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Thor Hanson’s Feathers: The Evolution of a Natural Miracle

The views expressed are those of the author and are not necessarily those of Scientific American.


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The complex structure, development and growth of feathers can, to paraphrase one expert on the subject, be seriously damaging to your mental health. Feathers are just crazy, almost certainly the most complex structures to ever grow out of any animal’s external surface.

Yet for all their marvellous complexity, for all the interest that people have displayed in their evolutionary origins and diversity, for all their role in bird behaviour and ecology, and for all their economic and cultural significance to humans, it doesn’t seem that any one book has ever been devoted to feathers and feathers alone. Thor Hanson’s 2011 Feathers is thus a rather significant book, and very nice it is too.

Hanson, a Washington State-based conservation biologist, previously wrote The Impenetrable Forest: My Gorilla Years in Uganda. He’s published technical research on such topics as the ecology of tropical trees, forest fragmentation and its impact on bird nest predation, the impact that warfare can have on biodiversity hotspots, and the behaviour of Neotropical monkeys and birds.

Hanson might not be a feather specialist, or even a dedicated ornithologist, but his many encounters with feathers, and with their structure, role, significance and uniqueness, obviously created the urge that culminated in this book. And Feathers is not the provincial view of someone only interested in ecology or conservation biology; on the contrary, this is a remarkably well-rounded review of the subject. Chapters look at the evolution and origin of feathers, their use in flight, thermoregulation and display, and their importance to humans.

Feathers from the Mesozoic

♥ Alan Feduccia.

A discussion of feathered non-avialan theropod dinosaurs, and a review of feather origin theories make up early sections in the book. Hanson is very much up to date (as of 2011!), providing appropriate discussion of Richard Prum’s feather origins hypothesis (Prum & Brush 2002) and of Xu Xing and his numerous exciting feathered theropod discoveries. As per usual, we get the theropod origins model pitted against Alan Feduccia’s idea that birds just cannot be theropods, nor dinosaurs at all, but an independent derivation from non-dinosaurian diapsid reptiles of some sort. Feduccia is quoted as saying in the book that “If it has feathers, it’s a bird” (Hanson 2011, p. 57), which of course means that feathered oviraptorosaurs, deinonychosaurs and so on are now birds according to Feduccia. As Hanson notes, and as Prum and others have said before (Prum 2003), this means that Feduccia is now contradicting decades of bold assertion in which he has insisted that deinonychosaurs and other Mesozoic theropods are nothing whatsoever to do with birds. It must be understood that Feduccia’s opinion is not a valuable, informed alternative or anything like that; rather, it relies on deliberate obfuscation and misinformation and ignorance with respect to what we actually know. I cannot see that he and his colleagues have done anything but add confusion, contradiction and erroneous interpretations to our understanding of bird origins and early evolution. Hanson was able to see through this, as have previous authors who approached the topic of bird origins as apparent outsiders (e.g., Shipman 1998).

It’s often difficult to entangle the difference between the origin of birds and the origin of flight, but recently discovered small non-avialan maniraptorans and the distribution of vaned feathers in maniraptoran phylogeny may well show that flight of a sort was present in whatever taxa were ancestral to both the bird and deinonychosaur lineages. While the majority of non-avialan theropods were non-climbers, could climbing or branch-leaping, or some other way of acquiring height, help explain the earliest steps in the evolution of flight?

One of Ken Dial's WAIR diagrams. This figure shows that wing stroke is nearly invariant to gravity; the red lines represent the wing-tip trace in WAIR while the blue lines represent the wing-tip trace in level flight.

Hanson provides nice coverage of this topic, and is especially keen on Ken Dial’s Wing Assisted Incline Running (WAIR) hypothesis (Dial, Bundle & Dial 2003, Dial et al. 2006, 2008). As Hanson notes, WAIR has been embraced rather enthusiastically by palaeontologists “as the best flight evolution story to date” (p. 129). It has appeal in explaining how small, incremental steps might explain how terrestrial theropods with an early form of feathering could have evolved into scansorial animals with larger, increasingly complex feathery surfaces on the limbs. I think that WAIR is a pretty neat hypothesis. However, I note that some who work on flight origins are highly sceptical of it, stating in particular that non-ornithurine birds lacked the bony architecture required to permit the vigorous, high-amplitude flapping needed for WAIR to function.

The 1911 Trans-Saharan Ostrich Expedition, Vegas showgirls, and other feather-based tales from the human world

Frontispiece to Richard Brookes's 1790 volume The Art of Angling.

While all of these topics might be quite familiar if you’re well-read on bird and feather origins, Hanson’s other chapters cover feather growth and moulting, avian thermoregulation, the down industry, the aerodynamic and water-repellent qualities of feathers, and the use of feathers in display (both among birds and among humans), fly-fishing and writing.

The anthropological sections were the most novel. We’re all familiar with the use (or former use) of feathers in hats, dusters, cloaks and so on, but overall this subject certainly isn’t something I’ve ever had the chance to read much about. Most people interested in birds know that the feather trade was so substantial during the early decades of the 20th century that egrets and other species were being slaughtered in their millions expressly for the purpose, and indeed that conservation bodies, laws and reserves were created in direct response to the scale and nature of this trade. Feathers were so valuable at this time that the more than 40 cases of plumes lost on the Titanic would have an insurance value of more than $2.3 million in today’s currency (Hanson 2011, p. 176).

Ostriches plucked of ALL their feathers. This image shows ostriches that belonged to Shua people in Nigeria; it's from Hugo Bernatzik's 1931 book The Dark Continent; Africa, the Landscape and the People (digitized by the New York Public Library).

One of my favourite sections in the book is that on the Trans-Saharan Ostrich Expedition, whereby Russel William Thornton led a 1911 expedition from South Africa to Nigeria in order to track down, capture and exploit the fabled Barbary ostrich. The plumes of this ostrich are (or were) ‘double-flossed’ and more luxuriant than those of other ostriches. I’m somewhat uncertain of the taxonomic status of this form but, then, I think that everyone might be, since the population concerned is apparently now extinct. It has at least been suggested that ‘Barbary ostriches’ were a local form of the North African, Sudan or Red-necked ostrich Struthio camelus camelus (Freitag & Robinson 1993), but I don’t know if this has ever been demonstrated. Anyway, you might be as surprised as I was to learn that captured ostriches were plucked of all their feathers.

Stuff I saw in Las Vegas. You should be able to see pink plumes on the photo of the showgirl at top right.

Hanson’s section on the role of feathers in display talks about birds-of-paradise, sexual display, the ‘sexy son’ hypothesis, Wallace and Darwin. But he goes on to discuss Las Vegas showgirls and the tradition of using showy, enormous feather plumes in dancing costumes. Some of the largest feathery pieces used in showgirl costumes might cost “tens of thousands of dollars” should they need to be replaced (Hanson 2011, p. 172). I was actually reading the book while staying in Las Vegas, and got to walk past the famous pink-plumed dancing girls of Bally’s Hotel and Casino on a twice-daily basis. It was weird… like everything else in Las Vegas.

Hanson also covers the massive use of birds by the Aztecs. The aviaries at Tenochtitlán were described by Hernán Cortés as being enormous, housing every kind of bird and requiring the services of 300 human attendants. They were completely burnt down during the Spanish siege of Tenochtitlán in 1521.

On vultures

Vultures play an important role in the book since Hanson says in the preface that they’re what got him interested in feathers in the first place. He relates a delightful tale from field research where he had to handle a rotting zebra caecum, destined for use at a vulture feeding station. It exploded, “blowing my hair back and coating me with a spray of old blood, strands of ropy goo, and flecks of half-digested bush grass. The smell was indescribable.” (Hanson 2011, p. 250).

Thermographic image of a vulture (a cathartid, probably Cathartes aura). Image by Arno/Coen, licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

Hanson mostly includes vultures in the book because he argues that the reduced or absent feathering on their heads is an adaptation for carrion-feeding. This might be partly true, but in recent years it’s been questioned: some birds that regularly poke their heads into carcasses (giant petrels) get by fine with normal feathering, most vultures are not really naked-headed anyway, and it might be that reduced feathering on the head and neck is as much (or more) to do with thermoregulation than carrion feeding (Ward et al. 2008). Hanson also commits an oft-made mistake in writing that New World vultures are especially closely related to storks. This view was mooted a few decades ago but hasn’t been supported by any of the more recent studies published on bird phylogeny.

White-backed vulture (Gyps africanus) in flight. Image by Mark Rosen, licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

I can’t leave this mention of vultures without referring to the continuing decline of these magnificent birds due to human greed, stupidity and laziness. The die-off of Indian vultures due to use of the veterinary drug diclofenac is well known: the decline has been so rapid that, in 2008, some experts were predicting the extinction of certain vulture species within a ten-year period. Despite being banned from sale in 2005, diclofenac is still being sold illegally and some reports say that it’s continuing to have a deleterious effect. Vulture ‘restaurants’ set up by the Indian government have not been adequately funded or maintained, and an article from February of this year said that these feeding stations haven’t benefited vulture conservation at all. A symposium on the continuing decline of Asian vultures was in fact held just a few days ago (early May 2012).

The problems in India (which mostly effect the Slender-billed vulture Gyps tenuirostris, Indian vulture G. indicus and White-rumped vulture G. bengalensis) have received a reasonable amount of press interest. Less well known is that massive declines seem to have occurred in Africa as well, with some data from Mali and Niger indicating that vulture species have either disappeared entirely, or have declined by something like 98%. Here, diclofenac is less of a problem. Habitat destruction and degradation, poisoning, and killing for use in traditional and quack medicine – known as muti – have all contributed to decline. Particularly infuriating is the belief that smoking vulture brains will give people supernatural powers when gambling (yes, I said smoking vulture brains will give people supernatural powers when gambling). The demand for vulture products used in muti has soared in step with the growth of national lotteries and with events such as the 2010 World Cup, hosted by South Africa (Langley 2011). Clearly, the health of vulture populations across many areas is now a major cause for concern and urgent measures are needed.

Anyway… I digress, back to the book review. Other highlights include the discussion of the peregrine feather dropped on the surface of the moon by Commander David R. Scott in 1971, and the section on snarge. Yes, I said snarge, and will leave it at that.

Feathers is a handy, compact volume, well illustrated throughout, and with a compelling, enjoyable prose. It’s fully referenced, with footnotes (arranged at the back) providing details that would have derailed or slowed the main flow of the text. Appendices discuss and illustrate the different kinds of feathers. I appreciated and agreed with Hanson’s perspective on all the areas he discusses, I enjoyed and respected the enthusiasm and sense of wonder that he conveys when talking about the natural world, and I congratulate him on thorough research and on being up-to-date on such a fast-moving topic. In short, Feathers is required reading for anyone interested in bird biology or evolution, and I strongly recommend it.

Hanson, T. 2011. Feathers: The Evolution of a Natural Miracle. Basic Books, New York, pp. 336. ISBN 978-0-465-02013-3. Hardback, index, refs. Here on amazonHere on amazon.co.uk.

For previous articles relevant to feathers, early bird evolution and other topics mentioned in this article, see…

Refs – -

Bundle MW, & Dial KP (2003). Mechanics of wing-assisted incline running (WAIR). The Journal of experimental biology, 206 (Pt 24), 4553-64 PMID: 14610039

Dial, K. P. 2003. Wing-assisted incline running and the evolution of flight. Science 299, 402-404.

- ., Jackson, B. E. & Segre, P. 2008. A fundamental avian wing-stroke provides a new perspective on the evolution of flight. Nature 451, 985-989.

- ., Randall, R. J. & Dial, T. R. 2006. What use is half a wing in the ecology and evolution of birds? BioScience 56, 437-455.

Freitag, S. & Robinson, T. J. 1993. Phylogeographic patterns in mitochondrial DNA of the Ostrich (Struthio camelus). The Auk 110, 614-622.

Hanson, T. 2011. Feathers: The Evolution of a Natural Miracle. Basic Books, New York.

Langley, N. 2011. Africa’s emptying skies. World Birdwatch 33 (2), 16-18.

Prum, R. O. 2003. Are current critiques of the theropod origin of birds science? Rebuttal to Feduccia (2002). The Auk 120, 550-561.

- . & Brush, A. H. 2002. The evolutionary origin and diversification of feathers. The Quarterly Review of Biology 77, 261-295.

Shipman, P. 1998. Taking Wing. Weidenfeld & Nicolson, London.

Ward, J., McCafferty, D. J., Houston, D. C. & Ruxton, G. D. 2008. Why do vultures have bald heads? The role of postural adjustment and bare skin areas in thermoregulation. Journal of Thermal Biology 33, 168-173.

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.

The views expressed are those of the author and are not necessarily those of Scientific American.



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  1. 1. Eric Dolha 9:00 pm 05/7/2012

    Is it just me or does those ostriches look like they have scales underneath their feathers, or is that pebbly surface just weird bird skin?

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  2. 2. dohertyc9 10:06 pm 05/7/2012

    Purchased! Great article.

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  3. 3. Heteromeles 11:32 pm 05/7/2012

    Great book, and I’m glad you wrote this review, Darren.

    For those of us outside the ivory tower, are New World Vultures near Falconiformes, Ciconiformes, or in some sort of Austroamericaniform clade?

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  4. 4. Mythusmage 12:44 am 05/8/2012

    People forget that feathers are actually rather simple structures, it’s just that there’s so much to those structures. It’s the sure mass of features that produces the complexity.

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  5. 5. Dartian 1:03 am 05/8/2012

    Darren:
    I was actually reading the book while staying in Las Vegas, and got to walk past the famous pink-plumed dancing girls of Bally’s Hotel and Casino on a twice-daily basis.

    Did you go and see the show? (For the purpose of research, of course.) ;)

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  6. 6. naishd 4:11 am 05/8/2012

    Thanks for comments. Ostrich skin texture (comment 1): the bumpy look of the skin is the pimpled, ‘gooseflesh’ appearance typical of plucked bird skin. Those bumps represent the feather attachment sites.

    Position of New World vultures (comment 3): both morphological and molecular analyses find them to be Accipitriformes, as the sister-group to a secretarybird + accipitrid clade.

    Finally, no, I did not pay to see any dancing girls in Las Vegas :) (comment 5). I did see them a lot, however, since I walked past the front of the theatre at Bally’s numerous times.

    Darren

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  7. 7. ChasCPeterson 1:55 pm 05/8/2012

    smoking vulture brains will give people supernatural powers when gambling

    But…but…what?

    feathers are actually rather simple structures, it’s just that there’s so much to those structures. It’s the sure mass of features that produces the complexity.

    What language is that, Kelloggian?

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  8. 8. Michelle de Villiers 3:52 pm 05/8/2012

    I am reading it. Great article, good book. I really like the book’s cover design too.

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  9. 9. Hydrarchos 4:02 pm 05/8/2012

    “Feduccia is quoted as saying in the book that “If it has feathers, it’s a bird” (Hanson 2011, p. 57), which of course means that feathered oviraptorosaurs, deinonychosaurs and so on are now birds according to Feduccia. As Hanson notes, and as Prum and others have said before (Prum 2003), this means that Feduccia is now contradicting decades of bold assertion in which he has insisted that deinonychosaurs and other Mesozoic theropods are nothing whatsoever to do with birds. ”

    So… presumably, the further the origin of feathers gets pushed back down the dinosaur lineage, the more dinosaurs Feduccia will consider to actually be birds… in which case, if all dinosaurs are found to be within the clade of “animals who had feathers or were descended from ancestors who had feathers” (I vaguely remember there being a suggestion a year or so ago that at least one ornithischian had feathers or at least something vaguely like them?), then Feduccia’s views will end up lining up with reality (unless he will then move to claiming “Dinosaurs Are Not Archosaurs”, or some such…)?

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  10. 10. naishd 4:34 pm 05/8/2012

    Hydrarchos (comment 9): at the moment, Feduccia and colleagues maintain that the ‘stage 1′ feathers (the simple, quill-like, cylindrical, unbranched integumentary structures seen on Sinosauropteryx, Dilong and so on) are not feathers of any sort, but actually internal collagenous skin fibres. Theagarten Lingam-Soliar in particular continues to publish technical papers pushing this view – most recently, he has argued that Sinosauropteryx had a continuous, ribbon-like frill running along its dorsal midline, and that the existence of such a structure explains the presence of the integumentary fibres. This hypothesis has already been falsified. Collagenous skin fibres do not project for a great distance beyond the epidermal surface, they don’t look like the fibres present on the theropods (they are much smaller and finer, for one thing), they don’t possess melanosomes, and so on.

    Erroneously, Feduccia et al. therefore believe that they only need to worry about those theropods with true, vaned feathers (oh, and this is despite the fact that those ‘stage 1′ feathers are present on forms with vaned feathers too). So, for now, they only concern themselves with oviraptorosaurs, deinonychosaurs, and perhaps therizinosaurs (and Yixianosaurus?).

    Darren

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  11. 11. Therizinosaurus 5:12 pm 05/8/2012

    “I cannot see that he and his colleagues have done anything but add confusion, contradiction and erroneous interpretations to our understanding of bird origins and early evolution.”

    I once thought this too, but then someone pointed out BANDits did actually correct BAD paleontologists on a couple points. Namely that Deinonychus’ semilunate is a distal carpal instead of a proximal carpal, and that Archaeopteryx lacks interdsental plates. If there are more examples, I’d be interested of course.

    The exploding zebra caecum reminds me of a similar experience I had while unwisely trying to cut a raccoon eye in half with a pair of scissors. Ahh memories…

    Hydrarchos- Alas, no. BANDits deny stage 1 feathers are feathers, since they think feathers’ flat shape is homologous to scales’ flat shape. Thus they deny feathers of non-maniraptoran theropods and the possibly homologous filaments of Tianyulong and pterosaurs. Indeed, they don’t even think those taxa have integumentary filaments, believing them to be collagen fibers instead. The pterosaur example is especially amusing, since they aren’t particularly important to their case, but they act as if the consensus is that pterosaurs were naked-skinned. In any case, since stage 3 feathers are unlikely to have evolved long before Maniraptora, we’re unlikely to see MANIACs extending the term ‘bird’ to other dinosaurs.

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  12. 12. naishd 5:49 pm 05/8/2012

    Mickey says (comment 11)…

    “I once thought this too, but then someone pointed out BANDits did actually correct BAD paleontologists on a couple points. Namely that Deinonychus’ semilunate is a distal carpal instead of a proximal carpal, and that Archaeopteryx lacks interdsental plates. If there are more examples, I’d be interested of course.”

    I’m totally not convinced. Several people – none of them fans of the ‘birds are not dinosaurs’ movement – have worked on the homology of the theropod semilunate since the 1990s, and the line of argumentation (in Chure’s work on allosaurs, in Longrich’s thesis on wrists etc.) indicates that identification of the semilunate as a distal carpal was coming, with or without Martin or Tarsitano…

    As for interdental plates in Archaeopteryx, Martin & Stewart (1999) and James & Portless (2009) said that they were absent, but this is not correct – they’re clearly present (e.g., Makovicky & Zanno 2011).

    Darren

    Refs – -

    James, F. C. & Pourtless, J. A. 2009. Cladistics and the origin of birds: a review and two new analyses. Ornithological Monographs 66, 1–78

    Makovicky, P. J. & Zanno, L. E. 2011. Theropod diversity and the refinement of avian characteristics. In Dyke, D. J. & Kaiser, G. (eds) Living Dinosaurs: The Evolutionary History of Modern Birds. John Wiley & Sons, Ltd, Chichester, pp. 9-29.

    Martin, L. D. & Stewart, J. D. 1999. Implantation and replacement of bird teeth. Smithsonian Contributions to Paleobiology 89, 295–300.

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  13. 13. Jerzy v. 3.0. 5:51 pm 05/8/2012

    Question about Velociraptor bumps indicating secondaries – is there any Velociraptor specimen which DOESN’T show them?

    About vultures in West Africa – not just vultures, but all big birds and mammals are rapidly becoming extinct there – including local subspecies of lion and giraffe…

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  14. 14. Jerzy v. 3.0. 6:01 pm 05/8/2012

    BTW, I just discovered that hypothesis formulated publicly in 2005

    Was checked and published in 2009 (and see here), but without giving the author any credit.

    Interesting, and I must start charging co-authorship for such comments!

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  15. 15. David Marjanović 6:47 pm 05/8/2012

    I vaguely remember there being a suggestion a year or so ago that at least one ornithischian had feathers or at least something vaguely like them?

    That’s Tianyulong, published in Nature (where it fucking belongs).

    This hypothesis has already been falsified. Collagenous skin fibres do not project for a great distance beyond the epidermal surface, they don’t look like the fibres present on the theropods (they are much smaller and finer, for one thing), they don’t possess melanosomes, and so on.

    And the feathers of Sinosauropteryx are not limited to the dorsal midline. If I’m not grossly misremembering, this was already explicitly mentioned in the 1998 Nature paper.

    they act as if the consensus is that pterosaurs were naked-skinned

    …which it hasn’t been for what, 40 years?

    Question about Velociraptor bumps indicating secondaries – is there any Velociraptor specimen which DOESN’T show them?

    I don’t know how many V. ulnae are known in total, but there can’t be many. The quill knobs were only reported in 1997, and the Nature paper that did that only mentioned one specimen, IIRC.

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  16. 16. Therizinosaurus 6:48 pm 05/8/2012

    Well, it would hardly be fair to deny someone credit for an idea merely because someone else would come up with it later. That’s true for any true fact, after all (given the same or increasingly better materials to work with).

    And as for interdental plates in Archaeopteryxm, that actually opens up quite the can of worms. Makovicky and Zanno argue that BANDits were wrong in thinking interdental plates were separate ossifications from the jaw bone, but Senter (2003) showed that the combined plate+septum is a separate ossification plesiomorphically at least (he used Euparkeria). In any case, Senter also determined the interdental plate and interdental septum are one unit, and everyone agrees Archaeopteryx at least has interdental septa. So we just have to make the somewhat semantic decision of whether that septum develops a lingual plate. Since undoubted interdental plates like those of Sinraptor are separated very narrowly from each other (and taxa with fused plates like Dromaeosaurus lack any separation), I’d say Archaeopteryx’s widely separated septa haven’t expanded into plates that cover tooth bases lingually more than an obliquely angled (labial side higher) alveolus would. And now I feel a bit dirty for agreeing with Martin… ;)

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  17. 17. Heteromeles 1:20 am 05/9/2012

    Oh dear, so turkey vultures are hawks with a working schnoz and peregrines are were-parrots. I love convergent evolution!

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  18. 18. Heteromeles 1:24 am 05/9/2012

    Scratch the “I love convergent evolution.” I just love evolution, period. Who needs creation when you have cladistics?

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  19. 19. Bill_Crofut 11:06 am 05/9/2012

    Is the following quote still considered of any relevance to this discussion?

    The feather is a marvel of natural engineering. It is at once extremely light and structurally strong, much more versatile than the stretched skin on which a bat supports itself in flight or the rigid structure of an aircraft’s wing–and far more readily repaired or replaced when damaged.

    Examine the cut-off quill feather of a pigeon. Though nearly weightless it has strength. The stiff shaft of the quill provides rigidity where support is needed, yet it is supple toward its tip, where flexibility is required for split-second aerial maneuvering. Feel the sleekness of the web, soft yet firm. Separate the barbs; zipper them together again by running them through the fingertips as a bird would preen with its bill. The intricacy of the design that allows this can be appreciated by putting the feather under a microscope. It will be seen that each parallel barb, slanting diagonally from the shaft, is not hairlike, but appears as a][miniature replica of the feather itself, with numerous smaller side branches, or barbules, that overlap those of the neighboring barbs in a herringbone pattern. These in turn have tiny projections called barbicels, many of which are equipped with minute hooks that neatly hold everything in place. The single pigeon feather under scrutiny may have several hundred thousand barbules and millions of barbicels and booklets.

    How did this structural marvel evolve? It takes no great stretch of imagination to envisage a feather as a modified scale, basically like that of a reptile--a longish scale loosely attached, whose outer edges frayed and spread out until it evolved into the highly complex structure that it is today.

    [Roger Tory Peterson and The Editors of Life . 1963. The Birds. New York: Time Incorporated, pp. 33-34]

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  20. 20. naishd 11:08 am 05/9/2012

    Interdental plates in Archaeopteryx (comment 16): I’m confused. Martin & Stewart (and authors who’ve followed them) say that interdental plates are absent in Archaeopteryx, with the structures identified as plates actually being “distinct alveolar septa (interdental plates?)” (Martin & Stewart 1999, p. 299). But just look at the excellent, detailed close-ups of the Archaeopteryx mandible in Elzanowski & Wellnhofer (1996, p. 92). How are those structures not interdental plates? It seems to me that Martin & Stewart (and the authors who followed them, like James & Pourtless) were simply trying to make birds as un-dinosaur-like as possible, and hence making false claims that the interdental plates of Archaeopteryx are somehow fundamentally different from those of other theropods.

    Darren

    Refs – -

    Elzanowski, A. & Wellnhofer, P. 1996. Cranial morphology of Archaeopteryx: evidence from the seventh skeleton. Journal of Vertebrate Paleontology 16, 81-94.

    Martin, L. D. & Stewart, J. D. 1999. Implantation and replacement of bird teeth. Smithsonian Contributions to Paleobiology 89, 295-300.

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  21. 21. naishd 11:26 am 05/9/2012

    Bill_Crofut (comment 19): the stuff about the structure of feathers still holds true, of course, but the idea alluded to at the end about feathers being modified scales has been very much superseded. The idea that scales might have split during evolution, eventually forming flat, vaned feathers that functioned as heat shields, was mooted during the 1970s by Philip Regal. It doesn’t work because feathers and scales are not homologous: they’re formed from different kinds of keratin, and feathers appear to be evolutionary novelties – new structures that did not develop from scales. It has been hypothesised that the earliest feathers – ‘stage 1 feathers’, if you will – were simple filaments, and that incremental, increasingly complex branching of this structure led to the diversity of later feather stages (Prum & Brush 2002, 2003).

    Darren

    Refs – -

    Brush, A. H. 1996. On the origin of feathers. Journal of Evolutionary Biology 9, 131-142.

    - . 2001. The beginnings of feathers. In Gauthier, J. & Gall, L. F. (eds) New Perspectives on the Origin and Early Evolution of Birds: Proceedings of the International Symposium in Honor of John H. Ostrom. Peabody Museum of Natural History, Yale University (New Haven), pp. 171-179.

    Prum, R. O. & Brush, A. H. 2002. The evolutionary origin and diversification of feathers. The Quarterly Review of Biology 77, 261-295.

    - . & Brush, A. H. 2003. Which came first, the feather or the bird? Scientific American 286 (3), 84-93.

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  22. 22. Therizinosaurus 8:37 pm 05/9/2012

    “But just look at the excellent, detailed close-ups of the Archaeopteryx mandible in Elzanowski & Wellnhofer (1996, p. 92). How are those structures not interdental plates? It seems to me that Martin & Stewart (and the authors who followed them, like James & Pourtless) were simply trying to make birds as un-dinosaur-like as possible, and hence making false claims that the interdental plates of Archaeopteryx are somehow fundamentally different from those of other theropods.”

    Oh, I agree that was their (stupid) intention, but birds had to lose their interdental plates sometime, so why not at the Archaeopteryx node? I suppose my question would be if Archaeopteryx had interdental septa that were not developed into plates (but were tilted to have the labial edge higher), how would you expect Elzanowski and Wellnhofer’s (1996) figure 12A to look different?

    Link to this
  23. 23. Therizinosaurus 9:18 pm 05/9/2012

    And because I just realized I asked you a question without answering yours…

    “How are those structures not interdental plates?”

    First, the supposed plates are placed far apart from each other, so that there is ~2/3 of a FABL between the base of each. But mostly look at the supposed plate behind the sixth tooth. It expands at the top, which I can’t recall seeing a free interdental plate do, but does make sense if it’s a tilted surface that’s passing behind a round tooth. Ditto for the area behind the second tooth. Sure I could imagine the surfaces behind the third and fourth teeth being plates, but they grade posteriorly into the fifth and particularly sixth surfaces which as I say above I find to be clearly not vertical plates placed lingually to the teeth.

    Link to this
  24. 24. Jurassosaurus 12:11 am 05/10/2012

    “It doesn’t work because feathers and scales are not homologous: they’re formed from different kind of keratin, and feathers appear to be evolutionary novelties – new structures that did not develop from scales. It has been hypothesised that the earliest feathers – ‘stage 1 feathers’, if you will – were simple filaments, and that incremental, increasingly complex branching of this structure led to the diversity of later feather stages (Prum & Brush 2002, 2003).”

    Prum and Brush’s model is certainly the most popular for feather origins, but it is far from the only model of feather evolution.

    Roger Sawyer and his lab have been working on the origin of feathers for decades(at least since 74 for some stuff) and do not come to the same conclusions as Prum and Brush.

    For one thing they have been able to experimentally show evidence for homology in avian beta keratins and crocodylian beta keratins. This includes experimental expression of both avian scale and feather beta keratins in the embryonic epidermis of developing alligators (Sawyer et al. 2000, 2003). In contrast to Prum and Brush, the Evo-Devo work from Sawyer’s lab suggests that rather than being evolutionary novelties, feathers did develop from scales using a heterochronic “hijacking” of the embryonic scale layers, in particular the secondary periderm, subperiderm, and alpha stratum (which have been found to be homologous with the sheath, barb ridge, marginal and axial plate cell populations of feathers). Also in contrast to Prum and Brush’s model, Sawyer et al. argue that feathers first appeared as elongated filaments of barb-ridge-like structures, looking very similar to what is seen in developing bird feathers (Sawyer et al. 2003), as well as from experimental data (Konig & Sawyer 1985, Yu et al. 2002).

    So I’d say that the “feathers are just modified scales” argument is still out there and even has some good empirical backing. It’s just that the modification seems to have happened much earlier on in development than was initially thought (so the elongated, feathery scales argument is still invalidated).

    It’s disappointing that Hanson didn’t seem to cover any of the alternate models for feather origins. Looking at their references list (I don’t have the book, but I can read the references on the Amazon preview) it looks like they only mention Prum and Brush’s model.

    References

    Konig, G., Sawyer, R.H. 1985. Analysis of Morphogenesis and Keratinization in Trans-Filter Recombinants of Feather-Forming Skin. Dev.Biol. Vol.109:381–392.

    Sawyer, R.H., Salvatore, B.A., Potylicki, T-T.F., French, J.O., Glenn, T.C., Knapp, L.W. 2003. Origin of Feathers: Feather Beta Keratins are Expressed in Discrete Epidermal Cell Populations of Embryonic Scutate Scales. J.Exp.Zool.(Mol.Dev.Evol.) Vol.295B:12-24.

    Sawyer, R.H., Glenn, T., French, J.O., Mays, B. et al. 2000. The Expression of Beta Keratins in the Epidermal Appendages of Reptiles and Birds. Amer.Zool. Vol.40:530-539.

    Yu, M., Wu, P., Widelitz, R.B., Chuong, C-M. 2002. The Morphogenesis of Feathers. Nature. Vol.420:308-312.

    Link to this
  25. 25. Mythusmage 1:31 am 05/10/2012

    Chas, #7

    You and English are not on speaking terms, are you?

    Link to this
  26. 26. naishd 6:01 am 05/10/2012

    Interdental plates of Archaeopteryx (comment 23): I can’t see that there’s any real difference between what Archaeopteryx possesses, and the condition in several non-avialan theropods. The structures in Archaeopteryx have subtriangular apices, are located between the tooth bases and lingual to them, and do not completely cover the tooth bases. So – pretty much exactly the same as the interdental plates of Scipionyx (Dal Sasso & Maganuco 2011, fig. 30, p. 40) and Sinornithosaurus (Xu & Wu 2001, fig. 4, p. 1743; fig, 6, p. 1048), then?

    Martin and colleagues are either saying that we should stop calling these structures ‘interdental plates’ once they become as widely spaced and non-extensive as this (though they’re ambiguous on this, since Martin & Stewart (1999) still called them “interdental plates?” on p. 299), or they’re implying that these structures have a distinct evolutionary history from the more extensive interdental plates seen in other theropods (and other archosaurs). Seeing as it’s an inaccurate effort to obfuscate the similarities between Archaeopteryx and other theropods, I don’t think that following their arguments does us any favours.

    Darren

    Refs – -

    Dal Sasso, C. & Maganuco, S. 2011. Scipionyx samniticus (Theropoda: Compsognathidae) from the Lower Cretaceous of Italy: osteology, ontogenetic assessment, phylogeny, soft tissue anatomy, taphonomy, and palaeobiology. Memorie della Società Italiana di Scienze Naturali e del Museo Civico di Storia naturale di Milano 37, 1-281.

    Martin, L. D. & Stewart, J. D. 1999. Implantation and replacement of bird teeth. Smithsonian Contributions to Paleobiology 89, 295-300.

    Xu, X. & Wu, X.-C. 2001. Cranial morphology of Sinornithosaurus millenii Xu et al. 1999 (Dinosauria: Theropoda: Dromaeosauridae) from the Yixian Formation of Liaoning, China. Canadian Journal of Earth Sciences 38, 1739-1752.

    Link to this
  27. 27. naishd 6:14 am 05/10/2012

    Jurassosaurus (comment 24): thanks for bringing attention to that work and for citing the references. In comment 21, I had Regal’s model of ‘fraying scales’ in mind, as it’s this that Roger Tory Peterson was referring to (see comment 19). No, Hanson doesn’t discuss the work by Sawyer et al. But I note that Prum, Dyck, Brush and others cite the work by Sawyer et al. as being consistent with their own model: Prum & Dyck (2003) say that “feathers, bird scales, and crocodilian scales all share detailed molecular homologies at the level of the placode, but that all subsequent stages of the feather development occur through derived, novel mechanisms of morphogenesis” (p. 88).

    Darren

    Ref – -

    Prum, R. O. & Dyck,. J. 2003. A hierarchical model of plumage: morphology, development, and evolution. Journal of Experimental Zoology (Mol Dev Evol) 298b:73-90.

    Link to this
  28. 28. David Marjanović 9:25 am 05/10/2012

    You and English are not on speaking terms, are you?

    First you said feathers are simple, then you say they have a mass of features that makes them complex. You appear to contradict yourself from one sentence to the next.

    When I was starting to write scientific papers, the first thing my supervisor said to me was, paraphrasing, “no matter what you do, you will be misunderstood – by someone, sometime, somewhere –, so it’s your job to minimize the opportunities for that”.

    Link to this
  29. 29. Gigantala 10:22 am 05/10/2012

    In regards to vulture phylogeny, the original results from THE STUDY, showed that New World vultures are actually basal falcons, not Accipitriformes, meaning that New World vultures are essencially part of the seriema+falcon+parrot+passerine clade, and probably evolved from a caracara like ancestor.

    The reason why everyone is lumping them with the Accipitriformes was due to an error in the phylogenetic cladogram.

    Link to this
  30. 30. accipiter 11:02 am 05/10/2012

    comment #15: on Tianyulong: “published in Nature (where it fucking belongs).”

    why? is there anything wrong with Tianyulong i missed?

    very interesting on the “feathers are actually not elongated scales that branched later” discussion, i didn’t knew that view was outdated!
    but so, what are the avian scales in Prum & Dyck’s model then? are THEY surviving reptilian scales while the feathers are not, are they novel creations along with the feathers, or even more crazy; are they derived from basal, ribbon-like feathers that whould have got “flattened” and thickened, hence meaning that some theropods lost and re-evolved scales!
    whould be especially ironic given that when i try to explain that dinosaurs where never extinct to poeples not familiar with paleontology, one of the first things i tell them is to look at a bird’s legs…

    Link to this
  31. 31. BrianL 12:15 pm 05/10/2012

    @Gigantala:
    What is this THE STUDY you refer to? If you’re right in saying that cathartids are actually sister to falconids, the combination of falconids, cathartids and Cariamae goes some way to validating Storrs Olson’s out-there-theory of a clade consisting of these birds plus touracos, hoatzins and accipittrids. I guess that those who shoot wildly and often occasionally hit the mark.

    By the way, would this also bring friggin’ TERATORNS into this clade? My dreams of teratorns and Cariamae being closely related would somewhat come true.:)

    Link to this
  32. 32. naishd 12:38 pm 05/10/2012

    Ericson’s latest dataset finds New World vultures to be the sister-group to an (accipitriforms + (owls + (mousebird + Picocoraciae))) clade, but most other recent works find New World vultures to be part of Accipitriformes, not close to falconids. No idea what THE STUDY is.

    Darren

    Link to this
  33. 33. Heteromeles 2:44 pm 05/10/2012

    @Naishd: Now I’m wondering about birds’ sense of smell. We know that vultures have a good sense of smell, and I believe the list of advanced sniffers includes kiwis and tubenoses.

    That makes me curious: has anyone checked the sense of smell in, say accipitriforms? Old world vultures supposedly find carcasses by sight, but it strikes me as a wee bit bizarre that all those predatory birds have no sense of smell, even though some of them hunt in dense brush.

    How does olfaction map onto bird phylogeny? Is it something that is gained and lost repeatedly, or is it a basal trait that was lost in more derived clades?

    I do know, from first hand experience, that pigeons have little or no sense of smell (see story at end of paragraph), but it still seems unusual that as a clade, birds have such highly variable senses. How did they evolve? The story: I had a young pet pigeon who burned his tail feathers off on an old halogen floor lamp and didn’t notice (he was warming his butt on a cold night). After rescuing him and trimming of the burned ends, I had to open the windows and leave the apartment for half an hour before I could stand to be in there. The lamp stank so badly afterwards that I had to pitch it. That’s what “no sense of smell” means to me. The smell of burning feathers didn’t really make it into Hanson’s book, which, overall, is probably a good thing…

    Link to this
  34. 34. Gigantala 4:32 pm 05/10/2012

    The famous Hackett study, obviously.

    Appearently, the original results did show New World vultures as closer to falcons, but the graph screwed up and showed them as sister clade to Accipitriformes. The whole thing was cleared up in the author’s blog, but unfortunately the mistake has become dogma.

    Link to this
  35. 35. Cameron McCormick 4:37 pm 05/10/2012

    In regards to avian olfactory capabilities,

    Balthazart & Taziaux (2009):

    Until the second half of the 20th century, it was broadly accepted that most birds are microsmatic if not anosmic and unable to detect and use olfactory information… During the past 20–30 years, many publications have appeared indicating that this view is definitely erroneous. We briefly review here anatomical, electrophysiological and behavioral data demonstrating that birds in general possess a functional olfactory system and are able to use olfactory information in a variety of ethological contexts… The widespread idea that birds are anosmic or microsmatic is thus not supported by the available experimental data and presumably originates in our anthropomorphic view that leads us to think that birds do not smell because they have a rigid beak and nostrils and do not obviously sniff.

    Link to this
  36. 36. Cameron McCormick 4:50 pm 05/10/2012

    Huh, it appears my last comment got eaten. [from Darren: sorry, both of your comments were detained as spam.]

    Anyways, in regards to avian olfactory capabilities, Balthazart & Taziaux (2009) provide an excellent review. Long story short, the reduction or absence of olfactory capabilities in birds is a myth.

    Link to this
  37. 37. Bill_Crofut 7:45 pm 05/10/2012

    Darren,

    Thank you for the clarification and the references for future research (comment 21).

    Bill

    Link to this
  38. 38. Therizinosaurus 11:02 pm 05/10/2012

    “why? is there anything wrong with Tianyulong i missed?”

    Heehee, exactly what I was thinking, but the apparent innocence of your question makes it all the more hilarious.

    Darren @26: Well, assuming Senter’s (2003) work is right in that interdental plates and interdental septa together form an interdental unit, Archaeopteryx’s interdental septa are formed from the same bone interdental plates are but aren’t homologous (since theropods with interdental plates still have interdental septa too). Note that if they are just septa instead of plates, we’d also expect half of each to be lingual to the teeth and because each tooth has a rounded base, the lingual half of each septum would appear tapered dorsally (triangular) if its lingual edge is lower than its labial edge. But unlike an interdental plate, the labial side would expand dorsally, as seen behind the sixth dentary tooth of Archaeopteryx. I am still curious how you think figure 12A would look different if Archaeopteryx just had tilted septa and not plates.

    And though this whole discussion is quite off topic (maybe I should blog on it), as for Sinornithosaurus and Scipionyx…

    In Sinornithosaurus, I don’t see any obvious plates in the premaxillae (figure 4A of Xu and Wu, 2001). Between most of the teeth, the surface looks undifferentiated and rounding toward the labial side. In fact, the space behind the fourth left tooth (at the top of the image) is actually concave. The only perhaps differentiated plate in the one behind the fourth right tooth, which is labeled. But that one’s also apically expanded, seemingly co-extensive with the labial wall behind it, and because its associated tooth has more root exposed than others, I suspect part of the lingual wall of its alveolus is missing. And that would eliminate the supposed anterior edge of the plate, leaving only the apparent basal edge to be problematic. Maybe when the lingual alveolar wall broke off, it took the lingual bone wall posterior to it as well? And in this case the ‘interdental plate’ is just a rectangle where the lingual premaxillary bone is missing, making the basal edge just the broken edge of the bone above it? Hard to say, but I’m extra wary since the opposite premaxilla certainly lacks a free interdental plate in this position (as noted above). It’s possible the lingual wall of the alveoli are fused interdental plates as in eudromaeosaurs (compare to figure 3e of Currie’s 1987 Troodon jaw paper), but I wouldn’t want to say that for certain since some look concave.

    For Sinornithosaurus’ dentary (figure 6), it was reported to have fused plates posteriorly, and I agree there. There is a differentiated (from the jaw bone) and continious wall below the alveoli like that in eudromaeosaurs. The supposed unfused anterior plates are what resembles Archaeopteryx though. Only two are visible (behind the third and fourth teeth), and they both taper apically. They may indeed be small, separated plates like you think Archaeopteryx has, or they could be oblique septa like I think Archaeopteryx has. Based on the figure, either hypothesis works.

    For Scipionyx (figure 30), I agree they’re interdental plates. Mostly because the one that’s second from the left has a clear tapered anterior edge separating it completely from the labial wall of the empty alveolus in front of it. Thus unlike Archaeopteryx, it doesn’t expand labially/apically to wrap around the tooth. Scipionyx’s plates are widely separated though, so there goes that reason I had for doubting Archaeopteryx’s.

    Link to this
  39. 39. David Marjanović 5:08 am 05/11/2012

    the original results from THE STUDY

    Which study?

    The reason why everyone is lumping them with the Accipitriformes was due to an error in the phylogenetic cladogram.

    That’s a conclusion, not an explanation. What was that error, and what caused it? And cladograms are phylogenetic hypotheses by definition.

    why? is there anything wrong with Tianyulong i missed?

    ~:-| I answered your question: Tianyulong is the ornithischian with stage I feathers that you were asking about. I was surprised that you didn’t know more about it, because it was published in the most famous of all (yes, all) scientific journals.

    The famous Hackett study, obviously.

    “Obviously”? That’s one of two big studies that came out in the same year (within a few months even), and several more have come out in the four years since that.

    Appearently, the original results did show New World vultures as closer to falcons, but the graph screwed up and showed them as sister clade to Accipitriformes. The whole thing was cleared up in the author’s blog, but unfortunately the mistake has become dogma.

    Oh. So the illustration in the paper didn’t actually represent the cladogram correctly. That’s interesting.

    …but doesn’t change what I just wrote above.

    Link to this
  40. 40. naishd 5:39 am 05/11/2012

    I have just corresponded with one of the authors of Hackett et al. – they did not exactly confirm what Gigantala is saying, so I’m curious as to where the relevant claim (viz, that NW vultures grouped close to falconids) comes from.

    And, thanks Mickey, but I think we need to stop there on interdental plates for now…

    Darren

    Link to this
  41. 41. John Harshman 9:26 am 05/11/2012

    Speaking as the aforesaid author of Hackett et al., I want to reiterate that there are no mistakes in any of the figures. Cathartids are shown exactly where the analyses put them. You may think that’s wrong, but not on the basis of our data. Other data may in fact contradict our tree, but if so I don’t know about it. Suh et al. included a cathartid, and it isn’t near falcons; the method they used is incapable of telling us where it should go, but definitely not near falcons.

    I would be very curious to know about this “author’s blog”. As far as I’m aware, none of the authors has a blog. And anyway, nobody would be announcing something that isn’t true if they had one.

    Link to this
  42. 42. Gigantala 11:22 am 05/11/2012

    This site is where I got the information of the misunderstanding.

    I hope it solves this problems.

    Link to this
  43. 43. naishd 2:07 pm 05/11/2012

    Gigantala: read the comments attached to that article, specifically comments 10 and 11.

    Darren

    Link to this
  44. 44. Heteromeles 2:10 pm 05/11/2012

    @Gigantala: In the blog you linked to, the blogger said “OOPS! thanks for spotting that error.” (comment 11) about new world vultures being next to Falconidae, not Accipitridae.

    Link to this
  45. 45. John Harshman 4:33 pm 05/11/2012

    Also, for the record, Grrlscientist is not one of the authors of the Hackett et al. paper, though she is an ornithologist.

    Link to this
  46. 46. David Marjanović 7:58 am 05/12/2012

    @Gigantala: In the blog you linked to, the blogger said “OOPS! thanks for spotting that error.” (comment 11) about new world vultures being next to Falconidae, not Accipitridae.

    Well, no. She had said it both ways and then “corrected” the place where she said the New World vultures belonged together with Accipitridae. *facepalm* Read comment 25 instead.

    Link to this
  47. 47. accipiter 9:09 am 05/12/2012

    comment #39: @ David Marjanović
    yes of course i knew about tianyulong, it’s only that the way you said “where it fucking belongs” about the fact of it beeing in Nature made me think you hinted it turned out to be one of those overhyped, yet poorly suported “new findings” like the alleged venomosity of Sinornithosaurus for example…
    as someone said before on this blog, written sarchasm can be easily misunderstood… my bad :p

    Link to this
  48. 48. Mythusmage 7:37 pm 05/12/2012

    David, #28

    You do understand the difference between complicated and complex. Both are made up of simple elements, but where a complex mechanism can be broken down into simple elements again, a complicated mechamism can’t.

    Link to this
  49. 49. CS Shelton 1:35 am 05/13/2012

    OMG, those ostriches! Could they grow any of it back, and if not, how long could they live?

    Link to this
  50. 50. naishd 6:28 am 05/13/2012

    Yes, they grew all of their feathers back, and this whole-body plucking can be done every seven months or so. There are, as you might guess, welfare issues attached to this kind of treatment. It still goes on, and some organisations (like PETA) argue that it should be banned.

    Darren

    Link to this
  51. 51. David Marjanović 6:31 am 05/13/2012

    You do understand the difference between complicated and complex.

    …No, that’s the first time in my life that I encounter these definitions. I’m not being sarcastic.

    Where did you get those definitions from?

    Link to this
  52. 52. Heteromeles 10:31 am 05/13/2012

    @David: I’ve seen these too, in complexity theory in ecology. Complex systems are defined by having a hierarchical structure (as noted above, they can be decomposed into simpler elements). Complicated systems don’t have a hierarchical structure.

    Example: A river system flowing out of mountains is complex, because it follows a fractal structure of smaller streams feeding into bigger ones. A swamp is complicated, both because hydrologically it occupies a flat ground where the water can go in any direction (not just downhill), and because the vegetation growing out of the water somewhat constrains the water’s paths, making for a complicated pattern of water movement that is impossible to describe based solely on the physical properties of water and the rock underneath.

    I didn’t get much into complexity theory, because the stuff I’m interested in tends to be complicated.

    Link to this
  53. 53. Heteromeles 10:52 am 05/13/2012

    To get back to the context of feathers, structurally, feathers are complex. Birds’ use of feathers is complicated.

    Feathers’ structural complexity comes both from the fact that they are generated by a fairly simple set of cells and genes, and from the fact that they have somewhat similar structures on multiple levels of scale (in other words, they’re fractals. Often you can spot complexity theorists by the fractals in their offices).

    Birds use feathers for a complicated mix of locomotion, protection, thermoregulation, and social display, among other things. Feathers can be put to multiple uses simultaneously, and those uses depend not only on how the bird interacts with its environment (something which changes continuously) but also on the interplay among different feathers. This is a complicated system, and while sciences as different as aerodynamics, physiology, sexual selection, and evolution (among many others) can be used to study particular aspects of feather use, no one field provides a comprehensive understanding of how birds use feathers. Hence, it’s a complicated subject.

    Link to this
  54. 54. David Marjanović 9:52 am 05/14/2012

    Thanks for the explanation.

    I didn’t get much into complexity theory, because the stuff I’m interested in tends to be complicated.

    Thread won!

    Link to this
  55. 55. kuartus 12:33 am 05/15/2012

    If theropods are lizard hipped dinosaurs, and birds are well bird hipped, then doesnt it make more sense for birds to be descendants from onithischians or bird hip dinosaurs instead?

    Link to this
  56. 56. naishd 4:01 am 05/15/2012

    Birds belong to a group of ‘lizard-hipped dinosaurs’ (saurischians) that have the ‘bird-hipped’ configuration. So, the ‘bird-hipped’ configuration (where the pubic bone is directed backwards rather than forwards) evolved more than once within Dinosauria. Note that this does not diminish the evidence supporting monophyly of Ornithischia.

    Darren

    Link to this
  57. 57. David Marjanović 10:07 am 05/15/2012

    It’s simply not possible to do phylogenetics with a single character. It’s always necessary to look at as much evidence as possible.

    Link to this
  58. 58. CS Shelton 8:58 pm 05/15/2012

    Thanks for the info about ostriches, Darren. That picture was hella disturbing.

    Link to this
  59. 59. hcrepin 5:50 pm 08/18/2013

    Great piece. Just to mention about those interested in birds thermography, it is some others available here:
    http://www.thethermograpiclibrary.org/index.php?title=Cat%C3%A9gorie:Animaux

    Link to this

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