rhythm and time of evolution of the highly strange and derived alvarezsaurian skeleton, concluding in a gradual evolution. The Bremer and Bootstrap supports of the nodes (Haplocheirus + Aorun), [Bannykus + (Tugulusaurus + Xiyunykus)], and Patagonykinae, show indices that represent very robust values for these nodes. Likewise, these values suggest that two endemic clades originated early in Asia, while one endemic clade is observed in Patagonia, i.e., Patagonykinae. The analysis of the directional trends of the Alvarezsauria clade, tested by means of a own database on body masses based on the Christiansen and Fariña method, subsequently calibrated with the group's phylogeny using the R software, shows two independent miniaturization events in the alvarezsaurid evolution, namely the former originating from the base of the Alvarezsauridae (sustained by Alvarezsaurus), and the latter within the Parvicursorinae. Analysis of the Alvarezsauria dentition reveals possible dental synapomorphies for the Alvarezsauria clade that should be tested in an integrative phylogenetic analysis. The general characterization of the forelimb and a partial reconstruction of the myology of alvarezsaurs demonstrate different configurations for Patagonykinae and Parvicursorinae. The multivariate analyzes carried out from the databases of Elissamburu and Vizcaíno, plus that of Cau and collaborators, show that the Patagonykinae would have had ranges of movements greater than those observed in Parvicursorinae, although the latter would have had a greater capacity to carry out more strenuous jobs. The morphometric analysis of the hindlimb and the use of the Snively and collaborators equations, show that the configuration of this element in Alvarezsauria is indicative of a highly cursorial lifestyle, as well as possible particular strategies for more efficient locomotion. The topology obtained in the phylogenetic analysis that was carried out in this Doctoral Thesis, allowed clarifying the ontogenetic changes observed in the ontogenetic series of the manual ungueal element II-2 within the clade Alvarezsauridae. In addition, the multivariate analysis carried out from the manual phalanx II-2 allows us to infer that alvarezsaurs could have performed functions such as hook-and-pull and piercing, where the arm would function as a single unit. The anatomy and myology of the alvarezsaurian tail show that the caudal vertebrae of alvarezsaurians exhibit a combination of derived osteological features that suggests functions unique among theropods, such as considerable dorsal and lateral movements, as well as exceptional abilities to support distal loading of their long tail without compromising stability and/or mobility.
Dinosaur tracks have been known and reported sporadically from the coal-bearing beds of the Fuxin Formation (upper Aptian–Albian, upper Lower Cretaceous) of Liaoning Province, northeastern China for some time but have not been described in detail. Here available material is illustrated suggesting a diversity of theropod track morphotypes, including small grallatorid, eubrontid and possible Gigandipus-like forms, a Magnoavipes-like form and an isolated small ornithopod track. Some of the tracks show the characteristic distortion of flattened footprints. The ichnofauna supplements our knowledge of the Fuxin Biota by adding a more diverse dinosaur fanua, indicated by the footprint record.
A total of 227 theropod teeth have so far been recovered from the upper Campanian Laño site (northern Iberian Peninsula). The teeth were studied for their qualitative and quantitative features. From the theropod sample found at Laño, seven morphotypes attributed to five taxa are identified: a medium to large abelisaurid (Arcovenator sp.) and four small coelurosaurians (Dromaeosauridae indet., Paraves indet., cf. Paronychodon sp. and cf. Richardoestesia sp.) Together with the ground bird Gargantuavis and a possible ornithomimosaur, the theropod fauna of Laño might be composed of two medium–large-sized non-avian theropods, four small-bodied non-avian theropods and a large terrestrial bird. This makes the Laño site the richest and most diverse latest Cretaceous theropod site in Europe. Furthermore, the Laño site and the Upper Cretaceous localities of Europe that have yielded theropod remains suggest that the medium–large-sized theropods were abelisaurids or indeterminate theropods. The small theropods are more abundant, diverse and represented by different dromaeosaurids, Paronychodon, Richardoestesia or related forms, troodontids and, probably, by other paravians. Of the birds, enantiornithines, gargantuaviids and ornithurines are also common in the European Upper Cretaceous sites. The theropod assemblage of Laño, together with the taxa of other Upper Cretaceous sites, supports the idea that several theropod dispersal events took place during the Cretaceous. This resulted in a mixture of European endemic, Asiamerican and Gondwanan forms. This study also supports the hypothesis that the intra-Maastrichtian faunal turnover that occurred in the Ibero-Armorican landmass seems to have had no apparent effect on theropods.