ArticlePDF Available

Diversification in an Early Cretaceous avian genus: Evidence from a new species of Confuciusornis from China

Authors:

Abstract and Figures

A new species of Confuciusornis, the oldest known beaked bird, is erected based on a nearly complete fossil from the Early Cretaceous Yixian Formation of western Liaoning, northeast China. C. feducciai is the largest and shows the highest ratio of the forelimb to the hindlimb among all known species of Confuciusornis. The skeletal qualitative autapomorphies, including a V-shaped furcula, a rectangular deltopectoral crest, the absence of an oval foramen at the proximal end of the humerus, the very slender alular digit, a relatively much longer ischium which is two-thirds the length of the pubis, and the morphology of sternum, strongly suggest the new specimen is a valid distinctive taxon. Detailed comparison with other described species provides sound evidence for diversification in the Early Cretaceous avian genus Confuciusornis. Anatomical features suggest an arboreal habit of the new bird.
Content may be subject to copyright.
ORIGINAL ARTICLE
Diversification in an Early Cretaceous avian genus: evidence
from a new species of Confuciusornis from China
Zihui Zhang ÆChunling Gao ÆQingjin Meng Æ
Jinyuan Liu ÆLianhai Hou ÆGuangmei Zheng
Received: 13 September 2008 / Accepted: 16 February 2009 / Published online: 3 March 2009
ÓDt. Ornithologen-Gesellschaft e.V. 2009
Abstract A new species of Confuciusornis, the oldest
known beaked bird, is erected based on a nearly complete
fossil from the Early Cretaceous Yixian Formation of
western Liaoning, northeast China. C. feducciai is the largest
and shows the highest ratio of the forelimb to the hindlimb
among all known species of Confuciusornis. The skeletal
qualitative autapomorphies, including a V-shaped furcula, a
rectangular deltopectoral crest, the absence of an oval
foramen at the proximal end of the humerus, the very slender
alular digit, a relatively much longer ischium which is
two-thirds the length of the pubis, and the morphology
of sternum, strongly suggest the new specimen is a valid
distinctive taxon. Detailed comparison with other described
species provides sound evidence for diversification in the
Early Cretaceous avian genus Confuciusornis. Anatomical
features suggest an arboreal habit of the new bird.
Keywords Confuciusornis feducciai, sp. nov.
Early Cretaceous Yixian Formation Taxonomy
Diversification
Introduction
Confuciusornis is the oldest known beaked bird and the
most primitive avian after Archaeopteryx (Hou et al.
1995a), Jeholornis (Zhou and Zhang 2002a,2003) and
Sapeornis (Zhou and Zhang 2002b). Most of the speci-
mens were excavated from the Yixian Formation; a
newly reported specimen was from the Jiufotang For-
mation which is about 5 million years younger than the
Yixian Formation (Dalsa
¨tt et al. 2006). Extensive
researches focusing on anatomy, evolution, phylogeny,
life style, diet, and sexual dimorphism have been carried
out (Hou et al. 1995b,1999; Hou 1997; Martin et al.
1998; Zhou and Hou 1998; Chiappe et al. 1999;
Hembree 1999;Ji2001; Elzanowski et al. 2005; Dalsa
¨tt
et al. 2006).
Being one of the most famous components of Jehol
Biota, Confuciusornis is more abundant than any other
species and about 1,000 well-preserved specimens have
been collected(Chang et al. 2003). Two major questions
arise: was Confuciusornis a tree-dweller, or a ground-
dweller as often depicted; and was there diversification
within the genus? The new completely preserved specimen
reported herein allows us to test both hypotheses at a fine
level. With respect to the former question, the specimen
exhibits abundant evidence of a morphology that con-
vincingly argues for an arboreal habit; and with respect to
the latter question, the new specimen provides qualitative
and quantitative evidence for diversification of an Early
Cretaceous bird.
Communicated by F. Bairlein.
Z. Zhang G. Zheng (&)
College of Life Sciences, Beijing Normal University,
Beijing 100875, China
e-mail: zhenggm@bnu.edu.cn; zihui.zhang@tom.com
Z. Zhang L. Hou
College of Life Sciences, Capital Normal University,
Beijing 100048, China
C. Gao Q. Meng J. Liu
Dalian Natural Museum, Dalian 116023, China
L. Hou
Institute of Vertebrate Paleontology and Paleoanthropology,
Chinese Academy of Sciences, PO Box 643,
Beijing 100044, China
123
J Ornithol (2009) 150:783–790
DOI 10.1007/s10336-009-0399-x
Materials and methods
The holotype is housed at Dalian Natural Museum, China.
Osteology terminology follows Howard (1929). Measure-
ments are in millimeters and represent the maximum length
of the bone along its longitudinal axis.
Systematic paleontology
Aves Linnaeus 1758
Confuciusornithiformes Hou et al. 1995
Confuciusornithidae Hou et al. 1995
Confuciusornis Hou et al. 1995
Confuciusornis feducciai, sp. nov.
Holotype
A nearly complete and articulated skeleton preserved in
ventral view (Fig. 1a). Dalian Natural Museum, collection
number D2454.
Locality and Horizon
Sihetun, Shangyuan, Beipiao city, Liaoning Province,
China. Yixian Formation, Early Cretaceous (*125 Ma)
(Zhou et al. 2003; Swisher III et al. 2002).
Diagnosis
Largest known species of Confuciusornis. The ratio of the
forelimb to hindlimb is 1.15. Proximal end of the humerus
flat and thin, without an oval depression or a pneumatic
foramen; deltopectoral crest more rectangular. The first
phalanx of alular digit is very slender. Furcula near
V-shaped. The sternum is broader than long. Ischium
relatively long, accounting for two-thirds of the length of
the pubis.
Measurements
See Table 1
Etymology
The species name is dedicated to Professor Alan Feduccia
of the University of North Carolina at Chapel Hill for his
contribution to the study of the origin and evolution of
birds.
Description
The skull is preserved in ventral view (Fig. 2a). The
mandible protrudes beyond the rostral end of the upper jaw
and is more similar to that of C. sanctus than to C. dui in
morphology. The dentary is robust and spear-shaped at the
anterior end; it bifurcates caudally into dorsal and ventral
rami: the ventral branch is long and reaches the articular;
the dorsal branch ends in the rostral two-thirds of the
mandible. A notch and a distinct suture between two
dentary bones indicate that they have not fused into a single
unit as in extant birds. A long, flat bone displaced from the
medial of the right lower jaw is interpreted as the splenial.
The jugal is relatively short and bears a robust triangular
process directing dorsal-laterally. The quadratojugal is
small and L-shaped as in Archaeopteryx and C. dui. The
left quadrate is preserved completely and resembles a
dumbbell in ventral view; the internal condyle is much
larger than the external condyle.
Eight cervical vertebrae are distinguishable, but the
exact number of cervical vertebrae is unknown (probably
9*10). A little crushed ring-shaped atlas is visible sur-
rounding the occipital condyle (Fig. 2a). The axis is the
longest vertebra in the cervical series with the centrum
formed by two parts. Anterior is a stout, convex odontoid
Fig. 1 a Holotype of Confuciusornis feducciai sp. nov., scale bar
5 cm; bcomparison of sterna in C. dui (a) (Hou et al. 1999),
C. sanctus (b) (Martin et al. 1998) and C. feducciai (c), scale bar
1 cm; cdistal tail feathers of C. feducciai,scale bar 3cm
784 J Ornithol (2009) 150:783–790
123
process (dens axis) bearing a pair of short cervical ribs. It
does not fuse with the following centrum, and a clear
suture can be seen between them; the centrum beyond the
dens is relatively much larger with well-developed prezy-
gapophyses, postzygapophyses, and costal processes, as
well as the ventral process (ventral crest). Cervicals 3*8
are heterocoelous and similar to the axis in morphology
except for the measurements which are slightly shorter and
broader than the axis. Eleven dorsal vertebrae are preserved
in ventral view; they are shorter than the cervicals; the
centra are concave laterally and the articular surfaces are
apparently amphyplatian. Seven completely fused verte-
brae form the synsacrum; the individualized robust
transverse processes project laterally except for that of the
Table 1 Measurements (mm) and proportions of selected elements of Confuciusornis feducciai, in comparison with other species of
Confuciusornis
C. feducciai C. sanctus C. dui
c
C. suniae
d
GMV-2132
a
GMV-2133
a
GMV-2130
a
V11794
b
V11795
b
V11640
b
Humerus 78.5 69.15 52.58 47.78 63.5 44 65 42 51
Ulna 75 58.45 45.38 40.73 55 37 55 39 46
Carpometacarpus 32 33.15 – 21.11 32 30 19 25.5
Femur 59 46.85 41.78 55 36 55 35 45
Tibiotarsus 69 66.05 53.29 48.70 66 42 65 41 55
Tarsometatarsus 33.5 25.64 23.25 – 30 19.5 26
Forelimb/hindlimb 1.15 – – 0.96 1.00 1.05 0.97
Humerus/femur 1.33 1.12 1.1 1.15 1.22 1.18 1.2 1.13
Ulna/femur 1.27 0.97 0.97 1.00 1.03 1.00 1.11 1.02
Ulna/tibiotarsus 1.09 0.88 0.85 0.84 0.83 0.88 0.85 0.95 0.84
a
From Chiappe et al. (1999)
b
From Hou et al. (2002)
c
From Hou et al. (1999)
d
From Hou (1997)
Fig. 2 Palatal view of the skull
of Confuciusornis feducciai (a),
pelvic girdle and synsacrum of
Confuciusornis feducciai (b). at
Atlas, de dentary, fe femur, hy
hyoid, idp dorsal process of
ischium, il ilium, is ischium, ju
jugal, pu pubis, py pygostyle, qu
quadrate, sp splenial, syn
synsacrum. Scale bar 1cm
J Ornithol (2009) 150:783–790 785
123
terminal two that are relatively longer and incline caudally
(Fig. 2b). The cranial articular surface of the synsacrum is
concave, as in Enantiornithes and the Alvarezsauridae
(Chiappe et al. 1996). The number of the free caudal ver-
tebrae is unknown because of the poor preservation. The
pygostyle is near 40% the length of the tibiotarsus, and
most of it is overlapped by a long pubic symphysis; the
proximal end can be seen enclosed in the V-shaped area
formed by two ischiadic extremities.
The sternum is flat and keelless, and there is a con-
spicuous small notch at the middle of the cranial margin
(Fig. 1b). On the rostral half, the concave lateral margin
serves as the attachment sites for four short sternal ribs;
caudal to the sternal rib facets, the presence of a large
prominent lateral process makes the sternum broader than
it is long. Eight pairs of vertebral ribs preserved in the new
taxon. Six distinct uncinate processes (Fig. 3c) are visible
near the middle points of six right vertebral ribs
(2nd*7th), and seem unfused with the ribs. The absence of
uncinate processes on the left side is probably due to
preservation or preparation reasons. Gastralia are present
behind the rib cage.
The coracoids are well-preserved and exposed in ventral
view (left) and dorsal view (right), respectively; they are
stout and short, accounting for 53% the length of scapula.
The width of the expanded sternal end is 60% the length of
the coracoid. The lateral margin is straight compared with
the oblique and slightly concave medial margin (Fig. 3a).
The dorsolateral aspect of the sternal half of coracoid is a
little concave. The coracoid lacks a procoracoid process
but has a distinct acrocoracoid process that is rostroventral
to the glenoid. The scapula is expanded in the cranial end
and tapers distally; the acromion is prominent. The furcula
is unique in being robust and near V-shaped (Fig. 3a)
rather than U-shaped as C. sanctus and Archaeopteryx.
There is no hypocleideum; the interclavicular angle is a
little larger than 90°.
The thoracic limb of the new species is longer than the
pelvic limb (Table 1). The ratio of the forelimb
(humerus ?ulna ?carpometacarpus) to hindlimb (femur ?
tibiotarsus ?tarsometatarsus) is 1.15, but it is about 1.0 in
C. sanctus, and 1.05 in C. dui. The length ratios of the
humerus to the femur, the ulna to the femur and the ulna to
the tibiotarsus in C. feducciai are much higher than that in
other species of Confuciusornis. The humerus is typical of
Confuciusornis in having an expanded proximal end, but
the absence of a large oval foramen or depression at the
bicipital area and the shape of the deltopectoral crest makes
the new specimen different from all known species of
Confuciusornis (Figs. 3b, 4a). The deltopectoral crest is
Fig. 3 Close-up photos of
Confuciusornis feducciai.
aFurcula and coracoid,
bproximal end of left humerus,
cuncinate process. co Coracoid,
fu furcula, up uncinate process.
Scale bar 1cm
786 J Ornithol (2009) 150:783–790
123
proximally expanded and more rectangular in C. feducciai,
but it is distally expanded and triangular in other species of
Confuciusornis. The distal end of the humerus is similar to
that of C. sanctus (Chiappe et al. 1999). The ulna is slightly
shorter than the humerus, and the olecranon is short and
stout. The radius is relatively robust, nearly two-thirds the
width of the ulna. The two components of the forearm are
tightly attached at both ends; there is a long spindle-shaped
space between the ulna and the radius along the entire
length. The major metacarpal is thicker and longer than the
minor metacarpal. The first phalanx of alular digit (digit I)
is very slender compared with C. sanctus, and as wide as
the penultimate phalanx of the minor digit (digit III). The
claw of the alular digit is robust and nearly as large as that
of the minor digit, rather than about one-third larger as in
C. sanctus; deep groove on lateral side and prominent
flexor tubercle at the proximal end of the ungular phalanx
is visible. The major digit (digit II) is composed of three
phalanges; the proximal one is robust and broad; being the
longest of all manual phalanges, the intermediate phalanx
tapers distally and bears a small claw. Phalanges of the
minor digit are slender; the proximal one is the shortest.
The pelvic girdle is preserved in articulation and exposed
in ventral view (Fig. 2b). The preacetabular part of the
ilium is broad at the cranial end. The dorsal surface presents
a little depression especially in the medial side, thus indi-
cating the beginning of an anterior iliac crest for muscle
origins. The postacetabular part is shorter and narrower than
the preacetabular, and ends near the beginning of the dorsal
process of ischium and approximately 60% the length of the
preacetabular ilium. The ischium of the new species is
relatively long, about two-thirds the length of the pubis
versus 44% in C. sanctus,A. lithographica and nonavian
maniraptorans (Chiappe et al. 1999). It is laterally com-
pressed and bears a large triangular dorsal process that
seems to abut against the transverse processes of the last
two sacral vertebrae. The two ischia might be in contact at
the distal end. The pubis is robust with a long straight
symphysis which is 30% the total length of the pubis.
The femur is straight with a big round head and a less
prominent trochanter in the proximal end, and a clear
suture is visible between the head and the shaft of the left
femur. The distal end is poorly preserved preventing a
careful observation. The tibiotarsus is exposed in posterior
view bearing two tubercles on the proximal end, and there
is a short fibula crest at the proximal one-eighth of the
shaft. The fibula is clearly preserved on the left leg, near
four-fifths the length of the tibiotarsus. The tarsometatarsus
is short, about half the length of the tibiotarsus; the internal
cotyla is larger than the external one. Metatarsi III and IV
are straight compared with metatarsus II which curves
medially in the distal one-third. Metatarsal V attaches to
the lateral aspect of the proximal third of the metatarsus IV.
Two long tail feathers were preserved. The fan-shaped
expansive distal ends show clearly the occurrence of rachis,
barbs and symmetrical vane as in modern birds; the shafts
become progressively narrower toward the extremities
(Fig. 1c).
Comparison and discussion
To date, four species of Confuciusornis have been named.
C. suniae and C. chuongzhous were described briefly (Hou
1997). C. chuongzhous was studied based on the lower part
of left hindlimb; it is difficult to make direct comparisons
with the other three species. Regarding C. suniae, some of
the described characteristics fall within the morphological
spectrum of C. sanctus (Chiappe et al. 1999); also, the
measurements and proportions of some main skeletons
show minor difference comparing that with C. sanctus
(Table 1). Thus, further study of C. suniae is needed.
However, contrary to Chiappe’s conclusion that C. suniae,
C. chuongzhous and even C. dui were junior synonyms of
C. sanctus (Chiappe et al. 1999), there is compelling evi-
dence that the new species C. feducciai is distinctive, as are
C. sanctus and C. dui. They are valid distinctive taxa based
on the size and skeletal differences which are paramount in
avian systematics and taxonomy (Fisher 1944; Pettingill
1985). Morphological differences (qualitative characters),
the primary differences, suggest that C. feducciai is separate
from (but closely related to) C. sanctus, rather than part of a
developmental series lying on a growth trajectory. These
features include: (1) Morphology of the mandible: the
dentary is robust and spear-shaped in C. feducciai and
C. sanctus, versus slender anteriorly and pointed in C. dui.
(2) Sternum and the attachment sites for sternal ribs
(Fig. 1b). The sternum of C. dui is more elongated with a
pair of short and pointed lateral processes that serve as
attachment sites for four short sternal ribs (Hou et al. 1999).
The sterna of C. feducciai and C. sanctus are relatively
broader, and the lateral processes in C. sanctus is stout and
wide; the new species represents a pair of more prominent
and anterolaterally prolonged lateral processes. Sternal ribs
attach to the concave lateral margin on the rostral half of the
sternum in C. sanctus and C. feducciai. (3) Configuration of
the proximal end of humerus (Fig. 4): a triangular delto-
pectoral crest, and the presence of an oval foramen or
depression in C. sanctus and C. dui respectively; contrary to
the rectangular deltopectoral crest and the absence of a
foramen in C. feducciai. (4) Alular digit: C. feducciai pos-
sesses a relatively more slender first phalanx of alular digit
(Fig. 4); it is nearly as wide as the penultimate phalanx of
the minor digit, rather than about two times broader as in
C. sanctus and C. dui. And (5), the ischium: the new species
is different from the others in possessing relatively long
J Ornithol (2009) 150:783–790 787
123
ischia which might connect at the distal ends. To those
differences may be added the marked difference in size,
which can be the distinguishing features of closely related
species (Howgate 1984; Wellnhofer 1988; Elzanowski
2001; Christiansen 2006). C. feducciai is an adult individual
in having a completely fused synsacrum (Gauthier 1986); it
is the largest individual known for any species of Confu-
ciusornis and shows distinct characters in the ratios between
different elements of limb skeleton (quantitative differ-
ences) (Table 1). Unlike enantiornithine birds (and
presumably Archaeopteryx) that exhibit ectothermic growth
rings in the long bones (Chinsamy et al. 1995), an indication
of indeterminate growth rates, Confuciusornis exhibits the
bone microstructure of modern birds (Zhang et al. 1998;De
Ricqle
´s et al. 2003), and therefore is thought to have had a
modern type, determinate, avian growth pattern. Marked
morphological and size differences provide critical evi-
dence for diversification of an Early Cretaceous bird, and
are important to show that diversification in Confuciusornis
is not due to indeterminate growth. A further statistical
analysis, while desirable, is not feasible at this time, mainly
because specimens are scattered all over the world, and
most of them still await further preparation (Chiappe et al.
1999).
Fig. 4 Comparison of
forelimbs in C. feducciai (a),
C. sanctus (b) (Hou et al. 2002),
C. dui (c) (Hou et al. 1999).
I–III Manual digits. Scale bars
3cm(a, b), 1 cm (c)
788 J Ornithol (2009) 150:783–790
123
The presumed habits of Confuciusornis have previously
been discussed (Martin et al. 1998; Chiappe et al. 1999;
Olson 2000; Zhou and Farlow 2001; Feduccia et al. 2007).
Since the correlation between the morphology of the loco-
motor apparatus and the behavior and adaptive radiation of
extant birds has been demonstrated (Partridge 1976; Nor-
berg 1979; Miles and Ricklefs 1984), it sheds light on our
understanding of the ecology of fossil birds. Adaptation to a
cursorial mode of locomotion requires a shortening of
proximal segments and a lengthening of distal segments of
hindlimb, especially in the tarsometatarsus (Fisher 1946;
Berger 1952; Dilger 1956; Osterhaus 1962). C. feducciai,
contrary to the above, possesses a short and broad tarso-
metatarsus and a relatively long femur (nearly as long as the
tibiotarsus) and fibula (nearly reaches the ankle); these are
all strong indications of an arboreal bird. Such an interpre-
tation is also supported by its large reversed hallux and sharp
curved, laterally compressed claws (Yalden 1985; Feduccia
1993; Griffiths 1993). The fact that the basal phalanges are
relatively shorter than the distal phalanges in the hands
indicates that the hands of Confuciusornis are important to
its arboreal habits; they could be used in the climbing and
grasping of trunks rather than any other functions.
Zusammenfassung
Diversifikation einer Vogelgattung in der fru
¨hen
Kreidezeit: Erkenntnisse aus einer neuen Art von
Confuciusornis aus China
Eine neue Art der Gattung Confuciusornis, dem a
¨ltesten
bekannten Vogel mit Schnabel, wird beschrieben anhand
eines fast vollsta
¨ndigen Fossils aus der Yixian Formation
der fru
¨hen Kreidezeit im westlichen Liaoning, Nordost-
China. Confuciusornis feducciai ist die gro
¨ßte Art und hat
das gro
¨ßte Verha
¨ltnis zwischen vorderen und hinteren
Extremita
¨ten von allen bekannten Confuciousornis-Arten.
Die qualitativen Autapomorphien des Skeletts, darunter
eine V-fo
¨rmige Furcula, ein rechteckiger Deltopektoral-
kamm, die Abwesenheit eines ovalen Foramen am
proximalen Ende des Humerus, der sehr schlanke Daumen,
ein relativ la
¨ngeres Ischium, das 23 der La
¨nge der Pubis
hat, und die Morphologie des Sternum geben deutliche
Hinweise, dass der neue Fund ein eigenes gu
¨ltiges Taxon
darstellt. Detaillierte Vergleiche mit anderen beschriebenen
Arten ergeben starke Hinweise auf eine Diversifikaiton der
Gattung Confuciusornis in der fru
¨hen Kreidezeit. Ana-
tomische Hinweise deuten auf eine arborikole Lebensweise
des Vogels.
Acknowledgments We are greatly indebted to Nick Longrich, Shu-
an Ji and Fucheng Zhang for their careful review of the manuscript
and valuable suggestions; Larry D. Martin, Luis M. Chiappe and
Zhonghe Zhou for help in the early stages of this work and examining
the fossil. This work was supported by the National Natural Science
Foundation of China (30670223), and Scientific Research Common
Program of Beijing Municipal Commission of Education
(KM200710028012).
References
Berger AJ (1952) The comparative functional morphology of the
pelvic appendage of three genera of Cuculidae. Am Midl Nat
47:513–605
Chang M, Chen P, Wang Y, Wang Y, Miao D (eds) (2003) The Jehol
Biota. Shanghai Scientific and Technical Publishers, Shanghai
Chiappe LM, Norell MA, Clark JM (1996) Phylogenetic position of
Mononykus from the Upper Cretaceous of the Gobi Desert. Mem
Queensl Mus 39:557–582
Chiappe LM, Ji S, Ji Q, Norell MA (1999) Anatomy and systematics of
the Confuciusornithidae (Theropoda: Aves) from the Late
Mesozoic of northeastern China. Bull Am Mus Nat Hist 242:3–89
Chinsamy A, Chiappe LM, Dodson P (1995) Mesozoic avian bone
microstructure: physiological implications. Paleobiology
21:561–574
Christiansen P (2006) Allometry in phylogeny and Archaeopteryx.
J Vertebr Paleontol 26:480–486
Dalsa
¨tt J, Zhou Z, Zhang F, Ericson PGP (2006) Food remains in
Confuciusornis sanctus suggest a fish diet. Naturwissenschaften
93:444–446
De Ricqle
´s AJ, Padian K, Horner JR, Lamm E-T, Myhrvold N (2003)
Osteohistology of Confuciusornis sanctus (Theropoda: Aves).
J Vertebr Paleontol 23:373–386
Dilger WC (1956) Adaptive modifications and ecological isolating
mechanisms in the thrush genera Catharus and Hylocichla.
Wilson Bull 68:171–199
Elzanowski A (2001) A new genus and species for the largest
specimen of Archaeopteryx. Acta Palaeontol Pol 46:519–532
Elzanowski A, Manegold A, Peters DS (2005) Redescription of a
skull of Confuciusornis sanctus. Archaeopteryx 23:51–55
Feduccia A (1993) Evidence from claw geometry indicating arboreal
habits of Archaeopteryx. Science 259:790–793
Feduccia A, Martin LD, Tarsitano S (2007) Perspective in ornithol-
ogy: Archaeopteryx 2007: quo vadis? Auk 124:373–380
Fisher HI (1944) The skulls of cathartid vultures. Condor 46:272–296
Fisher HI (1946) Adaptations and comparative anatomy of the
locomotor apparatus of New World vultures. Am Midl Nat
35:545–727
Gauthier J (1986) Saurischian monophyly and the origin of birds.
Mem Calif Acad Sci 8:1–55
Griffiths PJ (1993) The claws and digits of Archaeopteryx litho-
graphica. Geobios 16:101–106
Hembree D (1999) Re-evaluation of the posture and claws of
Confuciusornis. J Vertebr Paleontol 19:50A
Hou L (1997) Mesozoic birds of China. Feng-Huang Ku Bird Park of
Taiwan, Nantou
Hou L, Zhou Z, Gu Y, Zhang H (1995a) Confuciusornis sanctus,a
new Late Jurassic sauriurine bird from China. Chin Sci Bull
40:1545–1551
Hou L, Zhou Z, Martin LD, Feduccia A (1995b) A beaked bird from
the Jurassic of China. Nature 377:616–618
Hou L, Martin LD, Zhou Z, Feduccia A, Zhang F (1999) A diapsid
skull in a new species of the primitive bird Confuciusornis.
Nature 399:679–682
Hou L, Zhou Z, Zhang F, Gu Y (2002) Mesozoic birds from western
Liaoning in China. Liaoning Science and Technology Publishing
House, Shenyang
J Ornithol (2009) 150:783–790 789
123
Howard H (1929) The avifauna of Emeryville shellmound. Univ Calif
Publ Zool 32:301–394
Howgate ME (1984) The teeth of Archaeopteryx and a reinterpreta-
tion of the Eichsta
¨tt specimen. Zool J Linn Soc 82:159–175
Ji S (2001) New advances in the study of the primitive bird
Confuciusornis. Geol Sci Technol Inf 20:30–34 (in Chinese with
English summary)
Martin LD, Zhou Z, Hou L, Feduccia A (1998) Confuciusornis
sanctus compared to Archaeopteryx lithographica. Naturwis-
senschaften 85:286–289
Miles DB, Ricklefs RE (1984) The correlation between ecology and
morphology in deciduous forest passerine birds. Ecology
65:1629–1640
Norberg UM (1979) Morphology of the wings, legs, and tail of three
coniferous forest tits, the goldcrest, and the treecreeper in
relation to locomotor pattern and feeding station selection. Philos
Trans R Soc Lond B Biol Sci 287:131–165
Olson SL (2000) Review of ‘‘anatomy and systematics of the
Confuciusornithidae (Theropoda: Aves) from the late Mesozoic
of Northeastern China’’ by L. M. Chiappe, S. Ji, Q. Ji, and M. A.
Norell. 1999. Bulletin of the American Museum of Natural
History, vol. 242. Auk 117:836–839
Osterhaus MB (1962) Adaptive modifications in the leg structure of
some North American warblers. Am Midl Nat 68:474–486
Partridge L (1976) Some aspects of the morphology of blue tits
(Parus caeruleus) and coal tits (P. ater) in relation to their
behavior. J Zool 179:121–133
Pettingill OS (1985) Ornithology in laboratory and field, 5th edn.
Academic, London
Swisher CCIII, Wang X, Zhou Z, Wang Y, Jin F, Zhang J, Xu X,
Zhang F, Wang Y (2002) Further support for a Cretaceous age
for the feathered-dinosaur beds of Liaoning, China: New
40
Ar/
39
Ar dating of the Yixian and Tuchengzi Formations. Chin
Sci Bull 47:135–138
Wellnhofer P (1988) A new specimen of Archaeopteryx. Science
240:1790–1792
Yalden (1985) Climbing Archaeopteryx. Archaeopteryx 15:107–108
Zhang F, Hou L, Ouyang L (1998) Osteological microstructure of
Confuciusornis: preliminary report. Vertebr PalAsiat 36:126–
135
Zhou Z, Farlow JO (2001) Flight capability and habits of Confuci-
usornis. In: Gauthier J, Gall LF (eds) New perspectives on the
origin and early evolution of birds: proceedings of the interna-
tional symposium in honor of John H. Ostrom. Peabody Museum
of Natural History. Yale University, New Haven, pp 237–254
Zhou Z, Hou L (1998) Confuciusornis and the early evolution of
birds. Vertebr PalAsiat 36:136–146
Zhou Z, Zhang F (2002a) A long-tailed, seed-eating bird from the
Early Cretaceous of China. Nature 418:405–409
Zhou Z, Zhang F (2002b) Largest bird from the Early Cretaceous and
its implications for the earliest avian ecological diversification.
Naturwissenschaften 89:34–38
Zhou Z, Zhang F (2003) Jeholornis compared to Archaeopteryx, with
a new understanding of the earliest avian evolution. Naturwis-
senschaften 90:220–225
Zhou Z, Barrett PM, Hilton J (2003) An exceptionally preserved
Lower Cretaceous ecosystem. Nature 421:807–814
790 J Ornithol (2009) 150:783–790
123
... Confuciusornis is the most common bird in the Jehol Biota, with thousands of specimens reported, mostly from the Yixian Formation (Wang et al., 2019c). Specimens range considerably in size although no clear juveniles are known (humerus length ranging from 41.01 to 78.5 mm; Chiappe et al., 1999Chiappe et al., , 2008Zhang et al., 2009;Wang and O'Connor, 2017;Wang et al., 2019c). 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. ...
... Specimens range considerably in size although no clear juveniles are known (humerus length ranging from 41.01 to 78.5 mm; Chiappe et al., 1999Chiappe et al., , 2008Zhang et al., 2009;Wang and O'Connor, 2017;Wang et al., 2019c). 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). ...
... All elements were previously prepared free from the matrix. The humerus measures 66 mm, which falls within the larger half of the known size range of Confuciusornis specimens (humeral length: 41.01-78.5 mm; Chiappe et al., 1999Chiappe et al., , 2008Zhang et al., 2009;Wang and O'Connor, 2017;Wang et al., 2019c). As the scapula is incomplete in this specimen, the length of the scapula was not measured. ...
Article
Full-text available
As key components of the tetrapod pectoral girdle, the scapula and coracoid have played a significant role in the evolution of forelimb locomotion among terrestrial vertebrates. The transition from a rigid fused scapulocoracoid in ancestral non-avian theropods to a presumably more flexible separated scapula-coracoid in early birds is considered to be one of the key morphological transitions related to the rapid refinement of flight. In most Mesozoic birds (e.g., Enantiornithes and Ornithuromorpha) and crown birds the scapula and coracoid are separate (unfused), with few exceptions (e.g., flightless paleognaths). In contrast, in Confuciusornis, a basal pygostylian from the Early Cretaceous Jehol Biota known from thousands of specimens, the scapula and coracoid remain plesiomorphically fused. This raises questions regarding the influence of shoulder girdle architecture on the early evolution and refinement of avian flight. The paravian scapula-coracoid joint has never previously been investigated using histology, and thus joint morphology has only been inferred superficially. In order to better understand the evolution of this joint in Mesozoic birds, we make the first histological study of the scapulocoracoid glenoid joint in Confuciusornis. The results demonstrate that the scapula and coracoid both consist of cancellous and compact bone, with both fibrolamellar and parallel-fibered structure. A thin layer of calcified cartilage is present on the glenoid fossa surface, representing remnants of the articular surface for the humerus. Both histology and computed tomography reveal that the scapulocoracoid of Confuciusornis is fully fused, forming a synostosis. Humeral histology suggests the studied individual was nearing completion of its first year of growth, suggesting the Confuciusornis scapulocoracoid fused before skeletal maturity was achieved, as in flightless paleognaths, whereas in the plesiomorphic condition fusion occurs late in ontogeny. We hypothesize the fused scapulocoracoid of Confuciusornis is secondarily evolved and suggest the primary factor responsible for this morphology may have been a decrease in mechanical stimulation at the glenoid of Confuciusornis relative to other volant birds, linked to the unique flight style of this taxon. Further investigation into the histology of the glenoid joint in other Mesozoic paravians and extant birds will help to clarify the morphological transition of the scapula-coracoid joint in early avian evolution.
... jianchangensis', Changchengornis hengdaoziensis, 'Jinzhouornis yixianensis', 'J. zhangjiyingia', and Eoconfuciusornis zhengi) (Hou et al., 1995(Hou et al., , 2002Hou, 1997;Chiappe et al., 1999;Zhang et al., 2008Zhang et al., , 2009Li et al., 2010). More than half of these taxa have only ever been described in Chinese (Hou, 1997;Hou et al., 2002;Li et al., 2010), which has hindered evaluation of their validity through direct study or phylogenetic analysis by the international research community. ...
... yixianensis ' Hou et al., 2002; zhangjiyingia ' Hou et al., 2002; 'C. feducciai ' Zhang et al., 2009; 'C. jianchangensis Holotype IVPP V 10918. ...
... 'Confuciusornis feducciai ' Zhang et al., 2009 Remarks The holotype and the only known specimen of 'C. feducciai', DNHM D2454, is nearly complete and preserved in a single slab (Fig. 12A), collected from Yixian Formation deposits at Sihetun, Shangyuan Village, Beipiao City, Liaoning Province (Zhang et al., 2009). ...
Article
Full-text available
The Confuciusornithiformes is a basal clade of Early Cretaceous birds that includes the oldest and most basal birds with a toothless beak and an abbreviated bony tail. Over the last two decades, thousands of specimens have been collected, more than for any other group of Mesozoic birds or non-avian dinosaurs. Ten species separated into four genera have been erected with limited taxonomic phylogenetic scrutiny. Here, we perform a comparative study of these ten species, and demonstrate that most of these taxa were originally diagnosed by characters that prove to be either preservational artifacts, intraspecifc variations, subject to ontogenetic variation, or widely distributed among the Confuciusornithiformes or a more phylogenetically inclusive group. Our results suggest that ‘Confuciusornis suniae’, ‘C. feducciai’, ‘Jinzhouornis yixianensis’, ‘J. zhangjiyingia’, and ‘C. jianchangensis’ are all junior synonyms of C. sanctus. ‘C. chuonzhous’ lacks autapomorphies of C. sanctus and is referred to Confuciusornithiformes incertae sedis. Our taxonomic reappraisal of published materials indicates that the Confuciusornithiformes consists of one family, three genera, and four species: C. sanctus, C. dui, Changchengornis hengdaoziensis, and Eoconfuciusornis zhengi, for which we provide revised diagnoses.
... 'Confuciusornis feducciai ' Zhang et al., 2009 Remarks The holotype and the only known specimen of 'C. feducciai', DNHM D2454, is nearly complete and preserved in a single slab (Fig. 12A), collected from Yixian Formation deposits at Sihetun, Shangyuan Village, Beipiao City, Liaoning Province (Zhang et al., 2009). ...
... 'Confuciusornis feducciai ' Zhang et al., 2009 Remarks The holotype and the only known specimen of 'C. feducciai', DNHM D2454, is nearly complete and preserved in a single slab (Fig. 12A), collected from Yixian Formation deposits at Sihetun, Shangyuan Village, Beipiao City, Liaoning Province (Zhang et al., 2009). This taxon was originally diagnosed as "a confuciusornithiform that is distinguishable from feducciai' as a valid taxon, although the specimen exhibits numerous synapomorphies of C. sanctus: robust mandible with rostral part of ventral margin convex (Fig. 12B); mandibular symphysis notched rostrally (Fig. 12B); humerus expanded proximally with large, triangular deltopectoral crest; deltopectoral crest perforated by a suboval fenestra (Fig. 13A, B); penultimate phalanx of the major digit bowed and longer than the preceding phalanx (Fig. 13C); and hallux short, less than half the length of the second toe. ...
... C. sanctus in the following features: large body size; forelimb elongated with a length ratio (humerus+ulna+carpometacarpus)/(femur+tibiotarsus+tarsometatarsus) approximately 1.15; proximal end of humerus flat and thin; deltopectoral crest rectangular and imperforated; proximal phalanx of alular digit slender; furcula V-shaped; sternum wider than long; and length ratio of ischium/pubis about 2/3" (Zhang et al., 2009). Zhang et al. (2009) described the humeral deltopectoral crest of 'C. ...
Article
Full-text available
The Confuciusornithiformes is a basal clade of Early Cretaceous birds that includes the oldest and most basal birds with a toothless beak and an abbreviated bony tail. Over the last two decades, thousands of specimens have been collected, more than for any other group of Mesozoic birds or non-avian dinosaurs. Ten species separated into four genera have been erected with limited taxonomic phylogenetic scrutiny. Here, we perform a comparative study of these ten species, and demonstrate that most of these taxa were originally diagnosed by characters that prove to be either preservational artifacts, intraspecific variations, subject to ontogenetic variation, or widely distributed among the Confuciusornithiformes or a more phylogenetically inclusive group. Our results suggest that ‘Confuciusornis suniae’, ‘Confuciusornis feducciai’, ‘Jinzhouornis yixianensis’, ‘Jinzhouornis zhangjiyingia’, and ‘Confuciusornis jianchangensis’ are all junior synonyms of Confuciusornis sanctus. ‘Confuciusornis chuonzhous’ lacks autapomorphies of C. sanctus and is referred to Confuciusornithiformes incertae sedis. Our taxonomic reappraisal of published materials indicates that the Confuciusornithiformes consists of one family, three genera, and four species: Confuciusornis sanctus, Confuciusornis dui, Changchengornis hengdaoziensis, and Eoconfuciusornis zhengi, for which we provide revised diagnoses.
... Elzanowski et al. (2005) redescribed a small, nearly complete skull of a specimen that was once made available to the Institute of Paleontology of the University of Bonn (Germany) and has since been referred to as the 'Bonn' specimen. Zhang et al. (2009) provided a perfunctory description (with the majority of bones unidentified) of the skull of the Dalian Natural Museum specimen D2454, which they considered to be the largest specimen of Confuciusornis and assigned it to a new species. In fact, this specimen, with a mandibular length of 70-73 mm (based on the scale bar in their Figure 2, because no cranial measurements were given) is smaller than the Freiburg specimen (Table 1). ...
... 18C and D), they identified the longer, more protruding condyle as the lateral condyle that carries "a shallow depression" for the quadratojugal. However, Zhang et al. (2009) confirmed that the medial condyle is much larger than the lateral condyle, and the quadrate fragment of SMF Av 423 shows a deep quadratojugal socket as in most modern birds. ...
... 19) tentatively identified an ectopterygoid and a pterygoid fragment in GMV-2146. The palate bones preserved in the large Dalian Natural Museum specimen (Zhang et al., 2009) remain undescribed. ...
Article
Full-text available
Confuciusornis sanctus has been heralded as a bird with an ancestrally diapsid skull, although this does not match its phylogenetic position as determined by other skeletal features. Based on 13 cranial specimens in European collections, we demonstrate that the observed scaffolding in the temporal region is highly derived and comparable to some of 21–23 cases of secondary bridges across the temporal fossa that evolved in modern birds. In Confuciusornis, the temporal fossa is crossed by a secondary temporal bar (absent in Eoconfuciusornis) that is continuous with the braincase but discontinuous with the postorbital process. A small postorbital bone (if present) is covered by this secondary ossification. The postorbital process is continuous with a prominent supraorbital rim and extends to the jugal as in sally-striking birds, including some Podargidae (Podargus), Leptosomidae, Brachypteraciidae, Coraciidae, Bucconidae, and Galbulidae, which tend to have wide gapes, large jaws with deep cranial rostra (and the nasal opening in a caudal position), and require additional attachments of musculus adductor mandibulae externus for fast and powerful snatching of the prey. The best modern analogue for the secondary temporal scaffolding seen in Confuciusornis is provided by Podargus, in which the long postorbital process is propped up by the temporal bar in addition the secondary bridge across the temporal fossa. The cranial evidence identifies Confuciusornis sanctus as a sally-striking predator. Citation for this article: Elzanowski, A., D. S. Peters, and G. Mayr. 2018. Cranial morphology of the Early Cretaceous bird Confuciusornis. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1439832.
... Statistics on the morphological characteristics of hindlimbs of extant birds reveal that features such as the length ratio of the three long bones (femur, tibia, and sacrum) of the hindlimbs, different morphological patterns of the distal trochlea, variation of the length of the distal phalanges and the radian changes of the terminal claw arc were related to the habitat behavior [17,[35][36]. The length of the Confuciusornithidae femur is longer than that of tarsometatarsus; the width of trochlea of the distal tarsometatarsus is larger, and the position of the second trochlea is between that of enantiornithes and ornithurae; the 2-4th phalanx of the third digit increases distally, and the first phalanx segment is longer than the second phalanx segment; the third phalanx is strongly hooked for gripping, and the arc angle of the claw exceeds 100° [17,36,38]. These characteristics indicate that the habitat behavior of basal birds such as Confuciusornithidae is close to that of extant climbing birds and a few arboreal birds. ...
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.
... IVPP V18929 has a normal-sized claw on the major digit compared with other confuciusornithids. The most distinguishable feature of confuciusornithids is the presence of a progressively reduced major digit claw (Chiappe et al., 1999;Zhang et al., 2008Zhang et al., , 2009Wang et al., 2018); the ungual is wedge shaped in lateral view, without a flexor process and the lateral neurovascular sulci, and Abbreviations: ad-1,2, proximal and distal phalanx of alular digit; am, alular metacarpal; ma-1,2,3, proximal, intermediate and distal phalanx of major digit; md-1,2,3,4, proximal, second, penultimate and distal phalanx of minor digit; mi, minor metacarpal; mm, major metacarpal; ra, radius; ul, ulna; ur, ulnare. Scale bars: 10 mm (A-E). ...
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.
... So far among Mesozoic Aves traces of the rhamphotheca have only been reported in four specimens referable to the Early Cretaceous basal pygostylian clade, the Confuciusornithiformes: the holotype of Eoconfuciusornis zhengi, the holotype of Confuciusornis dui, and two referred specimens of Confuciusornis sanctus (Hou et al., 1999;Zhang et al., 2008;Chiappe and Meng, 2016;Falk et al., 2019). More avian specimens from the Jehol Group are referable to the Confuciusornithiformes than to any other clade (Hou et al., 1995a(Hou et al., ,b, 1996(Hou et al., , 1999(Hou et al., , 2002Chiappe et al., 1999Chiappe et al., , 2008de Ricqlès et al., 2003;Dalsätt et al., 2006;Zhang et al., 2008Zhang et al., , 2009Li et al., 2018;Marugán-Lobón et al., 2011;Chinsamy et al., 2013Chinsamy et al., , 2019Zheng et al., 2013Zheng et al., , 2017Falk et al., 2016;Jiang et al., 2017;Elzanowski et al., 2018;. A large number of described specimens boast well-preserved soft tissues most commonly in the form of feathers and keratinous ungual sheaths (e.g., Chiappe et al., 1999-Figure 8, Falk et al., 2016-Figure 1, Li et al., 2018-Figure 1, Zheng et al., 2017 Figure 1). ...
Article
Full-text available
The keratinous beak is inferred to have evolved multiple times in the Archosauria and in Aves. Unfortunately, this feature rarely preserves in the fossil record. Here we examine a collection of 603 specimens belonging to the Confuciusornithiformes, a clade of edentulous basal avians, only two of which preserve visible traces of the rhamphotheca. Preservation is very different between the two specimens, offering no clues as to the taphonomic conditions that are conducive to preservation of this feature. These differences suggest that preservation of the rhamphotheca is not limited to a very narrow set of specific chemical conditions. We suggest the more common preservation of feathers over rhamphotheca is due to the higher melanin content in the former. The well-preserved traces in one specimen described here suggests that the rhamphotheca covering the upper and lower jaws each may consist of a pair of right and left elements, thus differing from the condition in neornithines in which the premaxillary nail and mandibular nail covering the rostral half of the upper and lower jaws respectively each form a single unit.
... Mei was first described on the basis of an exquisitelypreserved skeleton with a bird-like sleeping posture, which is arguably the most complete Early Cretaceous troodontid specimen known (Xu and Norell, 2004;Pan et al., 2013). Sinusonasus, Daliansaurus, and Liaoningvenator all have a similar size as Sinovenator, and each of them were reported from a single, near com- Hou et al., 1995Hou et al., , 1996Hou et al., , 1997bHou et al., , 1999aHou et al., , 1999bHou et al., , 2004Hou, 1996Hou, , 1997bChiappe et al., 1999Chiappe et al., , 2007Chiappe et al., , 2014Chiappe et al., , 2019bJi et al., 1999Ji et al., , 2002aJi et al., , 2002bZhang et al., 2006Zhang et al., , 2009Zhou and Zhang, 2005, 2006bGao et al., 2008Gao et al., , 2012O'Connor et al., 2009O'Connor et al., , 2011aO'Connor et al., , 2013O'Connor et al., , 2016cWang et al., 2013dWang et al., , 2013e, 2019c;Zheng et al., 2007Zheng et al., , 2013Zheng et al., , 2014 Dames, 1884;Heller, 1959;Wellnhofer, 1974Wellnhofer, , 1988Wellnhofer, , 1993Wellnhofer, , 2009Mayr et al., 2005;Wellnhofer and Marsh, 1872Marsh, , 1877Marsh, , 1880Martin and Tate, 1976;Martin, 1984;Clarke, 2004;Bell and Chiappe, 2015;Field et al., 2018b Belly River Group Case et al., 2007;Turner et al., 2012;Ely and Case, 2019;Cordes-Person, 2020 ...
Chapter
Full-text available
An unabated surge of new and important discoveries continues to transform knowledge of pen-naraptoran biology and evolution amassed over the last 150+ years. This chapter summarizes progress made thus far in sampling the pennaraptoran fossil record of the Mesozoic and Paleocene and proposes priority areas of attention moving forward. Oviraptorosaurians are bizarre, nonparavian pennaraptorans first discovered in North America and Mongolia within Late Cretaceous rocks in the early 20th century. We now know that oviraptorosaurians also occupied the Early Cretaceous and their unquestionable fossil record is currently limited to Laurasia. Early Cretaceous material from China preserves feathers and other soft tissues and ingested remains including gastroliths and other stomach contents, while brooding specimens and age-structured, single-species accumulations from China and Mongolia provide spectacular behavioral insights. Less specialized early oviraptorosaurians like Incisivosaurus and Microvenator remain rare, and ancestral forms expected in the Late Jurassic are yet to be discovered, although some authors have suggested Epidexipteryx and possibly other scansoriopterygids may represent early-diverging oviraptorosaurians. Long-armed scansoriopterygids from the Middle-Late Jurassic of Laurasia are either early-diverging oviraptorosaurians or paravians, and some have considered them to be early-diverging avialans. Known from five (or possibly six) feathered specimens from China, only two mature individuals exist, representing these taxa. These taxa, Yi and Ambopteryx, preserve stylopod-supported wing membranes that are the only known alternative to the feathered, muscular wings that had been exclusively associated with dinosaurian flight. Thus, scansoriopterygid specimens-particularly those preserving soft tissue-remain a key priority for future specimen collection. Dromaeosaurids and troodontids were first discovered in North America and Mongolia in Late Cretaceous rocks. More recent discoveries show that these animals originated in the Late Jurassic, were strikingly feathered, lived across diverse climes and environments, and at least in the case of dromaeosaurids, attained a global distribution and the potential for aerial locomotion at small size.
Article
Since the 1990s, the avian fossil record has been greatly advanced with the oldest record found from the Upper Jurassic and a pan-global distribution discovered in the Cretaceous. Birds possess highly modified skeletal characteristics such as the pygostyle, keeled sternum, forelimbs developed as wings, and toothless jaws, all of which are considered to have evolved in relation to flight. Recent discoveries have also revealed that Mesozoic birds had made various ecological developments including sexual dimorphism and differential growth rates. Although the reasons for the limited diversification of flightless birds in the Mesozoic and for the survival of the Neornithes through the K-Pg mass extinction event are still not well understood, they may be attributed to environmental and physiological limitations. In this paper, I suggest that the development of flight capability, endothermy, and efficient digestive systems may have been involved in the diversification and wide geographical distribution of birds. Although physiological characteristics are rarely preserved in the fossil record, new fossil discoveries and advancements in research on soft tissue reconstruction might reveal more details of the ecology of extinct birds in the near future.
Article
Full-text available
We investigated the correspondence between feeding behavior and morphology among 19 species of passerine birds in the Hubbard Brook Experimental Forest, New Hampshire, using data in Holmes et al. (1979). Fourteen categories of foraging behavior were ordinated by reciprocal averaging. The first and second derived axes accounted for 61% of the total variance, and distinguished foraging substrate and maneuver. A morphological space was defined by eight external measurements. The correspondence between the positions of species in spaces defined by reciprocal averaging and morphology was determined by canonical correlation analysis. This analysis revealed two strong correlations: the first (R^2 = 0.94) related substrate utilization to the lengths of the tarsus and midtoe, and the second (R^2 = 0.70) related foraging maneuver to midtoe length. The canonical correlation analysis accounted for 83 and 74% of the variation on reciprocal averaging axes I and II; of the morphological variables, only tarsus (76%) and midtoe (64%) contributed strongly to the correlations. Therefore, although morphology predicts foraging behavior in this data set, considerable morphological variation is not related to the foraging variables that characterize the species' ecological relationships.
Article
Full-text available
Reports on the bone microstructure of the Late Cretaceous birds Patagopteryx deferrariisi and members of the Enantiornithes. These birds represent the most primitive birds ever studied histologically. The occurrence of growth rings indicating alternating periods of slowed and fast growth suggests that these basal birds had slower growth rates, and differed physiologically from their modern relatives. The findings also call into question previous ideas suggesting that nonavian theropods developed a full avian degree of homeothermic endothermy, which was later inherited by birds. On the contrary, the findings suggest that birds developed classic endothermy relatively late in their phylogenetic history. -Authors
Article
Confuciusornis, the earliest avian taxon with beak and pygostyle, is extremely important in the study of the early evolution of birds. Its skull is of typical diapsid plan. The beak is quite robust-its teeth were lost independently of other birds. The presence of the long uncinate processes in Confuciusornis is thought to be primitive for birds. The flight feathers are well developed, but the alula is not present. Confuciusornis is the sister-taxon of Changchengornis, and both are placed within the same family of Confuciusornithidae, which is considered to be the sister-group of the Ornithothoraces composed of the Enantiornithes and the Ornithurae. Within the four species of Confuciusornis, C. chuanzhous and C. sunae are considered to be junior synonyms of C. sanctus. It is argued that the Confuciusornis were ill suited for tree climbing, but were able to fly and take off from the ground. Most fossil animals produce the evidence that the Confuciusornis-bearing beds should be the Late Jurassic in age alth ough the Early Cretaceous is accepted by some researchers.
Article
In order to assess the phylogenetic relationships of Mononykus, a cladistic analysis was performed. Using velociraptorine theropods as outgroups, the analysis resulted in a single most parsimonious cladogram. In this cladogram the monophyletic Alvarezsauridae (including Mononykus and the Argentine Alvarezsaurus and Patagonykus) is the sistergroup of all other birds except Archaeopteryx. The monophyly of Aves (= Avialae sensu Gautnier) is supported by seven unambiguous synapomorphies, four of which are present in Mononykus. These characters include fewer than 26 caudal vertebrae, caudal vertebrae with short distal prezygapophyses, teeth with unserrated crowns and a caudal tympanic recess opening only inside the tympanic cavity. The monophyly of Metornithes (Aves exclusive of Archaeopteryx) is supported by six unambiguous synapomorphies all of which occur in Mononykus. Among these characters are the presence of prominent ventral processes on the cervicodorsal vertebrae, a carpometacarpus, a prominent antitrochanter in the pelvis and a rectangular, carinate sternum. Furthermore, six synapomorphies (all present in Mononykus) ambiguously diagnose both Aves and Metomithes. The distribution among avian and nonavian taxa of all these characters is discussed. Several authors have criticised the hypothesis of avian relationships for Mononykus. In this paper we address those criticisms. We also discuss the rationale of testing phylogenetic hypotheses within a cladistic framework and establish that our critics have not furnished much beyond a priori speculation.
Article
Data presented here reveal a greater degree of individual variation in certain skeletal elements than literature on birds in general indicates. This is especially true of the number of fused vertebrae in the synsacrum and the number of free caudal vertebrae, the former varying from 11 to 13 and the latter from 4 to 6. Geococcyx californianus and Crotophaga sulcirostris possess 14 cervical vertebrae each, whereas two species of Coccyzus possess only 13 cervical vertebrae each. The cervical region seems to show little or no variation, in contrast with the more caudal portions of the vertebral column. Members of the three genera possess 4 dorsal vertebrae each. The length of the cranium is less variable than either the length of the synsacrum or the length of the dorsal vertebral region.
Article
Adaptive radiation is reflected in the correlation of foraging habits and mensurations of the pelvic skeletal appendages of five species of parulid warblers. The Black-throated Green Warbler, a general crown foliage gleaner, is considered the most generalized of the group. The Yellowthroat is adapted to a reed-shrub-tall-grass habitat by means of a long pelvic appendage and long toes necessary for security of perch in this habitat. The Black-and-White Warbler, with shorter distal segments, a long hallux, and a considerable ungual arc, is at an advantage in clambering over the trunks and larger limbs of trees. The short pelvic appendage of the Ovenbird is compensated for by equilibrating tail-lifting and wing-flicking movements as it forages on a leaf-littered forest floor. A longer third digit in the Redstart, the only significant difference from the Black-throated Green, may aid in rapid take-offs in pursuit of flying insects. Adaptive radiation in warblers as exemplified by variation in the hind limb appears to be quite extensive and reflects the spread of the group into many niches. Sympatry may well have reinforced such adaptive trends.