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