Fossil birds: Contributions to the understanding of avian evolution Johan Dalsätt

MEDDELANDEN
från
STOCKHOLMS UNIVERSITETS INSTITUTION
för
GEOLOGISKA VETENSKAPER
No. 349
___________________________________________________________________________
Fossil birds: Contributions to the
understanding of avian evolution
Johan Dalsätt
Stockholm 2012
Department of Geological Sciences
Stockholm University
SE-106 91 Stockholm
Sweden
© Johan Dalsätt, Stockholm 2012
ISBN 978-91-7447-462-6
Cover picture: Confuciusornis sanctus (from Paper II)
Printed in Sweden by US-AB Stockholm University, Stockholm 2012
A dissertation for the degree of Doctor of Philosophy in Natural Sciences
Department of Geological Sciences
Stockholm University
SE-106 91 Stockholm
Sweden
___________________________________________________________________________
Abstract
The study of the evolution of birds began about 150 years ago with the finding of Archaeopteryx.
Since then several different opinions about the origin and earliest evolution of birds have been put
forward. However, in the last 15 years most researchers have favoured a dinosaur (theropod) origin
based not least on the many Early Cretaceous fossils discovered in northeastern China. Yet, many
unsolved questions about avian evolution remain to be answered. This thesis aims at addressing some
of these questions.
The Early Cretaceous Confusiusornis from China is the most well-represented Mesozoic bird in
the fossil record, with probably more than 2000 specimens recovered. This abundance of fossils
facilitates a study of the preservation of specimens in the two geological formations in which this
taxon is found. It was demonstrated that specimens in the older Yixiang Formation always are
represented by complete, articulated skeletons, while those in the younger Jiofutang Formation often
lack the pectoral girdle and the wings.
Despite the many specimens available of Confusiusornis few clues to the diet of this taxon have
been found. Several alternatives have been suggested but no evidence have been presented. We
describe a Confusiusornis specimen with a pellet of fish remains preserved in the throat region.
Although the location of the pellet cannot be regarded as direct evidence for the diet of
Confusiusornis, this at least suggests that this bird was not a pure herbivore as has been inferred from
its sturdy beak.
The enantiornithid birds probably constituted the most species-rich and diverse bird group during
the Cretaceous. More than 25 species have been described and they have been documented from a
wide range of habitats. Several well-preserved specimens have been found in China, e.g. Grabauornis
lingyuanensis described herein. The species-richness within this early group of birds seems to
resemble that of modern birds. Grabauornis seems to be a good flyer as indicated by its brachial index
(the ratio between humerus and ulna).
The mass extinction at the end of the Cretaceous probably gave the only surviving group of birds,
Neornithes, chance to radiate and evolve into new niches. Just a few million years into the Cenozoic,
basically all modern bird groups are represented in the fossil record. One such group is the
Strigiformes (owls) with the oldest confirmed fossil from the Paleocene. We describe a new species
from the Eocene Green River Formation in USA that we suggest is closely related to the contemporary
European Prosybris antique and P. medius. The occurrence of this genus in Eocene faunas in both
North America and Europe is probably another example of the intercontinal exchange of terrestrial
groups in the Paleogene. The two continents were much closer during at this time and may even have
been connected by land bridges between during the Paleocene and Eocene.
Although birds are known from several Miocene localities in Europe, only one of these was
situated in northwestern Europe, the Belgian site Antwerp. The discovery of vertebrate fossils in the
Hambach opencast lignite mine was thus unexpected and remarkable. Among these vertebrate fossils
are several from birds, e.g., mostly ducks and galliforms, but also from a rail. However, the most
significant bird found in Hambach is a specimen of darter, genus Anhinga. It agrees in size,
proportions and morphology the fossil species Anhinga pannonica to which we refer the Hambach
specimen. This specimen is also the oldest evidence of darters in the Old World and it bear witness of
that the climate in Miocene Europe was much warmer than today. Fossils of ducks and galliforms
have also been found in deposits at Hambach dated to the Pliocene.
List of papers
This thesis is based on the following papers, referred to by their Roman numerals:
I
Dalsätt J., Zhou Z., Zhang F.and Ericson P.G.P. Differential preservation of
Confuciusornis specimens in the Yixian and Jiufotang formations. Submitted
manuscript.
II
Dalsätt J., Zhou Z., Zhang F., and Ericson P.G.P. 2006. Food remains in Confuciusornis
sanctus suggest a fish diet. Naturwissenschaften 9, pp.: 444-446.
III
Dalsätt J., Ericson P.G.P., and Zhou Z 2012. A new Enantiornithes (Aves) from the
Early Cretaceous of China. Acta Geologica Sinica, 86:2, pp 801-807.
IV
Dalsätt J., and Ericson P.G.P. A new species of owl (Aves: Strigiformes) from the
Eocene Wasatch Formation, Wyoming. Submitted manuscript.
V
Dalsätt J., Mörs T. And Ericson P.G.P. 2006. Fossil Birds from the Miocene and
Pliocene of Hambach (NW Germany). Palaentographica abt. A. 277: pp. 113-121.
This thesis, including manuscript IV, is disclaimed for purpose of Zoological nomenclature
(international Code of Zoological Nomenclature, Fourth Edition, Article 8.3). That means that the
thesis may be cited in its own right, but should not be cited as a source of nomenclature statements.
Contents
Page
An introduction to the evolution of birds
1
Archaeopteryx and other tailed birds
3
Pygostylia - short tailed birds
5
Confuciusornithidae
5
Ornithothoraces
6
Enantiornithidae – the largest bird group of its time
6
Ornithuromorpha
7
Ornithurae
8
Carinatae
9
Neornithes
9
This thesis
11
The Jehol biota
12
The preservation of Confuciusornis sanctus (Paper I)
13
The feeding of Confuciusornis sanctus (Paper II)
14
A new species of an Enantiornitid (Paper III)
15
A new Eocene owl (Paper IV)
15
Birds from the Miocene and Pliocene of Hambach, Germany (Paper V)
18
Conclusions
21
Acknowledgements
22
Svensk sammanfattning
23
References
28
An introduction to the
evolution of birds
Linneus first used the name Aves in 1758.
Obviously, he knew nothing about fossil birds and
he thus meant only the feathered animals we see
today, the crown group. To restrict the name Aves
to the crown group was also suggested by Gauthier
(1986) when he established the name Avialae for
the larger group that contained both extant and
extinct birds. However, this definition seems not to
have reached a wide acceptance, and a brief look
through the literature over the last years suggests
that most writers use the term Aves for the more
inclusive group. Herein the clade Aves consists of
the common ancestor of Archaeopteryx and all
living birds (Fig.1). This is also what I personally
prefer. However, in the future, with new fossil
finds, or new and better phylogenetic data sets and
methods, we might have had to redefine the name
aves or “move the boundary” from what we today
separate as “non-flying dinosaurs” and birds.
The origin of birds and the search for their
closest relatives has for a long time been cause for
heated debates. Fishes, turtles, lizards, pterosaurs,
ornithischian dinosaurs and even mammals have
been pointed out as the birds’ closest relatives
(Gauthier 1986; Padian and Chiappe 1998,
Chiappe 2004). The most popular theories are the
“crocodylomorph” hypothesis, the “thecodont” (or
“archosauromorph”) hypothesis and the “theropod
dinosaur” hypothesis (Padian and Chiappe 1998).
There are no doubts that birds and crocodiles
are each others nearest extant relatives (Gauthier
1986). Walker (1972) based on studies and
comparison of the braincase, quadrate and ear
region of the early Jurassic crocodylomorph
Sphenosuchus even suggested that birds have
descended from crocodiles. This theory was
supported by Martin et al. (1980) based on
characters in the skull, teeth and tarsus. Gauthier
(1986) suggested that several of the
synapomorphies proposed by Martin et al. (1980)
were too universal or plesiomorphic among the
compared taxa and Walker later concluded that the
bird-crocodile hypothesis could not sustain
(Walker 1985).
The thecodont hypothesis was first proposed
by Broom in1913, but it was after the publication
Fig.1: The phylogenetic relationchip of Mezozoic
birds.
1
of the book “The Origin of Birds” by the Danish
palaeontologist Heilmann (1926) that this
hypothesis was clearly formulated. Heilmann
noticed (as Huxley had already in 1868) that birds
and theropod dinosaurs shared a many characters,
but unlike Huxley he did not believe that birds
could have descended directly from theropods. One
reason for this was that theropods lack clavicles
while they in birds are fused into the furcula. Under
Dollo´s law of irreversibility Heilmann did not
believe that this feature could have re-evolved in
birds. Heilmann instead suggested that the origin of
birds lays with the thecodonts, a more ancient
group that were known to possess clavicles
(Heilmann 1926). However, phylogenetic studies of
the thecodonts have shown this group to be
paraphyletic (basically everything that where not
dinosaurs, pterosaurs or crocodiles was regarded as
“thecodonts”), and the name is now obsolete.
Instead the more inclusive name Archosauria is
used for the entire group of animals to which e.g.
crocodiles, “thecodonts”, dinosaurs and birds
belong (Gauthier 1986). But the question remains:
from which group of archosaurs did birds evolve?
Just a few years after Heilmann´s book was
published in 1926, the firs report of clavicles in
theropods was published (Camp 1936), and today
the possession of clavicles is a well established
synapomorphy for theropod dinosaurs (Chiappe
2004). Both Gegenbaur (1864) and Cope (1867)
suggested a close relationship between birds and
theropods, but it was Huxley who after his studies
of
Archaeopteryx really established the idea that
birds originated from theropods (Huxley 1868,
1870; Chiappe 2004). Huxley´s hypothesis lost
ground when Heilmann published his book and it
was not resurrected until the beginning of the
1970s, after Ostrom´s (1976) detailed comparisons
between Archaeopteryx and the small dinosaur
Deinonychus (Chiappe 2004). The discussion about
the ancestry of birds was not over, however. To the
contrary, the debate about their proposed theropod
origin has been intense and hard (Witmer 2002).
Since Ostrom´s 1976 publication a wide range
of quantitatively and qualitatively good fossils
have been collected and reported, and they all
point at a theropod origin of birds (Chiappe 2004).
Comparisons of osteological characters have
revealed the most striking similarities between
maniraptoran theropods and birds. Several authors
have analysed these characters within a
phylogenetic context, and they have all found that
birds are well nested within the coelurosaur clade
of theropod dinosaurs, although the exact
phylogenetic position of birds may differ between
the studies (Gauthier 1986; Clark et al. 2002;
Mayr et al. 2005; Senter 2007).
The coelurosaurs is a diverse group of
dinosaurs containing a wide range of well known
dinosaurs as tyrannosaurids, Oviraptoridae,
Troodontidae and Dromaeosauridae. At first
glance it can be difficult to discern a relationship
between these animals and extant birds, but there
is a number of synapomorphies for this large
clade; e.g. clavicles fused into a furcula, hollow
limb bones, sternal plates, prolongations of the
arms, a semilunate carpal bone, three fingers on
the hand (Chiappe 2004). But not only
morphological characters points towards a
theropod dinosaur origin of birds. They also share
similarities in eggshell microstructures, brooding
behaviour and resting postures, and in the small
size of their genomes (Chiappe 2004; Xu and
Norell 2004; Organ et al. 2007). But the perhaps
most important synapomorphy is the possession of
feathers in both coelurosarian dinosaurs and birds.
A feather is a branched, or pinnate, epidermal
derivative composed of keratin and growths as
skin projections from follicles in the skin (Prum
1999). Feathers have been the key character to
define birds since mankind started to classify
organisms. The debate about the origin of feathers
is basically as long as the debate about the origin
of birds. For many years the most popular view
was that feathers had evolved from scales (Prum
1999). Based on developmental and molecular
studies this view has been challenged and it has
2
instead been suggested that feather did evolve from
follicles by an undifferentiated collar, through a
cylindrical epidermal folding (Prum 2002).
Although feathers are delicate structures and are
rare in the fossil record, several dinosaurs have
been found with feather imprints (Norell and Xu
2005). They also show different stages of feather
evolution, supporting Prum´s (1999) view, from
simple
unbranched
structures
in
e.g.
Sinosauropteryx and Dilong, via more advaced in,
e.g., Caudipteryx, to real flight feathers in
Microraptor (Chen et al. 1998; Xu et al. 2004; Ji et
al. 1998; Xu et al. 2003). Other dinosaurs have
indirect evidences, as the quill knobs found in e.g.
Velociraptor and Rahonavis (Turner et al. 2007,
Forster et al. 1998). However, some fossil feathers
and feathered dinosaurs have been claimed to be
degraded collagen fibres or secondarily flightless
birds, respectively (Lingham-Soliar et al. 2007;
Martin 2008). Instead, creatures like the Triassic
archosaur Longisquama, with its long scales, have
been put forward as a candidate for the origin of
birds and feathers (Martin 2008). The problem with
Longisquama is first that the interpreted feathers
more likely are modified scales (Reisz and Sues
2002) and second, that it falls outside the dinosaur
clade in a phylogenetic analysis (Senter 2004).
If the origin and evolution of feathers is
complex, the same can be said about why feather
evolved in the first place. Even here there are
almost as many suggestions as there are scientists,
but most at least agree that feathers did not
originally evolve for flight. Some of the proposals
have been that they evolved for display, incubation,
trauma protection, food trapping and insulation
(Sumida and Brochu 2000).
The origin of flight is more puzzling because
there is no direct evidence from the fossil record.
The debate over this subject has sometimes been as
heated as the discussion about the origin of birds.
On the other hand, there are only two opposing
views bearing on the question of why and how
flapping flight evolved; the arboreal theory and the
cursorial theory (Bock 1986; Ostrom 1986). The
arboreal theory suggests that some small proavians
became tree living and through various
evolutionary steps, as jumping between trees,
parachuting and gliding, they finally achieved
flapping flight (Chatterjee 1997). This theory has
mainly been supported by scholars who also
support an archosaur origin of birds (Feduccia
2002). The arguments have been that flight must
have originated with the help of gravitation and
that it must have involved relatively small animals
that easily could climb trees. The cursorial theory,
or ground-up theory, follows the assumption that
the first step towards flapping flight was wingassisted running or leaping followed by horizontal
take-off to vertical take off (Dial 2003). In general
this theory finds its advocates among people that
believe that dinosaurs are the closest relatives to
birds (Feduccia 2002). Their arguments have been
that the dinosaurs were terrestrial and did not
climb trees (Chiappe 2005). This view has been
challenged by new fossils and now there are also
supporters of a dinosaur arboreal theory (Zhou
2004). They claim that small, obviously feathered,
dinosaurs
as
Microraptor,
Anchiornis,
Epidendrosaurus and Epidexipteryx, possibly were
tree-living or at least able to climb trees (Xu et al.
2003; Xu et al. 2009; Zhang Z. et al. 2002; Zhang
F. et al. 2008b). The feathers of Microraptor were
very well developed and even asymmetric (Xu et
al. 2003). Interestingly, phylogenetic analyses
have
placed
both
Anchiornis
and
Scansoriopterygidae
(Epidendrosaurus
and
Epidexipteryx) as the closest relatives to the birds
(Xu et al. 2008; Zhang et al. 2008b). One
argument against tree-living dinosaurs has been
that the pedal claws were not adapted for an
arboreal life (Glen and Bennet 2007). The
geometry of claws in those dinosaurs and some
early birds, in comparison to extant birds, indicate
that those creatures foraged mainly on the ground
(Glen and Bennet 2007). Currently there is no
convincing evidence for neither of the proposed
theories of the origin of flight.
3
and a respiratory system similar to modern birds
suggests that it was capable to take off from the
ground. On the other hand, Senter (2006) argued
that Archaeopteryx could not raised the wings
above the body and Mayr et al. (2005) reported
that the hallux was most likely not reversed as in
modern arboreal birds, but probably medially
spread and probably spent most of its time on the
ground. The debate about Archaeopteryx flight
capability will probably continue for a long time.
My personally reflection is that if
Archaeopteryx had been found today, I don’t think
it had been treated as a bird but probably as a
feathered dinosaur and its avian status is mainly
based on its historical background.
The early Cretaceous turkey-sized Jeholonis
prima was reported in 2002 (Zhou and Zhang
2002). The name prima means primitive and refers
to the tail which with its 23 caudal vertebrae is
longer than Archaeopteryx (Zhou and Zhang
2003a). Jeholonis prima share several characters
with Archaeopteryx, especially in its pelvis, hind
limbs and caudal vertebrae (Zhou and Zhang
2003a). It is however more advanced in other
characters such as a scapula with a dorso-laterally
exposed glenoid facet, a strut-like coracoid, a
sternum with a lateral trabecula with a fenestra; a
wing having a well fused carpometacarpus, bowed
metacarpal III, and a shortened and more robust
digit II, which is more suitable for attachment of
the primary feathers (Zhou and Zhang 2003a).
Another interesting aspect of Jeholornis is the
seeds found in the stomach region – a direct
evidence of the diet among those early birds (Zhou
and Zhang 2002). In contrast to the debate about
Archaeopteryx, there are no doubts that Jeholornis
with its reversed hallux, long and curved claws
and long and asymmetric wing feathers, had an
arboreal lifestyle and was capable of active flight
(Zhou and Zhang 2002; 2003a).
Even though Zhongornis haoae probably is a
juvenile it is interesting in other aspects. The 10
centimetre long, early Cretaceous, bird is the first
evidence of shortening of the tail. It consists of
Archaeopteryx and other tailed birds
Archaeopteryx, often referred to as the “urvogel”,
from the late Jurassic of Germany, has become an
icon within palaeontology. In 1860 the first feather
turned up and a year later the first more or less
complete specimen was obtained by Karl Häberlin,
who showed it to Hermann von Meyer, who named
it Archaeopteryx lithographica, meaning ancient
feather or wing (Chiappe 2007). This was just two
years after Darwin had published his book The
Origin of Species and Archaeopteryx, with its many
dinosaur characters, immediately became a tool for
evolutionary advocates. In the last 150 years, nine
more specimens of Archaeopteryx have been
described. Archaeopteryx is not only the first and
oldest bird found; it is also viewed as the most
basal shoot of the avian phylogenetic tree.
Even though Archaeopteryx has been declared
to belong to Aves, it has many characters showing
its close relationship with dinosaurs such as
dromaesaurids and troodontids (Ostrom 1976). The
most obvious is the long tail, teeth and clawed
fingers, but there are several other features as well,
see e.g. Elzanowski (2002) or Chiappe (2007) for a
review of anatomical characters. If it were not for
the feather impressions, it may have not been
identified as a bird at all, but instead been treated as
a dinosaur. This actually happened to one specimen
that first was recognized as a Compsognathus, a
small dinosaur found in the same area (Ostrom
1975).
What has made Archaeopteryx to a bird is the
feather structure and anatomy that is similar to that
in modern birds with a central shaft and
asymmetrical vanes (Elzanowski 2002). The
arrangement of the flight feathers is also like in
extant birds with about 11-12 primaries and 12-15
secondaries (Mayr et al. 2005). Whether
Archaeopteryx could take off from the ground and
had active flight (i.e. fly by its own power) has
been widely debated. Chiappe (2007) argued that
the fact that Archaeopteryx had wings that could be
raised above the body, a brain adopted for flight
4
only 13–14 caudal vertebrae (Gao et al. 2008). This
is maybe the first step towards forming a pygostyle.
It has also been suggested that this is the basalmost
bird with manual phalangeal reduction (Gao et al.
2008). In Archaeopteryx and dinosaurs the hand
phalangeal formula is 2-3-4-X-X, while in
Zhongornis it is 2-3-3-X-X, similar to the condition
in enantiornithids and ornithuromorphs (Gao et al.
2008). However, the phalangeal formula in
Confuciusornis is 2-3-4-X-X and in Sapeornis 2-32-X-X (Zhou and Hou 2002; Zhou and Zhang
2003b). Whether these different phalangeal
formulae really represent the evolution towards that
in modern birds is in my opinion not clear.
the scientific society (Chiappe et al. 2008; Dalsätt
pers. obs.). Even though Confuciusornis sanctus is
very common, Eoconfuciusornis zhengi and
Changchengornis hengdaoziensis, the other two
taxa within Confuciusornithidae, are only known
from one specimen each (Zhang et al. 2008a;
Chiappe et al. 1999). Between the oldest
Confuciusornithidae, Eoconfuciusornis, to the
youngest find of Confuciusornis, there is a time
span of 11 million years.
It has been suggested that the genus
Confuciusornis comprises more than one species,
e.g. C. sanctus, C. chuonzhous, C. dui, C. suniae
and C. feducciai (Hou 1997; Zhang et al. 2009).
However, the only observable variation among
these taxa is size (Chiappe et al 1999), which may
instead be attributed to different age of the
specimens and to sexual dimorphism (Chiappe et
al. 2008). There is thus no solid evidence for that
Confuciusornis
consists
of
more
than
Confuciusornis sanctus, albeit the status of C. dui
and C. feducciai remains to be investigated
(Chiappe et al. 2008; Zhang et al. 2009).
Sexual dimorphism has also been interpreted
in Confuciusornis based on feather imprints. Some
individuals have long, ribbon-like, tail feathers
while others are lacking them, and these two
variants have even been found on the same slab
(Chang et al. 2003). It has been suggested that
those with long feathers are males and the ones
without, females (Hou et al. 1996).
To distinguish Confuciusornis from other
fossil or extant birds is not difficult. The most
obvious characters are its toothless and robust
beak with a the straight culmen; the well
developed deltopectoral crest of the humerus
being pierced by an oval fenestra; the rather big,
but keel-less, sternum; a short metatarsal V; a
short hallux and a pygostyle (Chiappe et al. 1999;
Zhou and Hou 2002). Confuciusornis is the most
basal bird that has developed a true beak, a good
example of convergent evolution, also seen in the
enanthiornithid bird Gobipteryx (Chiappe et al.
2001). Otherwise, this feature doesn’t turn up until
Pygostylia - short tailed birds
The clade Pygostylia is supported by four
synapomorphies:
absence
of
hyposphenehypantrum; presence of a pygostyl; a retroverted
pubis separated from the main synsacral axis by an
angle ranging between 65-45 and the presence of a
wide and bulbous medial condyle of the tibiotarsus
(Chiappe 2002). At the moment Pygostylia includes
the ancestor of Confuciusornithidae and all other
more derived birds and their descendants (Chiappe
2002). Sapeornis, one of the largest Lower
Cretaceous birds, has been considered as the most
basal member of Pygostylia, but its phylogenetic
placement is not fully resolved and it has been
placed in a more derived position by some authors
(Zhou and Zhang 2003b; Gao et al. 2008).
Confuciusornithidae
The far most common Cretaceous bird is
Confuciusornis sanctus from north-east China
(Chiappe and Dyke 2006). In total as many as 2000
specimens may have been found of this bird but no
one really knows. Many specimens have been sold
on the black market and are now in private
collections inside and outside of China (Dalton
2000; Chiappe et al. 2008). This is most
unfortunate as many specimens are unaccessible to
5
the end of Cretaceous in the clade Neornithes
(Clarke et al. 2005).
Other
characters
shared
between
Confuciusornis and more derived birds are a longer
synsacrum with further incorporated vertebrae, the
stout coracoids, and the completely fused
anklebones, forming a tibiotarsus, as well as the
metatarsals of the foot form the tarsometatarsus
(Chiappe 2007).
But even though Confuciusornis is the most
basal beaked bird with a pygostyle, it is still
primitive and shares characters and morphology
with Archaeopteryx and other tailed birds in many
aspects. For example, the postorbital and squamosal
bones are not part of the braincase construction, the
infratemporal fenestra is completely enclosed
behind the orbit with help of the postorbital bone,
the proportions of the neck and trunk, the furcula is
robust and lacks a hypocledium, the ratio between
humerus, ulna and radius in comparison to the
hand, the possession of claws of the hand, the
overall morphology of the pelvis, the large
acetabulum, the ishium is shorter than pubis, and a
quite short hallux (Chiappe 2007).
and has been referred to that tarsometatarsus is
fused proximally, instead of distally as in extant
birds (Feduccia 1996). But Walker (1981) never
presented a formal explanation of the etymology.
He wrote “A cladistic analysis of the remaining
characters of this group, for which the new name
Enantiornithes (´opposite birds`) is proposed, “,
and further on in the same paper “Perhaps the
most fundamental and characteristic difference
between the Enantiornithes and all other birds is
in the nature of the articulation between the
scapula (Fig. 2a, C) and the coracoid, where the
'normal' condition is completely reversed.”
(Walker 1981). What is said about tarsometatarsus
has nothing to do with the fusion of the proximal
end. In the list of synapomorphies, shared by
Odontornithes and Neornithes, is the fusion of the
tarsometatarsus referred as “only partial” (Walker
1981).
Nevertheless, Enantiornithids are found
throughout the whole Cretaceous, from
Protopteryx fengningensis (dated to c. 131 Mya),
to Avisaurus archibaldi (dated to c. 70.6-65.5
Mya) (Zhou 2004; Brett-Surman and Paul 1985).
More than 25 valid species and several unnamed
specimens have been reported from all continents
except Antarctica (Chiappe and Walker 2002).
There are also lots of bits and pieces of supposed
enantiornithines, but these are too fragmentary to
allocate to a certain taxon, and there are species
that have been considered as Enantiornithids that
have been questioned by other authors (Chiappe
2007). Another problem is that some individuals
of the same species have been described under
different names e.g. Vescornis and Hebeiornis (Jin
et al. 2008). There are also reports of juveniles and
embryos (Chiappe et al. 2007; Zhou and Zhang
2004).
Enantiornithids inhabited a wide range of
habitats with variable adaptations. The most
common finds are from inland lake deposits as in
Liaoning, China, and Las Hoyas, Spain (Chiappe
2007). But they also occupied coastal and marine
environments, as shown by the late Cretaceous
Ornithothoraces
The clade Ornithothoraces includes the common
ancestor of Enantiornithidae and Ornithuromorpha
and all their descendants. The clade is strongly
supported by twelve synoapomorphies (Chiappe
2002).
Enantiornithidae – the largest bird group of
its time
The Enantiornithids was probably the most
diversified group of birds during the Cretaceous
and maybe the whole Mesozoic (Chiappe and Dyke
2006). The name was established by Walker in
1981. Even though the Enantiornithes is a well
established and a stable group there are some
doubts concerning the etymology of the name
Enantiornithes. The name means “opposite birds”
6
Halimornis from North America (Chiappe et al.
2002), and dry inland environments, as the late
Cretaceous Gobipteryx from central Asia (Chiappe
et al. 2001).
Most enantiornitid species are found in single
localities (Walker et al. 2007). However, at least
one enantiornitid, the late Cretaceous Martinornis
(Walker et al. 2007), has been shown to be
geographically widespread occurring in France,
North America and Argentina. If the wide
distribution of Martinornis shows a migratory
behaviour or if it was a cosmopolitan, sedentary
species cannot be resolved on the basis of the fossil
record (Walker et al. 2007). Nevertheless, given
this wide distribution the flight capability of at least
this Enantiornithid species must have been good.
Most of the Enantiornithids were relatively
small, similar in size to extant songbirds, although
some birds could be relatively big, as Pengornis
with a wingspan of roughly 50cm and the
Argentine Enantiornis with a wingspan of almost
one meter (Zhou et al. 2008; Chiappe 1996). With
an anisodactyl arrangement of the toes, the
enantiornitine were well adapted for a perching
lifestyle (Chiappe 2007). However, at least one
genus, Dalingheornis, may have had a heterodactyl
arrangement, similar to extant parrots and
woodpeckers (Zhang et al. 2006). The feet of
enantiornitines could also be used for seizing and
slaying preys (Chiappe 2007). Other adaptations in
this diverse group of birds were the long and
slender bills of Longirostravis and Longipteryx.
Longirostravis, with its tiny teeth probably probing
in mud, similar to extant charadriiformes, and
Longipteryx, used the bill, with massive teeth, for
catching fish (Hou et al. 2004). Yungavolucris had
asymmetrical feet that probably were adapted for
swimming, while the long and slender legs of
Lectavis seem ideal for wading (Chiappe 1993).
The only toothless enantornithine, Gobipteryx, has
been described to be a seed eater with its robust,
toothless bill, similar to that in Confusiusornis
(Chiappe et al. 2001). The diet of the
enantiornithids is largely unknown. Some
indications are given by Eoalulavis in which
remains of crustaceans was found in the gut region
(Sanz et al. 1996), and a fragmentary specimen
from Lebanon in which remains of sap (preserved
as amber) was found (Dalla Vecchia and Chiappe
2002).
Even though the Enantiornithids was first
described in 1983 there has been disagreement on
the phylogenetic position of the group and
numerous papers have been published on the
subject. Walker (1981) first proposed them to be
placed between Archaeopteryx and Hesperornis.
Later, Martin (1983) included enantiornithines in
Sauriurae, a group erected by Ernst Haeckel in
1866 when he divided the, at the time, known
birds in two subclasses, Sauriurae (lizard tails) and
Ornithurae (bird tails). Archaeopteryx was
consequently placed in Sauriurae. Martin’s
hypothesis was further supported by a
phylogenetic analysis with 36 characters, of which
four characters were supposed to be
synapomorphies for Sauriurae (Hou et al. 1996).
In this analysis also Confuciusornis was included
in Sauriurae (Hou et al. 1996). Another
phylogenetic analysis based on 73 characters was
carried out by Cracraft (1986). He came up with
three possible alternatives for the placement of
Enantiornithes. A: Enantiornithes are placed
between Archaeopteryx and Neornithes and
Ichthyornis. B: Enantiornithes and Neornithes are
sister groups. C: Enantiornithes and Neognathae
are sister groups. None of these alternatives agree
with Martin’s idea. Subsequent analyses based on
more data have all come to the same conclusion:
Enantiornithes are well nested between
Confuciusornithidae
and
Ornithothoraces
(Chiappe and Walker 2002; Zhou et al. 2008).
Ornithuromorpha
Ornithuromorpha was defined by Chiappe (2001)
and includes the common ancestor of
Patagopteryx and Ornithurae and all its
descendants. The clade is supported by eight
7
characters: scapula curved dorsoventrally, scapula
as long or longer than the humerus, semilunate
carpal and metacarpals completely fused into
carpometacarpus, ilium, ischium, and pubis
completely fused proximally, M. iliofemoralis
internus fossa not demarcated by broad,
mediolaterally oriented surface cranioventral to
acetabulum, cranial trochanter of femur absent,
distal tarsals and metatarsals completely fused and
metatarsals fused distally to enclose a distal
vascular foramen, and hypotarsus with a flat caudal
surface developed as caudal projection of
tarsometatarsus (Chiappe 2002; You et al. 2006
Supporting material). If Ornithuromorpha will
“survive” as a valid name is not sure. Very few
authors use this term and some instead use
Ornithurae for this clade (Zhou and Zhang 2006;
Hone et al. 2008).
The lark sized, early Cretaceous Archaeorhynchus
from Yixian formation of China is so far not only
the most basal member within Ornithuromorpha,
but also one of the oldest. Even though it has
certain primitive features, as e.g. a broad sternum, a
synsacrum with only seven sacrals, a long fibula
and a tarsometatarsus as lacking a distinct vascular
foramen (Zhou and Zhang 2006), it also possesses
more derived characters as, e.g., an U-shaped
furcula, a well developed keel extending the full
length of sternum, a prominent humeral head and
the first phalanx of the major manual digit is
dorsoventrally compressed and expands posteriorly
(Zhou and Zhang 2006).
Another early ornithuromorph bird is
Yixianornis, which is from the Jiufotang formation
of northeastern China and therefore slightly
younger than Archaeorhynchus (Clarke et al. 2006).
It is somewhat bigger than Archaeorhynchus and
also more derived in having relatively modern
wings but still retaining primitive pelvic and less
developed hind limbs (Clarke et al. 2006).
Ornithurae
Ornithurae “bird tail” refers to birds with a
skeletal tail shorter than the femur, or a tail shorter
or of the same length as the tibiotarsus, and with a
pygostyle (Gauthier and Queiroz 2001). The name
was established already in 1866 by Haeckel.
The Ornithurae are supported by four
unambiguous synapomorphies: dorsal surface of
coracoid flat to convex, extensor canal of
tibiotarsus comprised of an emarginate groove,
fossa for metatarsal I on metatarsal II a
conspicuous, ovoid fossa, and metatarsal II shorter
than metatarsal IV (You et al. 2006, supporting
material). Some authors use the name Ornithurae
for everything that is more derived than the
Enathiornitids (Zhou and Zhang 2006; Hone et al.
2008).
Gansus from the Early Cretaceous (ca. 115 –
105 Mya), Xiagou Formation in Gansu province in
China, is the worlds oldest known Ornithurae
(You et al. 2006). It was the size of a pigeon and
had a webbed foot. Supposedly it could dive,
although not as good as grebes, loons and diving
ducks (You et al. 2006).
For a long time the remains of Hesperornis
and Ichthyornis were the only known Mesozoic
birds except Archaeopteryx. The first Hesperornis
was discovered and named by Marsh (1872a). The
hesperornithids was a successful group of
flightless birds that were adapted for a marine life
similar to that of extant penguins. They existed for
almost 45 mya, the oldest species being the late
Early Cretaceous (ca. 100 mya) Enalornis from
Great Britain, and the youngest the midMaastrichian (68 mya) Canadaga from Canada
(Hou 1999). Hesperornithids were rather big birds,
one of the biggest, Canadaga arctica, could reach
over 1.5 meter (Hou 1999). Their geographical
distribution was restricted to the northern
Hemisphere; North America, Europe, Russia,
Kazakhstan and Mongolia (Rees and Lindgren
2005). Altogether twelve species have been
described but the true number is uncertain as
8
several taxa are based on isolated elements (Rees
and Lindgren 2005).
The end of Cretaceous (65.5 Mya) is marked
by a mass extinction event where non-avian
dinosaurs, pterosaurs, marine reptiles and several
other groups disappeared (Feduccia 2003).
[Traditionally it has always been the Cretaceous–
Tertiary (K-T) extinction event. But Tertiary is an
abandoned definition with no official rank.
Instead, the terms Paleogene and Neogene are
used for the Cenozoic time interval (65.5–2.5
Mya) (ICS). Thus it should be Cretaceous–
Paleogene (K-Pg) instead (ICS)]. The rapid
extinction in turn gave rise to a lot of empty niches
that the survivors could adapt to and radiate in
(Feduccia 2003). However, there have been
arguments for a decline of species in some of
those major groups over a longer period towards
the end of Cretaceous instead of rapid extinction
(Archibald 1992). Also Hope (2002) used this
argument to explain that other birds than
Neornithes decreased or disappeared before the
end of Cretaceous. On the other hand, other claims
have been made that the absence of dinosaurs is
just a chimera of a poor fossil record at the very
end of the Cretaceous (Fastovsky et al. 2004;
Wang and Dodson 2006). If Hope’s (2002)
argument of a decline of more basal birds even
though no such event can be established, then the
loss of other birds then Neornites can either point
to a biological shift - the modern birds were
already on their way to take over from the more
“primitive” ones, or a poor fossil record.
Whether or not the extinction was rapid; the
known fossil record of Neornithes in the
Cretaceous consists of fragments and dissociated
specimens (Hope 2002). Basically every Mesozoic
specimen that was supposed to belong to
Neornithes has later been found to be of dubious
identification or age (Chiappe and Dyke 2002).
Feduccia (1995, 2003) went as long as he
disqualified all Cretaceous Neornithes, except
some putatively related taxa as he lumped together
as “transitional shorebirds” and some possible
paleognaths. According to Feduccia (2003), those
relatively few “transitional shorebirds” and
Carinatae
The Carinatae consists of Ichthyornis and
Neornithes. The group is united by five
unambiguous synapomorphies: thoracic vertebrae
with ossified connective tissue bridging the
transverse processes, intermuscular line present on
ventral surface of coracoid; acrocoracoid process of
coracoid hooked medially, ulnare V-shaped with
well-developed dorsal and ventral rami and
postacetabular portion of ilium oriented medially
(You et al. 2006 Supporting material).
The late Cretaceous (ca. 93 - 72 Mya)
Ichthyornis from North America was first described
by Marsh (1972b). It is of the size of gulls or terns
and probably inhabited the same habitats (Olson
1985). Despite the fact that it had teeth, Ichthyornis
was basically modern anatomically and is likely to
have been a strong flyer. Even though it has been
known since the end of the 1900th century, and is
quite abundant in the fossil record with several
described species, it was not until recently the
picture of Ichthyornis was clarified (Clarke 2004).
Many of the described species was shown to be the
same, Ichthyornis dispar, while others are more
closely related to neornithes than to Ichthyornis
(Clarke 2004).
Neornithes
Neornithes, to which all extant species belong, is
one of the most successful vertebrate groups of
today, consisting of ca 10000 species (Dyke and
van Tuinen 2004). However, there is an ongoing
debate concerning the origin and early evolution of
Neornithes. Did the major radiation of Neornithes
occur in the Cretaceous or did they radiate in the
early Paleogene (Dyke 2001)? The competing
hypotheses have been the paleontological against
the molecular clock model (Cracraft 2001; Hackett
et al. 2008).
9
paleognaths, survived the K-Pg bottleneck and
then, radiated and diversified within a time span of
5-10 million years to become ancestors of all major
lineages of today. This view, however, is
surrounded by some problems because there are
around 50 specimens comprising seven orders of
Cretaceous age that can be assigned to Neornithes:
Galliformes, Anseriformes, ?Charadriiformes,
Gaviiformes, ?Procellariiformes, Pelecaniformes
and Psittaciformes (Hope 2002; Dyke and van
Tuinen 2004). There are also some additional taxa
that cannot be placed to a certain order of
Neornithes, as Ceramornis, Elopteryx and
Iaceornis (Mayr 2009).
The bottleneck hypothesis is also contradicted
by molecular data analysed using molecular clock
models. At least two studies in the last few years
suggest a late Cretaceous diversification of the
major lineages of Neornithes (Ericson et al. 2006;
Hackett et al. 2008). Ericson et al. (2006) used
several fossils as calibration points in their analysis,
however, none of these was of Cretaceous age. But
if the fossils of cretaceous age as with confidence
has been assigned to extant clades of birds are plot
in the phylogenetic trees by Ericson et al. (2006)
and Hackett et al. (2008), an interesting picture
emerged. An even greater and earlier radiation of
Neornithes occurred already at the end of
Cretaceous. Similar to the timeline suggested by
Brown et al. (2008), even though they didn’t either
used any cretaceous birds in their analysis.
The division of Neornithes into two subgroups (infraclasses or superorders according to
some taxonomists) Palaeognathae and Neognathae
was made by Huxley already in 1867 based on
their palatal structure. This division is still well
supported by both morphological and molecular
data (Livezey and Zusi 2007; Hackett et al. 2008).
The further division of Neognathae into
Galloanserae and Neoaves is also well supported
(Ericson 2008) (Fig.2). Whether or not they
diverged already in the Cretaceous, most major
clades of extant birds are present in the early
Paleogene fossil record (Ericson et al. 2006).
Unfortunately the fossil record of birds is sparse
from the Paleocene and it does not really increase
until the Eocene (Dyke and van Tuinen 2004).
Based on fossils it seems that Neornithes were the
Palaeognathae
Galliformes
Galloanserae
Anseriformes
Neornithes
Land birds
Neognathae
Coronaves
1 e.g. Passeriformes, parrots, falcons and seriemas
2 e.g. Hawks, Old World vultures, ospreys, rollers,
woodpeckers, hopoes, trogones, mousebirds,owls
and cuckoo-rollers
Aquatic and semi-aquatic birds
Shorebirds
Neoaves
Caprimulgiform nightbirds, swifts and hummingbirds
Metaves
A diverse group of birds e.g. flamingos, grebes,
pigeons, doves and sandgrouse, hoatzin and tropic
birds
Fig. 2: The major lineages of Neornithes.
10
only birds that survived the K-Pg extinction
(Feduccia 2003), but there is at least one taxon that
may represent a non- neornithine lineage in the
Paleocene, Qinornis paleocenica (Mayr 2007).
This thesis
Fossil birds are extremely rare in Sweden and if
you are interested in avian paleontology you must
find international cooperation. In my case this has
mainly been possible through collaborations with
researchers in China. The thesis was planned to
rely entirely on material from the Early Cretaceous
Jehol biota, and particularly on confuciusornithids
and enantiornithids. I thus visited the Institute of
Vertebrate Paleontology and Paleoanthropology in
Beijing to examine birds belonging to these groups
at several occasions. This work resulted in the
papers I – III, but I had to give up a few other
planned studies based on this material. Most
importantly a study aiming at determining the diet
of the confuciusornithids using data from stable
isotopes was abandoned after several months work
because the preliminary results were not
conclusive. Further work in this field would
demand more time than was available within the
framework of this thesis. In order to finish the
thesis I instead have included the results from two
other studies of fossil birds from the Paleogene and
Neogene of the United States and Germany,
respectively. The North American material is a
tarsometatarsus collected from the Eocene Green
River formation and was originally thought to
belong to the anseriform species Presbyornis
pervetus. My supervisor, Per Ericson, realized that
this fossil was not anseriform and suggested me to
study it. This work resulted in paper IV. The
German specimens were collected from Miocene
deposits by Thomas Mörs at the Swedish Museum
of Natural History, along with numerous of other
vertebrate specimens. My work to describe the bird
Fig. 3: Approximate distribution of the Jehol biota.
11
fauna from this site resulted in paper V. Although
not ideal for a thesis, the wide temporal and
geographic ranges of these fossils have given me
the opportunity to study a considerably larger part
of the evolutionary history of birds than I
originally planned for.
also yielded other vertebrates, such as fish, turtles
and pterosaurs, together with a wide range of
invertebrates and plants, including angiosperms
(Chang et al. 2003). In the early Cretaceous, the
climate in the region was warm with lot of rain,
ideal for high biodiversity (Chang et al. 2003).
Even though the Jehol Biota has been studied
since the 1920s, it was not until the 1990s this part
of northeastern China became really famous
(Chang et al. 2003). The Jehol Biota is mainly
distributed in western Liaoning province, but
stretch out in northern Hebei and south-eastern
Inner Mongolia (Fig.3) (Zhou et al. 2003).
Similar biotas have been found in Kazakhstan,
Mongolia, Siberia, Japan and Korea (Zhou et al.
2003). The Jehol biota comprises of the Dabeigou,
Yixian and Jiufotang formations (Zhou 2006). The
dating for these formations have been controversial
and biostratigraphical correlations and radiometric
dates have supported either a Late Jurassic or an
Early Cretaceous age (Zhou et al. 2003). However,
re-evaluation
of
the
biostratigraphy,
palaeochronological
studies
and
further
radiometric dating, indicates a late Early
Cretaceous age for the Jehol Biota (Zhou 2006).
The U-Pb method has given an age of 130-136 Ma
for the andesite that underlay the Dabeigou
formation, which gives a maximum age for the
Jehol biota (Zhou 2006). Accordingly 40Ar-39Ar
datings gives an age of 131 Ma for the oldest part
of the Jehol Biota, the Dabeigou formation, while
the middle Yixian formation is about 125 Ma and
the youngest Jiufotang formation 120 Ma (He et al.
2004; 2006). The dating of the upper part of Yixian
formation has not yet been published and the
dating of the Jiufotang formation, which seems
younger than previously assumed, is probably not
conclusive (Zhou 2006). Altogether, this gives a
total age range from about 131–120 Ma of the
entire Jehol biota.
In all three formations the sediments were
deposited in freshwater, lacustrine environments
and weakly laminated to finely bedded siliclastic
sediments, low energy sandstones and shales
The Jehol Biota
Many of the dinosaurs and birds discussed in this
thesis have been unearthened in northeastern China
during the last 15 years. This area, which has
yielded a wide range of tremendously well
preserved fossils that together constitute the Jehol
biota has sometimes been called a “Mesozoic
Pompeii”. Particularly the theropod dinosaurs,
birds and mammals have received a lot of
attention, even in the daily press. The region has
Fig. 4: A simplified stratigraphic log of the
Dabeigou, Yixian and Jiufotang formations (not to
scale).
12
(Fig.4) (Zhou et al. 2003). These sediments are
intercalated with extrusive basalts and tuffs,
crosscut by dykes and sills, indicating a
geologically active area (Zhou et al. 2003). The
volcanoes, with the gases, ash and rocks that they
spread in the area, are not only good for
radiometric dating. They were probably also
responsible for events of mass mortality among the
organisms inhabiting the area (Zhou et al. 2003;
paper 3).
Confuciusornis individuals in the Yixian
Formation (110 out of 112 studied specimens,
Johan Dalsätt pers. obs.) are preserved as complete
skeletons, or nearly so. In contrast, 22 out of 23
specimens (Johan Dalsätt pers. obs.) collected in
the Jiufotang Formation lack all skeletal elements
in the pectoral girdle and wings (cf. Fig. 1 in paper
I). Indeed, this state of preservation is so common
in the Jiufotang Formation that local farmers and
private collectors long believed that these fossils
belonged to a different kind of bird (Zhonghe Zhou
personal communication). Although the most
obvious explanation of these observations is that
the birds in the Yixian Formation had been buried
faster than those in the Jiufotang Formation, the
taphonomic history may be more complicated.
Bickart (1984) in his experiments with extant birds
deposited at a streamside noted that the
disarticulation process of the carcasses continues
also after they have become embedded in the
ground. Nevertheless, the completely preserved
specimens in the Yixian Formation must have been
better protected from both scavengers and rapid
decomposition than those of the Jiufotang
specimens. The finds of loose pectoral girdles and
wings (with the bones in articulation) in the
Jiufotang Formation suggests that very little further
decomposition of the carcasses took place after that
these elements had become detached from the rest
of the body.
The absence of bones from the pectoral girdle
and the wings in the specimens from the Jiufotang
Formation raises another interesting issue in that
this represents a rather unusual state of
preservation of bird fossils. Previous observations
have indicated that the disarticulation of the
carcasses is similar in fossil and extant birds, and
that they follow the general stages observed in
experiments with extant birds by Schäfer (1972)
and Bickart (1984):
Mesozoic birds
The preservation of Confuciusornis sanctus
(Paper I)
In our study of Confuciusornis specimen we noted
that the birds were preserved differently. With just
a few specimens at hand this may have passed
unnoticed, but given the large number of fossils it
became clear that the Confuciusornis specimens
differed in average preservation between different
localities and formations. Most Confuciusornis
specimens have been collected in the Early
Cretaceous Yixian Formation near the village of
Sihetun in Liaoning province, northeast China,
although this taxon
recently has been reported
also from the ca 5 myr younger Jiufotang
Formation (Dalsätt et al. 2006). The Yixian and
Jiufotang formations are conformable, with
lithologically similar deposits of weakly laminated
to finely bedded siliciclastic sediments, mainly
low-energy sandstones and shales, intercalated
with extrusive basalts and tuffs and crosscut by
occasional dykes and sills (Zhou et al. 2003; Jiang
and Sha 2006).
In paper I we describe a new specimen of
Confuciusornis from the Jiufotang Formation. At
the same time we also noted that major parts of the
skeleton were missing. There is a notable
difference in the anatomical representation
between specimens collected in the Yixian and
Jiufotang Formations, respectively, suggesting that
the birds at these localities were subject to different
taphonomic processes after their death. Almost all

13
First
the
hind
limbs
disarticulated from the trunk.
become

Thereafter the skull, with or without
cervical vertebrae, separates from the
rest of the carcass.

In the third stage, the pectoral girdle and
wings separate from the trunk as one
unit, keeping the wing bones, sternum,
furcula, coracoids
and scapulae
connected.
eruption itself or following ash fall. The
explanation may instead be the burst of lethal gases
that often occur before an eruption. It is easy to
envision a large flock of birds falling to the ground
after having been exposed to poisonous gas (Storrs
L. Olson personal communication). Indeed, Guo et
al. (2003), in their analyses of inclusions from the
Sihetun excavating profile of the Jehol Biota,
found hydrofluoric acid (HF), hydrochloric acid
(HCl), sulfur dioxide (SO2) and hydrogen sulfide
(H2S). Guo et al. (2003) suggested that
hydrofluoric acid was the main factor responsible
for the mass-deaths, and this gas is responsible for
the most lethal gas-related events coupled to
volcanism (William-Jones and Rymer 2000).
However, carbon dioxide may also be involved, as
shown by the events in Cameroon in 1984 and
1986 where two bursts of carbon dioxide from
crater lakes killed almost 1800 people, more than
8000 cattle and countless of wild animals,
including birds, as far away as 23 km from the lake
(Sigurdsson 1987, Stupfel 1989, Holloway 2000).
Carbon dioxide is unfortunately impossible to
detect by the methods used by Guo et al. (2003)
(Hans Harrysson personal communication).
Besides lethal gas, mass mortality among birds
may also be explained by violent weather
associated with volcanic activity (Ericson 2000),
rapidly frozen lakes (Oliver and Graham 1994),
botulism (Leggit 1996), or cyanobacteria
(Matsunaga 1999).
The confuciusornithids differ remarkably from this
pattern in that the pectoral girdle detach from the
body before both the legs and the skull. This
suggests that the attachment of the pectoral girdle
and wings to the rest of the body was considerably
less solid in confuciusornithids than in extant birds.
In modern birds the pectoral girdle is loosely
connected to the axial skeleton via the sternum,
ribs and a series of muscles, but the poorly
developed sternum and ribs in Confuciusornis most
likely did not provide such a solid connection.
Many of the animals collected in the formations of
the Jehol Group may have died because of volcanic
activity in the area (Guo et al. 2003; Wang et al.
2000; Qi et al. 2007; Fürsich et al. 2007).
However, in comparison with other fossil sites
where ash beds indicate that volcanism has played
a significant role in the death of the animals
(Pickford 1986) the proportion of birds in the Jehol
Biota is unusally large. Of course, if
Confuciusornis was a colonial breeder many
individuals may have been trapped by a sudden
volcanic eruption, but we would then expect to find
nestlings and young birds. Confuciusornithid
specimens of these age categories are almost nonexisting, however. An interesting comparison can
be made with the explosive eruption of Mount St.
Helen in 1980, in which bird nests were buried in
ash and eggs never hatched. However, the
mortality in the adult birds was low as most of
these could leave during the eruption and ash fall
(Hayward et al. 1982). If this observation is
generally true and if volcanism had caused the
mass-mortality of confuciusornithids, their death
most likely is then not the consequence of the
The feeding of Confuciusornis sanctus
(Paper II)
Despite the large numbers of specimens of
Confuciusornis found its life style is still
unsatisfactorily known. For example, the diet of
these birds has long been discussed. Based on its
big and robust bill as seems capable of cracking
seeds (Zhou and Zhang 2003) it has been
speculated that the diet diet of Confuciusornis was
either granivorous or herbivorous. However neither
seeds nor gastrolithes has ever been reported in any
14
find of Confuciusornis, unlike in several other
Early Cretaceous birds in the Jehol biota. For
example, seeds have been found in e.g. Jeholornis
and gastrolithes in, e.g., Sapeornis (Zhou and
Zhang 2003) and Yanornis (Zhou and Zhang
2003).
In paper II we present a new specimen of a
Confuciusornis with fish remains as may spread
some light on this question. The remains of the fish
Jinanichthys formed a cluster in the ventral region
of the seventh and eight cervical vertebrae (Paper
II). The status of the remains suggested that the
fish has been consumed, processed and now
formed a pellet that was about to be regurgitated. If
Confuciusornis was a fish eater, how did it fish? In
my opinion there are two possible ways if it was an
active fisher. First, Confuciusornis may have
“foraged on the wing by seizing prey from the
surface of the water or ground” as suggested by
Elzanowski (2002). Second, it may have fished by
diving from a tree like an extant kingfisher. The
large quantities of Confuciusornis specimens found
in lacustrine environments may also suggest a life
near water and that it also searched for food in or
near these lakes. But was Confuciusornis really
capable of such actions? Both scenarios require
power and strength of the flapping flight and
rigidness of the pectoral girdle. An alternative
scenario suggested by the heavy bill may be that
Confuciusornis had an omnivorous diet and
possibly a lifestyle similar to, e.g., extant crows.
Grabauornis groups together with other
enantiornithids,
Cathayornis,
Concornis,
Neuquenornis, Gobipteryx, Pengornis and
Protopteryx. However, as shown in the
phylogenetic tree, the interrelationship within the
enantiornithids is not solved and is surrounded by a
considerable uncertainty, mostly because the
incompleteness of the data matrix used in the
phylogenetic analysis.
Even though Grabauornis is similar to
Vescornis (not included in the phylogenetic
analysis) in many characters, it can be separated
from this and other Chinese enantiornitids by
certain autapomorphic characters in the sternum
and manus. In comparison of the nearest related
enantiornithids
Vescornis,
Protopteryx,
Cathayornis and Eocathayornis projects the
caudocentral portion of the sternum farther distally
than the lateral sternal processes and the distal
expansion of the lateral trabeculum are more fanshaped. In the manus are the second and third
phalanges of digit II more robust than in Vescornis
and the length of the manus is shorter than the ulna
in contrast to Sinornis and Eocathayornis.
There are about 17 enantiornithid species
described from China. In paper 3 we compared the
brachial index between those birds. The brachial
index, the BI, is the ratio between the length of the
humerus and ulna, an index that has been shown to
correlate with flight capability and body mass in
extant birds. Values over 1.3 indicate
flightlessness. The Chinese enantiornithines BI
ranges from 0.77 to 1.25 showing that they all were
relatively good flyers. Grabauornis, with a BI of
0.95, takes a place in the middle of the range.
A new species of an Enantiornitid (Paper
III)
In paper 3 we present a new enantiornitid species
from Yixian Formation of China, named
Grabauornis lingyuanensis. The type specimen is
an almost complete skeleton preserved in a slab.
Several morphological characters show that
Grabauornis is an enantiornithid, e.g., a well
developed hypocledium of the furcula and that
metacarpal III projecting further distally than
metacarpal II. Also in the phylogenetic analysies,
Cenozoic birds
A new Eocene owl (Paper IV)
In paper IV I present a new owl, ?Prosybris
storrsi, from the Green River Formation in USA.
This formation consists of early to middle Eocene
lake deposits that crop out in western Colorado,
eastern Utah and southwestern Wyoming (Fig.5).
15
The order Strigiformes (owls) was described
by Wagler 1830 and is divided into two extant
families, Strigidae and Tytonidae, comprising
around 154 and 17 species, respectively (Sibley
and Monroe 1990). The fossil record shows that
the Strigiformes has a long evolutionary history,
spanning at least 60 mya. Furthermore, the large
morphological variation observed among these
fossils indicates that the group was taxonomically
considerably more diverse in the Paleogene than
today.
The oldest confirmed fossil strigiform is the
Paleocene Ogygoptynx wetmorei (65 – 56.5 Ma)
described from a tarsometatarsus collected in
Colorado (Rich and Bohaska 1976). Somewhat
younger is a group of specimens collected from
Paleocene deposits in France that were placed in
the fossil family Sophiornithidae (MourerChauviré 1987). This family is also recorded from
the Eocene (56.5 – 35.5 Ma). Other families to
which fossil strigiforms from Eocene deposits have
been assigned are the Protostrigidae (Wetmore
1938), Palaeglaucidae (Mourer-Chauviré 1987;
Peters 1992), and the extant Tytonidae (barn owls).
The morphological variation within the family
Protostrigidae is so large that it has been suggested
that this family possibly should be divided into two
(Olson 1985). Palaeoglaux originally was placed
in Tytonidae, but based on a find of an almost
complete individual in Germany the genus was
placed in a family of its own, Palaeoglaucidae
(Peters 1992). Five Eocene genera of Tytonidae
have been described; Necrobyas, Nocturnavis,
Palaeobyas, Paleotyto, Prosybris and Selenornis
(Mourer-Chauvirè 1987, Mlikovski 1998). The
incomplete anatomical knowledge about these taxa
raises suspicion about their validity – some of them
may be synonymous. Familial allocations may be
especially problematic when the tarsometatarsus is
lacking, as most family assignments of fossil owls
are based on this skeletal element. Another
problem has arisen as a consequence of the poor
work by some early palaeontologists – it has been
shown that some elements referred to as from owls
in fact belong to other orders of birds, or even was
first described as mammals (c.f. Mourer-Chauvirè
1983). During the Oligocene (35.5 – 23.5 Ma) the
family Tytonidae split into the two extant
subfamilies Tytoninae and Phodilinae (MourerChauvirè 1987). The most species-rich family of
owls today, Strigidae, is not known from the
Paleogene and began to radiate extensively only in
Fig. 5: The approximate distribution of the
Gren river formation
16
the Miocene (23.5 – 5.2 Ma).
?Prosybris storrsi consists of distal part of left
tarsometatarsus. It is very small, resembling a
pygmy owl (Glaucidium passerinum) in size. It
was collected by Paul McGrew around 1970 in
Wyoming, Sweetwater Co., V-58006 Bird Quarry,
Green River formation and is stored at the
Geological Museum, University of Wyoming. It
was first identified as being two parts of a hallux of
Presbyornis pervetus but Per Ericson (pers.
comm.) found it to be a wrongly glued
tarsometatarsus of an owl.
In order to resolve the taxonomy of this fossil I
compared it with the following fossil specimens:
Protostrix mimica (USNM 14874) and Eostrix
martinelli (KUMNH 16601), and casts of
Necrobyas minimus (Fo 1), Necrobyas medius
(Q.H. 150), Necrobyas rossignoli (QU 16230),
Necrobyas harpax (QU 15696), Palaeobyas
cracrafti (QU 15746), Berruornis orbisantiqui (L.
3096, BR 14571, R 4155), Sophiornis quercynus
(PQ 1202), and Palaeoglaux perrierensis (PRR
2576). In addition, I studied skeletal elements of
the following recent taxa in the collections of the
Swedish Museum of Natural History: Tyto alba,
Strix nebulosa, S. aluco, Asio flammeus, A. otus
and Aegolius funereus. An important taxon that I
did not have access to is Ogygoptynx wetmorei, but
this fossil are well described and depictured in
Rich and Bohaska (1976, 1981).
There is a general similarity between the new
fossil and the extant species of Strigidae in the
straight form of trochlea IV in lateral view. The
progressive widening of tarsometatarsus to its
distal parties is also similar, except for Strix nebula
in which it is more angulated. Furthermore,
trochlea III is longer than trochlea II in the new
fossil, Strix nebula, S. aluco and Asio flammeus,
but they are equally long in Asio otus and Aegolius
funerus.
Morphologically the new owl is most similar to the
genus Prosybris (Tytonidae). A general
characteristic for Tytonidae is the thick distal part
of trochlea IV (in lateral view) with a straight edge.
Except for this feature, which is not present in the
new fossil, the recent Tyto alba also resembles
?Prosybris storrsi in the soft transition between the
shaft and the trochlea. Tyto differs from ?Prosybris
storrsi in having trochlea II and III of the same
length; a thickened wing on trochlea II; a more
prominent trochlea III (in lateral view); and an
external intertrochlear that is less distinct, although
of the same depth. The members of the genus
Necrobyas agree with ?Prosybris storrsi in having
a soft transition from the shaft to the trochlea; a
thin wing on trochlea II; the distal part of trochlea
IV thick with a straight edge; a curvature of
trochlea in distal view. This group differs from
?Prosybris storrsi in having the trochleas II and III
of same length; the trochlea III more prominent in
lateral view; and the external intertrochlear less
distinct (although of the same depth).
The species in the genus Prosybris (Prosybris
antique and P. medius) share with ?P. storrsi the
soft transition from the shaft to the trochlea; a
trochlea III that is somewhat longer than trochlea
II; a thin wing on trochlea II; a prominence of
trochlea III in lateral view; a thick distal part of
trochlea IV with a straight edge; a slender trochlea
IV (in lateral view); and the curvature in distal
view. However, ?P. storrsi differs from Prosybris
antique and P. medius in the more distinct
thickening in the distal part of trochlea IV; and a
less deep and wide external intertrochlear. Due to
the poor preservation, the morphology of
Palaeobyas cracrafti is difficult to compare with
that of ?P. storrsi. They seem to differ in the more
distinct transition from the shaft to the trochlea in
Palaeobyas and an external intertrochlear that is
less deep.
Unfortunately, only the distal most part of the
tarsometatarsus of ?Prosybris storrsi is known.
Although many of the studied fossils are more or
less damaged, we can extrapolate the morphology
of some of the missing parts based on the size and
shape of the fractures, as well as comparison with
bones from others taxa. The present study has been
hampered by the fact that the analyses of some taxa
17
had to be based on the published descriptions and
illustrations, rather than the actual fossil. In some
cases, characters used in the literature seem more
useful in comparisons between individuals, than
for describing morphological variation within a
larger group of species. Hopefully, future finds of
more complete individuals of Paleogene owls will
give us a more complete picture.
The North American and European continents
were much closer during the Paleogene than today
(Scotese 2003) and land bridges between Europe
and Greenland may have existed during the
Palaeocene, and perhaps even the Eocene (Cox
2000). The climate during this period was warm as
shown by the finds of, for example, palm trees and
crocodiles in Paleogene deposits in Greenland
(Scotese 2003). During such conditions it is not
surprising that birds and mammals spread between
the continents. For example, out of 60 Lower
Eocene mammal genera known from Europe, 34
also occurred in North America (Hallman et al.
1994). The morphological resemblance between
the North American ?P. storrsi and certain
European species of Prosybris could then be
another evidence of the intercontinental exchange
of organisms that must have been common in the
Paleogene.
unexpected and remarkable. The fossils are found
in channel fills and consist of disarticulated, but
mostly well preserved teeth, jaws, and other bones.
The Lower Rhine Basin is a graben structure
that has served as depositional centre for the debris
of the Rhenish Massif since the Oligocene
resulting in more or less continuous stratigraphic
sequences from the Neogene. There are excellent
exposures due to the intensive brown coal strip
mining activities of the local mining company
(RWE POWER AG), which runs one of the world’s
deepest open-pit mines. Widespread lignite seams
interfinger with marine (beach) sands of the
transgressing North Sea and with floodplain and
fluvial sediments. Lignites were deposited from the
Upper Oligocene to the Late Pliocene, indicating
similar depositional environments reoccurring over
a time span of about 20 Ma (Schäfer et al. 2004).
The Middle Miocene (late Orleanian)
Hambach 6C fauna was found in a huge channel
fill within seam Frimmersdorf, which is part of the
Rhenish Main Seam (Ville Formation: Schäfer et
Birds from the Miocene and Pliocene of
Hambach, Germany (Paper V)
Berlin
Although there are several bird localities known
from the Miocene of Europe, there was only one
in northwestern Europe, the Belgian site Antwerp
(Cheneval 1996). Two decades ago a second
locality was discovered when a rich assemblage of
vertebrates was excavated in the Lower Rhine
Basin of NW Germany (Mörs et al. 2000). The
lignite-rich Neogene deposits of the Lower Rhine
Basin had long been regarded as devoid of
vertebrate fossils. The discovery of a rich
vertebrate faunas in Miocene and Pliocene strata
exposed in the Hambach opencast lignite mine,
about 35 km west of Cologne (Fig.6), was thus
Düsseldorf
Hambach
Cologne
Fig. 6: The Hambach locality.
18
al. 2004). The fauna consists of both marine and
freshwater fishes (sharks, rays, teleosts: Hierholzer
& Mörs 2003), amphibians (salamanders, anurans),
reptiles (turtles, alligators, squamates: Klein &
Mörs 2003; Joyce et al. 2004), marine and semiaquatic mammals (whale, dolphin, beavers,
mustelids) as well as terrestrial mammals (both
small and large mammals: Ziegler & Mörs 2000;
Rössner & Mörs 2001; Nemetschek & Mörs 2003;
Mörs & Kalthoff 2004), indicating an estuarine
environment containing extended coal swamps and
a large fluviatile system (Mörs et al. 2000; Mörs
2002). Sedimentological and palaeobotanical
evidence support this reconstruction (see Schäfer et
al. (2004) for further references). Based on the rich
mammal association, the Hambach 6C fauna can
be correlated with late MN 5 of the European Land
Mammal Zonation (Mörs et al. 2000; Mörs 2002).
The age of the fauna (approx. 15.5 Ma) is
supported by the very high tetrapod diversity as
well as the occurrence of tropical elements (e.g.
chameleon,
carettochelyine
turtle,
primate
Pliopithecus), documenting the “Mid-Miocene
climate optimum”. The palaeofloras found in the
Lower Rhine Basin indicate also a most tropicallike climate at the time of deposition of the
Rhenish Main Seam (Utescher et al. 2000).
In contrast to the Hambach 6C fauna, the Late
Pliocene (early Villanyian) Hambach 11/13 fauna
consists mainly of small vertebrates (Mörs 2002).
The material was collected from two smaller
channel fills within the Reuver clay (Öbel beds:
Kemna 2005). The two sites Hambach 11 and
Hambach 13 are of approximately the same age.
The fauna consists of freshwater fishes (Hierholzer
& Mörs 2003), amphibians (salamanders, anurans),
reptiles (turtles, squamates), and both semi-aqatic
and terrestrial mammals (Mörs et al. 1998),
indicating oxigenated waters and currents in what
appears a river channel setting in close association
with
lakes
or
oxbows
(Mörs
2002).
Sedimentological and palaeobotanical evidence
support this reconstruction (e.g. Schwarz & Mörs
2000; Heumann & Litt 2002; Schäfer et al. 2004;
Kemna 2005). Based on the rodents, the Hambach
11/13 fauna can be correlated with MN 16a (Mörs
et al. 1998; Mörs 2002). The Late Pliocene age
(approx. 2.5 Ma) is also visible in the depleted
tetrapod diversity, but the fauna is still
characterized by some “Tertiary” faunal elements
(e.g.
Andrias,
Latonia,
Chelydropsis,
Pliopetaurista). The biostratigraphical dating is
supported by palaeomagnetics and heavy mineral
analysis (Kemna 2005).
The most interesting bird found in Hambach
6C is a specimen of Anhinga. To distinguish
Anhingidae from Phalacrocoracidae, Miller (1966)
stated that in the proximal end of the humerus the
sulcus ligamentosus transversus on the cranial
surface is longer, deeper and extends transversely
to, but is narrowly separated from, the impressio
coracobrachialis in cormorants, while it is shorter
and only ventrally deep in anhingas. Becker (1986:
804) added: “anhingas have a strong sulcus on the
cranial face of the humerus paralleling the distal
portion of the crista pectoralis. In cormorants this
sulcus is absent, causing the crista pectoralis to
merge more smoothly with the shaft. Also,
anhingas tend to have a proportionally longer crista
pectoralis than do cormorants”. Miller’s (1966) and
Becker’s (1986) characters can all be observed in
specimen IPB HaH-4000 (Plate 1, fig. 4 in paper
V). A. pannonica was first described by Lambrecht
(1916, 1933) from the Late Miocene (MN 10) of
Tartaros, Bihar County in Romania, based on a
carpometacarpus and a cervical vertebra. The
proximal humerus from Hambach 6C fits well in
morphology and size with a humerus described by
Rich (1972: fig. 6) from the Late Miocene Beglia
Formation of Tunisia. This specimen was linked to
Anhinga pannonica by Rich (1972) by an
associated cervical vertebra that shows a strong
resemblance to the type material.
Most Old World remains of anhingas have
been assigned to A. pannonica. Besides the
Tunisian and Romanian finds mentioned above, the
species has been described from the Upper
Miocene Nagri Formation in Pakistan (Harrison &
19
Walker 1982) and from the Late Miocene (MN 9)
of Götzendorf in Austria (Mlíkovský 1992a). The
Pakistani evidence was questioned by Mlíkovský
(1992a). The fossil record of anhingas in the Old
World is poor in contrast to that in the New World,
where a number of Neogene species have been
described (e.g. Martin and Mengel 1975; Noriega
1992; Campbell 1996; Rinderknecht and Noriega
2002; Alvarenga and Guilherme 2003). The
earliest record of Anhingidae dates back to the
Early Miocene (early Hemingfordian) of the
Thomas Farm in Florida (Becker 1986). All other
anhinga fossils are much younger and from Upper
Miocene and Pliocene deposits. The new specimen
from the Middle Miocene (MN 5) of Hambach 6C
provides the oldest evidence of the family in the
Old World. It is also the northernmost occurrence
of A. pannonica. All Late Miocene findings of this
taxon come from the Pannonian Basin in Europe,
from Northern Africa and from Pakistan (if the
identification is correct). Today the anhingas live
in tropical, subtropical, and warm temperate
climate zones. Thus A. pannonica is another
“tropical” faunal element in Hambach 6C,
documenting the Mid-Miocene climate optimum. It
is remarkable that no anhinga has been found so far
in the numerous Middle Miocene sites in Southern
and Southwestern Europe (Mlíkovský 1996).
Three bones of Anatidae have been identified
from Hambach 6C. The smallest specimen, IPB
HaH-4005 (Plate 1, fig. 5 in paper V), compares
well in both size and morphology with the fossil
species Anas velox (Milne-Edwards 1867) and
Mionetta natator (Milne-Edwards 1867). Both
these small duck species are known from Miocene
deposits (MN 2 to MN 9) in Western and Central
Europe (Cheneval 2000; Göhlich 2002). However,
the fragmented status of the Hambach specimen
precludes any closer taxonomic assignment. The
coracoid, IPB HaH-4003 (Plate 1, fig. 2 in paper
V), documents a fairly big anatid species. A few
other big representatives of Miocene Anatidae
have been reported: Cygnus atavus from Southern
Germany (Fraas 1870; Mlíkovský 1992b;
Heizmann & Hesse 1995) and Anser thraceiensis
from Bulgaria (Burchak-Abramovich & Nikolov
1984) are both significantly larger, and
Cygnopterus alphonsi from France (Cheneval
1984) is both larger and more compact than the
Hambach specimen. Also a right carpometacarpus
IPB HaH-4004 (Plate 1, fig. 6 in paper V) belongs
to Anatidae, but no closer identification is possible
due to its fragmentary status.
Two galliform specimens have been identified.
Neither of them can conclusively be assigned to a
lower taxonomic level, although a proximal end of
a right femur (IPB HaH-4002, Plate 1, fig. 3 paper
V) resembles Miophasianus altus from the Middle
Miocene of Sandelzhausen (as illustrated in
Göhlich 2002) in size and superficial morphology.
The second galliform element is a coracoid (IPB
HaH-4006, Plate 1, fig. 8 in paper V).
A distal part of a right tarsometatarsus, IPB
HaH-4001, (Plate 1, fig. 10 in paper V) has been
identified as a member of Rallidae. It can be
separated
from
other
Gruiformes
and
Charadriiformes (with which it also shares some
features) based on the following characters: in
plantar view the proximal part of the trochlea III is
more asymmetric, the foramen vasculare distale is
larger, and the distal surface of the trochlea II is
concave. In lateral view the transition from the
shaft to the trochlea II is slightly more recurved
and the wing on trochlea II is less protruding.
Unfortunately the fragmentary status of this
specimen allows no closer identification than to the
family level.
From the sites Hambach 11 and Hambach 13
two anseriform and one galliform species have
been identified. The overall morphology of the two
radii, IPB HaR-4002 (Plate 1, fig. 1 in paper V)
(Hambach 11) and IPB HaR-4100 (Plate 1, fig. 7 in
paper V) (Hambach 13), shows that they belong to
Anatidae. A furcula, IPB HaR-4000 (Plate 1, fig. 9
in paper V) (Hambach 11), is from a galliform bird
as indicated by the v-shaped angle between the
clavicles and the well-developed apophysis
furculae. Based on the observations that the
20
apophysis furculae in medial view follows the
clavicles in a straight line the two extant galliforms
families Megapodiidae and Cracidae can be
excluded. In these families the apophysis furculae
bends downward and meets the clavicles at an
angle. Among fossil families of galliforms the
furcula is more U-shaped in Gallinuloididae
(Lambrecht 1933). No furcula has been described
from
the
families
Paraortygidae
and
Quercymegapodiidae, therefore they cannot be
excluded (Mourer-Chauviré 1992). However, these
families have not been reported from any deposits
younger than Upper Oligocene (Bochenski 1997)
indicating an environment consisting of rivers and
lakes in a cooler environment (Mörs 2002). The
very few avian species (only three) also support the
view of a climate change in comparison to
Miocene.
pectoral girdle of Confuciusornis was less fixed to
the body compared to the condition in modern
birds where this part of the body is the last to
detach from the rest of the carcass. The different
preservation in these geological formations may be
explained by differences in the mean time between
death to burial – shorter in the Yixian formation
and longer in the Jiufotang formation.
In paper 2 we describe a specimen of
Confuciusornis with fish remains formed as a
pellet found in the bird’s alimentary system,
approximately where one would expect a crop. The
diet of Confuciusornis is unknown but it has been
suggested to be herbivorous or granivorous.
Although we cannot be conclusively sure that this
pellet was a food item it provides the first
indication of what kind of food this bird ate.
In paper 3 we describe a new Chinese
enantiornithid bird, Grabauornis lingyuanensis.
The Enantiornithites was probably the most species
rich and successful bird group in the Cretaceous.
Even though there perhaps is nothing special with
the ecological adaptations of Grabauornis as can
be deducted from the fossil remains it is interesting
in other aspects. It testifies to the large diversity of
enantiornithine birds in the Cretaceous, which
shows that the evolution towards modern birds was
not as straight as one may think. Some bird groups
were very successful in the Cretaceous and lived
alongside non-avian dinosaurs and pterosaurs. The
Chinese enantiornithes were also rather good flyers
as indicated by their brachial indices (the ratio
betweeb the lengths of humerus and ulna) that
range between 0.77 to 1.25 (modern birds with an
index below 0.80 is characterised as “strong
flapping fliers” while birds with an index above
1.30 is considered flightless).
The end of the Cretaceous is marked by a mass
extinction event where dinosaurs, pterosaurs and
many other animals and plants disappeared. Even
the birds were reduced and several groups
disappeared, among them the enantiornitids.
However, several groups survived and radiated in
the Paleogene. As far as is known today, all
Conclusions
The evolution of birds from the “primitive”
Archaeopteryx until the present diversity is long
and complex. Our understanding of this process
has improved tremendously over the last 15 years.
This is mostly thanks to the discovery of many new
fossils from all over the globe, and not least those
from the early Cretaceous Jehol biota in China.
New insights into the radiation of modern groups
around the Cretaceous-Paleogene boundary have
also come from molecular systematics.
This thesis consists of five studies of fossil
birds that span a considerable part of the avian
evolution, both in time and space. In paper 1 and 2
we present new information about the early
Cretaceous Confuciusornis sanctus from China, the
possibly most well-represented Mesozoic bird in
the fossil record. In paper 1 we make comparisons
between the preservation status of Confuciusornis
specimens in two different geological formations.
In the Yixian formation the specimens are mostly
complete, while in the Jiufotang formation the
pectoral girdle and wings are almost always
missing. This observation indicates that the
21
surviving bird groups belong to a single
evolutionary lineage, Neornithes.
The owls is one of the successful groups that
radiated in the Paleogene and also is rather
common in the fossil record. In paper 4 we
describe a new, small Eocene owl, ?Prosybris
storrsi from the Green River Formation in
Wyoming. Unfortunately, the distal part of
tarsometatarsus is the only part of ?Prosybris
storrsi found. Although being from North
America, ?Prosybris storrsi is most similar to
species in the Paleogene of Europe. At this time
the North American and European continents were
situated much closer to each other than today.
Several groups of mammals and birds spread
between the continents and ?Prosybris storrsi is
another evidence for this faunal exchange.
In the following million years, the birds
evolved towards forms that we recognise today. In
paper 5 we list a number of Neogene fossils from
Germany belonging to modern bird groups, such as
the Anatidae, Galliformes and Rallidae.
Unfortunately, all of those specimens are rather
poorly preserved and it is not possible to determine
them closer than to the family level. However, the
most interesting specimen in this collection is from
an anhinga, family Anhingidae. In size, proportions
and morphology, this single bone, a humerus,
agrees with the fossil species Anhinga panonica.
This is the oldest anhinga reported from Europe
and it confirms the tropical climate in Europe
during this period.
These five papers constitute a few steps further
in increasing our understanding of the earliest
evolution of birds. The ever growing fossil record
along with implementation of new techniques will
eventually result in a more complete picture of the
fascinating history of birds.
Acknowledgement
I would like to acknowledge all those who have
been involved and helped me during my work on
the papers which make up this thesis. First of all I
would thank my supervisor Per Ericson (Swedish
Museum of Natural History) for supporting the
work and guide me into the world of paleoornithology, but also for his patience with my
badly scientifically written English.
Otto Hermelin for his support in beginning of
the process (application etc.) and support in my
teaching as has been part of my PhD. studies. A
part that has been very funny and that I wouldn’t
be without.
For the Chinese part of the thesis I particularly
want to thank Zhonghe Zhou and Fucheng Zhang
on IVPP (The Institute of Vertebrate Paleontology
and Paleoanthropology) in Beijing. They let me
cooperate with them and study their outstanding
specimens and participate in their fieldwork.
Meemann Chang and Zhang “chairman” Jianyong
for joyful and interesting discussions spanning over
such different subjects as paleontology, food,
culture, politics and other misunderstandings
between east and west, discussions often ending in
laughs. I will of course not either forget the rest of
the staff on IVPP that always has been very
friendly and helped my, even though we couldn’t
understand each other. Due to those trips to China I
have got new insights into a country I didn’t know
much about earlier. It has fascinated me
tremendously and has also given me completely
new experiences when it comes to food. What
actually are eatable and how different “stuff” can
be cooked. Altogether very pleasant acquaintance
and unforgettable memories.
I also want to thank Thomas Mörs (Department
of Palaeozoology, Swedish Museum of Natural
History) for his friendly manner and patience with
the Hambach paper.
22
In addition, I would like to thank Jan Ohlson,
Magnus Gelang, Martin Irestedt and Ulf Johansson
for interesting discussions about the more modern
part of the birds evolution.
Peter Nilsson, Peter Mortensen, Ingrid
Sederholm, Olavi Grönvall, Bo Delling, Göran
Frisk, Nisse Jacobsson, Erik Åhlander, for
interesting discussions in al kind of subjects
around the coffee table, that has contributed to my
comfort at the Department of Vertebrate Zoology
(Swedish Museum of Natural History).
I have probably forgotten several people as has
supported me both direct and indirect, thanks to
you all. Financial support for this study was
provided by Stockholm University, Swedish
Research Links programme from the Swedish
Research Council, the Major Basic Research
Projects (2006CB806400) of MST of China and
the National Natural Science Foundation of China.
Svensk sammanfattning
Det var Linné som först använde sig av
namnet Aaves (fåglar) 1758. Han visste inget om
fossila fåglar och menade således endast de
befjädrade djur vi ser idag, det vill säga
krongruppen. Det var vad Gauthier (1986) också
föreslog när han etablerade namnet Avialae för
både levande och utdöda grupper. Den
definitionen har dock inte slagit igenom och en
genomgång av de senaste årens litteratur på
området visar att de flesta författarna använder
namnet Aves i ett bredare perspektiv, vilket
inkluderar de fossila djuren. Själv föredrar jag att
inkludera allt som kan kallas fågel, både levande
och utdöd, inom namnet Aves (fig.1). Fåglarnas
ursprung och sökandet efter deras närmaste
släktingar har under lång tid varit orsak till heta
debatter. Fiskar, sköldpaddor, ödlor, flygödlor,
fågelhöftade dinosaurier och till och med
däggdjur har i olika sammanhang förts fram som
fåglarnas närmaste släktingar (Gauthier 1986;
Padian and Chiappe 1998; Chiappe 2004). Några
de mer långlivade och populäraste teorierna har
dock varit “thecodont”, eller archosauriemorfhypotesen (Padian and Chiappe 1998) och
theropod- (ödlehöftade dinosaurier) hypotesen
(Padian and Chiappe 1998).
Archosauriemorf-hypotesen föreslogs så tidigt
som på 1870 talet. Men det var 1926 som den
verkligen fick sitt genomslag med den danska
paleontologen Heilmanns bok The origin of birds
(1926). Hypotesen kom att gälla för en lång tid.
Heilmann ansåg att fåglarna inte kunde ha
utvecklats ur dinosaurierna, något som Huxley
föreslagit 1868. Anledningen till detta vara att hos
dinosurierna hade inte nyckelbeneen smält samman
till det för fåglarna så karakteristiska önskebenet
(Huxley 1868; Heilmann 1926). Nyckelben var vid
den tiden bara kända hos archosaurierna (Heilmann
1926). Men bara några år efter att Heilmann
publicerat sin bok kom de första rapporterna om
önskeben även hos theropoder och idag är det en
väl etablerad synapomorfi för dessa djur (Camp
1936; Chiappe 2004). Archosauromorf- hypotesen
stod sig dock och det var inte förrän på 1970-talet,
efter Ostroms (1976) jämförelse mellan
Archaeopteryx och theropoden Deinonychus, som
idén kom tillbaka (Chiappe 2004). Sedan dess har
en lång rad välbevarade fossil hittats och samtliga
pekar de i samma riktning: fåglarnas närmaste
släktingar är de theropoda dinosaurierna (Gauthier
1986; Clark et al. 2002; Mayr et al. 2005; Senter
2007). Vid ett första ögonkast kan det verka svårt
att se släktskapet mellan dessa djur och moderna
fåglar, men några av de osteologiska karaktärer
som återfinns hos båda är: nyckelbenen
sammansmälta till ett önskeben, ihåliga ben,
23
bröstbenet, förlängning av armarna, tre fingrar
(Chiappe 2004). Det är inte bara osteologiska
likheter som pekar på ett theropodursprung. Det
finns också likheter i äggskalens mikrostruktur
(Chiappe 2004), kroppsställningen vid vila och
ruvning (Chiappe 2004; Xu and Norell 2004),
genomets storlek (Organ et al. 2007) och, det
kanske det viktigaste av allt, fjädrar.
Fjädrar är döda hornbildningar som växer ur
fjädersäckar i fåglarnas skinn (Prum 1999).
Länge var fjädrar en synapomorfi för ordningen
fåglar (Aves), men vi vet nu att de återfinns även
hos många grupper av dinasaurier. Man har
ansett att fjädrarna har utvecklats ur reptilfjäll
men nya molekylära och utvecklingsstudier pekar
istället på att de utvecklats ur hårsäckar (Prum
2002). De olika stegen av fjäderutveckling kan
studeras hos olika grupper av dinosaurier, från
enklare strukturer hos t.ex. Sinosauropteryx och
Dilong, via mer avancerade hos t.ex.
Caudipteryx, till riktiga flygfjädrar hos
Microraptor (Norell and Xu 2005; Chen et al.
1998, Xu et al. 2004, Ji et al. 1998, Xu et al.
2003). Hos andra dinosaurier finns indirekta
bevis för teorin om hårsäckar som ursprung
genom fjäderinfästningsknölar som hittats hos
t.ex. Velociraptor (Turner et al. 2007).
Uppkomsten av flygförmåga är nästan lika
omtvistad som fåglarnas ursprung. Det finns två
motstridiga åsikter, ”tree-down” teorin och
”ground-up” teorin. Huvudfrågan är varför och
hur flaxandet uppstod (Bock 1986; Ostrom
1986). ”Tree-down” teorin hävdar att fåglarnas
förfäder blev trädlevande och senare utvecklade
flygförmågan i tre steg från att hoppa mellan
träden, via glidflygning till aktivt flaxande
(Chatterjee 1997). Denna teori kommer först och
främst från archosaurie-förespråkarna som
hävdar att flygförmågan måste ha utvecklats med
hjälp av gravitationen (Feduccia 2002). ”Groundup”teorins förespråkare hävdar å sin sida att det
första steget mot aktiv flykt var att man ökade
farten under löpning genom att flaxa med
vingarna (Dial 2003). De flesta som har stött
denna teori har varit förespråkare för ett ursprung
bland dinosaurierna och som hävdat att dinosaurier
inte klättrade i träd (Feduccia 2002; Chiappe
2005). Fynd av små och eventuellt trädlevande
dinosaurier
som
Microraptor,
Anchiornis,
Epidendrosaurus och Epidexipteryx har dock fått
vissa forskare att ändra åsikt (Xu et al. 2003; Xu et
al. 2009; Zhang et al. 2002; Zhang et al. 2008). Det
är dock tveksamt om dessa djur verkligen levde i
träd eftersom klorna inte tycks ha varit anpassade
för detta, kanske var de alla marklevande (Glen
and Bennet 2007).
Jeholbiotan
Jeholbiota är samlingsnamnet för den fauna och
flora av vilka fossil påträffats i geologiska lager i
Kina daterade till tidig Krita. Många dinosaurier,
fåglar
och
däggdjur
har
fått
mycket
uppmärksamhet i forskarvärlden och ofta även i
dagspressen. Området har även bidragit med andra
vertebrater som fiskar, sköldpaddor och flygödlor,
samt en lång rad evertebrater och växter (Chang
2003) och det kallas populärt för ett ”mesozoiskt
Pompeji” (Zhou et al. 2003). Huvudområdet finns i
provinsen Liaoning men lager med lämningar från
Jeholbiotan påträffas också i Hebei och Inre
Mongoliet (fig.3). Liknade biotor har även hittats i
Kazakstan, Mongoliet, Sibirien, Japan och Korea
(Zhou et al. 2003). Jeholbiotan påträffas i de tre
geologiska formationerna Dabeigou, Yixian och
Jiufotang vilka med hjälp av biostratigrafi och
radiometriska dateringar daterats till en ålder av
tidig krita (ca. 131–120 miljoner år) (Zhou et al.
2003; Zhou 2006). De fossilförande sedimentära
bergarterna (skiffrar och sandsten) är avsatta i
limnisk miljö. De innehåller också lager av basalter
och tuffer samt är genomkorsade av kanaler och
intrustioner som visar att området var geologiskt
aktivt (fig.4) (Zhou et al. 2003). Vulkanerna har
inte bara bidragit till att öka möjligheten att datera
lagren, de bär troligen också ansvaret för den
massdöd som belagts i området (Zhou et al. 2003;
papper 3).
24
Jag har vid flera tillfällen haft förmånen att
studera fynd från Jeholbiotan på Institute of
Vertebrate Paleontology and Paleoanthropology i
Beijing vilket resulterat i artiklarna 1-3.
Confuciusornithidae
Den vanligaste krittida fågeln är Confuciusornis
sanctus som hittills endast påträffats i Kina. Exakt
hur många fossil som hittats är inte känt eftersom
många exemplar har försvunnit på den svarta
marknaden, men det kan vara så många som 2000
stycken.
De
andra
två
arterna
inom
Confuciusornithidae, Eoconfuciusornis zhengi och
Changchengornis hengdaoziensis, är dock bara
kända från ett exemplar vardera (Zhang et al. 2008;
Chiappe et al. 1999). Det har föreslagits att
Confuciusornis består av flera arter som C.
sanctus, C. chuonzhous, C. dui, C. suniae och C.
feducciai (Hou 1997, 1999; Zhang et al. 2009).
Enda skillnaden mellan dessa arter är dock
storleken och denna går inte att använda eftersom
den kan bero på ålders- eller könsvariation
(Chiappe et al. 2008). Det finns alltså inga direkta
bevis för fler än en art Confuciusornis sanctus,
även om C. dui och C. feducciai kan komma att
visa sig vara valida. En möjlig könsskillnad mellan
olika exemplar av Confuciusornis kan vara de
långa stjärtfjädrar som finns hos vissa individer
(Hou et al. 1996).
Confuciusornis har hittats i både Yixian (125
Mya) och Jiufotang (120 Mya) formationerna
(Wang et al. 2001; He et al. 2004), dock med stora
variationer i hur de har bevarats. I Yixian är de i
stort sätt alltid kompletta, ofta med fjäderavtryck,
medan i Jiufotang saknas nästan alltid bröst och
vingar (artikel 2). Hos moderna fåglar är bröst- och
vingpartiet det sista som avskiljs från ett
sönderfallande kadaver, långt efter att huvud och
ben ramlat bort (artikel 2). Detta kan tyda på att
Confuciusornis inte hade ett lika utvecklat
bröstparti som de moderna fåglarna, men hur
mycket detta påvekat flygförmågan hos
Confuciusornis är svårt att veta. Däremot så råder
det ingen tvekan om att Confuciusornis verkligen
kunde flyga. Ytterligare en fråga som varit svår att
besvara är av vilken föda som Confuciusornis
livnärde sig. Den kraftiga näbben kan ha varit
lämplig för att öppna frön, men varken frön eller
Archaeopteryx och andra svansförsedda
fåglar
Archaeopteryx, som betyder gammal fjäder
eller vinge, är hittad i senjurassiska lager i södra
Tyskland (Chiappe 2007). Det första fyndet
skedde redan 1860 och har sedan dess utökats
med nio till. Eftersom Archaeopteryx är det första
fyndet av ett fjäderklätt djur är det också med
detta fossil man jämför alla andra tidiga fåglar
och närbesläktade dinosaurier. Archaeopteryx,
med sin svans, tänder och kloförsedda fingrar,
hade troligen blivit klassificerad som en
dinosaurie om det inte varit för fjädrarna
(Chiappe 2007). Dessa är modernt asymmetriskt
anpassade för flygning och Archaeopteryx kunde
troligen lyfta från marken av egen kraft (Chiappe
2007).
Jeholornis prima är en svansförsedd fågel från
tidig krita hittad i Kina som delar vissa karaktärer
med Archaeopteryx men där andra är mer
utvecklade, t.ex. bröstbnet och vingen (Zhou and
Zhang 2003). Hos Zhongornis haoae, även den
från krittida lager daterade i Kina, kan första
steget mot formandet av en pygostyl möjligen
iakttas samt en eventuell reduktion av fingrarnas
ben (Gao et al. 2008).
Pygostylia
Pygostylia är som namnet antyder en grupp
som förenas av att de delar förekomsten av en
pygostyl. Pygostylen är en förkortning och
sammansmältning av svansen och utgör
infästningen för stjärtfjädrarna.
25
gastroliter har rapporterats hos Confuciusornis,
medan sådana påvisats hos såväl Jeholornis
(frön) och Sapeornis (gastroliter) (Zhou and
Zhang 2003). I artikel 1 beskriver vi ett fynd av
en Confuciusornis med rester av fisken
Jinanichthys som bildar en klump i halsregionen.
Mycket talar för att fågeln har ätit och processat
fisken och nu var på väg att stöta upp resterna i
form av en spyboll (artikel 1).
simma, men de flesta har varit anpassade för att
leva i träd (Hou et al. 2004; Chiappe 1993, 2007).
Enantiornithidernas fylogenetiska position har
varit omdebatterad men flertalet släktskapsanalyser
har på senare tid placerat dem mellan
Confuciusornithidae
och
Oornithothoraces
(Chiappe and Walker 2002; Zhou et al. 2008).
I artikel 3 presenteras en ny art av
enantiornithid. Den är hittad i Kina och är från
tidig krita (Yixian formationen). Den liknar andra
kinesiska enantiornithder men skiljer sig från dessa
på vissa karaktärer i bröstbenet och i handen.
Ornithothoraces
Ornithothoraces
inkluderar
den
sista
gemmensamma förfadern för enantiornithiderna
och Ornithuromorpha och alla dess avkomma.
Ornithuromorpha
Ornithuromorpha definierades av Chiappe men
det är få författare som använder termen. Vissa
forskare använder Ornithurae i den här, något
vidare, definitionen. Archaeorhynchus från Yixian
formationen i Kina är ännu så länge den både
äldsta och mest basala ornithuromorfen. De mer
utvecklade karaktärerna i jämförelse med mer
”primitiva” fåglar är bl.a. ett mer U-format
önskeben och mer utvecklat bröstben.
Enantiornithes
Som grupp var enantiornithiderna troligen den
mest diversa under Krita och kanske under hela
Mesozoikum. De levde under hela kritaperiden.
Den som påträffats i de äldsta geologiska lagren
är Protopteryx (ca. 131 miljoner år), och en av
dem som hittats i de yngsta är Avisaurus (70.665.5 miljoner år) (Zhou 2004; Brett-Surman and
Paul 1985). Fler än 25 arter har beskrivits (flera
är ännu ej namngivna) och de har rapporterats
från alla kontinenter förutom Antarktis (Chiappe
and Walker 2002). Där finns också rapporter om
embryon och juveniler (Chiappe et al. 2007;
Zhou and Zhang 2004). Enantiornithiderna levde
i flera olika slags miljöer och uppvisar olika
anpassningar. De flesta fynden är gjorda i
insjösediment i Kina och Spanien, men det finns
även fynd från marina och torra inlands miljöer
(Chiappe 2007; Chiappe et al. 2001, 2002). De
flesta enantiornithiderna var stora som moderna
sångare men de största kunde ha ett vingspann på
en meter (Zhou et al. 2008; Chiappe 1996). Vissa
hade långa näbbar och ben som påminer påminde
om dagens vadare. Andra hade näbb och tänder
för att fånga fisk eller fötter anpassade för att
Ornithurae
Namnet Ornithurae etablerades redan 1866 av
Haeckel och betyder fågelsvans, d.v.s. en svans
kortare än lårbenet eller en svans kortare än
skenbenet och med pygostyl (Gauthier and Queiroz
2001). Den duvstora Gansus från tidig krita i Kina
är ännu så länge den äldsta kända Ornithuraen
(You et al. 2006).
Under lång tid var Hesperornis och Ichthyornis,
förutom Archaeopteryx, de enda kända mesozoiska
fåglarna. Hesperornis hittades och namngavs redan
1872 av Marsh (Marsh 1872a). De levde i slutet av
Krita och var anpassade till ett marint liv på
samma sätt som dagens pingviner, d.v.s. de kunde
inte flyga. De hade relativt stor spridning och har
hittats i Mongoliet, Europa (Sverige) och
Nordamerika (Rees and Lindgren 2005).
26
åtminstone ca.omkring 50 relativt säkra krittida
fossil av Neornithes tillhörande åtminstone sju
ordningar (Hope 2002).
Neornithes delas upp i två väl definierade
grupper, paleognater och neognater (Hackett et al.
2008).
Paleognaterna består av kända fåglar som t.ex.
strutsar, nanduer och kiwi som till sammans är ca
60 arter (del Hoyo et al. 1992). Däremot så finns
inga säkra paleontologiska fynd äldre än Paleocene
(Houde 1988). Neognaterna i sin tur delas upp i
Galloanserae (änder och hönsfåglar) och Neoaves
(övriga) (fig. 2). Denna indelning stöds både
morfologiskt och molekylärt (Mayr 2009).
I artikel 4 beskriver vi en ny uggla (?Prosybris
storrsi) från den eocena Green River formationen i
USA (fig. 5). Det är en liten fågel och i storlek
ligger den nära den moderna sparvugglan. I
släktskapsjämförelser hamnar den nära samtida
arter som levde i Europa. Under Miocen låg
Europa och Nordamerika betydligt närmare
varandra än idag (landbryggor har tidvis
förekommit) och klimatet var milt. Det är alltså
inte konstigt att fåglar och däggdjur kunde ta sig
från en kontinent till en annan. Av 60 europeiska
däggdjur från Paleogene, är 34 också kända i
Nordamerika. Fyndet av den nya ugglan stärker
således bilden av det utbyte av djur mellan
kontinenterna som tycks skett under denna tid.
I artikel 5 presenteras en lista på fåglar
(andfåglar, hönsfåglar, rallar och ormhalsfåglar)
funna i miocena och pliocena lager från Hambach i
Tyskland (fig. 6). De flesta miocena fynden (inte
hönsfåglarna) representerar grupper anpassade för
ett liv i vatten. Ormhalsfågeln (Anhinga
pannonica) är dessutom det äldsta fyndet i Europa
och stärker bilden av ett Europa som under Miocen
präglades av ett tropiskt klimat. De fåtaligare
pliocena fynden, änder och hönsfåglar, visar att
diversiteten fortfarande var hög.
Carinatae
Carinatae består av Ichthyornis och
Neornithes. Ichthyornis var stor som en mås eller
tärna och levde troligen på samma sätt (Olson
1985). Trots att den varit känd så länge är det inte
förrän nyligen som vi fått en tydligare bild av
denna fågel. Bland annat har flera beskrivna arter
visat sig vara en och samma, Ichthyornis dispar
(Clarke 2004). Trots att den hade tänder var
Ichthyornis anatomiskt modern på många sätt och
troligen en duktig flygare.
Neornithes – moderna fåglar
Neornithes, de moderna fåglarna är en av de
mest framgångsrika vertebratgrupperna idag och
består av ungefär 10 000 arter (Dyke and van
Tuinen 2004). Deras ursprung och tidiga
utveckling är dåligt kända. En av huvudfrågorna
har varit huruvida de utvecklades redan under
Krita eller om radiationen kom igång först i
Paleogene, efter det stora massutdöende som
skedde för 65 miljoner år sedan (Dyke 2001). De
hypoteser som stått mot varandra kan beskrivas
som den paleontologiska mot den molekylära
klockmodellen (Cracraft 2001; Hacket et al.
2008). Den paleontologiska innebär att det har
varit väldigt få krittida fynd av moderna fåglar
medan de paleogena är desto rikligare. Slutsatsen
har varit att de moderna fåglarna fick sin chans
först efter massutdöendet (Feduccia 1995). Den
molekylära hypotesen däremot har pekat på en
ganska kraftig radiation redan i slutet av Krita.
De senaste rönen är däremot något mer
nyanserade. Dessa pekar på en viss radiation i
slutet av Krita men att den stora radiationen
skedde i början av Paleogene (Ericson et al.
2006; Hackett et al. 2008). Dessutom finns det
27
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