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A primitive confuciusornithid bird from China and its implications for early avian flight

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Confuciusornithids, lived from 120–125 million years ago, form a basal bird group and include the oldest birds with horny beaks. Here we describe Eoconfuciusornis zhengi, gen. et sp. nov. from the Early Cretaceous Dabeigou Formatio (131 Ma) in Fengning, Hebei Province, northern China. It represents a new and, more primitive than other known, member of this group and extends the lifespan of this family to 11 Ma, the longest of any known Early Cretaceous avian lineages. Furthermore, Eoconfuciusornis and its relatives present many osteological transformations, such as the size increase of the deltopectoral crest of the humerus and the keel of the sternum, apparently an adaptation toward improved flight in the evolution of the Confuciusornithidae.
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Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | 625-639
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A primitive confuciusornithid bird from China and its
implications for early avian flight
ZHANG FuCheng1,2, ZHOU ZhongHe1 & Michael J. BENTON2
1 Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese
Academy of Sciences, Beijing 100044, China;
2 Department of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, UK
Confuciusornithids, lived from 120125 million years ago, form a basal bird group and include the
oldest birds with horny beaks. Here we describe Eoconfuciusornis zhengi, gen. et sp. nov. from the
Early Cretaceous Dabeigou Formation (131 Ma) in Fengning, Hebei Province, northern China. It repre-
sents a new and, more primitive than other known, member of this group and extends the lifespan of
this family to 11 Ma, the longest of any known Early Cretaceous avian lineages. Furthermore,
Eoconfuciusornis and its relatives present many osteological transformations, such as the size
increase of the deltopectoral crest of the humerus and the keel of the sternum, apparently an
adaptation toward improved flight in the evolution of the Confuciusornithidae.
Birds, Early Cretaceous, confuciusornithids, flight
1 Introduction
In quantity, confuciusornithid birds exceed all other
avian groups in the Jehol Biota[1]. Phylogenetically, they
are more derived only than Archaeopteryx, Jeholornis,
Sapeornis, and Rahonavis, but are more basal than the
two major Mesozoic avian lineages: Enantiornithes and
Ornithurae[24].
In osteology, confuciusornithids are mainly different
from other birds in the following features: both upper
and lower jaws are toothless, and the mandibular sym-
physis is forked; the deltopectoral crest of the humerus
is prominent; the alular metacarpal is not fused with
metacarpals II and III complex; the first phalanx of
manual digit III (minor digit) is much shorter than other
non-ungual phalanges; the ungual of manual digit II
(major digit) is significantly shorter than those of other
manual digits, and the caudal end of the sternum is “V”
shaped[5].
The first confuciusornithid bird, Confuciusornis
sanctus, was found from the Early Cretaceous Yixian
Formation in western Liaoning Province[6,7]. In 1999 and
2000, two other genera referable to the Confuciusor-
nithidae, Changchengornis[8] and Jinzhouornis[9], were
established respectively. They are all from the Yixian
Formation. In 2006, a new specimen (IVPP V13313)
from the Jiufotang Formation was referred to Confuciu-
sornis sanctus[10], representing the first report of a con-
fuciusornithid from this formation.
Deposits of both the Jiufotang Formation and Yixian
Formation are distributed mainly in Liaoning Province,
and their ages are about 120 Ma and 125 Ma, respec-
tively[11,12]. Most of the Jehol Biota animals come from
these two formations[1,4,13,14].
Eoconfuciusornis zhengi was discovered from the
Dabeigou Formation at Sichakou in Fengning, Hebei
Province (Figure 1). Mesozoic lacustrine deposits from
this locality comprise the Huajiying Formation and the
underlying Dabeigou Formation. The former is roughly
comparable to the Yixian Formation in Liaoning Pro-
Received November 23, 2007; accepted February 27, 2008
doi: 10.1007/s11430-008-0050-3
Corresponding author (email: ZhangFucheng@ivpp.ac.cn, FCZhang@gmail.com)
Supported by the National Natural Science Foundation of China (Grant Nos.
40472018, 40121202), the Chinese Academy of Sciences (Grant No. KZCX3-SW-
142), the Major Basic Research Projects of the Ministry of Science and Technology
of the People’s Republic of China (Gtant No. 2006CB806400), and the Royal Soci-
ety and Natural Environment Research Council (Grant No. NE/E011055/1)
626 ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | 625-639
Figure 1 Map of Hebei Province in North China showing the locality of
Eoconfuciusornis zhengi, Sichakou, Fengning County.
vince whereas the latter is slightly older[15], and
SHRIMP U-Pb and 40Ar/39Ar [16,17] dating indicated that
the age of the Dabeigou Formation is about 131 Ma. The
newly discovered avian is a middle-sized confuciusor-
nithid, similar to that of an extant rook[18]. In contrast to
the extremely abundant vertebrate fossils found from the
Yixian and Jiufotang formations, so far only four verte-
brate taxa have been reported from the Dabeigou For-
mation, including two birds, Eoconfuciusornis zhengi,
and Protopteryx fengningensis[19], and two acipenseri-
form fish Peipiaosteus fengningensis and Yanosteus
longidorsalis[15,20].
2 Material and methods
The specimen is housed at the Institute of Vertebrate
Paleontology and Paleoanthropology, Chinese Academy
of Sciences. The phylogenetic relationships between the
new bird, Eoconfuciusornis zhengi, and other major
primitive birds was analyzed with PAUP 4.0 beta 10[21];
the data matrix comprise 169 osteological and integu-
mental characters for 25 bird and dinosaur taxa (24×169
taxon matrix is from ref. [3], see S1 and S2).
3 Description of specimen
3.1 Taxonomy
Aves Linnaeus 1758
Confuciusornithiformes Hou et al. 1995
Confuciusornithidae Hou et al. 1995
Eoconfuciusornis zhengi gen. et sp. nov.
3.2 Etymology
The genus name “Eoconfuciusornis” is derived from the
Greek prefix “eo” (dawn), and “confuciusornis”, indi-
cating that some features of this new bird are more
primitive than other confuciusornithid birds; the species
name “zhengi” is dedicated to the distinguished Chinese
ornithologist ZHENG Guangmei.
3.3 Holotype
Institute of Vertebrate Paleontology and Paleoanthro-
pology Collection IVPP V11977; a nearly complete
specimen including skull, mandible, postcranial ele-
ments and feather impressions, preserved on the main
and/or counterpart slabs (Figures 25).
3.4 Locality and horizon
Sichakou, Fengning County, Hebei Province, China;
Dabeigou Formation, Early Cretaceous, the lowest fossil
horizen of the Jehol Biota, about 131 Ma ago[17].
3.5 Diagnosis
The new taxon is distinguishable from other known
confuciusornithids by a combination of the following
features: lateral depressions in thoracic vertebrae unde-
veloped; scapula without prominent acromion and gle-
noid facet; coracoid short, with relatively wide sternal
facet; deltopectoral crest of humerus not prominent;
proximal end of humerus no more than twice the width
of distal end and lacking a fenestra; astragalus pierced
by foramina; tarsometatarsus slightly longer than half of
the length of tibia.
3.6 Description
(1) Skull and mandible. Most skull elements are
exposed in left lateral to ventral views; while mandible
elements are usually exposed in ventral view. They are
either articulated naturally, or disarticulated but pre-
served closely together. Like those of other confuciusor-
nithids, the rostral region of the skull and mandible is
pointed, robust and toothless. Both the neurovascular
foramina and grooves located on the rostral region of the
upper and the lower jaws indicate that the beak is cov-
ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | 625-639 627
Figure 2 Eoconfuciusornis zhengi, skeleton and feather impression in counterslab (a) and mainslab (b).
ered with rhamphotheca[57,22] and what is more, it is
proved by the beak impression at the rostral ends of both
upper and lower jaws, which is very difficult to be ob-
served in other specimens (Figures 25).
In lateral view, the premaxilla is asymmetrically
“V”-shaped, a rostrally tapering body with a long dorsal
ramus (frontal process) and a short ventral one (maxil-
lary process). At the body, left and right premaxillae are
fused, although the rostralmost part is slightly apart,
forming a small notch. The long frontal process is
straight and robust, reaching the dorsal middle-margin
of the orbit; the maxillary process is not as robust as the
frontal process, tapering gradually, and appears to end at
the narrowest region of the premaxilla-maxilla complex.
The maxilla is triradiate, possessing three processes in
lateral view. The premaxillary process appears rostrally,
meeting with the premaxilla at the narrowest region of
the premaxilla-maxilla complex; the boundary between
these two processes is not clear. Dorsally there is a long
ascending process, reaching the level of the frontal
process of premaxilla. However, it is very difficult to
identify whether this process is an intact nasal process,
or just the frontal margin of the foramen of nasal process,
as in Confuciusornis[5]. The jugal process is the most
robust; caudally it meets or fuses with the jugal bar; it is
very difficult to identify the suture or other boundary
between these two elements.
At the caudal end of the frontal process of the pre-
maxilla is a small ossification, which is interpreted as
the nasal based on its location, morphology, and com-
628 ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | 625-639
Figure 3 Eoconfuciusornis zhengi, skeleton on the counter slab (a) and main slab (b). ac, acetabulum; as, astragalus; ce, cervical vertebrae; co, coracoid;
cv, caudal vertebrae; fe, femur; fi, fibula; fu, furcula; py, pygostyle; ga, gastralia; hu, humerus; IIV, pedal digits IIV; il, ilium; ma, mandible; MI,
alular metacarpal; MII, major metacarpal; MIII, minor metacarpal; MtV, metatarsal V; PI1-2, 1st and 2nd phalanx of alular digit; PII1-3, 1st to 3rd phalanx
of major digit; PIII1-4, 1st to 4th phalanx of minor digit; PIV4, 4th phalanx of pedal digit IV; pu, pubis; py, pygostyle; r, rib; ra, radius; rd, radiale; sc,
scapula; se, semilunate carpal; sf, supracoracoid nerve foramen; sk, skull; sy, synsacrum; ti, tibia; tm, tarsometatarsus; tv, thoracic vertebrae; ul, ulna; un,
ulnare.
parison with Confuciusornis sanctus[5]. This element is
partly overlapped by the frontal process of premaxilla;
the exposed part is subrectanglar. Its rostral end reaches
the level of the dorsal process of the maxilla, while its
caudal end abuts the frontal.
The external naris is nearly oval in shape and far from
the skull’s rostral tip as in Confuciusornis sanctus[5]. The
formation of naris is involved with different parts of the
premaxilla, maxilla, and presumed nasal. The ventral
margin of the frontal process of the premaxilla forms the
dorsal and part of the rostral boundary; the dorsal mar-
gin of the maxillary process of the premaxilla forms the
ventral and part of the rostral boundary. The caudal naris
is demarcated by the rostral margin of the ascending
process of the maxilla. In lateral view it is very difficult
to identify whether or not the presumed nasal contri-
buted to the formation of nares although it should be
involved as in other birds or dinosaurs[23].
The frontal is expanded and inflated, and its bony
wall is thin and fragile as in other confuciusornithids or
other primitive and extant birds[5,24,25]. The wall is
crashed and lots of gaps or breaks are easily observed.
Rostrally the frontal is connected with the frontal pro-
cess of the premaxilla; caudally it connects with the pa-
rietal, although the suture is not easy to identify. In fact
these two elements may have fused together as do those
of other confuciusornithids and more derived birds.
Compared with the frontal, the parietal is more ex-
panded and inflated. Its bony wall is also thin and full of
gaps.
ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | 625-639 629
Figure 4 Skull and mandible of Eoconfuciusornis zhengi. 1, Atlas; 2, axis; cf, caudal mandibular fenestra; d, dentary; dp, dorsal process of dentary; en,
external nares; ex, exoccipital; f, frontal; hy, hyoid; is, interorbital septum; j, jugal; l, lacrimal; m, maxilla; n, nasal; oc, occipital condyle; p, parietal; pm,
premaxilla; po, postorbital; pt, pterygoid; q, quadrate; rf, rostral mandibular fenestra; rh, rhamphotheca impression; s, splenial; sa, surangular; sq, squamo-
sal; vp, ventral process of dentary.
Ventral to the frontal, the postorbital is obliquely lo-
cated on the caudal margin of the orbit. There appear to
be only two processes in the postorbital, the frontal and
the jugal, rather different from other confuciusornithids.
The frontal process tightly abuts the frontal. The jugal
process, which is smaller than the frontal, overlaps the
jugal. Between these two processes the body is ex-
panded.
Caudal to the postorbital is fragment, tentatively in-
terpreted as part of the squamosal based mainly on its
position. It is impossible to identify whether the su-
pratemporal and infratemporal fossa exist or not for the
postorbital-squamosal bar cannot be identified, which is
present usually in some other confuciusornithid speci-
mens[57].
From its rostral end, with a faint suture with the ma-
xilla, the jugal becomes gradually narrow; its caudal part
is overlapped by the quadratojugal.
The quadratojugal is long and slender. Its rostral end
reaches the boundary between the maxilla and the jugal;
630 ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | 625-639
Figure 5 Close-up photos of Eoconfuciusornis zhengi. (a) Scapulae and scapular part of right coracoid in dorsal view; (b) furcula and sternal part of right
coracoid in ventral view; (c) right humerus; (d), (e) some proximal elements of left hand and distal elements of right hand; (f) right ankle. as, astragalus; co,
coracoid; fo, foramen in the astragalus; fu, furcula; h, humerus; PI1, 1st phalanx of alular digit; PII1-3, 1st to 3rd phalanx of major digit; PIII1-4, 1st to 4th
phalanx of minor digit; MI, alular metacarpal; MII, major metacarpal; MIII; minor metacarpal; r, ribs; ra, radius; rd, radiale; s, sternum; sc scapula; se,
semilunate carpal; sf, supracoracoid nerve foramen; ti, tibia; tv, thoracic vertebra; ul, ulna; un, ulnare.
its caudal end is connected with the quadrate; from cau-
dally to rostrally the quadratojugal tapers off evenly.
Dorsal to the quadratojugal is a small and stout ossi-
fication, which is partly overlapped by the quadratojugal.
By the position and its stout morphology it is tentatively
interpreted as the pterygoid.
The orbit margin is composed of the lacrimal, pre-
maxilla, jugal, quadratojugal, postorbital and frontal.
The caudal margin of the lacrimal forms the rostral
boundary of the orbit. The dorsal boundary is formed by
the ventral margin of the frontal process of the prema-
xilla; the caudal boundary is formed by the rostral margin
of the postorbital; and the ventral boundary is formed by
the dorsal margin of the quadratojugal and the jugal re-
spectively. There are other elements that should contri-
bute to the formation of the orbit, such as the assumed
nasal, and the palpebral if it is present as in other con-
fuciusornithids[5]. The sclerotic plates are not preserved,
and yet these are commonly found in other birds[25].
Overlapped by the left hyoidal branch, the occipital
condyle is dislocated to the caudal region of mandible.
There is a low concave notch on the caudoventral end of
ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | 625-639 631
the occipital condyle, which is comparable to the medial
condylar incisura of modern birds[26]. From the lateral
side of the occipital condyle two ridge-like ossifications
are interpreted as part of the exoccipital.
The mandible is tapering, stout and toothless. It is
compressed dorsoventrally; however, some of its ele-
ments are exposed in lateral view, and some in medial
view. In ventral view, both the straight dorsal margins of
the dentary and surangular, and their rostralmost pointed
end form the mandible as a subtriangular projection.
Two dentary rami are not completely fused. There is a
clear suture throughout their rostral one third, rostrally
forming a small notch at their tips. Caudal to the stout
body the dentary bifurcates into two asymmetric pro-
cesses. The dorsal one appears remarkably shorter than
the ventral. The ventral process is robust and long,
forming about two thirds of the total length of the den-
tary. Its caudalmost end reaches the caudal fenestra of
the surangular.
The surangular forms the main caudal region of the
mandible. Its dorsal margin is straight throughout, and
so is the dorsal margin of the dentary. The ventral mar-
gin of the angular forms the caudal two-thirds of the
ventral border of the mandible. Laterally the angular was
partly overlapped by the dentary. The caudalmost
surangular and angular appear totally fused with the ar-
ticular. In the caudal region there is a round foramen
comparable to the caudal mandibular fenestra of some
modern birds, and the surangular foramen of non-avian
theropods as previously suggested[5]. The rostral man-
dibular fenestra is remarkably larger than the caudal
fenestra, and it is a long opening which is intermediate
between oval and rhombic in shape.
There are two enantiomorphous ossifications over-
lapped by the dentary and angular. From their position
and morphology, they are assumed as the splenials,
which appear partly comparable in morphology to those
of Archaeopteryx and Vescornis[27,28].
In the left mandibular ramus, the articular appears to-
tally fused with the caudal ends of the angular and
surangular; in the right mandible ramus, however, there
is a long and slender structure, which should be inter-
preted as the caudal end of the angular from its mor-
phology and position. If this interpretation is correct, the
articular is not completely fused with the angular.
Two hyoidal branches are preserved roughly along
the middle longitudinal line of mandibles. Rostrally they
are overlapped by the splenial; caudally they are beyond
the level of the articular.
(2) Vertebral column. From the atlas to the py-
gostyle most of the vertebral elements of Eoconfuciu-
sornis are articulated, while other elements are either
connected closely/loosely, or fused completely.
Seven cervical vertebrae are preserved including the
atlas and axis; but with vertebral impressions and the
space between the last preserved cervical vertebra and
the first assumed thoracic vertebra, the total number of
cervical vertebrae appears to be nine. Caudal to the oc-
cipital condyle and rostral to the axis is a band-like ossi-
fication, identified as the atlas (Figure 4). Its morphol-
ogy and position is comparable to that of Vescornis[28].
Compared with the atlas, the axis is stout and strong
(Figure 4). There is no sign of ventral process on the
axis, which is usually present in enantiornithine and
modern birds[26]. The caudal articular process of the axis
is strong and round in ventral view.
The other five preserved cervical vertebrae share
similar morphology (Figures 2 and 3). They are roughly
subquadrate in ventral view; the longitudinal length is
slightly greater than the transverse width. The ventral
process is robust or blunt, which is different from the
modern bird’s lamella-like ventral process. The cranio-
caudal length of the ventral process is about half the
longitudinal length of the cervical vertebra (LoV); it is
larger than those of modern birds in which the length of
the ventral process is usually no more than one third of
the LoV. Another feature of the ventral process which is
different from that of modern birds is that the caudal end
of the ventral process reaches the caudalmost extent of
the vertebral body. This feature, i.e., the robust, blunt,
and long ventral process, is similar to that of primitive
birds such as other confuciusornithids and some enan-
tiornithine birds[5,25]. In ventral view the prezygapophy-
sis is a robust projection with an expanded rostralmost
end. Caudally it is continued with the ventral process,
forming a “Y”-shaped structure. Cervical vertebrae 3 to
7 possess ribs that are tightly connected to the lateral
side of the vertebrae, while they appear not fused with
the diapophyses or parapophyses. These ribs are long
and connected rostrocaudally with each other throughout
the cervical series. Because all preserved cervical verte-
brae are connected together, Eoconfuciusornis does not
show the central articulation type, i.e., heterocoelic or
non-heterocoelic.
The number of thoracic vertebrae is estimated to be
between 12 and 14; the anterior six or seven are crashed
632 ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | 625-639
and/or disarticulated; the posterior six or seven are
tightly connected with the synsacrum, making it very
difficult to identify the exact number. Generally the cra-
nial series is exposed in dorsal aspect on the counter slab.
The dorsal processes are compressed sometimes, show-
ing their lateral sides. These dorsal processes are high
and narrow (in lateral view), and roughly subquadrate in
shape, but possess slightly expanded dorsal extreme
ends. The assumed second thoracic vertebra is shorter
than the cervical vertebrae; its dorsal process appears
slimmer than those of the middle ones; its caudal-
oblique costal process is long, reaching the level of its
caudalmost end (Figures 2, 3, 5(a) and (c)).
The posterior six or seven thoracic vertebrae (pre-
served on the main slab) are counted from a disarticu-
lated one with strong vertebral body, 1), to the last ver-
tebra with a pair of ribs, or 2), and then to the next one
whose caudal end reaches the level of the ilium. All the
above-mentioned vertebrae are ventrolaterally exposed,
in contrast to the ventrally exposed sacrals. The verte-
bral centrum is sandglass-shaped, its body is narrow in
the middle region, and is expanded at both cranial and
caudal ends. The anterior articular surface is slightly
concave. The ventral surface of the vertebral body is
smooth. There is a slight and narrow longitudinal con-
cavity on the lateral side of the vertebral body, which is
comparable, in position, with lateral excavations of the
thoracic centra of Confuciusornis. These concavities are
varied in size, but even the largest concavity is relatively
far smaller than that of Confuciusornis sanctus[5]. In late-
ral view the dorsal processes are wide, almost equal to
those of vertebrae. This is different from those of the
cervical vertebrae, which are no more than half of the
vertebral length. Another difference between these two
dorsal processes is that the dorsal margin of the dorsal
process is arc-like in lateral view, contrasting to the
subquadrate shape of the cervical vertebra. Craniocau-
dally the transverse processes and other projections be-
come more elongate or developed gradually (Figures 2,
3, 5(a) and (c))
The exact number of vertebrae in the synsacrum is
not easy to count, because of 1) poor preservation, 2) the
absence of obvious distinguishing features to identify
them either from thoracic vertebrae rostrally or from
caudal vertebrae posteriorly, and 3) the disarticulation of
some synsacral vertebrae. Only three medial synsacral
vertebrae are tightly fused. Anterior to the fused synsac-
ral vertebrae are two vertebrae with long transverse
processes which contact the medial surface of the
preacetabular wings of the ilia; while posteriorly there
are two vertebrae with long and expanded transverse
processes contacting the medial surface of the posta-
cetabular wings of the ilia. All seven vertebrae are inter-
preted as synsacral vertebrae. The ventrolateral sides of
the first two synsacral vertebrae are smooth and without
excavation. The centrum of the synsacral vertebra is
sandglass-shaped. The middle of the vertebral centrum
is laterally and ventrally obviously thinner than those of
the two expanded ends. Both the rostral and caudal ar-
ticular facets are slightly concave. Synsacral vertebrae 3
to 5 are tightly fused together. They possess long and
strong transverse processes. In ventral view the ventral
facet of the third synsacral vertebra is smooth, while the
fourth and fifth possess shallow longitudinal grooves.
The distal ends of transverse processes of the sixth and
seventh are extremely expanded, broadly connected with
the ilia (Figures 2 and 3).
Six closely connected free caudal vertebrae are pre-
served between the synsacrum and the pygostyle. Their
centra are relatively short compared to those of the tho-
racic or synsacral vertebrae, possessing concave cranial
articular facets. In ventral view the ventral faces of the
vertebral bodies are not as smooth as those of the syn-
sacral vertebrae. The transverse processes are not ex-
panded at their ends, and become gradually shorter from
the first to the last. There are also two isolated caudals
which are far from the above-mentioned closely con-
nected caudal series. The pygostyle is about the same as
the tarsometatarsus in length. Anteriorly it bears an ex-
panded proximal end connected to the free caudal series
(Figures 2 and 3).
(3) Thoracic girdle. In caudal view the furcula is
boomerang-shaped with a long and shallow concavity
along its longitudinal middle line. The ascending region
is slightly wider than the middle one in caudal view,
while the former is more rostrocaudally compressed than
the latter. There is no sign of a hypocleideum or slightly
caudal swelling as in Confuciusornis sanctus, or a dis-
tinct tubercle as in Changchengornis hengdaoziensis[5,8].
At the ascending extreme end an oval area near the me-
dial margin possesses a rough surface, contacting the
smooth neighboring area. It can be interpreted as the
articular facet for the scapula. The lateral area of the
dorsalmost end of the right clavicular ramus is tightly
connected with the right coracoid (Figures 2, 3 and
5(b)).
ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | 625-639 633
The right scapula is exposed with its lateral side visi-
ble, while the left scapula shows its medial side. In late-
ral view the cranial region of the scapula possesses a
large lateral swelling which may be comparable with the
articular facet, the glenoid process or tuberosity of more
derived birds for articulating with the coracoid or hu-
merus. Its dorsolateral projecting tuberosity is extremely
developed. The acromion, usually distinctly preserved in
more derived birds, is not prominent in Eoconfuciusor-
nis. The cranial extremity is spherical both in lateral and
medial views. There appears to be no distinctive neck of
the scapula both in lateral and medial views. At the mid-
dle of the shaft the cross section of the scapula appears
oval, not as round as in some modern birds. In the shaft
region the medial surface appears more convex than the
lateral. The distal region of the scapula is not expanded
as in some more advanced birds, but thins out me-
diolaterally and gradually posteriorly (Figures 2, 3 and
5(a)).
Only the right coracoid is preserved; its scapular part
is preserved on the main slab in ventral view and its
sternal part on the counter slab in dorsal view. The me-
dial side of the scapular extremity, comparable to the
clavicular articular facet of more derived birds, is tightly
articulated to the articular facet of the furcula. The end-
most part of the shoulder extremity is located near the
lateral side, contrasting to the medial side of more de-
rived birds. In ventral view the endmost margin of the
scapular region is obliquely straight to the lateral side. In
cross section, almost half of the lateral region of the
coracoid is curved ventrally, at least from the scapular
limit to the longitudinal midpoint of the coracoid. In this
part, in cross section the medial and lateral regions
nearly form a right angle. Another distinctive feature of
the coracoid is that the shoulder extremity is pierced
dorsoventrally by a large foramen for supracoracoidal
nerve. This foramen is elliptical, and its long axis is
roughly parallel to the longitudinal axis of the coracoid;
its width is no more than one third the diameter of the
coracoid at the same level. The sternal part of the cora-
coid has a concave lateral margin and convex sternal
articulation. Its lateral region appears thinner than the
medial region (Figures 2, 3, 5(a) and (b)).
(4) Sternum, ribs and gastralia. The sternum appears
not completely ossified as in Confuciusornis or some
other primitive birds. Its shape is recognized mainly by
the dark red color presumably left by the sternum bone,
which distinguishes the sternum from the surrounding
skeleton elements, integuments, and matrix, although in
the caudal region the sternum appears a little ossified as
a thin lamina-like structure. The sternum is roughly
subquadratic in shape. Its longitudinal axis is slightly
longer than the tibia, while it is narrower in transverse
width (Figures 2, 5(a), 5(c) and 6(b)).
Thoracic ribs and gastralia are interwoven together.
However, the thoracic ribs are usually longer than the
presumed gastralia, and some of them are attached to the
thoracic vertebrae. In the rostral part of the sternum
there are some interlaced elements that are interpreted as
the gastralia. These elements are shorter and thinner than
the thoracic ribs. The sternal ribs and uncinate processes
which are usually present in primitive birds are not rec-
ognizable in Eoconfuciusornis (Figures 2, 3 and 5(c)).
(5) Thoracic limb. The thoracic limb elements are
preserved in both the main and counter slabs (Figures 2
and 3).
The right humerus is exposed in cranial view. The in-
flated proximal region is more than one third of the total
length. The humeral head is slightly expanded with a
coarse surface. The ventral corner is not as developed as
that of other confuciusornithids[5,10], but it continues to a
prominent crest with coarse cranial surface, comparable
to the bicipital crest of modern birds. The deltopectoral
crest is large, but smaller than that of other confuciusor-
nithids, lacking a prominent angle of the deltopectoral
crest. It is very difficult to find a ridge on the cranial
margin of the crest, which is present in other confuciu-
sornithids[5]. On the other hand, in Eoconfuciusornis, the
ventral margin of the humeral proximal extremity is
straight, in contrast to the curved ventral margin of other
confuciusornithids[5]. The humeral body is straight to
slightly curved dorsally in the distal region. Its cranial
surface and adjacent distal extremity region are over-
lapped by the sternum and ribs, making it difficult to
identify its detailed morphology. However, a prominent
cranially swelling at the caudalmost end suggests the
presence of both dorsal and ventral condyles (Figures 2,
3, 5(c) and 6(f)).
The left humerus was broken and folded before being
embedded, and was preserved in the counter slab. Its
proximal extremity is exposed in caudal view; its shaft
portion is exposed in cranial view. The distal extremity
is turned and is exposed in caudal view because it is
preserved on the main slab. Caudally the humeral head
is more developed than in cranial view. It has a promi-
nent expanded cranialmost end. Caudal to the inflated
634 ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | 625-639
humeral head the proximal extremity surface is longitu-
dinally convex, without other distinctive structures such
as the tuberosity, fossa or foramen, which are usually
preserved in more advanced birds. Similar to the right
humerus, the cranial surface of the left humerus is
straight and compressed, with a long and fine crack
along its longitudinal midline, suggesting that the shaft
should be cylindrical in cross section before it became
embedded in the rock. The caudal surface of the humeral
distal extremity has a straight distalmost end, nearly
perpendicular to the longitudinal axis of the humerus,
but the ventral corner (near the comparable ventral epi-
condyle of modern birds) of the distal end appears more
acute than the dorsal corner (near the comparable dorsal
epicondyle). The sulcus or process which is commonly
present in modern birds is not found on the caudal sur-
face of the humeral distal extremity. The distinct hu-
meral foramen of Confuciusornis is not present in Eo-
Figure 6 Two flight-related trends showing the progressive morpho-
logical transitions among early primitive birds. (a)(d) Unfused sternal
plates (a) fused sternum (b) gradually elongate carina ((c),(d)). (a)
Jeholornis, IVPP V13274; (b) Eoconfuciusornis; (c) Confuciusornis, IVPP
V10928; (d) Confuciusornis, IVPP V13313; not to scale. (e)(h) proxi-
mal diameters of humerus are gradually increased. (e) Archaeopteryx,
Berlin specimen, 145 Ma; (f) Eoconfuciusornis, 131 Ma; (g) Confuciusor-
nis, IVPP V13156, 125 Ma; (h) Confuciusornis, IVPP V13313, 120 Ma.
Not to scale.
confuciusornis (Figures 2, 3 and 6(f)).
The ulna and radius are straight throughout their
length and lack a prominent interosseous space between
them. The line-shaped cracks, throughout the midshaft
surface, indicate that both the ulna and radius possessed
round or oval cross sections before burial, and are later-
ally compressed. The midshaft of the ulna is slightly
thinner in diameter than the proximal or distal regions of
the same bone. The distal extremity of the ulna is in-
flated, especially toward the ventral side, which may
correspond to the dorsal condyle of more derived birds.
The midshaft width of the radius is about three quarters
that of the ulna. The inflated distal extremity of the ra-
dius is relatively larger than that of the ulna. (Figures 2,
3 and 5(d)).
Between the ulna+radius and carpus+metacarpals
there are two isolated ossifications: the robust one lo-
cated at the distal end of the radius is interpreted as the
radiale, while the small one near the distal end of the
ulna is interpreted as the ulnare. The presumed radiale
appears tightly connected with the carpus which abuts
the proximal ends of the alular and major metacarpals
(Figures 2, 3 and 5(d)).
Apart from the radiale and ulnare, another carpal
bone, identified as the semilunate, is closely connected
with the proximal ends of the alular and major metacar-
pals. The semilunate is also closely connected with the
radiale and just as big (Figures 2, 3 and 5(d)).
In caudal view the ventral margin of the alular meta-
carpal is closely connected to the dorsal surface of the
major metacarpal with obvious boundary. Its proximal
end is oval-shaped with a small tuberosity near its ven-
tral corner. The dorsal margin is slightly convex in the
proximal two-thirds and becomes slightly concave in the
distal third. The ventral margin appears more complex:
the proximal third is conspicuously convex, followed by
a short and obvious concavity, and then a long slight
convexity. The distal end is mainly concave centrally
and expanded distally to articulate with the alular pha-
lanx. As in the pedal digit this articulation bears two
trochlea-like structures, divided by a longitudinal groove.
Cranial to the above-mentioned lateral trochlea-like
structure is a distinctive depression comparable to the
collateral ligamental fovea of the pedal digits (Figures 2,
3 and 5(d)).
The major metacarpal is the longest and strongest
among three metacarpals. It is more than three times the
length of the alular metacarpal. However, the latter is
ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | 625-639 635
slightly wider than the former in diameter. The proximal
extremity of the major metacarpal is slightly inflated
with a round to straight proximalmost articulation for
the semilunate carpal. The shaft is somewhat dorsally
curved; its dorsal margin is slightly concave while its
ventral margin is slightly convex. The caudal surface
was compressed postmortem, forming a longitudinal
fine crack. The distal extremity is expanded dorsoven-
trally, and especially the ventral corner is overly ex-
panded to an obvious ventral process, occupying about
one quarter of the whole distal diameter, and overlap-
ping the minor metacarpal for half its area. The minor
metacarpal is shorter and slimmer in length and diameter
respectively than those of the major metacarpal. Its
proximal end does not reach the level of the major
metacarpal, while its distal end shares the same level
with the major metacarpal. At midshaft, the diameter of
the minor metacarpal is about one third or quarter of the
major one. Both proximal and distal ends of the minor
metacarpal are closely connected to the major metacar-
pal, forming a less obvious intermetacarpal space. The
minor metacarpal is dorsally curved. The proximal one
third appears more dorsoventrally compressed and then
turned to be more craniocaudally compressed in the dis-
tal two thirds. The proximal end is sharply tapering,
forming a subtriangular articular facet. Along the mid-
line the distal half bears longitudinal cracks due to
postmortem compression. The distal extremity of the
minor metacarpal is not expanded, simply bearing a
round articular facet at its distalmost end (Figures 2, 3,
5(d) and (e)).
Eoconfuciusornis shares a similar manual phalangeal
formula with Archaeopteryx and other confuciusor-
nithids, 2-3-4, in contrast to more advanced birds in
which some phalanges are lost. All the preserved manual
elements of Eoconfuciusornis are naturally articulated
together (Figures 2, 3, 5(d) and (e)).
The alular digit bears two phalanges. The proximal
one is long and slender. It is about 90% of the major
metacarpal in length. Both the proximal and the distal
extremities are expanded, but the proximal end is sig-
nificantly larger than the distal. From proximal to distal,
the proximal alular phalanx is straight to slightly curved
dorsally and becomes gradually thinner in diameter. In
cross section this phalanx is round. The proximal articu-
lar facet is flat to slightly round; the distal articular facet
is more complex, possessing an obvious collateral liga-
mental fovea at the lateral side. The ungual phalanx is
about half of the proximal one in length. Its proximal-
most end is a curved articular cotyla in lateral view. The
flexor tubercle is developed. The curved phalangeal
sulcus is wide and long, almost running through the
whole phalangeal length. Its width is tapering gradually
from proximal to distal and about one third of the whole
width proximally. Like those of other manual or pedal
ungual phalanges, the remnant of horny sheath of the
phalanx is hardly preserved (Figures 2, 3, 5(d) and (e)).
The major manual digit possesses three phalanges.
The proximal phalanx is the most robust among all
manual phalanges. It is craniocaudally compressed; its
diameter is overwhelmingly larger than those of other
phalanges both in cranial and caudal view. Its length,
however, is merely 90% that of the proximal phalanx of
the alular digit. This proximal phalanx is subrectangular
although both its dorsal and ventral margins are slightly
convex, while it is slightly concave in its proximal one
quarter on the ventral margin. Both proximal and distal
extremities of the proximal phalanx are slightly inflated
caudally. The proximal articular facet is round to
slightly flat, while the distal articular facet is concave in
caudal view, corresponding with the convex proximal
articular facet of the intermediate phalanx. The interme-
diate phalanx is slightly longer than the proximal one,
and obviously curved ventrally in caudal view. Its
proximal extremity is conspicuously larger and more
expanded than the distal one. From proximal to distal
ends the diameter becomes gradually smaller. Like the
proximal phalanx of the alular digit, the intermediate
phalanx is round in cross section. The ungual phalanx of
the major digit is the most undeveloped among the three
ungual phalanges. It is only about two-thirds of the
length of the minor digit, while both of them share simi-
lar width at their proximal ends. Its flexor tubercle and
ungual lateral sulcus are smaller and shallower than
those of alular and minor ones, suggesting it is a degene-
rative ossification, for both its flexor which is connected
to the flexor tubercle, and lateral sulcus which carries
nerves and vessels are undeveloped (Figures 2, 3, 5(d)
and (e)).
The minor digit contains four phalanges. The proxi-
mal phalanx is the shortest among all manual phalanges;
it is only about one third the length of the first interme-
diate phalanx. However the proximal phalanx appears
more robust than the intermediate phalanges. The
proximal and distal articular facets of the proximal pha-
lanx appear slightly concave and convex respectively.
636 ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | 625-639
Two intermediate phalanges are more slender than the
others. The first intermediate phalanx is slightly shorter
than the second. Gradually both of them appear tapering
from the proximal to the distal ends. Their extremity
ends are slightly expanded, while their articular facets
are not as clear as those of other phalanges. The first
intermediate phalanx is straight in caudal view while the
second is ventrally curved, but the latter is not as curved
as the intermediate one of the major digit. The ungual
phalanx of the minor digit is intermediate in size be-
tween the alular and major ungual digits. It possesses a
similar flexor tubercle in shape and a lateral sulcus in
size with the alular ungual phalanx (Figures 2, 3, 5(d)
and (e)).
(6) Pelvic girdle. In ventral view the preacetabular
wing of the ilium is narrow with a round cranial end; the
medial margin of the preacetabular wing is thick and
strong, contracting the thin and slim lateral margin. The
medial surface of the ilium tightly abuts the series of
transverse processes of the synsacrum. In ventral view
the dorsal-inner surface of the acetabulum is thinner
than the connection area for the pubis and ischium. The
ischium appears ventrally exposed. Its acetabular region
is more robust than the following caudal part. The distal
parts of the pubes are preserved on the counter slab in
cranial view. They are totally fused distally to a sym-
physis, and at the distalmost end form an expanded pu-
bic foot-like structure that is perpendicular to the pubic
shaft. There is a thin and shallow groove on the medial
line of the symphysis (Figures 2 and 3).
(7) Pelvic limb. The femur is similar to the ulna in
length and diameter, but the former is slightly curved
craniocaudally in lateral view. At its proximal extremity,
the trochanter is not as developed as in more derived
birds; it is a small expanded ridge. The femoral head
appears undeveloped, lacking any sign of a femoral neck.
The shaft is slightly caudally curved, and is thinner than
both proximal and distal regions. Except for some cracks
due to postmortem compression, it is very difficult to
find any sign of an iliotrochanter impression, or inter-
muscular lines on the surface of the femoral shaft, which
are usually present in extant birds. At the distal extre-
mity the lateral epicondyle is expanded laterally. Both
lateral and medial supracondyle crests are developed,
which are long and caudally expanded. Between them is
a long and deep groove. Both lateral and medial
condyles are caudally developed, while the medial one
appears more caudally prominent than the lateral one.
The patellar articular facet between the two condyles is
obviously present (Figures 2 and 3).
The tibia is straight, about one fifth longer than the
femur. The proximal extremity is inflated laterally and
caudally. The expanded lateral margin of the proximal
articulation is extended to a significant fibular crest late-
rally. In caudal view there is an obvious groove dividing
the proximal articulation into two facets, which is re-
spectively comparable to the lateral and medial articular
facets of extant birds. The lateral facet is slightly wider
than the medial in caudal view, while the medial facet
projects more caudally. The groove between these two
facets should be comparable with the interarticular area
of modern birds. From the proximal end distally, the
shaft of the tibia becomes gradually thinner to the mid-
shaft and then thicker when approaching the distal ex-
tremity in caudal view. At the distal extremity, in caudal
view, the distalmost region is obviously expanded later-
ally and medially, while the caudal margin is flat. The
articulation is flat to slightly convex in caudal view. In
lateral view the distal extremity is craniocaudally com-
pressed (Figures 2, 3 and 5(f)).
The proximal tarsus, the astragalus, is neither fused to
the distal tibia as in some primitive and extant birds, nor
tightly connected to the tibia. As in some dinosaurs and
primitive birds, the astragalus possesses a long tapering
ascending process[29,30]. Different from those of dino-
saurs and primitive birds[29,31], however, the tarsal pos-
sesses an opening near the distal end in caudal view
(Figures 2, 3 and 5(f)). This opening appears compara-
ble to the upper opening of the extensor canal for the
tendon of the M. extensor digitorum longus in modern
birds[26].
The fibula is slender and long, and its distal end ap-
pears to reach the level of the ascending process of the
astragalus. The proximal extremity is inflated with a flat
to slightly round proximal articular facet. From proximal
to distal, the shaft of the fibula gradually tapers in dia-
meter, and its cross section also changes from oval to
round. The proximal three-quarters of the fibula are lo-
cated on the lateral side of the tibia and the distal
one-quarter is turned to the cranial side (Figures 2 and
3).
The metatarsals are slightly shorter than half the
length of the tibia. The left proximal first third of the
metatarsals is preserved on the main slab in plantar view;
while the distal two-thirds is preserved on the counter
slab in dorsal view. In plantar view, the right metatarsals
ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | 625-639 637
II-IV are totally fused in their proximal region; while, in
dorsal view, the left metatarsals II-IV appear not totally
fused, but tightly connected. Among metatarsals II to IV,
metatarsal II is the shortest which is about 83% of meta-
tarsal III, the longest one. Metatarsal IV appears slightly
shorter than metatarsal III, while obviously longer than
metatarsal II. The proximal end of metatarsal II is obvi-
ously expanded medially. Dorsally, the proximal ends of
metatarsals II-IV are slightly expanded; while in plantar
view the proximal ends of metatarsals II and III are also
slightly expanded. The shaft of metatarsal II is straight
throughout its full length, only medially curved or in-
flated at its distal extremity. Its distal articular facet pro-
jects medially instead of distally, forming an angle of
approximately 30 degrees to the shaft longitudinal mid-
line of metatarsal II. Centrally, its distal extremity is
slightly concave in plantar view. The width of this
trochlea is similar to that of metatarsal III, and appears
slightly greater than metatarsal IV. The shaft of meta-
tarsal III is straight to slightly medially curved, while its
distalmost articular facet is slightly medially curved.
Apparently, compared with metatarsal III, the shaft of
metatarsal IV is laterally curved in its distal half (Fig-
ures 2, 3 and 5(f)).
Metatarsal I is “J”-shaped in dorsal or plantar view.
Distally it is attached to the medial side of metatarsal II.
The length of the former is less than one quarter of the
latter. From distally to proximally, metatarsal I becomes
gradually mediolaterally compressed and tapering, end-
ing with an oblique tip. The distal articular facet is
ball-shaped which articulates to the proximal phalanx of
digit I (Figures 2 and 3).
Metatarsal V is delicate and thin, from proximally to
distally it tapers gradually. Both left and right metatar-
sals V are longer than metatarsal I, and at least 30% of
metatarsal II in length, although their exact size is not
confirmed, as the proximal region is overlapped by the
tibia and other metatarsals (Figures 2, 3 and 5(f)).
Like those of other known Early Cretaceous birds, the
foot of Eoconfuciusornis is anisodactyl, with the usual
phalangeal formula of 2-3-4-5. Digit I is the shortest toe,
which is less than half the length of digit III, the longest
of all toes and only slightly shorter than the tarsometa-
tarsus. Digits II and IV are of similar length, longer than
digit I but shorter than digit III. The non-ungual pha-
langes share similar morphological features such as the
developed flexor tubercles, the articular trochleae, col-
lateral ligamental foveae, and shallow longitudinal ven-
tral depressions, etc. The ungual phalanges bear similar
flexor tuberosities and vascular sulci. The variation of
these phalanges focuses on their longitudinal and trans-
verse size. The proximal phalanx of digit III and the
preungual phalanx of digit II are in the same length, and
are longer than other non-ungual toes. However the
former appears slightly more robust than the latter. Two
intermediate phalanges of digit IV are smaller than other
nonungual phalanges. They are only about half of the
longest toe in length (Figures 2 and 3).
The ungual phalanx of digit II is the longest, which is
nearly 1.5 times the length of digit I, the shortest toe.
The ungual phalanges of digits III and IV are roughly
equal in length, which are about 85% the length of digit
II. However, in proportion to its length, the ungual pha-
lanx of digit I appears more robust than other ungual
phalanges for its transverse size is relatively greater than
others (Figures 2 and 3).
In digit I, the proximal phalanx is thin, roughly same
as the ungual phalanx in length. In digit II, the proximal
phalanx is more than 75% the length of the distal one,
while it appears more robust than the latter. The distal
phalanx appears equal to the ungual phalanx in length.
In digit III, the proximal phalanx is about 120% that of
the intermediate and the distal phalanges in length, and
appears more robust than the latter two in width. The
latter two phalanges are roughly equal in length and
width. They are slightly shorter than the ungual phalanx.
In digit IV, the proximal phalanx is slightly longer than
the first intermediate one, which is slightly longer than
the second intermediate one, while either proximal or
intermediate ones are shorter than the distal phalanx
which is slightly shorter than its attached ungual phalanx
(Figures 2 and 3).
(8) Plumage. The plumage is obvious, for most of
the feathers are black to deep brown, while the bones
and matrix appear brown or grey. Like other Jehol Biota
birds or dinosaurs, the feathers of Eoconfuciusornis
were preserved as carbonizations or impressions (Fig-
ures 2)[25,3133].
Both shafted feathers and non-shafted feathers[32] are
preserved in Eoconfuciusornis; the former includes the
flight and covert feathers which are attached to the fore-
limbs, two elongate tail feathers, and several isolated
covert feathers near the skeleton; the latter only includes
the down feather which is scattered near the skull, neck
and free caudal vertebrae (Figures 2, 4(a) and 5). There
are also some feathers that are very difficult to identify
638 ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | 625-639
as shafted or non-shafted feathers, such as the ones near
the vertebral column.
4 Discussion
Eoconfuciusornis is obviously a confuciusornithid,
based on the following characters: both upper and lower
jaws are toothless; the rostral end of mandibular sym-
physis is forked; the alular metacarpal is subquadrangu-
lar, and not fused to the other metacarpals; the major
digital claw is significantly smaller than other two; the
proximal phalanx of the minor manual digit is much
shorter than other non-ungual phalanges. Phylogeneti-
cally, Eoconfuciusornis represents the most basal mem-
ber of the Family Confuciusornithidae (Figure 7).
Figure 7 Cladogram showing relationships between Eoconfuciusornis
and other major groups of birds. This strict consensus result is from 14
most parsimonious trees. (see Appendixes 1 and 2; tree length = 308;
consistency index = 0.5942; retention index = 0.7664)
On the other hand, Eoconfuciusornis lacks apomor-
phies of derived confuciusornithids, such as: the thoracic
centra lacks a prominent lateral groove; the proximal
end of the scapula lacks a prominent acromion and gle-
noid facet; the coracoid is relatively short with 1) a fo-
ramen seemingly comparable to the supracoracoidal
nerve opening of some dinosaurs, and 2) a wide sternal
facet; generally the coracoid is more like that of Ar-
chaeopteryx than other confuciusornithids; the pubic
foot is well developed, while other confuciusornithids
entirely lack this structure; the deltopectoral crest of the
humerus is not as prominent as in other confuciusor-
nithids; and the astragalus possesses an elongate as-
cending process.
There are some features suggesting that the type
specimen of Eoconfuciusornis is not a fully adult indi-
vidual. For instance, the tarsometatarsus is not com-
pletely fused at the proximal end, the proximal tarsus is
not fused with the tibia, and some articular surfaces of
long bones are slightly coarser than those of the mid-
shaft. Based on some morphological and integumentary
aspects, however, the type specimen of Eoconfuciusor-
nis is nearly an adult. Eoconfuciusornis is a middle-sized
confuciusornithid, and is larger than some other known
fully adult confuciusornithids, such as IVPP V 10928;
Eoconfuciusornis bears a pair of extremely long central
tail feathers, which is regarded as an indication of sexual
dimorphism in Confuciusornis[34], which is only present
in adult or very near adult individuals in modern
birds[24].
It is interesting to note that the most primitive confu-
ciusornithid (Eoconfuciusornis) comes from the Da-
beigou Formation (131 Ma), which is older than Yixian
Formation (125 Ma) which produced Confuciusornis,
Changchengornis and Jinzhouornis. Since the youngest
horizon that bears a confuciusornithid (Confuciusornis)
is the Jiufotang Formation (120 Ma), therefore the Con-
fuciusornithidae had a temporal span of about 11 Ma,
the longest duration of any Early Cretaceous avian line-
ages, documenting a novel example of slow evolution-
ary rate in early avian evolution.
Corresponding with its greater age, Eoconfuciusornis
exhibits many intermediate features in morphology be-
tween more basal birds and more advanced confuciusor-
nithids. For example, in sternal anatomy, there is a clear
trend from Jeholornis[29] to the confuciusornithids: 1)
Jeholornis possesses a pair of flat sternal plates; 2) Eo-
confuciusornis possesses an incompletely ossified ster-
num (but a brown outline of roughly rectangular shape
on both slab and counter slab indicates that the sternum
is more like that of other confuciusornithids (Figure 6);
3) the confuciusornithids from the Yixian Formation
either developed a modest carina restricted to the caudal
quarter of the sternum, as in some Confuciusornis sanc-
tus (Figure 6), or not preserved, as in Changchengornis
hengdaoziensis[5]; 4) the confuciusornithids from the
Jiufotang Formation have a marked sternal carina, ex-
ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | 625-639 639
tending more than three-quarters of the length of the
sternum (Figure 6). The depth of the carina is an indica-
tion of the size of the main flight muscles[2,24], and thus
the confuciusornithids appear to show osteological evi-
dence for increasing flight power throughout the 11 mil-
lion years of their evolution (Figure 6).
We thank Zheng G M and Jin F for discussions, and Shou H Q, Li Y T, Liu
X Z, Huo Y L, Gao W, and Xiang L for technical support.
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Shanghai: Shanghai Scientific & Technical Publishers, 2003
2 Feduccia A. The Origin and Evolution of Birds. 2nd ed. New Haven:
Yale University Press, 1999
3 Chiappe L M. Basal bird phylogeny: Problems and solutions. In:
Chiappe L M, Witmer L M, eds. Mesozoic Birds. Berkeley: California
University Press, 2002. 448472
4 Zhou Z H, Zhang F C. Mesozoic birds of China
A synoptic review.
Vert PalAsiat, 2006, 44: 1823
5 Chiappe L M, Ji S A, Ji Q, et al. Anatomy and systematics of the
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Appendix 1 Character list and character states used for the cladistic analysis
Skull and mandible
1. Rostral portion of the premaxillae in adults: unfused (0); fused (1).
2. Maxillary process of the premaxilla: restricted to its rostral portion (0); subequal or longer than the facial contribution of the maxilla
(1).
3. Frontal process of the premaxilla: short (0); relatively long, approaching the rostral border of the antorbital fenestra (1); very long,
extending caudally near the level of lacrimals (2).
4. Premaxillary teeth: present (0); absent (1).
5. Maxilla and dentary: toothed (0); toothless (1).
6. Caudal margin of naris: farther rostral than the rostral border of the antorbital fossa (0); nearly reaching or overlapping the rostral
border of the antorbital fossa (1).
7. Dorsal ramus of the maxillary nasal process: present (0); absent (1).
8. Cup-shaped caudal maxillary sinus: absent (0); present (1).
9. Rostral margin of the jugal: away from the caudal margin of the osseous external naris (0), or very close to the caudal margin of the
osseous external naris (1).
10. Jugal process of palatine: present (0); absent (1).
11. Ectopterygoid: present (0); absent (1).
12. Squamosal incorporated into the braincase, forming a zygomatic process: absent (0); present (1).
13. Postorbital: present (0); absent (1).
14. Postorbital-jugal contact: present (0); absent (1).
15. Quadratojugal: sutured to the quadrate (0); joined through a ligamentary articulation (1).
16. Quadratojugal-squamosal contact: present (0); absent (1).
17. Lateral, round cotyla on the mandibular process of the quadrate (quadratojugal articulation): absent (0); present (1).
18. Quadrate orbital process (pterygoid ramus): broad (0); sharp and pointed (1).
19. Quadrate pneumaticity: absent (0); present (1).
20. Quadrate: articulating only with the squamosal (0); articulating with both prootic and squamosal (1).
21. Quadrate distal end: with two transversely aligned condyles (0); with a triangular, condylar pattern, usually composed of three dis-
tinct condyles (1).
22. Caudal tympanic recess: opens on the rostral margin of the paraoccipital process (0); opens into the columellar recess (1).
23. Basicranial fontanelle on the ventral surface of the basisphenoid (basisphenoid recess): present (0); absent (1).
24. Deeply notched rostral end of the mandibular symphysis: absent (0); present (1).
25. Coronoid bone: present (0); absent (1).
26. Articular pneumaticity: absent (0); present (1).
27. Dentary tooth implantation: teeth in individual sockets (0); teeth in a communal groove (1).
28. Teeth: serrated crowns (0); unserrated crowns (1).
Vertebral column and ribs
29. Atlantal hemiarches: unfused (0); fused, forming a single arch (1).
30. One or more pneumatic foramina piercing the centra of midcranial cervicals, caudal to the level of the parapophysisdiapophysis:
present (0); absent (1).
31. Cranial cervical vertebrae heterocoelous: absent (0); present (1).
32. Prominent carotid processes in the intermediate cervicals: absent (0); present (1).
33. Postaxial cervical epipophyses: prominent, projecting farther back from the postzygapophysis (0); weak, not projecting farther
back from the postzygapophysis, or absent (1).
34. Prominent (50% or more the height of the centrum's cranial articular surface) ventral processes of the cervicothoracic vertebrae:
absent (0); present (1).
35. Cervicothoracic vertebrae with parapophyses located at the same level as the prezygapophyses: absent (0); present (1).
36. Thoracic vertebral count: 1314(0); 1112 (1); fewer than 11 (2).
37. Wide vertebral foramen in the midcaudal thoracic vertebrae, vertebral foramen/articular cranial surface ratio (vertical diameter)
larger than 0.40: absent (0); present (1).
38. Hyposphene-hypantrum accessory intervertebral articulations in the thoracic vertebrae: present (0); absent (1).
39. Lateral side of the thoracic centra: weakly or not excavated (0); deeply excavated by a groove (1); excavated by a broad fossa (2).
40. Parapophyses: located in the cranial part of the centra of the thoracic vertebrae (0); located in the central part of the centra of the
ii ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | i-x
thoracic vertebrae (1).
41. Synsacrum: formed by fewer than eight vertebrae (0); eight or more vertebrae (1).
42. Synsacrum procoelous: absent (0); present (1).
43. Caudal portion of the synsacrum forming a prominent ventral keel: absent (0); present (1).
44. Convex caudal articular surface of the synsacrum: absent (0); present (1).
45. Caudal vertebra prezygapophyses: present (0); absent (1).
46. Distal caudal vertebra prezygapophyses: elongate, exceeding the length of the centrum by more than 25% (0); shorter (1).
47. Procoelous caudals: absent (0); present (1).
48. First caudal with a ventrally sharp centrum: absent (0); present (1).
49. Proximal haemal arches: elongate, at least three times longer than wider (0); shorter (1); absent (2).
50. Pygostyle: absent or rudimentary (fewer than three elements) (0); present (1).
51. Pygostyle: longer than or equal to the combined length of the free caudals (0); shorter (1).
52. Caudal vertebral count: more than 35 (0); fewer than 2526 (1); fewer than 15 (2).
53. Ossified uncinate processes: absent (0); present (1).
Thoracic girdle and sternum
54. Coracoid and scapula: articulate through a wide, sutured articulation (0); articulate through more localized facets (1).
55. Scapula: articulated at the shoulder (proximal) end of the coracoid (0); well below it (1).
56. Humeral articular facets of the coracoid and the scapula: placed in the same plane (0); forming a sharp angle (1).
57. Procoracoid process on coracoid: absent (0); present (1).
58. Coracoid shape: short (0); elongated with trapezoidal profile (1); strutlike(2).
59. Distinctly convex lateral margin of coracoid: absent (0); present (1).
60. Bicipital tubercle (= acrocoracoidal process): present (0); or absent (1).
61. Supracoracoidal nerve foramen of coracoid: centrally located (0); displaced toward (often as an incisure or even without passing
through) the medial margin of the coracoid (1).
62. Supracoracoidal nerve foramen opening into an elongate furrow medially and separated from the medial margin of the coracoid by
a thick, bony bar: absent (0); present (1).
63. Broad, deep fossa on the dorsal surface of the coracoid: absent (0); present (1).
64. Sternocoracoidal process on the sternal half of the coracoid: absent (0); present (1).
65. Scapular caudal end: blunt and usually expanded (0); tapered to a sharp point (1).
66. Scapular shaft: straight (0); sagittally curved (1).
67. Prominent acromion in the scapula: absent (0); present (1).
68. Dorsal and ventral margins of the furcula: subequal in width (0); ventral margin distinctly wider than the dorsal margin (1).
69. Furcula: boomerang-shaped, with interclavicular angle of approximately 90° (0); U-shaped, with an interclavicular angle of less
than 70° (1).
70. Hypocleideum: absent or poorly developed (0); well developed (1).
71. Sternum: subquadrangular to transversely rectangular (0); longitudinally rectangular (1).
72. Distinctly carinate sternum, more prominent than a faint ridge: absent (0); present (1).
73. Sternal carina: near to, or projecting rostrally from, the cranial border of the sternum (0); not reaching the cranial border of the
sternum (1).
74. Lateral process of the sternum: absent (0); present (1).
75. Prominent distal expansion in the lateral process of the sternum: absent (0); present (1).
76. Medial process of the sternum: absent (0); present (1).
77. Rostral margin of the sternum broad and parabolic: absent (0); present (1).
78. Wide V-shaped caudal end of the sternum: absent (0); present (1).
79. Costal facets of the sternum: absent (0); present (1).
Thoracic limb
80. Proximal and distal humeral ends: twisted (0); expanded nearly in the same plane (1).
81. Humeral head: concave cranially and convex caudally (0); globe-shaped, craniocaudally convex (1).
82. Proximal margin of the humeral head concave in its central portion, rising ventrally and dorsally: absent (0); present (1).
83. Ventral tubercle of the humerus: projected ventrally (0); projected proximally (1); projected caudally, separated from the humeral
head by a deep capital incision (2).
84. Humerus with distinct transverse ligamental groove: absent (0); present (1).
85. Pneumatic fossa in the caudoventral corner of the proximal end of the humerus: absent or rudimentary (0); well developed (1).
86. Prominent, subquadrangular (i.e., subequal length and width) deltopectoral crest of the humerus: absent (0); present (1).
ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | i-x iii
87. Prominent bicipital crest of the humerus, cranioventrally projecting: absent (0); present (1).
88. Ventral face of the humeral bicipital crest with a small fossa for muscular attachment: absent (0); present (1).
89. Humeral distal condyles: mainly located on distal aspect (0); on cranial aspect (1).
90. Humerus: with two distal condyles (0); a single condyle (1).
91 Well-developed brachial depression on the cranial face of the distal end of the humerus: absent (0); present (1).
92 Well-developed olecranon fossa on the caudal face of the distal end of the humerus: absent (0); present (1).
93 Distal end of the humerus very compressed craniocaudally: absent (0); present (1).
94 Ulna: shorter than humerus (0); nearly equivalent to or longer than humerus (1).
95 Ulnar shaft: considerably thicker than the radial shaft, radial-shaft/ulnar-shaft ratio larger than 0.70 (0); smaller than 0.70(1).
96 Olecranon process of ulna: relatively small (0); hypertrophied, nearly one-third the length of the ulna (1); one-half the length of the
ulna (2).
97. Proximal end of the ulna with a well-defined area for the insertion of M. brachialis anticus: absent (0); present (1).
98. Semilunate ridge on the dorsal condyle of the ulna: absent (0); present (1).
99. Shaft of radius with a long longitudinal groove on its ventrocaudal surface: absent (0); present (1).
100. U-shaped to heart-shaped ulnare (scapholunar): absent (0); present (1).
101. Semilunate carpal and proximal ends of metacarpals: unfused (0); semilunate fused to the alular (I) metacarpal (1); semilunate
fused to the major (II) and minor (III) metacarpals (2); fusion of semilunate and all metacarpals (3).
102. Distal end of metacarpals: unfused (0); partially or completely fused (1).
103. Intermetacarpal space: absent or very narrow (0); at least as wide as the maximum width of minor metacarpal (III) shaft (1).
104. Extensor process on alular metacarpal (I): absent or rudimentary (0); well developed (1).
105. Minor metacarpal (III) projecting distally more than the major metacarpal (II): absent (0); present (1).
106. Round-shaped alular metacarpal (I): absent (0); present (1).
107. Alular metacarpal (I) large, massive, depressed, and quadrangular: absent (0); present (1).
108. Alular digit (I): long, exceeding the distal end of the major metacarpal (0); short, not surpassing this metacarpal (1).
109. Alular digit (I) large, robust, and dorsoventrally compressed: absent (0); present (1).
110. Prominent ventral projection of the proximolateral margin of the proximal phalanx of the alular digit (I): absent (0); present (1).
111. Ungual phalanx of major digit (II): present (0); absent (1).
112. Ungual phalanx of major digit (II) much smaller than the unguals of the alular (I) and minor (III) digits: absent (0); present (1).
113. Proximal phalanx of the minor digit (III) much shorter than the remaining nonungual phalanges of this digit: absent (0); present
(1).
114. Ungual phalanx of minor digit (III): present (0); absent (1).
115. Proximal phalanx of major digit (II): of normal shape (0); flat and craniocaudally expanded (1).
116. Intermediate phalanx of major digit (II): longer than proximal phalanx (0); shorter than or equivalent to proximal phalanx (1).
117. Alular ungual phalanx with two ventroproximal foramina: absent (0); present (1).
Pelvic Girdle
118. Pelvic elements: unfused (0); fused or partially fused (1).
119. Preacetabular process of ilium twice as long as postacetabular process: absent (0); present (1).
120. Small acetabulum, acetabulum/ilium length ratio equal to or smaller than 0.11: absent (0); present (1).
121. Postacetabular process shallow and pointed, less than 50% of the depth of the preacetabular wing at the acetabulum: absent (0);
present (1).
122. Orientation of proximal portion of pubis: cranially to subvertically oriented (0); retroverted, separated from the main synsacral
axis by an angle ranging between 65° and 45° (1); more or less parallel to the ilium and ischium (2).
123. Prominent antitrochanter: caudally directed (0); caudodorsally directed (1).
124. Iliac brevis fossa: present (0); absent (1).
125. Pubic pedicel: cranioventrally projected (0); ventrally or caudoventrally projected (1).
126. Supracetabular crest on ilium: well developed (0); absent or rudimentary (1).
127. Supracetabular crest: extending throughout the acetabulum (0); extending only over the cranial half of the acetabulum (1).
128. Ischium with a proximodorsal process approaching, or abutting, the ventral margin of the ilium: absent (0); present (1).
129. Ischiadic terminal processes forming a symphysis: present (0); absent (1).
130. Ischium: two-thirds or less the length of the pubis (0); more than two-thirds the length of the pubis (1).
131. Obturator process of ischium: prominent (0); reduced or absent (1).
132. Pubic apron: one-third or more the length of the pubis (0); shorter (1); absent (absence of symphysis) (2).
133. Pubic shaft laterally compressed throughout its length: absent (0); present (1).
134. Pubic foot: present (0); absent (1).
135. Laterally compressed and kidney-shaped proximal end of pubis: absent (0); present (1).
iv ZHANG FuCheng et al. Sci China Ser D-Earth Sci | May 2008 | vol. 51 | no. 5 | i-x
Pelvic limb
136. Femur with distinct fossa for the capital ligament: absent (0); present (1).
137. Femoral neck: present (0); absent (1).
138. Femoral anterior trochanter: separated from the greater trochanter (0); fused to it, forming a trochanteric crest (1).
139. Femoral posterior trochanter: absent to moderately developed (0); hypertrophied (1).
140. Conical and strongly distally projected lateral condyle of femur: absent (0); present (1).
141. Femur with prominent patellar groove: absent (0); present (1).
142. Femoral popliteal fossa distally bounded by a complete transverse ridge: absent (0); present (1).
143. Tibiofibular crest in the lateral condyle of femur: absent (0); poorly developed (1); prominent (2).
144. Fossa for the femoral origin of M. tibialis cranialis: absent (0); present (1).
145. Caudal projection of the lateral border of the distal end of the femur: absent (0); present (1).
146. Tibia, calcaneum, and astragalus: unfused or poorly coossified (sutures still visible) (0); complete fusion of tibia, calcaneum, and
astragalus (1).
147. Cranial cnemial crest on tibiotarsus: absent (0); present (1).
148. Round proximal articular surface of tibiotarsus: absent (0); present(1).
149. Medial border of medial articular facet strongly projects proximally: absent (0); present (1).
150. Extensor canal on tibiotarsus: absent (0); present (1).
151. Wide and bulbous medial condyle of the tibiotarsus: absent (0); present (1).
152. Narrow, deep intercondylar sulcus on tibiotarsus that proximally undercuts the condyles: absent (0); present (1).
153. Proximal end of the fibula: prominently excavated by a medial fossa (0); nearly flat (1).
154. Fibula: tubercle for M. iliofibularis craniolaterally directed (0); laterally directed (1); caudolaterally or caudally directed (2).
155. Fibula: reaching the proximal tarsals (0); greatly reduced distally, without reaching these elements (1).
156. Metatarsals IIIV completely (or nearly completely) fused to each other: absent (0); present (1).
157. Distal tarsals: free (0); completely fused to the metatarsals (1).
158. Metatarsal V: present (0); absent (1).
159. Proximal end of metatarsal III: in the same plane as metatarsals II and IV (0); reduced, not reaching the tarsals (arctometatarsalian
condition) (1); plantarly displaced with renpect to metatarsals II and IV (2).
160. Well-developed tarsometatarsal intercondylar eminence: absent (0); present (1).
161. Tarsometatarsal vascular distal foramen completely enclosed by metatarsals III and IV: absent (0); present (1).
162. Trochlea of metatarsal II broader than the trochlea of metatarsal III: absent (0); present (1).
163. Completely reversed hallux (arch of ungual phalanx of digit I opposing the arch of the unguals of digits IIIV): absent (0); pre-
sent (1).
164. Metatarsal IV significantly thinner than metatarsals II and III: absent (0); present (1).
165. Plantar surface of tarsometatarsus excavated: absent (0); present (1).
166. Tubercle on the dorsal face of metatarsal II: absent (0); present (1).
167. Hypotarsus: absent (0); present (1).
Integument
168. Feathers: absent (0); present (1).
169. Alula: absent (0); present (1).
v
Appendix 2 Data matrix used for the cladistic analysis
Taxon 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Allosauroidea 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Troodontidae 0 0 0 0 0 0 0 0 0 ? 0 0 0 0 ? ? ? 0 1 0 0 1 1 0 ? ? 1 0
Velociraptorinae 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ? 0 0 0 0 0 0 0 0 0
Archaeopteryx 0 0 1 0 0 1 0 0 0 1 0 0 0 1 1 1 0 0 0 ? 0 1 ? ? 1 ? 0 1
Rahonavis ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Mononykus ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 1 ? ? ? ? ? 1
Shuvuuia 0 0 0 ? 0 0 0 ? 0 1 ? 0 0 1 1 1 0 0 0 1 0 1 0 ? 1 ? 1 1
Alvarezsaurus ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Patagonykus ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Confuciusornis 1 0 2 1 1 1 0 0 0 ? 0 0 0 0 1 1 1 ? ? 1 0 ? ? 1 ? 0 n n
Changchengornis 1 ? ? 1 1 1 0 ? ? ? ? ? ? ? ? ? ? ? ? ? 0 ? ? 1 ? 0 n n
Eoconfuciusornis 1 ? 2 1 1 1 0 ? 0 ? ? ? 0 0 ? ? ? ? ? ? ? ? ? 1 ? 0 n n
Noguerornis ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Iberomesornis ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Patagopteryx ? ? ? ? ? ? ? ? ? ? ? 1 ? ? 1 1 1 0 1 1 1 ? 1 ? ? 0 ? ?
Vorona ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Concornis ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Cathayornis 1 0 1 0 0 1 0 ? ? ? ? ? ? ? ? ? ? 0 ? ? ? ? ? ? ? ? 0 1
Cobipteryx 1 0 2 1 1 1 1 1 0 1 0 ? ? ? ? ? ? 0 ? ? 0 ? ? 0 1 0 n n
Eoalulavis ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Neuquenornis ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Ambiortus ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Hesperornis 1 1 2 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1 0 0 1 0 1 1
Ichthyornis 1 ? 2 1 0 ? ? ? ? ? ? 1 1 1 1 1 1 1 1 1 ? ? ? ? ? 1 0 1
Anas 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1 0 1 1 n n
vi
Taxon 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56
Allosauroidea 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 n 0 0 0 0 0
Troodontidae ? 0 0 0 0 1 0 0 0 0 0 0 0 ? 0 0 0 0 0 0 0 0 n ? 1 0 0 0
Velociraptorinae 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 n 0 1 0 0 0
Archaeopteryx 0 0 0 ? 1 0 0 0 ? ? 0 0 0 0 ? 0 0 1 0 ? 1 0 n 1 0 0 0 0
Rahonavis ? ? ? ? ? ? 0 ? 1 0 2 0 0 1 0 ? 0 1 0 0 1 0 n ? ? 1 ? ?
Mononykus ? 1 0 1 1 1 1 ? 1 1 0 0 ? 1 1 1 ? ? 1 1 ? ? n ? ? 0 0 0
Shuvuuia 0 0 0 1 1 1 1 ? 1 1 0 0 0 1 1 1 0 1 1 1 0 0 n ? ? 0 0 0
Alvarezsaurus 0 ? ? ? 1 ? 0 ? ? ? 0 0 0 0 0 ? 0 1 1 1 0 ? n ? ? 0 0 0
Patagonykus ? 0 0 ? ? ? ? ? 1 0 0 0 ? 1 1 1 ? ? 1 1 ? ? n ? ? 0 0 ?
Confuciusornis ? ? 0 ? 1 1 ? 0 1 1 2 0 0 1 0 0 0 1 0 ? ? 1 0 1 1 0 0 0
Changchengornis ? ? ? ? ? ? ? ? ? ? 2 ? 0 ? 0 0 0 1 ? ? ? 1 0 1 ? 0 0 ?
Eoconfuciusornis ? ? 0 0 ? ? ? 0 ? ? 0 0 0 1 0 0 0 ? 1 ? ? 1 0 1 ? 0 0 ?
Noguerornis ? ? ? ? ? ? ? ? ? ? ? ? ? 0 ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Iberomesornis ? ? ? ? ? 1 0 1 ? ? 0 0 0 0 0 0 0 1 0 0 1 1 0 1 0 ? ? ?
Patagopteryx l 1 1 1 1 1 0 1 1 1 0 0 1 1 0 1 1 n 1 0 ? ? ? ? 0 1 1 1
Vorona ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Concornis ? ? ? ? ? ? ? ? ? ? 1 1 ? ? 0 ? ? ? 0 0 1 ? ? ? 0 1 1 1
Cathayornis ? ? ? ? ? ? ? ? ? ? 1 1 1 ? ? 0 ? ? 0 ? ? 1 ? 1 0 1 ? ?
Cobipteryx ? ? ? ? ? ? ? ? ? ? ? ? ? 1 ? ? 0 1 0 ? ? 1 ? ? ? 1 1 ?
Eoalulavis 0 ? ? ? 1 1 0 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 0 1 1 1
Neuquenornis ? ? ? ? ? ? ? ? ? ? 1 1 ? ? ? ? ? ? ? ? ? ? ? ? ? 1 1 ?
Ambiortus 0 ? 1 1 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 1 1 1
Hesperornis ? 1 1 1 0 1 0 2 1 1 2 0 1 0 0 ? 1 n 0 0 2 0 0 2 1 1 0 0
Ichthyornis 1 1 1 1 1 1 0 2 1 1 2 0 1 ? 0 0 0 1 0 ? 2 1 1 ? ? 1 1 1
Anas l 0 1 1 1 1 0 2 1 1 0 0 1 0 0 0 1 n 0 0 2 1 1 2 1 1 1 1
vii
Taxon 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84
Allosauroidea 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 n ? ? ? ? ? 0 0 0 0 0 0
Troodontidae 0 1 0 0 0 0 ? 0 ? ? 0 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 0 ?
Velociraptorinae 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 n 0 n 0 0 0 0 0 0 0 0 0
Archaeopteryx 0 1 0 0 0 0 0 0 0 0 1 0 0 0 ? 0 n ? ? ? ? ? ? 0 ? 0 0 0
Rahonavis ? ? ? ? ? ? ? ? 0 0 1 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Mononykus 0 0 0 1 0 0 0 0 0 0 0 ? ? ? 1 1 0 0 n 0 0 0 0 1 0 0 1 0
Shuvuuia 0 0 0 1 0 0 0 0 0 0 0 ? ? ? 1 1 0 0 n 0 0 0 0 1 0 0 1 0
Alvarezsaurus 0 ? ? ? 0 ? ? ? ? 0 0 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Patagonykus 0 0 0 1 0 0 0 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 0 0 1 0
Confuciusornis 0 2 0 0 1 0 0 0 0 0 0 0 0 0 1 0 n 1 0 0 0 1 1 0 0 0 0 1
Changchengornis 0 2 0 0 1 0 0 0 ? 0 0 0 0 0 1 0 n ? ? ? ? 1 ? 0 ? 0 ? ?
Eoconfuciusornis 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 ? n ? ? ? ? ? ? 0 ? 0 0 0
Noguerornis ? ? ? ? ? ? ? ? ? ? ? ? ? 1 ? ? ? ? ? ? ? ? ? ? 0 0 ? ?
Iberomesornis ? 2 0 0 1 ? ? 0 1 0 ? ? 1 1 ? ? ? ? ? ? ? ? ? ? 0 0 ? 0
Patagopteryx 0 2 0 0 1 0 0 0 1 1 1 ? ? ? ? ? ? ? ? ? 1 ? ? 1 0 0 ? ?
Vorona ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Concornis 0 2 1 0 1 1 1 0 ? 0 ? 1 1 1 1 1 1 1 1 1 1 0 ? 0 0 1 2 1
Cathayornis 0 2 1 0 1 1 1 0 1 0 1 ? 1 1 1 1 1 1 1 1 1 0 ? 0 0 1 2 ?
Cobipteryx 0 2 ? 0 ? ? 1 0 ? ? 1 1 ? 1 ? ? ? ? ? ? ? ? ? 0 ? ? ? ?
Eoalulavis 0 2 1 0 1 1 1 0 1 1 1 1 1 1 1 0 n 0 n n 0 0 0 0 1 1 2 1
Neuquenornis 0 2 1 0 1 1 1 0 ? 0 1 1 1 0 1 1 0 1 1 ? ? ? ? 1 ? ? 2 ?
Ambiortus 1 2 0 0 1 0 ? ? ? 1 1 0 1 0 ? 1 1 ? ? ? ? ? ? ? 1 0 ? 1
Hesperornis 1 2 0 n 0 0 0 0 0 1 0 0 0 0 1 0 n 0 n 0 1 0 1 n 1 0 n n
Ichthyornis 1 2 0 0 1 0 0 1 1 1 0 0 ? ? 1 1 0 ? ? ? 1 ? ? 1 1 0 2 1
Anas 1 2 0 0 1 0 0 1 1 1 1 0 1 0 1 1 0 1 0 0 1 0 1 1 1 0 2 1
viii
Taxon 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112
Allosauroidea 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 n 0 0 0 0 0 0 0 0 0 0 0
Troodontidae ? 0 ? ? ? ? ? ? ? 0 0 0 ? ? ? ? 0 0 0 0 0 0 0 0 0 0 0 0
Velociraptorinae 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Archaeopteryx 0 0 0 0 0 0 0 0 ? 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Rahonavis ? ? ? ? ? ? ? ? ? ? 1 0 1 0 0 ? ? ? ? ? ? ? ? ? ? ? ? ?
Mononykus 0 0 0 0 1 1 0 0 0 0 0 2 0 0 0 ? 1 1 0 0 0 0 1 0 1 1 ? ?
Shuvuuia 0 0 0 0 1 1 0 0 0 0 0 2 0 0 0 ? 1 0 0 0 0 0 1 0 1 1 ? ?
Alvarezsaurus ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Patagonykus 0 ? 0 0 1 1 0 0 1 ? 0 1 ? 0 ? ? 1 ? ? 0 ? 0 1 0 1 1 ? ?
Confuciusornis 0 1 0 ? 1 0 0 0 0 0 1 0 1 ? 0 1 2 0 0 0 0 0 0 0 0 0 0 1
Changchengornis ? 1 ? ? ? ? ? ? ? 0 1 0 ? ? 0 ? ? 0 0 0 0 0 0 0 0 0 0 1
Eoconfuciusornis 0 0 0 0 ? 0 ? ? 0 0 1 0 ? ? 0 ? 0 0 0 0 0 0 0 0 0 0 0 1
Noguerornis ? ? 0 ? ? ? ? ? ? 1 0 ? ? ? 0 ? 3 ? 0 0 1 1 0 ? 0 ? ? ?
Iberomesornis ? 0 0 ? ? 0 0 ? ? 1 1 0 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Patagopteryx ? 0 0 0 1 0 0 0 0 0 1 0 0 ? 0 ? ? 1 1 ? ? ? 0 ? ? 0 0 ?
Vorona ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Concornis ? 0 1 1 1 0 0 ? 1 1 1 0 ? ? ? ? ? ? 0 ? ? ? 0 1 0 ? 0 ?
Cathayornis 1 0 1 1 1 0 0 1 ? 1 1 0 ? 1 1 1 3 0 0 0 1 1 0 1 0 0 0 ?
Cobipteryx ? ? ? ? ? ? 0 ? ? 1 1 ? 1 1 1 ? ? 0 0 ? 1 ? ? ? ? ? ? ?
Eoalulavis 0 0 1 1 1 0 0 1 1 1 1 0 1 ? 1 ? ? 0 1 ? 1 ? 0 1 0 ? 0 ?
Neuquenornis 1 ? ? ? ? ? 1 1 1 1 1 ? ? 1 1 ? 3 0 0 0 1 1 0 ? ? ? ? ?
Ambiortus 0 0 0 0 ? ? ? ? ? ? 1 ? ? ? ? 1 3 ? ? 0 ? 1 0 ? ? ? 0 ?
Hesperornis 0 0 0 0 n n 0 0 0 n n n n n n n n n n n n n n n n n n n
Ichthyornis 0 0 0 1 1 0 1 1 0 1 1 0 1 1 0 ? 3 1 1 1 0 0 0 1 0 0 1 n
Anas 1 0 0 0 1 0 1 1 0 0 1 0 1 1 0 1 3 1 1 1 0 0 0 1 0 0 1 n
ix
Taxon 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140
Allosauroidea 0 0 0 0 0 0 0 0 0 0 n 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0
Troodontidae 0 0 0 0 0 0 0 0 0 0 0 0 1 1 n 0 0 0 0 0 ? ? ? ? 0 0 0 0
Velociraptorinae 0 0 0 0 0 0 0 0 0 1 0 0 1 1 n 0 0 0 0 0 0 0 0 0 0 0 0 0
Archaeopteryx 0 0 0 0 0 0 1 0 1 0 n ? 1 1 n 1 ? 0 0 0 0 0 0 ? 1 0 0 0
Rahonavis ? ? ? ? ? 0 1 0 1 0 0 1 1 1 n 1 1 0 0 0 0 0 ? 0 1 1 0 0
Mononykus ? ? ? ? 1 1 ? ? ? 1 0 ? 0 0 1 ? ? ? ? ? ? ? 1 0 0 1 ? 1
Shuvuuia ? ? ? ? 1 ? 0 0 0 1 0 0 0 0 1 0 1 1 1 2 1 1 1 ? 0 ? ? ?
Alvarezsaurus ? ? ? ? 0 ? 0 0 0 ? ? 0 0 0 0 ? ? ? ? ? ? ? ? ? 0 ? 0 ?
Patagonykus ? ? ? ? ? 0 ? ? ? 0 0 ? 0 0 0 ? ? ? ? 1 1 0 0 ? ? 0 0 1
Confuciusornis 1 0 0 0 0 1 ? 0 ? 1 1 1 1 1 n 1 1 0 1 1 0 1 ? 1 0 1 ? 0
Changchengornis 1 0 0 1 0 ? ? ? ? ? ? ? ? ? ? ? ? ? ? 1 0 ? ? ? ? ? ? 0
Eoconfuciusornis 1 0 0 0 0 1 ? 0 ? ? ? ? 1 ? ? ? ? ? ? 1 0 0 ? ? ? ? ? 0
Noguerornis ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 1 0 ? ? ? ? ? ? ? ? ? ? ?
Iberomesornis ? ? ? ? ? 1 ? ? ? ? ? ? ? ? ? 1 ? 1 1 ? 0 ? ? ? ? ? ? 0
Patagopteryx ? ? 0 0 ? 1 0 0 0 1 0 0 1 1 n 0 1 1 1 2 0 1 0 ? 0 ? ? 0
Vorona ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 1 0 1 ? 0
Concornis ? ? 0 1 ? ? ? ? ? ? ? ? ? ? ? 1 1 1 0 1 0 ? ? 0 0 ? ? ?
Cathayornis 0 1 0 1 0 ? 0 0 1 1 ? ? 1 1 n 1 ? 1 1 ? ? 0 ? ? 0 1 1 0
Cobipteryx ? ? 0 ? ? ? ? ? ? ? ? ? 1 ? ? ? ? ? ? 1 ? 1 ? ? ? ? ? ?
Eoalulavis 0 ? 0 1 0 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 1 1 ?
Neuquenornis ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 1 1 ?
Ambiortus ? ? 1 1 n ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Hesperornis n n n n n 1 0 1 0 2 1 1 1 1 ? 0 1 1 1 2 1 1 0 1 0 1 0 0
Ichthyornis n ? 1 1 ? 1 ? 1 ? 2 1 ? 1 1 n 1 1 1 1 2 1 1 ? 1 0 1 0 0
Anas n 1 1 1 n 1 0 1 0 2 1 1 1 1 n 1 1 1 1 2 1 1 0 1 0 1 0 0
x
Taxon 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169
Allosauroidea 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ? ?
Troodontidae 0 ? 0 0 0 0 0 0 0 0 0 0 ? 0 1 0 0 0 1 0 0 0 0 0 0 0 0 ? ?
Velociraptorinae 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 ? ?
Archaeopteryx 0 ? 0 ? 0 0 0 ? 0 0 0 0 ? ? 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0
Rahonavis 0 0 1 0 0 0 0 0 0 0 0 0 ? 2 1 0 0 ? 0 0 0 0 1 0 0 1 0 1 ?
Mononykus 0 0 0 0 0 0 0 0 1 0 0 0 1 ? 1 0 ? ? 1 0 0 0 ? 0 0 0 0 ? ?
Shuvuuia 0 0 ? ? 0 0 ? ? 1 0 0 0 1 1 1 0 0 0 1 0 0 0 ? 0 0 0 0 1 ?
Alvarezsaurus ? ? ? ? ? 0 ? ? ? 0 0 0 ? ? 0 0 ? ? 0 ? 0 0 ? 0 ? 0 0 ? ?
Patagonykus 0 0 0 0 0 0 0 0 0 0 0 0 ? ? 0 0 ? ? 0 0 ? ? ? ? ? ? 0 ? ?
Confuciusornis ? ? 1 ? ? 1 ? ? 0 0 1 0 ? 1 1 0 1 0 0 0 0 0 1 0 1 1 0 1 0
Changchengornis ? ? ? ? ? 1 ? ? ? ? ? ? ? ? 1 0 1 0 0 ? ? ? 1 0 0 ? 0 1 ?
Eoconfuciusornis ? ? ? ? ? 0 ? 0 0 0 0 0 ? ? ? 0 ? 0 0 0 0 0 1 0 0 ? 0 1 0
Noguerornis ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 1 ?
Iberomesornis 0 ? ? ? ? 0 0 1 0 ? ? ? ? ? ? 0 0 ? 0 0 0 ? 1 0 ? ? ? ? ?
Patagopteryx 0 1 2 ? 0 1 0 0 0 0 1 1 1 1 1 1 1 1 0 0 1 0 0 0 1 0 1 ? ?
Vorona 0 1 1 ? 1 0 0 0 0 0 1 1 1 1 1 1 1 0 0 0 1 0 ? 0 1 0 0 ? ?
Concornis 0 ? ? ? 1 1 0 1 0 ? 1 ? ? ? ? 0 1 ? 0 0 0 1 1 1 ? ? ? 1 ?
Cathayornis 0 1 1 ? 0 1 ? ? 0 0 1 1 1 ? 1 0 ? ? 0 0 ? ? ? ? 1 ? 0 ? ?
Cobipteryx ? ? ? ? ? ? 0 1 0 0 1 ? 1 ? 1 0 1 1 0 0 ? 1 ? 1 0 1 0 ? ?
Eoalulavis ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 1 1
Neuquenornis 0 ? ? ? 1 ? ? ? ? ? ? ? ? ? ? 0 ? ? 0 ? 0 1 1 1 ? ? ? ? ?
Ambiortus ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 1 ?
Hesperornis 1 1 2 1 0 1 1 0 0 1 0 0 1 2 1 1 1 1 2 1 1 0 0 0 0 0 0 ? ?
Ichthyornis 1 1 2 ? 0 1 1 0 0 1 0 0 ? 2 1 1 1 1 2 1 1 0 ? 0 0 0 1 ? ?
Anas 1 1 2 1 0 1 1 0 0 1 0 0 1 2 1 1 1 1 2 1 1 0 1 0 0 0 1 1 1
... Confuciusornithids were the earliest birds with a horny beak [2,7], occupying a critical position in early bird evolution. Many scholars have performed much work on the phylogenetic and microscopic features of different species, including the identification at the species level [13][14][15][16][17][18], growth patterns [8][9]19], body size and sex differences [20][21][22][23], feather patterns and colours [24][25][26], perching style and feeding habits [2,24,[27][28], and reproductive characteristics and pterygium structure [29]. An increasing number of findings facilitated reconstructions of the developmental characteristics of confuciusornithids, but the functional analyses of flightrelated structures were mainly based on qualitative results by analogy with the flight theory in extant bird. ...
... An increasing number of findings facilitated reconstructions of the developmental characteristics of confuciusornithids, but the functional analyses of flightrelated structures were mainly based on qualitative results by analogy with the flight theory in extant bird. The quantitative researches on the flight pattern, flight strategy, and regulatory mechanisms in confuciusornithid birds have developed somewhat slowly, with only a few brief descriptions published to date [17,[30][31]. ...
... This research status makes answering a series of questions, such as those on early birds' aerodynamic performance, the coordination of body parts in flight, and the evolutionary trajectory of fundamental flight structures, an urgent requirement. At present, it is generally agreed that confuciusornithids had many characters similar to those of modern birds and had a greater potential for flight than Archaeopteryx, based on morphological differences between confuciusornithids and other early birds and feathered dinosaurs [4,17,29]. In recent years, many new experimental techniques and methods are available for quantifying the relationship between morphology and function of fossilized animals, such as skeletal morphology and kinematics, muscle power, and aerodynamic output [3]. ...
Article
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Eastern Asia can be regarded as a dynamic environment during the Early Cretaceous in which the whole biota was complex and diverse, so the differentiation of early birds was also pronounced in this period. Confuciusornithids only uncovered from Eastern Asia, are an important early bird group for revealing the origin and early evolution of avian flight. However, results on confuciusornithid flight capabilities mainly come from qualitative analysis or speculation and analogism because of insufficient information from fossils, limited analogues in living birds, and no rigorous biomechanical testing. As an essential and popular tool in quantitative simulation and analysis, computational fluid dynamics (CFD) has major advantages over other techniques and has been well developed in recent years to solve general morphological-functional problems in palaeontolog-ical research. CFD is beneficial for studying the flight capability of confuciusornithids and will provide new quantitative evidence for the origin and evolution of early bird flight. In addition, we expect that interdisciplinary, exploratory, and tentative work will soon be applied in other similar studies, which will allow us to develop a quantitative method that can be applied effectively in functional-morphological analyses.
... Confuciusornithidae is an important group of fossil birds, which has developed tremendously in north China and other east Asian regions during Early Cretaceous. They were divided into 3 genera and 4 species: Confuciusornis sanctus, C. dui, Changchengornis hengdaoziensis, and Eoconfuciusornis zhengi [1][2][3][4][5][6]. As an important group of basal birds, it has experienced tremendous development both in quantity and evolution during Early Cretaceous, and has become the focus of paleornithology and paleoenvironment [2][3][4][5][6][7][8][9]. ...
... They were divided into 3 genera and 4 species: Confuciusornis sanctus, C. dui, Changchengornis hengdaoziensis, and Eoconfuciusornis zhengi [1][2][3][4][5][6]. As an important group of basal birds, it has experienced tremendous development both in quantity and evolution during Early Cretaceous, and has become the focus of paleornithology and paleoenvironment [2][3][4][5][6][7][8][9]. Now it was studied more detailed than many other fossil birds by reasons of its important phylogenetic position, abundant specimens, and exquisite preservation [6,[10][11][12][13][14][15][16]. ...
... As an important group of basal birds, it has experienced tremendous development both in quantity and evolution during Early Cretaceous, and has become the focus of paleornithology and paleoenvironment [2][3][4][5][6][7][8][9]. Now it was studied more detailed than many other fossil birds by reasons of its important phylogenetic position, abundant specimens, and exquisite preservation [6,[10][11][12][13][14][15][16]. As one of fossil birds groups with large feathers, there is no direct evidence to indicate its flight capability and no extant bird with aerodynamic hindlimb feathers. ...
Article
Full-text available
We investigated numerous related literatures of confuciusornithid birds and summarized in terms of environmental background, research status (includ-ing morphology, evolutionary characteristics, and flight capability) and prospects. It is expected to generate a new idea and perspective for the study of Early Cretaceous paleontology and paleoenviron-mentology. Confuciusornithidae is an important group of fossil birds, which has developed tremendously in north China and other east Asian regions during Early Cretaceous. They are studied deeper than many other birds, because of the significance of evolutionary status and many exquisite specimens unmatched by other birds in the same period. And confuciusornithid birds are also the focus of pale-ornithology and paleoenvironment in the reason of their coevolutionary relation. By now, the flight capability of Confuciusornithidae has not been proved, though it was one group of fossil birds with large feathers. There are also no extant birds with aerodynamic feathers on their hindlimbs. Therefore, the flight capability has not been knowed by accurate comparsion at present; the previous conclusions came from morphological analogy and functional speculation; and the research on the origin and evolution of bird flight is also limited by that. Fortunately , hindlimb feathers with aerodynamic characteristics have been found on the Deinonychus and other early birds in the past two decades, which strongly supports hindlimbs are important in the origin of birds flight. And the hindlimbs of birds play an irreplaceable role in aerial and ground locomotion. As a consequence, the hindlimbs aerodynamic performance of confuciusornithid birds will be a breakthrough in the future research. In addation, the proceeding of the digital revolution pleases us immensely that the advancements of computer technologies make the quantitative studies of birds flight more accessible. In the long run, the research of the life habits of Confuciusornithidae can provide valuable data for the coevolution of paleornithology and paleoenvironment in Early Cretaceous.
... Both features are traditionally considered unique to birds (Gill, 2007). Ever since the first discovery of Confuciusornis sanctus (Hou et al., 1995), thousands of Confuciusornis-like specimens have been unearthed from the Early Cretaceous Jehol Biota, northeastern China (Hou et al., 1995(Hou et al., , 1999(Hou et al., , 2002Chiappe et al., 1999;Zhang et al., 2008;Wang & Zhou, 2017a), with two specimens from the contemporary deposits in North Korea ). ...
... In C. sanctus, the dorsal process is trapezoidal in the lateral view (Wang et al., 2018), with the caudal margin rapidly sloping rostrodorsally from the point halfway down to the conjunction with the maxillary body ( Fig. 3C, D). In C. dui, the dorsal process is triangular in lateral view (Hou et al., 1999), whereas it is rostrocaudally compressed in E. zhengi (Zhang et al., 2008). The rostral portion of the jugal is laminar and forms a concave facet to receive the caudal end of the maxilla laterally. ...
... In C. sanctus, the ventral process is triangular ( Fig. 3D; Elzanowski et al., 2018), but this structure is absent in C. dui. As in C. sanctus and E. zhengi (Zhang et al., 2008;Elzanowski et al., 2018), the surangular is perforated by a round caudal mandibular fenestra caudally. The right splenial is exposed in the medial view. ...
Article
Confuciusornithidae is the clade of Early Cretaceous birds most rich in materials and plays a central role in our understanding of the evolution of avian horny beaks and pygostyles. A handful of specimens demonstrate that this avian group is distinguishable from other basal birds by their robust, toothless upper and lower jaws, a fused scapulocoracoid and a tiny claw on the middle manual digit, among other features. Here, we report a new taxon of Confuciusornithidae, Yangavis confucii gen. et sp. nov., from the Early Cretaceous Jehol Biota, northeastern China. This new bird, however, has a normal-sized major digit claw, as in other basal birds, which was probably regained independently as Confuciusornithidae evolved, based on our phylogenetic study. Unfortunately, the biological significance of this trait is unclear owing to a lack of analogues in modern birds (manual claws are completely lost in adults). Yangavis confucii is differentiated from other confuciusornithids by its proportionally much longer forelimb. Our morphometric analysis indicates that the morphospace of Confuciusornithidae, with the addition of Y. confucii, is greatly broadened to a degree that it overlaps with the Early Cretaceous Ornithuromorpha and Enantiornithines, indicating that the biological diversity of confuciusornithids is greater than previously thought.
... Chen (1999) further divided the Jehol Biota into early, middle and late evolutionary stages, and suggested the early Jehol Biota represented by the clam shrimp Nestoria-Keratestheria assemblage, the ostracod Luanpingella-Eoparacypris-Darwinula assemblage, the bivalve Arguniella assemblage, the gastropod Lymnaea websteri and the fish Peipiaosteus were best recorded in the Dabeigou Formation in the Luanping Basin and its equivalent Huajiying Formation in the Senjitu-Sichakou Basin, northern Hebei Province, northeastern China (Fig. 1). In addition, the mayfly Ephemeropsis trisetalis is also very common in the Dabeigou and Huajiying formations (Zhang et al., 2010); early birds with soft tissues were discovered from the Huajiying Formation in the Sichakou Basin (Zhang and Zhou, 2000;Zhang et al., 2008;Wang et al., 2014Wang et al., , 2015aWang et al., , 2017. In contrast to the middle and late Jehol Biota, which are best recorded in the Yixian and Jiufotang formations, respectively, in western Liaoning Province, northeastern China ( Fig. 1), the early Jehol Biota shows less diverse (Zhou et al., 2021). ...
Article
The Early Cretaceous Jehol Biota in northeastern China significantly increased our understanding of the Mesozoic terrestrial ecosystem and the origin and evolution of a number of biological groups. The early evolutional phase of the Jehol Biota is best recorded in the Members 2 and 3 of the Dabeigou Formation (D-M2–3) in the Luanping Basin and their equivalent Huajiying Formation in the Senjitu-Sichakou Basin in northern Hebei Province. To date, however, no complete, high-resolution time scale has been established for these early Jehol Biota-bearing strata, hindering our understanding of the origin of the Jehol Biota. Here we carried out a cyclostratigraphic analysis using a high-resolution relative lake level variation record, called “depth ranks” (i.e., a series of numerically ranked sedimentary facies) in the ∼185-m-thick, continuously lacustrine D-M2–3 in the Yushuxia section, Luanping Basin. Our results suggest that the climate/lake level fluctuations in the Luanping Basin during the development of the early Jehol Biota were strongly paced by orbital cycles, including the 405 kyr and ∼ 100 kyr eccentricity and ∼ 34 kyr obliquity and ∼ 21 kyr precession. By anchoring the 405 kyr-tuned depth ranks to a relatively high-precise zircon UPb age of one tuff layer at the base of Member 3 (131.5 ± 0.4 Ma), we built a high-resolution astronomical time scale, spanning from 132.4 to 130.7 Ma, for the D-M2–3, indicating a ∼ 1.7 Myr duration of the early Jehol Biota and an average sedimentation rate of ∼11 cm/kyr of the D-M2–3 in the Luanping Basin. In addition, we suggest that the periods characterized by warm summer, enhanced hydrological cycle and expanded lake at high obliquity and low precession at eccentricity maximum were most conducive for both development and preservation of the early Jehol Biota.
... The vertebrate assemblages are also very common. The fossil birds Protopteryx, Eoconfuciusornis, and Eopengornis document the earliest and lowermost member of the Enantiornithes, Confuciusornithidae, and Pengornithidae, respectively (34)(35)(36). Other important vertebrate assemblages include acipenseriform fishes, a compsognathid dinosaur, and a newly discovered mammal. ...
Article
Significance The Early Cretaceous Jehol Biota is a terrestrial lagerstätte that produces exquisitely preserved fossils that have furnished enormous evidence on the origins and early evolution of diverse vertebrate groups. On the basis of the latest paleontological and geochronologic evidence, we discuss the three stages of the biota, and suggest that the spatiotemporal evolution of the Jehol Biota coincides with the initial and peak stages of the North China craton destruction in the Early Cretaceous. Such linkage presents an example of how regional tectonics influence the terrestrial biota that points to a new path for future studies involving multidisciplinary methods to explore the biosphere in deep time.
... Fossilised rhamphothecae are invaluable when studying the diet of edentulous fossil taxa. Fossilised rhamphotheca impressions are known from a pterosaur (Frey, Martill & Buchy, 2003), hadrosaurid (Sternberg, 1935;Morris, 1970;Farke et al., 2013) and ceratopsian (Lingham-Soliar, 2008) ornithischians, and ornithomimosaurid (Norell, Makovicky & Currie, 2001;Barrett, 2005) and confuciusornithid (Hou et al., 1999b;Zhang, Zhou & Benton, 2008a;Chiappe & Meng, 2016, p. 156;Falk et al., 2019;Miller et al., 2020;Zheng et al., 2020) theropods. While preservation of rhamphothecae appears to be rare from this small sample size, the fact that half of known confuciusornithid rhamphothecae are only visible with the use of UV or laser-stimulated fluorescence (LSF) imaging (Chiappe & Meng, 2016, p. 156;Falk et al., 2019;Miller et al., 2020) shows promise for modern imaging techniques revealing previously unknown rhamphothecae. ...
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Birds are some of the most diverse organisms on Earth, with species inhabiting a wide variety of niches across every major biome. As such, birds are vital to our understanding of modern ecosystems. Unfortunately, our understanding of the evolutionary history of modern ecosystems is hampered by knowledge gaps in the origin of modern bird diversity and ecosystem ecology. A crucial part of addressing these shortcomings is improving our understanding of the earliest birds, the non‐avian avialans (i.e. non‐crown birds), particularly of their diet. The diet of non‐avian avialans has been a matter of debate, in large part because of the ambiguous qualitative approaches that have been used to reconstruct it. Here we review methods for determining diet in modern and fossil avians (i.e. crown birds) as well as non‐avian theropods, and comment on their usefulness when applied to non‐avian avialans. We use this to propose a set of comparable, quantitative approaches to ascertain fossil bird diet and on this basis provide a consensus of what we currently know about fossil bird diet. While no single approach can precisely predict diet in birds, each can exclude some diets and narrow the dietary possibilities. We recommend combining (i) dental microwear, (ii) landmark‐based muscular reconstruction, (iii) stable isotope geochemistry, (iv) body mass estimations, (v) traditional and/or geometric morphometric analysis, (vi) lever modelling, and (vii) finite element analysis to reconstruct fossil bird diet accurately. Our review provides specific methodologies to implement each approach and discusses complications future researchers should keep in mind. We note that current forms of assessment of dental mesowear, skull traditional morphometrics, geometric morphometrics, and certain stable isotope systems have yet to be proven effective at discerning fossil bird diet. On this basis we report the current state of knowledge of non‐avian avialan diet which remains very incomplete. The ancestral dietary condition in non‐avian avialans remains unclear due to scarce data and contradictory evidence in Archaeopteryx. Among early non‐avian pygostylians, Confuciusornis has finite element analysis and mechanical advantage evidence pointing to herbivory, whilst Sapeornis only has mechanical advantage evidence indicating granivory, agreeing with fossilised ingested material known for this taxon. The enantiornithine ornithothoracine Shenqiornis has mechanical advantage and pedal morphometric evidence pointing to carnivory. In the hongshanornithid ornithuromorph Hongshanornis only mechanical advantage evidence indicates granivory, but this agrees with evidence of gastrolith ingestion in this taxon. Mechanical advantage and ingested fish support carnivory in the songlingornithid ornithuromorph Yanornis. Due to the sparsity of robust dietary assignments, no clear trends in non‐avian avialan dietary evolution have yet emerged. Dietary diversity seems to increase through time, but this is a preservational bias associated with a predominance of data from the Early Cretaceous Jehol Lagerstätte. With this new framework and our synthesis of the current knowledge of non‐avian avialan diet, we expect dietary knowledge and evolutionary trends to become much clearer in the coming years, especially as fossils from other locations and climates are found. This will allow for a deeper and more robust understanding of the role birds played in Mesozoic ecosystems and how this developed into their pivotal role in modern ecosystems. Video abstract
... In all reported specimens of the basal pygostylian Confuciusornis the scapulocoracoid is described as fused (Hou, 1997;Chiappe et al., 1999;Ji et al., 1999;Hou et al., 2002;Dalsätt et al., 2006;Zhang et al., 2009;Wang et al., 2019c), in contrast to the condition in other non-ornithothoracine avians. In the subadult holotype of Eoconfuciusornis zhengi IVPP V11977, the oldest and basal-most member of Confuciusornithidae from the Huajiying Formation, the scapula and coracoid are reportedly only sutured (Zhang et al., 2008a). However, in BMNHC-PH870, an osteologically mature specimen also from the Huajiying Formation, the scapula and coracoid are reportedly fused (Navalón et al., 2017). ...
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... The d 13 C B-HA -based dietary analysis of early birds in the Mesozoic has not yet been reported; however, our research on the FTIR spectra of their bones shows that the d 13 C B-HA values of early birds can effectively reflect information about their diet. Confuciusornis and Sapeornis belong to the basal lineage of Early Cretaceous pygostylians (Hou et al., 1999;Zhou and Zhang, 2007;Zhang et al., 2008). Bones collected from their specimens (Confuciusornis STM 14-112 and Sapeornis STM 15-27) from northeastern China were prepared following Lee- Thorp (1989Thorp ( , 2008, for FTIR analysis. ...
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Although more than half of the evolution of birds occurred during the Mesozoic Era our understanding of this long history focused on the spectacular specimens of the Late Jurassic Archaeopteryx lithographica and the more derived Late Cretaceous hesperornithiforms and ichthyornithiforms for over a century of paleontological research. In the last decade, however, a tremendous burst of new evidence—perhaps unparalleled in the field of vertebrate paleontology—has been uncovered. Indeed, the number of species of early birds described during the 1990s nearly tripled the number of taxa discovered during the previous 130 years elapsed since the discovery of Archaeopteryx in the mid-1800s.
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