Alan Feduccia

Alan Feduccia

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Alan Feduccia is a paleornithologist
Paleornithology
Paleornithology also known as Avian Paleontology is the scientific study of bird evolution and fossil birds. It is a mix of ornithology and paleontology. Paleornithology began with the discovery of Archaeopteryx. The reptilian relationship of birds and their ancestors, the theropod dinosaurs, are...

, specializing in the origins and phylogeny of birds. He is now Professor Emeritus at the University of North Carolina
University of North Carolina at Chapel Hill
The University of North Carolina at Chapel Hill is a public research university located in Chapel Hill, North Carolina, United States...

. Feduccia's principal authored works include two books, The Age of Birds and The Origin and Evolution of Birds, and numerous papers in various ornithological and biological journals. Feduccia is best known for his criticisms of the widely-held view that birds originated from and are deeply nested within Theropoda
Theropoda
Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...

, and are therefore living theropod dinosaurs. He has argued for an alternative theory in which birds share a common stem-ancestor with theropod dinosaurs among more basal archosaur
Archosaur
Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...

ian lineages, with birds originating from small arboreal archosaur
Archosaur
Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...

s in the Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

.

Education


Feduccia graduated with a B.S. from Louisiana State University
Louisiana State University
Louisiana State University and Agricultural and Mechanical College, most often referred to as Louisiana State University, or LSU, is a public coeducational university located in Baton Rouge, Louisiana. The University was founded in 1853 in what is now known as Pineville, Louisiana, under the name...

, taking ornithological
Ornithology
Ornithology is a branch of zoology that concerns the study of birds. Several aspects of ornithology differ from related disciplines, due partly to the high visibility and the aesthetic appeal of birds...

 expeditions to Honduras
Honduras
Honduras is a republic in Central America. It was previously known as Spanish Honduras to differentiate it from British Honduras, which became the modern-day state of Belize...

, El Salvador
El Salvador
El Salvador or simply Salvador is the smallest and the most densely populated country in Central America. The country's capital city and largest city is San Salvador; Santa Ana and San Miguel are also important cultural and commercial centers in the country and in all of Central America...

 and Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

. He received his M.A. and Ph.D. (1969) from the University of Michigan
University of Michigan
The University of Michigan is a public research university located in Ann Arbor, Michigan in the United States. It is the state's oldest university and the flagship campus of the University of Michigan...

.

Academic career and research


Feduccia's research has focused on ornithology, evolutionary biology, vertebrate history and morphogenesis, and the tempo and mode of the Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...

 vertebrate radiation. His early work in the 1970s focused on clarification of the evolutionary history of modern birds (Neornithes), focusing, in particular, on the importance of the identification of conserved morphological characters that might elucidate phylogeny more readily than more functionally correlated characters. Using this approach, in a series of publications, Feduccia analyzed the morphology of the bony stapes, the ear ossicle of birds, to help elucidate the interrelationships of passeriform birds. This approach was extended to the analysis of non-passeriform birds as well, including owls and the shoebill, also known as the whalebill (Balaeniceps rex). Other studies in the 1970s focused on the analysis of the Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...

 avian radiation, with a particular focus on the origin and relationships of waterfowl Anseriformes
Anseriformes
The order Anseriformes contains about 150 living species of birds in three extant families: the Anhimidae , Anseranatidae , and the Anatidae, which includes over 140 species of waterfowl, among them the ducks, geese, and swans.All species in the order are highly adapted for an aquatic existence at...

. Based on his analysis of the osteology of the Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...

 and Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...

 duck Presbyornis
Presbyornis
Presbyornis is an extinct genus of anseriform bird. It contains two unequivocally accepted species; the well-known P. pervetus and the much lesser-known P. isoni. P. pervetus was approximately the size and shape of a goose, but with longer legs; P. isoni, known from a few bones, was much larger,...

, represented in large quantities from Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...

 deposits from outcrops of the Green River Formation in Utah and Wyoming, Feduccia concluded that Presbyornis
Presbyornis
Presbyornis is an extinct genus of anseriform bird. It contains two unequivocally accepted species; the well-known P. pervetus and the much lesser-known P. isoni. P. pervetus was approximately the size and shape of a goose, but with longer legs; P. isoni, known from a few bones, was much larger,...

represents a shorebird-duck mosaic and that waterfowl evolved from shorebirds (Charadriiformes
Charadriiformes
Charadriiformes is a diverse order of small to medium-large birds. It includes about 350 species and has members in all parts of the world. Most Charadriiformes live near water and eat invertebrates or other small animals; however, some are pelagic , some occupy deserts and a few are found in thick...

). This is contrary to the more widely held view that waterfowl are most closely related to chickens, turkeys, and related fowl (Galliformes
Galliformes
Galliformes are an order of heavy-bodied ground-feeding domestic or game bird, containing turkey, grouse, chicken, New and Old World Quail, ptarmigan, partridge, pheasant, and the Cracidae. Common names are gamefowl or gamebirds, landfowl, gallinaceous birds or galliforms...

), but Feduccia argues that this alternative phylogeny is unsupported by fossil evidence, and he suggests that any similarities between anseriform and galliform birds are attributable to homoplasy. Partly based on his analysis of the osteology of Presbyornis
Presbyornis
Presbyornis is an extinct genus of anseriform bird. It contains two unequivocally accepted species; the well-known P. pervetus and the much lesser-known P. isoni. P. pervetus was approximately the size and shape of a goose, but with longer legs; P. isoni, known from a few bones, was much larger,...

, Feduccia also argued that flamingos, the phylogenetic relationships of which remain disputed, with some recent studies suggesting a sister-group relationship with grebes, were actually derived from shorebirds. Feduccia summarized his position in the second edition of his book The Origin and Evolution of Birds: "The study of Presbyornis planted the idea that shorebirds are the basic ancestral stock for both flamingolike birds and the anseriformes, ducks and their allies...". Feduccia's early work on flamingos and waterfowl contributed to the development of his hypothesis that there was an explosive Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...

 adaptive radiation of neornithine birds following the extinction event at the end of the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

. According to this hypothesis, modern orders of birds initially radiated principally from a lineage of "transitional shorebirds", represented by the shorebird form-family Graculavidae, from the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

-early Paleogene
Paleogene
The Paleogene is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era...

, that managed to survive the Cretaceous extinction event, perhaps through eking out a living along marginal shoreline environments. This radiation is hypothesized to have been very rapid, as many orders of modern birds have fossil representatives from the early Tertiary. Feduccia has suggested that this rapid adaptive radiation of modern birds, compressed into such a short period of geologic time, might seriously obscure interordinal relationships and make elucidation of the phylogeny of modern birds particularly difficult, barring the isolation of conserved characters or mosaic fossils demonstrating transitional character states bridging extant orders. This reiterates an early theme from his research in the 1970s, in which Feduccia had repeatedly emphasized the importance of homoplasy in evolution, and its ability to confound the interpretation of phylogeny. This has also been a theme in his study of flightlessness in birds, a phenomenon the pervasiveness of which has been stressed in his work, and the mechanisms by which flight is lost, including heterochrony
Heterochrony
In biology, heterochrony is defined as a developmental change in the timing of events, leading to changes in size and shape. There are two main components, namely the onset and offset of a particular process, and the rate at which the process operates...

 and differential development. Feduccia has argued against the monophyly of the Ratitae, supporting instead independent derivation of ratite lineages, perhaps from flying ancestral paleognathous taxa, like the Lithornithiformes
Lithornithiformes
Lithornithiformes is an extinct order of early paleognath birds. Lithornithiform birds are known from fossils dating to the Upper Paleocene through the Middle Eocene of North America and Europe. All are extinct today....

.

Feduccia is best known for his criticisms of the hypothesis, accepted by most paleontologists, that birds originated from and are deeply nested within Theropoda
Theropoda
Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...

, and are therefore living theropod dinosaurs. Feduccia's first contribution relative to the origin and early evolution of birds, and their relationship with dinosaurs, was a critical review of the evidence then available for dinosaurian endothermy in 1973. In a 1979 paper, Feduccia and Tordoff argued, against the position taken by John Ostrom
John Ostrom
John H. Ostrom was an American paleontologist who revolutionized modern understanding of dinosaurs in the 1960s, when he demonstrated that dinosaurs are more like big non-flying birds than they are like lizards , an idea first proposed by Thomas Henry Huxley in the 1860s, but which had garnered...

, that Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...

was capable of powered flight, as indicated by the asymmetrical vanes of its primary feathers, a feature found only in flying birds. In a paper coauthored with Storrs Olson in the same year, Feduccia noted that the robust furcula
Furcula
The ' is a forked bone found in birds, formed by the fusion of the two clavicles. In birds, its function is the strengthening of the thoracic skeleton to withstand the rigors of flight....

 of Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...

could have served as a site of attachment for a well-developed M. pectoralis major, the principal depressor of the avian wing, responsible for powering the downstroke during avian flight. Olson and Feduccia concluded that this provided further evidence for the flight capability of Archaeopteryx. These initial excursions into the subject, and the argument that Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...

was clearly a bird, albeit primitive, were expanded upon in Feduccia's 1980 book, The Age of Birds. Feduccia here criticized the theropod hypothesis for the origin of birds, but his position was largely agnostic, conceding that there was evidence in support of both a theropod ancestry of birds and an ancestry from more basal archosaurs, perhaps similar in overall morphological organization to Euparkeria
Euparkeria
Euparkeria was a small African reptile of the early Triassic period between 248-245 million years ago, close to the ancestry of the archosaurs.- Palaeobiology :...

. Feduccia nevertheless suggested that on the basis of closer stratigraphic fit, ancestry from basal archosaurs rather than from coelurosaurian theropods might prove a better phylogenetic hypothesis. He thus, essentially, agreed with the model for the origin of birds proposed by Gerhard Heilmann
Gerhard Heilmann
Gerhard Heilmann was a Danish artist and paleontologist who created artistic depictions of Archeopteryx, Proavis and other early bird relatives apart from writing The Origin of Birds, a pioneering and influential account of bird evolution...

 in his influential 1926 book The Origin of Birds
The Origin of Birds (book)
The Origin of Birds is an early synopsis of bird evolution written in 1926 by Gerhard Heilmann, a Danish artist and amateur zoologist. The book was born from a series of articles published between 1913 and 1916 in Danish, and although republished as a book it received mainly criticism from...

. Feduccia also criticized "ground-up" theories for the origin of avian flight, arguing on biophysical grounds that they were implausible, and noting that in other cases in which flight has developed among vertebrates it has occurred in an arboreal context. He argued, instead, for a "trees-down" model for the origin of avian flight due to its lack of the biophysical constraints hindering "ground-up" acquisition of flight and due to the ability to call upon biologically functional stages, represented by living analogues, at each stage in the evolution of flight. Feduccia's skepticism about the origin of birds from theropods and a "ground-up" origin of avian flight, which in the absence of any evidence for small, arboreal theropods seemed a concomitant requirement of that hypothesis, increased following publication of The Age of Birds, culminating in a series of publications in the latter half of the 1980s and the early 1990s expanding upon arguments presented in The Age of Birds. In his 1985 contribution to the Eichstatt Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...

Conference, a major international meeting on the interpretation and significance of Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...

, as well as on the origin and early evolution of birds and avian flight, held in Eichstatt, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

, Feduccia criticized hypotheses for the evolution of feathers in non-aerodynamic contexts in endothermic small theropod dinosaurs. He argued that these hypotheses failed to account for the elaborate aerodynamic architecture of the feather
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...

 vane and rachis
Rachis
Rachis is a biological term for a main axis or "shaft".-In zoology:In vertebrates a rachis can refer to the series of articulated vertebrae, which encase the spinal cord. In this case the rachis usually form the supporting axis of the body and is then called the spine or vertebral column...

, and that thermoregulatory functions would have been adequately served by hair, which is a developmentally simpler structure. In a 1993 paper, Feduccia analyzed claw curvature arcs in the manual and pedal claws of Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...

and other birds, and found that Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...

clustered with other arboreal birds, suggesting that it was an arboreal animal rather than a terrestrial cursor or a bird which spent any considerable time on the ground, as is argued by some other workers. In other publications in the early 1990s, Feduccia expanded on earlier arguments for the evolution of feathers in a primarily aerodynamic rather than thermoregulatory context. In 1996, Feduccia published the first edition (second edition in 1999) of The Origin and Evolution of Birds, a comprehensive review of his research on both early avian evolution and a synopsis of the history of the Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...

 radiation of modern birds. The book presented a thorough overview of earlier criticisms of the theropod hypothesis for the origin of birds and a "ground-up" origin of avian flight, expanded on many of those arguments, and presented a series of new arguments questioning the hypotheses of homology
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...

 advanced as evidence for the theropod hypothesis. Feduccia argued that many of the proposed homologous similarities between theropods and birds were ambiguous, and that other similarities between birds and theropods could plausibly be explained as homoplasy, particularly those in the hindlimb and pelvis. Feduccia also focused upon the discrepancy between embryological evidence identifying the digits of the avian manus as the second, third, and fourth of the primitively pentadactyl archosaur
Archosaur
Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...

 manus, and paleontological evidence indicating that theropod dinosaurs primitively reduced their fourth and fifth manual digits, eventually retaining only the first, second, and third (with further reduction in some groups, like tyrannosaurs. This emerged as a principal argument in Feduccia's research on the origin of birds, and was the subject of developmental studies of the ostrich definitively identifying first and fifth digital condensations in the embryonic hand, confirming a pentadactyl ground state for the avian manus with symmetrical reduction, unlike the situation indicated by paleontological evidence for theropods. This conclusion has been supported by some other workers, but others have proposed various responses (see below, under Controversy).

In recent years, Feduccia has argued that the discovery of spectacular new fossils from the Cretaceous of China, like Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...

, and other taxa with unambiguous feathers, like the oviraptorosaur Caudipteryx
Caudipteryx
Caudipteryx is a genus of peacock-sized theropod dinosaurs that lived in the Aptian age of the early Cretaceous Period . They were feathered and remarkably birdlike in their overall appearance....

, suggest that there might have been an extensive, and hitherto unrecognized radiation of cryptic avian lineages, some of which rapidly lost flight and secondarily adopted a cursorial lifestyle, converging on theropods. On this argument, very birdlike groups like Dromaeosauridae
Dromaeosauridae
Dromaeosauridae is a family of bird-like theropod dinosaurs. They were small- to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek dromeus meaning 'runner' and sauros meaning 'lizard'...

 and Oviraptorosauria
Oviraptorosauria
Oviraptorosaurs are a group of feathered maniraptoran dinosaurs from the Cretaceous Period of what are now Asia and North America. They are distinct for their characteristically short, beaked, parrot - like skulls, with or without bony crests atop the head...

, which are currently considered by most workers to be theropod dinosaurs, are thought actually to represent avian lineages, probably more derived than Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...

, that through homoplasy associated with the loss of flight and secondary acquisition of cursoriality, converged on theropod dinosaurs. Other lineages, like that represented by Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...

and Anchiornis
Anchiornis
Anchiornis is a genus of small, feathered, deinonychosaurian dinosaur. The genus Anchiornis contains the type species Anchiornis huxleyi, named in honor of Thomas Henry Huxley, an early proponent of biological evolution, and the first to propose a close evolutionary relationship between birds and...

, are hypothesized to be have been flighted. This argument represents a shift from Feduccia's earlier position in the 1990s, as he acknowledged in a 2002 paper where he first endorsed this view. Feduccia has expanded upon this argument in subsequent papers.

Feduccia has appeared frequently on national TV and radio, including NPR, Voice of America, BBC, CNN, ABC (Australia), NHK (Japan) and McNeil/Lehrer Report, and is a popular university lecturer. Feduccia served as Chair of the Department of Biology at Chapel Hill from 1997–2002, and prior to that was Chair of the Division of Natural Sciences. He is an elected Fellow of the American Ornithologists’ Union and the American Association for the Advancement of Science.

Controversy


Feduccia's work has been unusually controversial, perhaps because of his skepticism about the theropod origin of birds, which is accepted by many biologists, and which has historically been a particularly divisive topic in vertebrate zoology. Feduccia's principal academic work, The Origin and Early Evolution of Birds, was well received by some workers, and was winner of the Association of American Publishers
Association of American Publishers
The Association of American Publishers is the national trade association of the American book publishing industry. AAP has more than 300 members, including most of the major commercial publishers in the United States, as well as smaller and non-profit publishers, university presses and scholarly...

 1996 award for Excellence in Biology. However, it received very negative reviews from several paleontologists, primarily on account of the book's criticisms of the theropod hypothesis for the origin of birds. Feduccia has been criticized for failing to use cladistics
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...

 in his studies of the origin and the evolution of birds, and this criticism has been related to further criticisms of, particularly, his arguments against the theropod origin of birds, as well as some of his hypotheses on the phylogeny of modern birds. In response to a 2002 paper by Rick Prum in The Auk, the journal of the American Ornithologists' Union
American Ornithologists' Union
The American Ornithologists' Union is an ornithological organization in the USA. Unlike the National Audubon Society, its members are primarily professional ornithologists rather than amateur birders...

, in which Prum presented a summary of the current state of the theropod hypothesis for the origin of birds, and urged its acceptance by and integration within ornithology
Ornithology
Ornithology is a branch of zoology that concerns the study of birds. Several aspects of ornithology differ from related disciplines, due partly to the high visibility and the aesthetic appeal of birds...

, Feduccia responded with criticism of this view, arguing that the origin of birds was a complex and as yet unresolved problem to which the theropod hypothesis as presently formulated was a simplistic answer, ignoring contrary evidence. Prum responded to this paper and criticized Feduccia's failure to use cladistics
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...

 and to specify an explicit alternative sister-group with which to ally birds. He particularly singled out Feduccia's adoption of the view that some theropod taxa are actually birds that have been mistaken for theropods through convergence associated with flight loss and secondary adoption of cursoriality. Prum argued, finally, that Feduccia's methodology and view of the origin and early evolution of birds are pseudoscientific.

Several of the arguments about whether similarities between birds and theropods are homologous that have been advanced by Feduccia have been particularly contentious. One example is identification of the digits of the avian and theropod hands, and whether, and if so by what mechanism, it might be possible to explain the discrepancy between the conflicting digital identities of tridactyl theropods and birds. Wagner and Gauthier proposed that a homeotic frame shift, whereby expression domains for groups of genes like the Hox d group, were repositioned during limb bud development, resulting in the development of the first, second, and third digits of the archosaur manus from what were originally condensations for the second, third, and fourth. This view has been supported by some other workers. Feduccia has responded to these counterarguments, and debate continues. Another response to Feduccia's digital homology argument is the counterargument that evidence from the transitional Limusaurus inextricabilis
Limusaurus
Limusaurus is a genus of toothless herbivorous theropod dinosaur from the Jurassic Upper Shishugou Formation in the Junggar Basin of western China. Limusaurus is also the first definitely known ceratosaur from Eastern Asia, including China...

suggests that theropods too have the three digits II, III and IV.

External links