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

1

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.

An introduction to the

evolution of birds

2

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

3

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 wing-

assisted 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.

4

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

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

5

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 2-3-

2-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.

Pygostylia - short tailed birds

The clade Pygostylia is supported by four

synapomorphies: absence of hyposphene-

hypantrum; 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

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

6

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).

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”

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

7

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

8

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 mid-

Maastrichian (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

9

several taxa are based on isolated elements (Rees

and Lindgren 2005).

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).

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

10

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 sub-

groups (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

Neornithes

Galloanserae

Neognathae

Palaeognathae

Neoaves

Land birds

Coronaves

Metaves

Galliformes

Anseriformes

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

Caprimulgiform nightbirds, swifts and hummingbirds

A diverse group of birds e.g. flamingos, grebes, pigeons, doves and sandgrouse, hoatzin and tropic birds

Fig. 2: The major lineages of Neornithes.

11

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).

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

This thesis

Fig. 3: Approximate distribution of the Jehol biota.

12

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.

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

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 40

Ar-39

Ar

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

Fig. 4: A simplified stratigraphic log of the

Dabeigou, Yixian and Jiufotang formations (not to

scale).

13

(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).

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

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):

First the hind limbs become

disarticulated from the trunk.

14

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.

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 non-

existing, 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

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 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

15

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.

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,

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 fan-

shaped. 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.

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).

16

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 (Mourer-

Chauviré 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 (Mourer-

Chauvirè 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

17

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

18

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.

Birds from the Miocene and Pliocene of

Hambach, Germany (Paper V)

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

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

Fig. 6: The Hambach locality.

Cologne

Düsseldorf

Berlin

Hambach

19

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 semi-

aquatic 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 tropical-

like 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 &

20

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

21

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.

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

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

22

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.

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 paleo-

ornithology, 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.

Acknowledgement

23

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.

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 archosauriemorf-

hypotesen (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,

Svensk sammanfattning

24

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). ”Ground-

up”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).

25

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.

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.

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

26

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).

Ornithothoraces

Ornithothoraces inkluderar den sista

gemmensamma förfadern för enantiornithiderna

och Ornithuromorpha och alla dess avkomma.

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 (70.6-

65.5 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

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.

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.

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).

27

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

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.

28

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