Not yet mentioned (my regular general queries didn't find it when it went online a few days ago it seems):
Introduction
Feathers are one of the most unique characteristics of modern birds and represent the most complex and colourful type of skin derivate within vertebrates, while also fulfilling various biological roles, including flight, thermal insulation, display, and sensory function. For years it was generally assumed that the origin of flight was the main driving force for the evolution of feathers. However, various discoveries of dinosaur species with filamentous body coverings, made over the past 20 years, have fundamentally challenged this idea and produced new evolutionary scenarios for the origin of feathers.
This book is devoted to the origin and evolution of feathers, and highlights the impact of palaeontology on this research field by reviewing a number of spectacular fossil discoveries that document the increasing morphological complexity along the evolutionary path to modern birds. Also featuring chapters on fossil feather colours, feather development and its genetic control, the book offers a timely and comprehensive overview of this popular research topic.Â
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Christian Foth (2020)
Introduction to the Morphology, Development, and Ecology of Feathers.
In: Foth C., Rauhut O. (eds) The Evolution of Feathers: 1-11
DOI:
https://doi.org/10.1007/978-3-030-27223-4_1https://link.springer.com/chapter/10.1007/978-3-030-27223-4_1Feathers are a characteristic of modern birds that differentiate them from all other extant non-avian reptiles. The origin of feathers goes back deep into the Mesozoic, preceding the origin of flight, and early protofeathers were probably present in the ancestral Tetanurae, Dinosauria, or even Ornithodira. Among extant vertebrates, the feathers of modern birds are morphologically the most complex integumentary structure with enormous shape diversity resulting from a hierarchical organization of repetitive morphological and developmental modules. In this chapter, the morphological ground patterns of modern feathers, their underlying developmental processes, and the biological roles of different feather types are reviewed.
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Gee-Way Lin, Ang Li & Cheng-Ming Chuong (2020)
Molecular and Cellular Mechanisms of Feather Development Provide a Basis for the Diverse Evolution of Feather Forms.
In: Foth C., Rauhut O. (eds) The Evolution of Feathers: 13-26
DOI:
https://doi.org/10.1007/978-3-030-27223-4_2https://link.springer.com/chapter/10.1007/978-3-030-27223-4_2Feathers are considered to be one of the most complex integumentary organs. The diverse morphology of a feather has made it a popular platform for investigating the cellular and molecular mechanisms for regional specificity, periodical patterning, organ shaping, and regeneration over the past two decades. Paleontological findings on feathered dinosaurs and Mesozoic birds have led to the identification of some unusual and unexpected intermediate or extinct feather forms, which can all be categorically called âprotofeathersâ. From the primitive protofeathers, every evolutionary novel step increases feather diversity and help the species adapt to diverse eco-spaces. Although it is compelling to trace the origin of morphological evolution, the proposed evolutionary transformations are constrained by the limited understanding of developmental mechanisms. In this chapter, we review some recent advances toward the understanding of the molecular and cellular mechanisms of these processes. We discuss how these mechanisms provide a basis for evolutionary novel steps to occur, as well as how the complexity of feather types increases successively. The important questions include the regional specification of feather tracts, the formation of periodically arranged feather buds and their anterior-posterior orientation, the formation of feather follicles, and the establishment of cyclic regeneration with clustered stem cells and dermal papilla. Within each follicle, the cylindrical feather filament undergoes branching morphogenesis. Because each follicle can have its own form, even on the same bird, complexity emerges with differential arrangement of radially symmetric barb branches, rachis and bilateral symmetric feather forms, medial-lateral asymmetric feather vanes, and pennaceous/plumulaceous regionalization along the proximal-distal axis. Each feather form has a functional implication for adaptation, and different forms can be produced under hormonal and seasonal regulation. Thus, collectively, the enormously diverse plumage patterns (the increased biological traits) of the avian integument are made possible by adaptive evolution.
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Oliver W. M. Rauhut & Christian Foth (2020)
The Origin of Birds: Current Consensus, Controversy, and the Occurrence of Feathers.
In: Foth C., Rauhut O. (eds) The Evolution of Feathers: 27-45
DOI:
https://doi.org/10.1007/978-3-030-27223-4_3https://link.springer.com/chapter/10.1007/978-3-030-27223-4_3Research in the late 1900s has established that birds are theropod dinosaurs, with the discovery of feather preservation in non-avian theropods being the last decisive evidence for the dinosaur origin of this group. Partially due to the great interest in the origin of birds, more phylogenetic analyses of non-avian theropod dinosaurs have probably been published than any other group of fossil vertebrates. Despite a lot of uncertainty in the exact placement of many taxa and even some major clades, there is a remarkable consensus about the hierarchical position of birds (here used for the total group, Avialae) within theropod dinosaurs. Thus, birds are part of Paraves, together with such well-known theropod groups as dromaeosaurids and troodontids; Paraves are part of Maniraptora, which furthermore include Oviraptorosauria, Therizinosauria, and Alvarezsauroidea; Maniraptora belong to Maniraptoriformes, which also include Ornithomimosauria; Maniraptoriformes are a subclade of Coelurosauria, to which Tyrannosauroidea and some other basal taxa also belong; Coelurosauria are part of Tetanurae, together with Allosauroidea and Megalosauroidea; finally, Tetanurae are a subclade of Theropoda, which also include Ceratosauria and Coelophysoidea.
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Pascal Godefroit, Sofia M. Sinitsa, Aude Cincotta, Maria E. McNamara, Svetlana A. Reshetova & Danielle Dhouailly (2020)
Integumentary Structures in Kulindadromeus zabaikalicus, a Basal Neornithischian Dinosaur from the Jurassic of Siberia.
In: Foth C., Rauhut O. (eds) The Evolution of Feathers: 47-65
DOI:
https://doi.org/10.1007/978-3-030-27223-4_4https://link.springer.com/chapter/10.1007/978-3-030-27223-4_4Recent studies on the origin of feathers have been stimulated by discoveries of feather-like structures in various nonavian theropod dinosaurs from Late Jurassic to Early Cretaceous deposits in northeastern China. Filamentous integumentary structures are also known in two ornithischian dinosaurs from China, but whether these filaments form part of the evolutionary lineage of feathers has been controversial. Kulindadromeus zabaikalicus, a basal neornithischian dinosaur from the Jurassic of Siberia, preserves diverse integumentary structures, including monofilaments, more complex protofeather structures and scales on its tail and distal parts of its limbs. These exceptionally preserved specimens suggest that integumental features were diversified even in ornithischian dinosaurs and that "protofeather"-like structures were potentially widespread among the entire dinosaur clade.
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Xing Xu (2020)
Filamentous Integuments in Nonavialan Theropods and Their Kin: Advances and Future Perspectives for Understanding the Evolution of Feathers.
In: Foth C., Rauhut O. (eds) The Evolution of Feathers: 67-78
DOI:
https://doi.org/10.1007/978-3-030-27223-4_5https://link.springer.com/chapter/10.1007/978-3-030-27223-4_5The discovery of Sinosauropteryx in 1996 marks the beginning of a new era in the research on the origin and early evolution of feathers. Subsequent discoveries of dinosaur fossils preserving feathers and feather-like integumentary appendages from both the Jurassic and Cretaceous deposits of China and other countries demonstrate a longer and more complex evolutionary history of feathers before the origin of birds than was previously thought. Currently, there are still many issues that continue to be debated or remain unresolved, such as at what point in phylogeny the first feathers originated (e.g., at the base of Avemetatarsalia vs. within Theropoda), how major microstructural features of feathers (e.g., barbules) evolved, whether early feathers developed ontogenetically in the same way as modern feathers, whether major features of feathers appeared incrementally in evolution or some appeared simultaneously (e.g., whether the feather follicle is a starting point for major feather features or these features appeared gradually), and what the primary functions of various early feathers were (e.g., display vs. insulation function for simple filamentous feathers and display vs. aerodynamic function for vaned feathers), among others. While insights from other fields such as developmental biology will help to address these various controversial issues pertaining to feather evolution, and a multidisciplinary approach is necessary to tackle and provide the full story of feather evolution, fossil specimens will continue to provide key data for the reconstruction and documentation of the evolutionary history of feathers, including evolutionary experiments and forms that no longer occur in nature.
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Christian Foth, Carolin Haug, Joachim T. Haug, Helmut Tischlinger & Oliver W. M. Rauhut (2020)
Two of a Feather: A Comparison of the Preserved Integument in the Juvenile Theropod Dinosaurs Sciurumimus and Juravenator from the Kimmeridgian Torleite Formation of Southern Germany.
In: Foth C., Rauhut O. (eds) The Evolution of Feathers: 79-101
DOI:
https://doi.org/10.1007/978-3-030-27223-4_6https://link.springer.com/chapter/10.1007/978-3-030-27223-4_6The discoveries of numerous theropod dinosaurs with filamentous integumentary structures in various stages of morphological complexity from the Upper Jurassic and Lower Cretaceous of China provided striking evidence that birds represent modern predatory dinosaurs and that feathers were originally filamentous. In the shadow of these impressive discoveries, two early juvenile theropod dinosaurs from the Upper Jurassic limestones of Bavaria (Germany), Juravenator starki and Sciurumimus albersdoerferi, were described. Both are preserved with phosphatized soft tissues, including skin and feathers. In the current study, the integumentary structures of both theropods are investigated and revised with the help of autofluorescence methods, using two different excitation wavelengths (UVA and cyan). Both theropods possessed monofilamentous feathers and scaleless skin. In J. starki, short feathers could only be traced in the tail region. The tubercle-like structures, originally described as scales, found in the anterior tail region of J. starki, show no autofluorescence signal and were reinterpreted as remains of adipocere, maybe indicating the presence of a fat body. S. albersdoerferi was probably entirely plumaged, possessing a filamentous crest on the dorsal edge in the anterior tail section. This current example emphasizes the importance of taphonomic reviews for the interpretation of integumentary structures. Furthermore, the new data give new insights into the early evolution of feathers. However, the placement of J. starki in multiple phylogenetic positions and differences in the morphological interpretation of filamentous feathers found in basal coelurosaurs produce contrasting reconstructions of character evolution that will need to be resolved in due course if greater clarity is to be obtained in this area.
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Two decades of paleontological discoveries of basal birds and non-avian theropods with preserved integumentary structures, especially in Late Jurassic to Early Cretaceous deposits from northeastern China, have greatly improved our understanding of the origin and early evolution of birds and their plumage. Here, we present a concise review of the plumage evolution within pennaraptora, the most inclusive clade containing Oviraptorosauria and Paraves. Feather or feather-like morphotypes were particularly diversified in non-avialan paravians, suggesting that they probably already fulfilled a wide array of biological roles, including thermoregulation and visual display. The feather-like structures in non-eumaniraptoran paravians were obviously not adapted for flight. However, Microraptor and maybe some of its relatives preserve large pennaceous feathers along the limbs and tail, similar in morphology and organization to those in modern birds, so that they could have functioned in active flight or passive gliding. Several aerodynamic innovations and flight-related morphological adaptations were (likely independently) experimented within the paravian clade close to the origin of birds. The origin and early evolution of complex feathers and flight abilities in paravian theropods were not linear processes, but more complex than previously thought.
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Nicholas R. Longrich, Helmut Tischlinger & Christian Foth (2020)
The Feathers of the Jurassic Urvogel Archaeopteryx.
In: Foth C., Rauhut O. (eds) The Evolution of Feathers: 119-146
DOI:
https://doi.org/10.1007/978-3-030-27223-4_8https://link.springer.com/chapter/10.1007/978-3-030-27223-4_8The Jurassic stem bird Archaeopteryx is an iconic transitional fossil, with an intermediate morphology combining features of non-avian dinosaurs and crown Aves. Importantly, fossils of Archaeopteryx preserve not only the bones but also details of the plumage and therefore help shed light on the evolution of feathers, wings, and avian flight. Plumage is preserved in multiple individuals, allowing a detailed documentation of the feathers of the wings, tail, hindlimbs, and body. In some features, Archaeopteryxâ plumage is remarkably modern, yet in others, it is strikingly primitive. As in extant birds, remiges and coverts are enlarged and overlap to form airfoils. Remiges and rectrices exhibit asymmetrical, pennaceous vanes, with interlocking barbules. The hindlimbs bear large, vaned feathers as in Microraptor and Anchiornis. Rectrices are numerous and extend the full length of the tail to the hips. The plumage of crown Aves was assembled in a stepwise fashion from Anchiornis through Archaeopteryx, culminating in a modern arrangement in ornithothoracines. Subsequent stasis in feather and wing morphology likely reflects aerodynamic and developmental constraints. Feather morphology and arrangement in Archaeopteryx are consistent with lift-generating function, and the wing loading and aspect ratio are comparable to modern birds, consistent with gliding and perhaps flapping flight. The plumage of Archaeopteryx is intermediate between Anchiornis and more derived Pygostylia, suggesting a degree of flight ability intermediate between the two.
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Jingmai OâConnor (2020)
The Plumage of Basal Birds.
In: Foth C., Rauhut O. (eds) The Evolution of Feathers: 147-172
DOI:
https://doi.org/10.1007/978-3-030-27223-4_9https://link.springer.com/chapter/10.1007/978-3-030-27223-4_9Early bird plumage is well known primarily due to numerous discoveries of specimens preserving feathers from Early Cretaceous deposits in China. Remiges and rectrices are most commonly preserved with rectrices showing the greatest variation. The long boney-tailed Jeholornis has a unique tail plumage employing two anatomically distinct rectricial pterylae serving both aerodynamic and ornamental functions. Basal pygostylians show disparate tail plumages that are reflected by differences in pygostyle morphology. Sapeornis has a proportionately shorter pygostyle wielding a fan-shaped array of rectrices, whereas the robust pygostyle of Confuciusornis is associated with a pair of elongate rachis-dominated feathers in some specimens, considered indicative of sexual dimorphism. The latter morphology is also present in many enantiornithines. Members of this diverse clade have primarily ornamental tail morphologies, whereas the earliest members of the Ornithuromorpha all possess tail morphologies that appear to be primarily aerodynamic. Body feathers in Archaeopteryx and adult enantiornithines trapped in amber are pennaceous suggesting that reported rachis-less body feathers in Jehol birds may be taphonomic artifacts. Rarely preserved, well-developed pennaceous crural feathers are present in Archaeopteryx and some enantiornithines, whereas crural feathers are short in the Confuciusornithiformes. Their preserved absence in nearly all Jehol ornithuromorph specimens most-likely reflects the smaller available sample size. Crural feathers in many basal ornithuromorphs were probably reduced, as in Yanornis and extant aquatic and semiaquatic birds. Overall, early birds show a trend towards the reduction of the distal hindlimb feathers present in closely related nonavian dinosaurs. However, well-developed tarsometatarsal feathers are present in Sapeornis and two exceptionally well-preserved enantiornithine specimens indicate this group was diverse in the distal extent of their hindlimb plumage, including at least one lineage with feathered pedal digits. Although remarkably modern in many aspects, early bird plumage still differed from that of their modern counterparts including extinct morphotypes and differences in ontogenetic patterns.
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Christian Foth (2020)
A Morphological Review of the Enigmatic Elongated Tail Feathers of Stem Birds.
In: Foth C., Rauhut O. (eds) The Evolution of Feathers: 173-184
DOI:
https://doi.org/10.1007/978-3-030-27223-4_10https://link.springer.com/chapter/10.1007/978-3-030-27223-4_10Several stem birds, such as Confuciusornithidae and Enantiornithes, were characterized by the possession of one or two pairs of conspicuous, elongated tail feathers with a unique morphology, so-called rhachis-dominated racket plumes. In the past, several studies reported contradictory interpretations regarding the morphology of these feathers, which sometimes failed to match with any morphology known from modern feathers. In this chapter, these interpretations are reviewed and compared with various modern feather types. The comparison confirms recent interpretations that the rhachis-dominated racket plumes are highly modified pennaceous feathers with ornamental function, originating at least two times independently from each other during evolution. While the gross organization (i.e., a short distal vane and a long, naked rhachis) of these feathers resembles that of filoplumes, they resemble pennaceous body feathers of penguins in terms of rhachis morphology and pigmentation pattern. As the rhachis-dominated racket plumes combine different morphologies that are apparent among modern feather types, this extinct morphotype does in fact not show any aberrant morphological novelties, but rather fall into the morphological and developmental spectrum of modern feathers.
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Fiann Smithwick & Jakob Vinther (2020)
Palaeocolour: A History and State of the Art.
In: Foth C., Rauhut O. (eds) The Evolution of Feathers: 185-211
DOI:
https://doi.org/10.1007/978-3-030-27223-4_11 https://link.springer.com/chapter/10.1007/978-3-030-27223-4_11Colour plays a key role in the ecology of living birds and has undoubtedly been important throughout their evolutionary history. Colour patterns influence all aspects of avian ecology, including interspecific communication such as predator-prey dynamics and intraspecific signalling such as sexual selection. The past decade has seen a revolution in our understanding of how colour influenced avian evolution in deep time. From the overturning of the paradigm that lithified bacteria were responsible for vertebrate integumentary preservation to the development of analytical techniques used to probe pigment preservation, we review the origins and development of the field of palaeocolour. We also explore how palaeocolour reconstructions in extinct dinosaurs have informed us about the ecologies and behaviours of long-extinct taxa that would otherwise be difficult to determine. This exemplifies the utility of palaeocolour in deepening our understanding of past life, particularly early avian evolution. Palaeocolour work is also helping unravel the intricacies of feather preservation and in turn has furthered our understanding of soft tissue taphonomy more generally.
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NicolÃs E. Campione, Paul M. Barrett & David C. Evans (2020)
On the Ancestry of Feathers in Mesozoic Dinosaurs.
In: Foth C., Rauhut O. (eds) The Evolution of Feathers: 213-243
DOI:
https://doi.org/10.1007/978-3-030-27223-4_12https://link.springer.com/chapter/10.1007/978-3-030-27223-4_12Over the last two decades, the dinosaur fossil record has revealed much about the nature of their epidermal structures. These data challenged long-standing hypotheses of widespread reptile-like scalation in dinosaurs and provided additional evidence that supported the deeply nested position of birds within the clade. Moreover, in recent years, the discovery of filamentous structures in numerous species across the dinosaurian evolutionary tree suggests a model of deep feather homology within dinosaurs, with the appearance of feathers hypothesised to coincide with the dinosaur origin. Thanks to phylogenetic comparative methods, these homologies can now be tested empirically and form the basis of this study. Based on a dataset of 77 dinosaur species that preserve integumentary structures, we undertake a series of model-fitting and ancestral state reconstruction analyses to interpret the evolutionary history and ancestral integumentary condition in dinosaurs. Our results provide the first empirical support for the evolution of feathers in an ordered fashion, but reveal that these evolutionary trends were not always towards âmore complexâ conditions. Ancestral state reconstructions demonstrate that irrespective of the preferred phylogenetic framework, the ancestral pterosaur condition or whether any one major dinosaur lineage had a Late Triassic-feathered representative, support values for a filamentous/feathered dinosaur ancestor are low. More examples of feathered taxa from across the dinosaur tree, and in particular the discovery of as yet unknown feathered Triassic taxa, will be needed in order to overturn current support for a scaly dinosaurian ancestor.