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A gigantic feathered dinosaur from the Lower Cretaceous of China

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Numerous feathered dinosaur specimens have recently been recovered from the Middle-Upper Jurassic and Lower Cretaceous deposits of northeastern China, but most of them represent small animals. Here we report the discovery of a gigantic new basal tyrannosauroid, Yutyrannus huali gen. et sp. nov., based on three nearly complete skeletons representing two distinct ontogenetic stages from the Lower Cretaceous Yixian Formation of Liaoning Province, China. Y. huali shares some features, particularly of the cranium, with derived tyrannosauroids, but is similar to other basal tyrannosauroids in possessing a three-fingered manus and a typical theropod pes. Morphometric analysis suggests that Y. huali differed from tyrannosaurids in its growth strategy. Most significantly, Y. huali bears long filamentous feathers, thus providing direct evidence for the presence of extensively feathered gigantic dinosaurs and offering new insights into early feather evolution.
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LETTER doi:10.1038/nature10906
A gigantic feathered dinosaur from the Lower
Cretaceous of China
Xing Xu
1,2
, Kebai Wang
3
, Ke Zhang
4
, Qingyu Ma
1
, Lida Xing
5
, Corwin Sullivan
1
, Dongyu Hu
2
, Shuqing Cheng
3
& Shuo Wang
1,6
Numerous feathered dinosaur specimens have recently been recovered
from the Middle–Upper Jurassic and Lower Cretaceous deposits of
northeastern China, but most of them represent small animals
1
.Here
we report the discovery of a gigantic new basal tyrannosauroid,
Yutyrannus huali
gen. et sp. nov., based on three nearly complete
skeletons representing two distinct ontogenetic stages from the
Lower Cretaceous Yixian Formation of Liaoning Province, China.
Y. huali
shares some features, particularly of the cranium, with derived
tyrannosauroids
2,3
, but is similar to other basal tyrannosauroids
4–12
in
possessing a three-fingered manus and a typical theropod pes.
Morphometric analysis suggests that
Y. huali
differed from tyranno-
saurids in its growth strategy
13,14
. Most significantly,
Y. huali
bears
long filamentous feathers, thus providing direct evidence for the pres-
ence of extensively feathered gigantic dinosaurs and offering new
insights into early feather evolution.
The Tyrannosauroidea was one of the longest-lived theropod sub-
groups, with a fossil record extending from the Middle Jurassic to the
uppermost Cretaceous
2
. Basal tyrannosauroids are relatively small, and
gigantic ones (adult body mass greater than 1,000 kg) are almost entirely
restricted to the latest Cretaceous
2,15
. Four tyrannosauroid taxa have
recently been reported from the Lower Cretaceous of China
6,8,9,15,16
,
although the provenance of one of them, Raptorex kriegsteini,hasbeen
seriously questioned
17
. These taxa range from 1.4 m to about 10 m in
body length
6,8
and show considerable morphological disparity: some taxa
closely resemble the highly specialized Tyrannosauridae
9,16
,whereas
others are more similar to generalized coelurosaurs
6,8
. Combined
with discoveries from outside China, these morphologically and
taxonomically diverse basal tyrannosauroid specimens document the
occurrence of a significant radiation in the early history of the group.
Here we report the discovery of a new feathered tyrannosauroid (Figs 1
and 2 and Supplementary Figs 1–3) from the Lower Cretaceous of China
that is close to some Late Cretaceous tyrannosauroids in adult size
(Supplementary Information). Phylogenetic analyses using two differ-
ent theropod matrices place this taxon among basal tyrannosauroids,
but relatively close to the Tyrannosauridae (Fig. 3 and Supplementary
Information). In combination with other recent discoveries, such as
that of the similarly sized Sinotyrannus from the Lower Cretaceous of
Liaoning
8
, the new find demonstrates that tyrannosauroids were the
dominant large predators in the middleEarly Cretaceous ecosystems of
northeastern China, suggesting that the ecological dominance of the
group was achieved early in their evolution in some geographical
regions at least.
Theropoda Marsh, 1881
Coelurosauria sensu Gauthier, 1986
Tyrannosauroidea Osborn, 1905
Yutyrannus huali gen. et sp. nov.
Etymology. The generic name is derived from ‘yu’ (Mandarin for
‘feathers’) 1‘tyrannus’ (Latin for ‘king’ or ‘tyrant’). The specific name
‘huali’ means ‘beautiful’ in Mandarin, referring to the beauty of the
plumage of this animal.
Holotype. ZCDM (Zhucheng Dinosaur Museum, Shandong)
V5000, a semi-articulated, nearly complete skeleton. A cast of the
specimen is housed at the Institute of Vertebrate Paleontology and
Paleoanthropology as IVPP FV1960.
Paratypes. ZCDM V5001, a nearly complete, articulated skeleton; and
ELDM (Erlianhaote Dinosaur Museum, Inner Mongolia) V1001, an
articulated skeleton missing the tail. Casts of these specimens are housed
at the Institute of Vertebrate Paleontology and Paleoanthropology as
IVPP FV1961 and IVPP FV1962, respectively.
Horizon and locality. Batuyingzi, Beipiao, Liaoning Province, China;
Lower Cretaceous Yixian Formation
18
.
Diagnosis. A gigantic tyrannosauroid distinguishable from other tyr-
annosauroids by the unique presence of a rugose, highly fenestrated
midline crest formed bythe premaxillae and nasals, ananteroventrally
projecting orbital process in the area of the junction between the
frontal and jugal processes of the postorbital, a large concavity on
the lateral surface of the main body of the postorbital, and an external
mandibular fenestra located mostly within the surangular. Also differs
from Sinotyrannus in that the morphologically lateral surface of the
maxillary process of the premaxilla faces dorsally, the maxilla lacks an
anterior ramus, the maxillary fenestra is posteriorly positioned, the
antorbital fossa has a posteroventrally sloping ventral margin, and
the ilium has a straight dorsal margin and a postacetabular process
whose ventral margin bears a lobe-like flange.
Description and comparisons. ZCDM V5000 probably represents an
adult individual, given that the neurocentral sutures on all of the visible
vertebrae are closed and the sacrals are fused together. With a femoral
length of 85 cm, ZCDM V5000 even exceeds the adult sizes of some
Late Cretaceous tyrannosauroids, such as Dryptosaurus (77 cm) and
Appalachiosaurus (79cm). ZCDM V5000 is estimated to have had a
mass of about 1,414 kg as a living animal, on the basis of an empirical
equation
19
, and ZCDM V5001 and ELDM V1001 are estimated to have
had respective masses of 596kg and 493kg. Both ZCDM V5001 and
ELDM V1001 display fusion features, such as visible neurocentral
sutures on all of the presacral vertebrae, suggesting an ontogenetic
stage considerably earlier than that inferred for ZCDM V5000. On
the basis of data on the growth of other large tyrannosauroids
13
,
ELDM V1001 is estimated to be at least 8years younger than
ZCDM V5000.
The most striking cranial feature of Y. huali is a highly pneumatic
midline crest resembling those of Guanlong
7
and the carcharodonto-
saurian Concavenator
20
, although in Y. huali the crest is formed by
premaxillary and nasal portions that are only loosely articulated
with each other. The dorsal margin of the crest bears a series of low
prominences that are likely to be homologous to the rugosities seen in
all Late Cretaceous tyrannosauroids
9
. The cranium of Y. huali also
exhibits some features thatoccur consistently in basal, butnotderived,
1
Institute of Vertebrate Paleontology and Paleoanthropology, Key Laboratory of Evolutionary Systematics of Vertebrates, Chinese Academy of Sciences, 142 Xiwai Street, Beijing 100044, China.
2
Liaoning
Paleontological Museum, Shenyang Normal University, 253 North Huanghe Street, Shenyang 110034, China.
3
Zhucheng Dinosaur Museum, Zhucheng, Shandong, 262200, China.
4
School of the Earth
Sciences and Resources, China University of Geosciences, 28 Xueyuan Road, Beijing 100083, China.
5
Department of Biological Sciences, University of Alberta, 11145 Saskatchewan Drive, Edmonton,
Alberta T6G 2E9, Canada.
6
Graduate University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China.
92 | NATURE | VOL 484 | 5 APRIL 2012
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©2012
tyrannosauroids
2,3,15
. The elliptical externalnaris is large and posteriorly
positioned; a sharp groove runs along the anterior margin of the
premaxilla; the maxilla bears a sharp groove paralleling the ventral rim
of the antorbital fossa; the jugal has a raised, anteroposteriorly orientated
rim; and the surangular has a long anterior flange. Previous studies have
suggested that some of these features are synapomorphies of the basal
clade Proceratosauridae
4,15
, but our phylogenetic analysis optimizes
several of these features as synapomorphies of the Tyrannosauroidea.
However, many other cranial features of Y. huali are more similar to
those of derived tyrannosauroids
2,3,21,22
. For example, the skull is large
and deep; the premaxilla has a proportionally deep main body and a
maxillary process whose morphologically lateral surface faces dorsally
in adults; the maxilla has a markedly convex ventral margin and a
posteriorly tapering main body; the lacrimal is in the shape of a ‘7’;
the cornual process of the lacrimal is a large conical structure; the
postorbital has a wide jugal process and a suborbital process extending
into the orbit; the squamosal has an anteroposteriorly orientated
quadratojugal process that intrudes into the infratemporal fenestra;
the quadratojugal has a large posterior process that overlaps the posterior
surface of the quadrate; the external mandibular fenestra is small; the
dentary has a strongly concave dorsal margin and a posteriorly located
inflection point between the anterior and ventral margins in lateral view;
and the surangular has a prominent horizontal ridge.
The vertebrae are not pneumatized to the degree seen in the
Tyrannosauridae, but they show initial development of some features
that are characteristic of derived tyrannosauroids
2,21
. These features
include prominent flanges for ligament attachment on the anterior and
posterior margins of the neural spines of the cervical and dorsal vertebrae,
tall neural spines on the posterior cervical vertebrae, laterally placed
prezygapophyses on the middle cervical vertebrae, and anteroposteriorly
shortened dorsal vertebrae with posteriorly placed neural spines.
The shoulder girdle is in general plesiomorphic, as indicated by the
relative robustness of the scapular blade, the weakly expanded distal
end of the scapula, and the large coracoid foramen. The forelimbs are
also similar to those of basal tyrannosauroids in retaining a typical
basal coelurosaurian design, including a three-fingered manus
15
.
The pelvis displays several derived features
15
: the dorsal margin of
the ilium is mostly straight, the ventral margin of the postacetabular
process of the ilium bears a prominent lobe-like flange, the pubic boot
is large and forms a distinct anterior expansion, and the ischium is
much more slender than the pubis. The hindlimbsare generally similar
to those of basal tyrannosauroids, and the distal segments are propor-
tionally short, more similar to allosauroids and basal tyrannosauroids
than to tyrannosaurids
2,14
.
Filamentous integumentary structures are preserved in all three
specimens. Those preserved in ZCDM V5000 are evidently associated
with the posterior caudal vertebrae. As preserved, they are parallel to
each other and form an angle of about 30uwith the long axis of the tail.
The filaments are at least 15 cm long. They are too densely packed for it
to be possible to determinewhether they are elongate broad filamentous
feathers (EBFFs) like those seen in the therizinosauroid Beipiaosaurus,
slender monofilaments, or compound filamentous structures. Those of
ZCDM V5001 are near the pelvis and pes. They are filamentous struc-
tures, but morphological details are not preserved. In ELDM V1001,
integumentary filamentsare visible extending fromthe dorsal side of the
neck, and near a limb bone that is tentatively identified as a humerus.
Those extending from the neck measure more than 20cm, and those
along the humerus at least 16cm. Although feather preservation is
patchy in these specimens, as occurs even in some fossil birds from
the Jehol Group that undoubtedly had plumage covering most of the
body, the distribution of the preserved filamentous feathers in the three
specimens of Y. huali implies that this taxon had an extensively
a
b
60 cm
cav l lp
lt sk
ma
ls
rc
rh
rm
rr
ru
rs
r
rt
rp
dr
rfe
ril
lil
sycev
sk
ma
ls
rs
rc
lh
lm
lr
lu ga lt l
lis
lil
lp
rp
pu
lfe
rfedv
dr
Figure 1
|
Yutyrannus huali
(ZCDM V5000 and ZCDM V5001).
a, Photograph of the slab preserving ZCDM V5000 and ZCDM V5001. b,Line
drawing of the slab. Abbreviations: cav, caudal vertebra; cev, cervical vertebra;
dr, dorsal rib; dv, dorsal vertebra; ga, gastralia; lfe, left femur; lfi, left fibula; lh,
left humerus; lil, left ilium; lis, left ischium; lm, left manus; lp left pes; lr, left
radius; ls, left scapula;lt, left tibiotarsus; lu, left ulna; ma, mandible; pu, pubis; rc,
right coracoid; rfe, right femur; rh, right humerus; ril, right ilium; rm, right
manus; rp, right pes; rr, right radius; rs, right scapula; rt, right tibiotarsus; ru,
right ulna; sk, skull; sy, synsacrum.
LETTER RESEARCH
5 APRIL 2012 | VOL 484 | NATURE | 93
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©2012
feathered integument in life. This has also been inferred for Dilong,
and some other non-avian feathered dinosaurs
1
.
Morphological variations. Some morphological differences between
ZCDM V5000, ZCDM V5001 and ELDM V1001 may represent
ontogenetic variations. With increasing maturity, for example, the
skull becomes deeper and more robust, the premaxilla becomes
narrower and taller, the anterior portion of the premaxilla becomes
more medially orientated, the lateral surface of the maxillary process of
the premaxilla rotates to face dorsally, and the maxillary fenestra
becomes more anteriorly located. Several other morphological varia-
tions, such as the presence of a relatively straight dorsal margin of the
ilium in ZCDM V5000 and ELDM V1001 and a convex one in ZCDM
V5001, are more difficult to interpret in ontogenetic terms. They may
reflect individual genetic variation or sexual dimorphism.
A morphometric analysis suggests that Y. huali differed in its growth
pattern from the highly specialized tyrannosaurids (Supplemen-
tary Information). Using femur length as a standard proxy for overall
size, the scapula and ilium display negative allometry in Y. huali
(in contrast to positive allometry and near isometry, respectively, in
tyrannosaurids
14
). The radius, metacarpus and distal hindlimb segments
are negatively allometric in both Y. huali and the Tyrannosauridae, but
the negative allometry of the metacarpus, tibia and metatarsus is much
stronger in Y. huali than in tyrannosaurids
14
.
This discovery has implications for early feather evolution.
Although some gigantic dinosaurs are likely to have been feathered
animals
23
, the largest previously known non-avian dinosaur in which
direct evidence for a feathery covering is available is Beipiaosaurus
24
(adult body mass about 1/40 that of ZCDM V5000). The discovery of
Y. huali provides solid evidence for the existence of gigantic feathered
dinosaurs and, more significantly, of a gigantic species with an extens-
ive feathery covering.
Gigantism affects many aspects of animal structure and function.
Extensive filamentous integumentary coverings such as feathers and
hair are partly or even primarily insulative in function, but some large
mammals have become almost entirely hairless because their low
surface-to-volume ratios permit them to retain metabolic heat even
without a pelage (although large mammals living in cold environ-
ments, such as the bovid Bison bison, retain substantial fur). Gigantic
tyrannosauroids have been suggested to lack an extensive feathery
covering for analogous reasons
6
. This interpretation derives some
support from reported impressions of small patches of scaly skin
25,26
,
and there is certainly no direct fossil evidence for the presence of
feathers in gigantic Late Cretaceous tyrannosauroids. The discovery
of Y. huali, however, indicatesthat at least one gigantic dinosaur had an
extensive insulative coatof feathers, showing in turn that drastic reduc-
tion of the plumage was not an inevitable consequence of very large
body size. If Late Cretaceous tyrannosaurids such as Tyrannosaurus
rex were similar to Y. huali in this respect, both basal and derived
tyrannosauroid dinosaurs would differ from mammals in lacking a
tendency to lose their integumentary covering as result of gigantism.
Alternatively, if scales were indeed the dominant integumentary
structures in most Late Cretaceous tyrannosauroids, the presence of
long feathersin the gigantic Y. huali could representan adaptation to an
unusually cold environment. Y. huali lived during a period (the
Barremian–early Albian) that has been interpreted as considerably
colder than the rest of the Cretaceous (a mean annual air temperature
of about 10 uC in western Liaoning, in contrast with about 18uCata
similar latitude in the Late Cretaceous)
27
. Most gigan tic Late Cretaceous
tyrannosauroids, by contrast, lived in a warm climate that was con-
ducive to the loss of an extensive insulative feathery covering, although
populations inhabiting cold environments such as the landthat is now
Alaska would have been a notable exception
28,29
.Itispossiblethatthe
extent and nature of the integumentary covering changed over time in
response to shifts in body size and the temperature of the environment
throughout tyrannosauroid evolutionary history, as has clearly
occurred in some mammalian taxa
30
. However, it must be noted that
a
a
cd e
fg h
b
d
mf
aop
pnr
r
pnr
np
g
lec
cp
sr
lpa
pnr
clp
cp
co
ls
sp
Figure 2
|
Selected elements of
Y. huali
(ZCDM V5000, ZCDM V5001 and
ELDM V1001). a, Photograph of the skull and mandible of ELDM V1001.
b, Line drawing of the skull and mandible of ELDM V1001. c–h, filamentous
integumentary structures preserved in the three specimens: c, along the
posterior caudal vertebrae of ZCDM V5000; d, along the cervical vertebrae of
ELDM V1001; e,f, along a limb bone of ELDM V1001; g,h, near the pes of
ZCDM V5001 (fand hare close-up views). Abbreviations: aop, accessory
orbital process; clp, cultriform process; co, concavity; cp, cornual process; g,
groove; lec, left ectopterygoid; lpa, left palatine; ls, left squamosal; mf, maxillary
fenestra; np, nasal prominences; pnr, pneumatic recesses; r, ridge; sp.,
suborbital process; sr, surangular ridge.
RESEARCH LETTER
94 | NATURE | VOL 484 | 5 APRIL 2012
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©2012
the plumage is only partly preserved in all three known specimens of
Y. huali, and the possibility that the feathers had only a restricted
distribution on the body cannot be completely excluded. If this was
so, the feathers might have functioned primarily as display structures
as in some other non-avian theropod groups
1
.
Received: 26 November 2011; accepted 27 January 2012.
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Supplementary Information is linked to the online version of the paper at
www.nature.com/nature.
Acknowledgements We thank L. Zhang for discussions, R. Li, H. Zang and X. Ding for
illustrations, and H. Wang, L. Xiang and R. Cao for preparing the specimens. We thank
the Zhucheng Municipal Government and Erlianhaote Municipal Government for
support. This study was supported by grants from the National Natural Science
Foundation of China and Special Funds For Major State Basic Research Projects of
China.
Author Contributions X.X.designed the project. X.X., K.W., K.Z., Q.M., L.X., C.S.,D.H., S.C.
and S.W. performed the research. X.X., C.S. and Q.M. wrote the manuscript.
Author Information Reprints and permissions information is available at
www.nature.com/reprints. The authors declare no competing financial interests.
Readers are welcome to comment on the online version of this article at
www.nature.com/nature. Correspondence and requests for materials should be
addressed to X.X. (xingxu@vip.sina.com).
Myr ago
65
L
L
M
Dilong
Guanlong
Yutyrannus
Eotyrannus
Xiongguanlong
Dryptosaurus
Tyrannosauridae
Jurassic Cretaceous
E
99
125
145
176
161
Figure 3
|
A simplified cladogram showing the systematic position of
Y. huali
among the Tyrannosauroidea. Silhouettes indicate body size and
possible extent of plumage. Different tyrannosauroids seem to have attained
gigantic body size independently in the Early and Late Cretaceous, but only in
the Early Cretaceous is there direct evidence of a gigantic form with an
extensively feathered integument. This may reflect the relatively cold climate of
the middle Early Cretaceous. See also Supplementary Information.
LETTER RESEARCH
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... New analyses of Proceratosaurus bradleyi from the Bathonian Taynton Limestone Formation of the UK (Rauhut, Milner & Moore-Fay, 2010) and Dryptosaurus aquilunguis from the Maastrichtian New Egypt Formation of the USA (Brusatte, Benson & Norell, 2011) have established that these taxa are additional members of the tyrannosauroid radiation. Furthermore, both Xiongguanlong baimoensis from the Aptian-Albian Xinminpu Group of western China (Li et al., 2009) and Yutyrannus huali from the Lower Cretaceous Yixian Formation of China (Xu et al., 2012) have been recovered as outside the Dryptosaurus + Tyrannosauridae clade (Brusatte et al., 2010bZanno et al., 2019) while Appalachiosaurus montgomeriensis from the Demopolis Formation of the USA (Carr, Williamson & Schwimmer, 2005) and Bistahieversor sealeyi from the Campanian Kirtland Formation of the USA (Carr & Williamson, 2010) are larger-bodied taxa successively closer to Tyrannosauridae and more like tyrannosaurids in cranial and other characters. It has also been proposed that Bagaraatan ostromi from the Maastrichtian Nemegt Formation of Mongolia (Osmólska, 1996) and Santanaraptor placidus from the ?Albian Santana Formation of Brazil (Kellner, 1999) might be non-tyrannosaurid tyrannosauroids (Holtz, 2004;Choiniere et al., 2010). ...
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Eotyrannus lengi Hutt et al., 2001 from the Lower Cretaceous Wessex Formation (part of the Wealden Supergroup) of the Isle of Wight, southern England, is described in detail, compared with other theropods, and evaluated in a new phylogenetic analysis. Eotyrannus is represented by a single individual that would have been c. 4.5 m long; it preserves the anterior part of the skull, a partial forelimb and pectoral girdle, various cervical, dorsal and caudal vertebrae, rib fragments, part of the ilium, and hindlimb elements excluding the femur. Lack of fusion with regard to both neurocentral and sacral sutures indicates subadult status. Eotyrannus possesses thickened, fused, pneumatic nasals with deep lateral recesses, elongate, tridactyl forelimbs and a tyrannosaurid-like scapulocoracoid. The short preantorbital ramus of the maxilla and nasals that are approximately seven times longer than they are wide show that Eotyrannus was not longirostrine. A posterodorsally inclined ridge on the ilium's lateral surface fails to reach the dorsal margin: a configuration seen elsewhere in Juratyrant. Eotyrannus is not arctometatarsalian. Autapomorphies include the presence of curving furrows on the dentary, a block-like humeral entepicondyle, and a distoproximally aligned channel close to the distolateral border of the tibia. Within Tyrannosauroidea, E. lengi is phylogenetically intermediate between Proceratosauridae and Yutyrannus and the clade that includes Xiongguanlong, Megaraptora, Dryptosaurus and Tyrannosauridae. We do not find support for a close affinity between Eotyrannus and Juratyrant. Our analysis supports the inclusion of Megaraptora within Tyrannosauroidea and thus increases Cretaceous tyrannosauroid diversity and disparity. A proposal that Eotyrannus might belong within Megaraptora, however, is based on character states not present in the taxon. Several theropods from the Wessex Formation are based on material that overlaps with the E. lengi holotype but none can be shown to be synonymous with it. Subjects Paleontology, Zoology
... Premaxilla-The body of the premaxilla is shallow in TMP 2009.12.14 and TMP 2016.14.1 (depth-to-length ratio of 1.01 and 0.89, respectively), similar to that of other immature tyrannosaurids (Carpenter, 1992;Carr, 1999;Tsuihiji et al., 2011). In contrast, the premaxilla is deeper in adult Gorgosaurus individuals and other mature tyrannosauroids (e.g., depth-to-length ratio of 1.39 in TMP 1986.36.116; see Currie, 2003a;Rauhut et al., 2010;Xu et al., 2012). ...
Article
Known from dozens of specimens discovered since the early 20th century, Gorgosaurus libratus has arguably contributed more than any other taxon to our understanding of the life history of tyrannosaurids. However, juvenile material for this taxon is rare. Here, we describe two small, articulated Gorgosaurus specimens (skull lengths of ca. 500 mm) that help advance our knowledge of the anatomy and ontogeny of this taxon and of tyrannosaurids in general. The new specimens exhibit hallmark juvenile tyrannosaurid features, including long, low, and narrow skulls, large circular orbits, absent or incipient cranial ornamentation, ziphodont dentition, and an overall gracile skull frame. Comparison with other Gorgosaurus specimens of various ontogenetic stages allows for an examination of the timing of morphological changes that occurred through ontogeny in this taxon relative to other tyrannosaurids. Of particular note, Gorgosaurus and the larger Tyrannosaurus rex are found to have experienced similar ontogenetic transformations at similar percent skull length relative to the large known individuals for each respective taxon but at different absolute body sizes and biological ages, occurring at a larger size and older age in Tyrannosaurus than in Gorgosaurus. These results suggest a dissociation between the timing of cranial development and body size in tyrannosaurids. Finally, the recognition of ontogenetically invariant characters in Gorgosaurus makes it possible to determine the taxonomic identity of previously misidentified specimens.
Article
An isolated theropod tooth was found in the HauterivianBarremian Itsuki Formation of the Tetori Group in the Kuzuryu district, Ono City, Fukui Prefecture, central Japan. The present specimen, OMFJ V-1, shows a thick lanceolate basal cross-section and small mesial and distal denticles. A cladistic analysis based on the dental characters suggested that OMFJ V-1 be classified as belonging to Allosauroidea or Tyrannosauroidea. Principal component and linear discriminant analyses also suggested that OMFJ V-1 belongs to either of these two theropod clades. The posterior probabilities obtained in the linear discriminant analyses indicated that the confidence of the classification as Allosauroidea is slightly higher than that for Tyrannosauridae. However, because these analyses also supported possibilities of OMFJ V-1 belonging to other theropod clades to lesser extents, its taxonomic referral remains ambiguous. If OMFJ V-1 belongs to Tyrannosauroidea, it would indicate that a medium-sized tyrannosauroid already appeared in central Japan during the HauterivianBarremian age. On the other hand, if OMFJ V-1 belongs to Allosauroidea, it would indicate that at least two medium-to-large-sized theropods, allosaurids and tyrannosaurids, lived almost coevally in this region. The third possibility is that OMFJ V-1 belongs to Megaraptora. If such affinities are established, it would represent the oldest record of this clade of theropods.
Article
Abundant lake ice-rafted debris in Late Triassic and earliest Jurassic strata of the Junggar Basin of northwestern China (paleolatitude ~71°N) indicates that freezing winter temperatures typified the forested Arctic, despite a persistence of extremely high levels of atmospheric P co 2 (partial pressure of CO 2 ). Phylogenetic bracket analysis shows that non-avian dinosaurs were primitively insulated, enabling them to access rich deciduous and evergreen Arctic vegetation, even under freezing winter conditions. Transient but intense volcanic winters associated with massive eruptions and lowered light levels led to the end-Triassic mass extinction (201.6 Ma) on land, decimating all medium- to large-sized nondinosaurian, noninsulated continental reptiles. In contrast, insulated dinosaurs were already well adapted to cold temperatures, and not only survived but also underwent a rapid adaptive radiation and ecological expansion in the Jurassic, taking over regions formerly dominated by large noninsulated reptiles.
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Tyrannosaurid theropods topped the terrestrial food chain in North America and Asia during the latest Cretaceous. Most tyrannosaurids, exemplified by Tyrannosaurus rex, had deep snouts, thick teeth, and large jaw muscles that could generate high bite forces. They coexisted in Asia with a morphologically divergent group of long-snouted relatives, called alioramins. Qianzhousaurus sinensis, from the Maastrichtian of Ganzhou, China, is the largest alioramin yet discovered, but has only been briefly described. Here we present a detailed osteological description of the holotype cranium and mandible of Qianzhousaurus. We identify several new autapomorphic features of the genus, and new synapomorphies that unite alioramins (Qianzhousaurus, Alioramus altai, Alioramus remotus) as a clade, including a laterally projecting rugosity on the jugal. We clarify that the elongate skull of alioramins involves lengthening of the anterior palate but not the premaxilla, and is reflected by lengthening of the posterior bones of the lower jaw, even though the posterior cranium (orbit and lateral temporal fenestra) are proportionally similar to deep-skulled tyrannosaurids. We show that much of the variation among the alioramin species is consistent with growth trends in other tyrannosaurids, and that A. altai, A. remotus, and Qianzhousaurus represent different ontogenetic stages of progressive maturity, across which the signature nasal rugosites of alioramins became less prominent. We predict that the holotype skull of Qianzhousaurus represents the adult level of maturity for alioramins, and propose that the skull morphology of Qianzhousaurus indicates a much weaker bite than deep-skulled tyrannosaurids, suggestive of differences in prey choice and feeding style.
Article
Modern birds are typified by the presence of feathers, complex evolutionary innovations that were already widespread in the group of theropod dinosaurs (Maniraptoriformes) that include crown Aves. Squamous or scaly reptilian-like skin is, however, considered the plesiomorphic condition for theropods and dinosaurs more broadly. Here, we review the morphology and distribution of non-feathered integumentary structures in non-avialan theropods, covering squamous skin and naked skin as well as dermal ossifications. The integumentary record of non-averostran theropods is limited to tracks, which ubiquitously show a covering of tiny reticulate scales on the plantar surface of the pes. This is consistent also with younger averostran body fossils, which confirm an arthral arrangement of the digital pads. Among averostrans, squamous skin is confirmed in Ceratosauria (Carnotaurus), Allosauroidea (Allosaurus, Concavenator, Lourinhanosaurus), Compsognathidae (Juravenator), and Tyrannosauroidea (Santanaraptor, Albertosaurus, Daspletosaurus, Gorgosaurus, Tarbosaurus, Tyrannosaurus), whereas dermal ossifications consisting of sagittate and mosaic osteoderms are restricted to Ceratosaurus. Naked, non-scale bearing skin is found in the contentious tetanuran Sciurumimus, possibly ornithomimosaurians (Pelecanimimus) and tyrannosauroids (Santanaraptor), and also on the patagia of scansoriopterygids (Ambopteryx, Yi). Scales are surprisingly conservative among non-avialan theropods compared to some dinosaurian groups (e.g. hadrosaurids); however, the limited preservation of tegument on most specimens hinders further interrogation. Scale patterns vary among and/or within body regions in Carnotaurus, Concavenator and Juravenator, and include polarised, snake-like ventral scales on the tail of the latter two genera. Unusual but more uniformly distributed patterning also occurs in Tyrannosaurus, whereas feature scales are present only in Albertosaurus and Carnotaurus. Few theropods currently show compelling evidence for the co-occurrence of scales and feathers (e.g. Juravenator, Sinornithosaurus), although reticulate scales were probably retained on the mani and pedes of many theropods with a heavy plumage. Feathers and filamentous structures appear to have replaced widespread scaly integuments in maniraptorans. Theropod skin, and that of dinosaurs more broadly, remains a virtually untapped area of study and the appropriation of commonly used techniques in other palaeontological fields to the study of skin holds great promise for future insights into the biology, taphonomy and relationships of these extinct animals.
Book
Evolution is the single unifying principle of biology and core to everything in the life sciences. More than a century of work by scientists from across the biological spectrum has produced a detailed history of life across the phyla and explained the mechanisms by which new species form. This textbook covers both this history and the mechanisms of speciation; it also aims to provide students with the background needed to read the research literature on evolution. Students will therefore learn about cladistics, molecular phylogenies, the molecular-genetical basis of evolutionary change including the important role of protein networks, symbionts and holobionts, together with the core principles of developmental biology. The book also includes introductory appendices that provide background knowledge on, for example, the diversity of life today, fossils, the geology of Earth and the history of evolutionary thought. Key Features: Summarizes the origins of life and the evolution of the eukaryotic cell and of Urbilateria, the last common ancestor of invertebrates and vertebrates. Reviews the history of life across the phyla based on the fossil record and computational phylogenetics. Explains evo-devo and the generation of anatomical novelties. Illustrates the roles of small populations, genetic drift, mutation and selection in speciation. Documents human evolution using the fossil record and evidence of dispersal across the world leading to the emergence of modern humans.
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Die Feder ist das augenscheinlichste Erkennungsmerkmal der Vögel, die ihnen sowohl ihre farbenfrohe Erscheinung als auch die Fähigkeit zum Fliegen verleiht. Im Vergleich zu anderen Hautstrukturen wie Schuppen oder Haaren, besitzen Federn eine sehr viel komplexere Morphologie, die mit einer großen Vielfalt an Formen und Funktionen (s.g., biologische Rollen) einhergeht. Daher ist es wenig überraschend, dass wir Menschen seit Jahrtausenden von Vögeln und ihrem Gefieder fasziniert und inspiriert sind (Lilienthal 1889; Müller-Eberling & Rätsch 2011). Auch in der modernen Paläontologie gilt die Evolution der Vögel und ihres Gefieders als eines der spannendsten Forschungsgebieten und wird jedes Jahr durch dutzende neuer Fossilienfunde und dem Einsatz moderner Technologien bereichert. Im folgenden Artikel möchten ich kurz die allgemeine Morphologie und Entwicklung der Feder zusammenfassen, um anschließend die neueste Erkenntnisse zur Evolution der Feder zu diskutieren.
Article
Phuwiangvenator yaemniyomi is a mid-sized, early branching megaraptoran theropod from the Lower Cretaceous Sao Khua Formation of Phu Wiang Mountain, Khon Kaen Province, northeastern Thailand. The holotype includes dorsal and sacral vertebrae, lower legs, hand and foot elements. Here we describe new skeletal material pertaining to the same individual representing the holotype of Phuwiangvenator based on size, shape, and shared phylogenetic affinities. This material was recovered at the same quarry as the holotype and consists of an incomplete fibula, left and right metatarsals. A new autapomorphy observed from the new material is the presence of a long, deep fossa between the lateral and medial distal condyles of the metatarsal II that extends to the distal articular facet is visible in anterior view. The metatarsal III of Phuwiangvenator is relatively short, more similar to the proportion present in basal carcharodontosaur Concavenator than in the derived megaraptorans, but more gracile than other basal allosauroids. Its hindlimb proportions are similar to the basal carcharodontosaur Neovenator than other more derived megaraptorans and coelurosaurs. Phuwiangvenator shows a combination of features shared with allosauroids and basal coelurosaurs and appears to be “intermediate” between non-megaraptorid and megaraptorid theropods. The present work adds anatomical data on this theropod and provides information on the early evolution of the Megaraptora.
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Fossils have stirred the imagination globally for thousands of years, starting well before they were recognized as the remains of once-living organisms and proxies of former worlds. This volume samples the history of art about fossils and the visual conceptualization of their significance starting with biblical and mythological depictions, extending to renditions of ancient life as it flourished in long-vanished habitats, and on to a modern understanding that fossil art conveys lessons for the betterment of the human condition. The 29 papers and accompanying artwork illustrate how art about fossils has come to be a significant teaching tool not only about evolution of past life, but also about conservation of our planet for the benefit of future generations.
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We report new 40Ar÷39Ar dating results obtained from total fusion and incremental-heating analyses of sanidine and biotite from three tuffs found interbedded within the fossil-bearing deposits of Liaoning, northeast China. The first is a new sample of the Bed 6 Sihetun tuff from the Yixian Formation, previously dated by our team as middle Early Cretaceous, and recently considered by Lo et al., partially reset due to metamorphism from a nearby basaltic sill. The second is the Yixian Bed 9 tuff from Hengdaozi considered by Lo et al. to be unaffected by metamorphism and whose age, based on total fusion 40Ar÷39Ar dating of biotite, argues for a Jurassic age for the Yixian Formation. The third tuff is a previously undated tuff from the upper part of the underlying Tuchengzi Formation. Single crystal total fusion 40Ar÷39Ar analyses of the Sihetun sanidine showed homogeneous radiogenic Ar, Ca÷K ratios, excellent reproducibility and gave a mean age of 125.0±0.18 (1SD)±0.04 (SE) Ma. Single sanidine crystal total fusion 40Ar÷39Ar analyses of the Hengdaozi tuff gave a mean age of 125.0±0.19 (1SD)±0.04 (SE) Ma, which is indistinguishable from the Sihetun tuff. The Tuchengzi Formation tuff gave a mean age of 139.4±0.19 (1SD)±0.05 (SE) Ma. Detailed laser incremental-heating analyses of biotite from Sihetun, Hengdaozi, and Tuchengzi tuffs show disturbed Ar release patterns and evidence of trapped argon components. We conclude from these analyses that the total fusion dates on biotite by Lo et al. are erroneously old and isotopic dating of both biotite and sanidine from tuffs of the Yixian Formation point to a middle Early Cretaceous age. The upper part of the Tuchengzi Formation can be referred to the Early Cretaceous.
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A detailed osteological description of Tyrannosaurus rex Osborn, 1905 is presented, based primarily on the most complete specimen yet collected of this taxon (FMNH PR2081, popularly known as “Sue”) but also including observations from other specimens.Skull morphology of FMNH PR2081 is largely congruent with that described for previous specimens, but new details are added. Palatal morphology of FMNH PR2081 differs slightly from that of previously-described specimens—the internal choanae are slightly larger relative to skull size, and the anterior expansion of the fused vomers is elongate. Posteriorly, the vomers pass medially for nearly the entire length of the pterygoids.High-resolution x-ray computed tomographic (CT) analysis of the skull reveals internal details not previously observed. Complex recess systems can be traced in the jugal, lacrymal, ectopterygoid, quadrate, exoccipital, supraoccipital, prootic, and basioccipital. The exoccipital recess was perforated by a small foramen on the posterodorsal surface of the paroccipital process, and may have communicated with pneumatic chambers in the atlas-axis complex. The maxillary antra were bound medially by a thin bony wall; traces of these walls in earlier CT studies of tyrannosaurid skulls may have led to the impression that these animals had bony maxillonasal turbintes. A digital endocast was constructed from these images, confirming many previous observations based on natural endocasts, but also yielding new details, such as the presence of a large and presumably pneumatic sinus in the prootic adjacent to the pathway for the maxillary-mandibular branches of the trigeminal nerve. The olfactory bulbs were very large.The postcranium is also largely congruent with previously published descriptions. The precaudal vertebral column was heavily pneumatized, with pneumatopores penetrating the centra and neural arches of all presacral vertebrae, the cervical ribs, and the anteriormost four sacral centra. Unusual structures are tentatively identified as a proatlas arch and a rib on the last presacral vertebrae, structures previously thought absent from tyrannosaurids. The “missing chevron” partially responsible for claims that FMNH PR2081 is female was actually present.The gastralia are extensively fused anteriorly, and the morphology of the anteriormost gastral segments closely resembles the only published account of a tyrannosaurid sternum. This raises several possibilities, including the complete absence of a bony sternum in tyrannosaurids.The appendicular skeleton is congruent with those of other tyrannosaurids. A slender rodlike bone may represent a partial furcula, but this is not certain. The scapulocoracoids would probably not have met at the midline, but would nonetheless have closely approached each other in articulation.Several abnormalities in the skeleton have attracted popular attention. There is no defensible evidence for bite trauma on the skull, but the rib cage does show evidence for healed fractures. Lesions on the right scapulocoracoid and humerus coincide with fractured ribs on the right cervical-dorsal transition and may indicate a single trauma to the right side of the body. The left fibula is pathological, but may not have been fractured. Two fused tail vertebrae may preserve natural molds of the tail muscles.
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Body size is a crucial life history parameter for an organism. Therefore, mass estimation for fossil species is important for many kinds of analyses. Several attempts have been made to yield equations applicable to dinosaurs. In this paper, we offer bi- and multivariate equations based on log transformed appendicular skeleton data from a sample of 16 theropods which were known from reasonably complete skeletal remains, and spanning a wide size range. Body masses of the included taxa had been found by displacement methods of scale models, based on measurements taken directly on the mounted skeletons. Seven of the bivariate regression analyses resulted in correlation coefficients equal to or above 0.975 and femoral length was the best available measurement (r=0.995; standard error of the estimate (%SEE)=19.26; percent prediction error (). Also, 32 multivariate analyses yielded equations with high correlation coefficients (r>0.990) and low standard errors.
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Theropod teeth are taxonomically diagnostic components of dinosaur assemblages. Seventy teeth have been recovered from six different localities in the Kogosukruk Tongue of the Prince Creek Formation (Upper Cretaceous) of the North Slope of Alaska. This assemblage of teeth shows slightly less diversity compared to well documented assemblages of teeth from the slightly older Judith River Formation of south-central Montana, the Aguja Formation of west Texas, and the Hell Creek Formation of eastern Montana. In addition, in contrast to the Judith River Formation assemblage of teeth in south-central Montana, the teeth assigned to Troodon dominated the Alaskan assemblage. The dominance of Troodon is attributed to adaptation by this theropod to low light conditions while over-wintering at a high paleolatitude.
Article
Tyrannosauroids are among the most distinctive and best known of Mesozoic theropods. Diagnostic skeletal material for Tyrannosauridae is at present limited to the last part of the Late Cretaceous of eastern and central Asia (China and Mongolia) and North America; the more inclusive Tyrannosauroidea includes taxa from the Late Jurassic of Europe and North America and the Early Cretaceous of Europe and Asia. Tyrannosaurids include some of the largest known theropod taxa (up to 13 m long and weighing six or more tonnes). The five most completely known species (Tyrannosaurus rex, Tarbosaurus bataar, Daspletosaurus torosus, Albertosaurus sarcophagus, and Gorgosaurus libratus) are all represented by individuals with femora more than 100 cm in length, reaching 138 cm in the largest Tyrannosaurus rex.
Article
An incomplete theropod skeleton including partial skull, mandibles, ilia was collected from the Early Cretaceous Jiufotang Formation of Kazuo County, western Liaoning Province. It can be estimated that this theropod may reach 9~10 meters in total length. It should be classified within Tyrannosauroidea by its tall premaxiUary body, median vertical ridge on the external surface of ilium. It differs from the Late Cretaceous tyrannosaurids by much large external naris, slightly concave anterior portion of maxillary dorsal margin, maxillary fenestra reaching past the rostral margin of antorbital fossa but keeping apart from the ventral margin of antorbital fossa. Thus, Sinotyrannus kazuoensis gen. et sp. nov. is erected, perhaps representing the earliest member of Tyrannosauridae. This is the largest known pre-Late Cretaceous tyrannosauroid, and also the largest theropod from the Jehol Biota of western Liaoning and the adjacent regions. The discovery of this taxon not only suggests that East Asia should be one of the most important evolutionary centers of tyrannosauroids, but also provides the significant evidences for studying the origin of Tyrannosauridae, and the composition and e-cosystem of the Jehol Biota.
Article
Fragmentary theropod remains from the Upper Jurassic (Kimmeridgian) of Guimarota, Portugal, represent a new taxon of theropod dinosaurs, Aviatyrannis jurassica gen. et sp. nov. Together with Stokesosaurus from the Morrison Formation of North America, Aviatyrannis represents the oldest known tyrannosauroid, indicating that tyrannosauroid origins may be found in the Middle-Late Jurassic of Europe/North America. Furthermore, current evidence suggests that early tyrannosaurs were rather small animals, which is in general accordance with their origin amongst the generally rather small coelurosaurs.
Article
Theropod teeth are taxonomically diagnostic components of dinosaur assemblages. Seventy teeth have been recovered from six different localities in the Kogosukruk Tongue of the Prince Creek Formation (Upper Cretaceous) of the North Slope of Alaska. This assemblage of teeth shows slightly less diversity compared to well documented assemblages of teeth from the slightly older Judith River Formation of south-central Montana, the Aguja Formation of west Texas, and the Hell Creek Formation of eastern Montana. In addition, in contrast to the Judith River Formation assemblage of teeth in south-central Montana, the teeth assigned to Troodon dominated the Alaskan assemblage. The dominance of Troodon is attributed to adaptation by this theropod to low light conditions while over-wintering at a high paleolatitude.
Article
A partial postcranial skeleton from the Late Jurassic (Tithonian) of Dorset, England represents a new species of the theropod dinosaur Stokesosaurus, Stokesosaurus langhami. S. langhami is a member of Tyrannosauroidea, showing a distinct median vertical ridge on the lateral surface of the ilium, a prominent shelf medial to the preacetabular notch, a pronounced ischial tubercle, and a tibia that is elongate relative to the femur. One of only two definitive Jurassic tyrannosauroids known from more than isolated elements, it is the largest Jurassic tyrannosauroid reported to date and provides additional evidence for the presence of relatively small-or medium-sized basal tyrannosauroids in Asia, North America, and Europe during the Late Jurassic. The occurrence of Stokesosaurus in the Tithonian of the UK and USA and the absence of tyrannosauroids in contemporaneous west African faunas supports the hypothesis of a paleobiogeographic link during the Late Jurassic between North America and Europe, to the exclusion of Africa.