Today sees the formal publication of the bizarre little Chinese maniraptoran theropod Epidexipteryx hui Zhang et al., 2008 from the Daohugou Formation of Ningcheng County, north-eastern China. Unfortunately the publication of this new species is not quite the surprise it should be, as the authors inadvertently submitted their manuscript to the wrong venue a few weeks ago, thereby making the article visible to the whole world some time before it was ready to be published. Anyway, we'll just have to pretend that never happened. Belonging to a recently discovered group called the scansoriopterygids, Epidexipteryx is tiny (less than 20 cm long I think), and very, very weird (Zhang et al. 2008). Its skull is short-snouted with a truncated antorbital fenestra, a nostril positioned in a relatively high position, and strongly procumbent, proportionally large anterior teeth (the teeth get smaller further back). Its arms and hands were very elongate (see figure below, from Zhang et al. 2008).
What makes it particularly odd - and this is probably the one 'take home' feature that everyone will be talking about - is that it preserves four super-long, strap-like structures growing from its distal-most ten tail vertebrae (these are termed ETFs by the authors, for 'Elongate ribbon-like Tail Feathers'). These structures are likely to have played a role in display (Zhang et al. 2008), and if they're homologous with feathers (which is likely), then here is possible evidence that feathers initially evolved for display (unlike birds and other feathered maniraptorans, Epidexipteryx does not have complex feathers on its arms). However...
... what's likely to be widely overlooked is that the body of Epidexipteryx is covered with 'non-ETF' structures that are even more interesting (see figure below, from Zhang et al. 2008). Looking something like flattened, closed flowers with their petals pointing upwards in parallel fashion, the 'non-ETFs' have their distal parts composed of filamentous parallel barbs, and they emerge from a membranous base. Epidexipteryx was hence covered in complex, filamentous structures. The potential significance of this will not have been lost on you if you're familiar with the development of feathers in modern birds, or with the model of feather evolution developed by Prum & Brush (2002, 2003). The latter authors proposed that feathers started out ('stage 1') as hollow cylinders, then ('stage 2') became unbranched barbs attached to a calamus. By stage 3, feathers were planar structures with the barbs diverging from a central rachis, and from hereon we get the complex vaned feathers that we know and love. It is conceivable the 'non-ETFs' of Epidexipteryx represent stage 2 structures, but - given that the structures on Epidexipteryx have a far wider base than the narrow calamus inferred by Prum & Brush (2002, 2003) - perhaps this new fossil hints at a more complicated sequence of steps. Also worth noting is that the pennaceous feathers of birds begin growth as a tubular structure: from a broad 'follicle collar' that extends around the base, the rachis extends upwards, the barbs emerging both from it and from the edges of the collar. Might the membranous bases of the 'non-ETFs' of Epidexipteryx be homologous with the follicle collar? This is all very speculative, but these are interesting questions that need to be examined.
The short-snouted skull and big, procumbent anterior teeth of Epidexipteryx are very interesting as the same features seem to be cropping up quite a bit among maniraptorans. Basal oviraptorosaurs (like Caudipteryx and Incisivosaurus) were like this, as were at least some basal birds. Based on the behaviour of some extant mammals with procumbent anterior teeth (notably the shrew-opossums or caenolestoids), the procumbency of the teeth in Epidexipteryx suggest that it was grabbing small prey, perhaps insects and/or their larvae. We know from the other scansoriopterygid specimens (read on) that at least some members of this group had very elongate third fingers: were they extracting insects in aye-aye fashion, and then grabbing the exposed prey with procumbent teeth? Having said all that, note that we don't yet have a taxon that combines both long third fingers and procumbent teeth: it's not possible to determine whether Epidexipteryx had a long third finger, and Epidendrosaurus (read on) lacks teeth. By the way, is it coincidental that we mostly see enlarged or procumbent anterior teeth in feathered theropod taxa? There is a ver 1 article on this very observation here.
By curious coincidence, I was writing about scansoriopterygids just yesterday (for a current book project) - now I can add the information on this new taxon. Two scansoriopterygids have previously been named, but both are now regarded as synonymous. The first of them is Epidendrosaurus ningchengensis Zhang et al., 2002 and, like Epidexipteryx, it's from the Daohugou Formation. The age of the Daohugou Formation is controversial: it might be as old as Middle Jurassic or as young as Early Cretaceous, with the most recent studies suggesting the latter. Epidendrosaurus was also tiny (less than 20 cm long), its near-complete skeleton revealing elongate hands and the impression of a long tail. It appears to be a juvenile, possibly a hatchling (Zhang et al. 2002) [adjacent Epidexipteryx by Qiu Ji and Xing Lida, from Carl Zimmer's blog at Discover magazine here].
The second animal is Scansoriopteryx heilmanni Czerkas & Yuan, 2002 from Liaoning Province in north-eastern China. Known from a somewhat more complete skeleton than Epidendrosaurus, its generic name means 'climbing wing' while the specific name honours Gerhard Heilmann, the Danish artist and author whose 1927 book The Origin of Birds had been the standard work on avian origins until the 1960s (for more on Heilmann see the discussion here). The Scansoriopteryx specimen preserves a far better skull than Epidendrosaurus, and it also possesses an articulated hand and more complete pelvic girdle (Czerkas & Yuan 2002). The skull was short, with enormous eye sockets and no evidence for teeth. The three-fingered hand was very unusual in that the third finger was much longer than either the first or second (usually, the second finger is the longest in theropods). In the foot, the first toe (the hallux) was positioned very low down and close to the other three toes, and its position on the foot suggested that it might have helped this animal to grab onto twigs and branches when climbing. In contrast to opisthopubic birds and dromaeosaurs, the Scansoriopteryx pelvis is propubic. Filament-like feathers appeared to be preserved adjacent to the hand and elsewhere on the specimen, and what was identified as a small patch of scales were present near the end of the tail. Like the Epidendrosaurus specimen, Scansoriopteryx also appeared to be a hatchling [skeletal reconstruction of Scansoriopteryx below by John Conway].
Epidendrosaurus and Scansoriopteryx appear to be essentially identical and it is now generally agreed that they are the same animal. As has been much discussed, the fact that both appeared in the literature at about the same time made it difficult to be sure which name was older (and thus which had technical priority). It seems that Epidendrosaurus was published first, so this is the name we now use for this animal (Harris 2004).
How did Epidendrosaurus live? The tiny size, very long arms and hands, and low position of the first toe all suggest that it was a climber. Its remarkable third finger might have been used in grasping branches, but it was also noted that the finger recalls that of the aye-ayes Daubentonia (Zhang et al. 2002), where the very long, slim third finger is used to extract grubs from their burrows. Given that both Epidendrosaurus specimens are very young juveniles, and given that substantial changes can occur in anatomy and skeletal proportions during growth, it is possible that adults were very different. Now that we have Epidexipteryx, is it just a grown-up Epidendrosaurus? Epidexipteryx and Epidendrosaurus would seem to differ in that the former reportedly has a shortened tail, whereas the latter had a long one including 22 vertebrae at least (Czerkas & Yuan 2002). However, a break in the Epidexipteryx tail leaves room for doubt: maybe it originally had a far longer, Epidendrosaurus-like tail [short-tailed reconstruction of Epidexipteryx shown below]. More work is needed to resolve this.
Previous work has established that Epidendrosaurus is a maniraptoran close to the clade that includes Archaeopteryx and other birds (Zhang et al. 2002, Senter 2007). Zhang et al. (2008) find that Epidexipteryx and Epidendrosaurus form a clade (for nomenclatural reasons this has to be called Scansoriopterygidae Czerkas & Yuan, 2002, even though the generic name Scansoriopteryx is not currently recognised), and that this clade is the sister-taxon to the Archaeopteryx + other bird clade. The name Aves has been used by some authors as node-based for Archaeopteryx + other birds (Chiappe et al. 1996), while the branch-based clade that includes all maniraptorans closer to modern birds than to other taxa is called Avialae (Gauthier 1986). If we follow these recommendations, the scansoriopterygids are the most basal known members of Avialae, but they're not part of Aves. Given that scansoriopterygids recall oviraptorosaurs and members of other maniraptoran clades in some of their characters, it is conceivable that this position might change in future however.
And with its short skull, procumbent teeth, propubic pelvis and bizarre integument, here is more evidence that the sequence of character acquisition among maniraptorans was more complicated, and more interesting, than conventionally thought.
PS - thoughts from one of the authors will be posted on Dave's Hone blog here, some time today, hopefully. Huh, he can make the promises: but can he deliver?
Refs - -
Chiappe. L. M., Norell, M. A. & Clark, J. M. 1996. Phylogenetic position of Mononykus (Aves: Alvarezsauridae) from the Late Cretaceous of the Gobi Desert. Memoirs of the Queensland Museum 39, 557-582.
Czerkas, S. A. & Yuan, C. 2002. An arboreal maniraptoran from northeast China. In Czerkas, S. J. (ed) Feathered Dinosaurs and the Origin of Flight. The Dinosaur Museum (Blanding, Utah), pp. 63-95.
Gauthier, J. 1986. Saurischian monophyly and the origin of birds. Memoirs of the California Academy of Science 8, 1-55.
Harris, J. D. 2004. 'Published works' in the electronic age: recommended amendments to Articles 8 and 9 of the Code. Bulletin of Zoological Nomenclature 61, 138-148.
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.
Senter, P. 2007. A new look at the phylogeny of Coelurosauria (Dinosauria: Theropoda). Journal of Systematic Palaeontology 5, 429-463.
Zhang, F., Zhou, Z., Xu, X. & Wang, X. 2002. A juvenile coelurosaurian theropod from China indicates arboreal habits. Naturwissenschaften 89, 394-398.
- ., Zhou, Z., Xu, X., Wang, X. & Sullivan, C. 2008. A bizarre Jurassic maniraptoran from China with elongate ribbon-like feathers. Nature 455, 1105-1108.
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So what we've got is a insectivourous/carnivorous dino phesant. What a cool little animal
My kids will love these!
Nope. The current rules make Scansoriopteryx the correct name (first in print on paper) and even the proposed amendments to the rules for electronic publications (which wouldn't be retrospective anyway) wouldn't support Epidendrosaurus as the correct name (advance online publications don't advance the publication date unless they themselves independently fulfill the requirements for online publication).
Oh. Thanks Chris. My understanding from discussion is that Epidendrosaurus had won out, I think mostly because Harris (2004) argued that it should. Can anyone confirm this?
A Middle Jurassic age can be ruled out, as demonstrated by this paper:
Wang Xiaolin, Zhou Zhonghe, He Huaiyu, Jin Fan, Wang Yuanqing, Zhang Jiangyong, Wang Yuan, Xu Xing & Zhang Fucheng: Stratigraphy and age of the Daohugou Bed in Ningcheng, Inner Mongolia, Chinese Science Bulletin (English edition) 50(20), 2369 -- 2376 (October 2005)
The Daohugou Bed lies above, not below, the volcanic Tiaojishan Formation that dates to the Middle-Late Jurassic boundary. This was not obvious because the whole region is very complexly folded.
It does underlie the Yixian Formation, the bottom of which dates to the end of the Barremian (middle Early Cretaceous), and reports that it overlies the Tuchengzi Fm, which is Berriasian (beginning of the Early Cretaceous) in age, were erroneous; its relationship to the Tuchengzi Fm (or for that matter the Hauterivian Dabeigou Fm, which is just older than the Yixian Fm) is unknown. So, the Daohugou Bed could be anywhere from Oxfordian (beginning of the Late Jurassic) to Barremian in age; the faunal similarities it shares with the Yixian Fm suggest an age closer to the younger end of this range.
Excellent article, even by Tetrapod Zoology standards. How you find the time to write all these posts I don't understand...
As for the subject matter itself, just one question. If those long tail feathers really were used for display, then why would a juvenile individual have them (assuming that this really is a juvenile)?
Harris (2004) argued that Epidendrosaurus should have won out, but also demonstrated how it didn't (while the electronic release of Epidendrosaurus preceeded the publication of Scansoriopteryx, the printed release didn't come until afterwards, and the ICZN currently only takes into account the printed release). As yet, the amendments suggested by Harris (2004) to help prevent such a situation haven't been accepted, and reading between the lines of the recent proposals it looks to me suspiciously like they won't be.
Good question. But then, is the main reason they're supposed to be for display simply that they don't appear to be suitable for anything else?
If you don't know what it's for, it must be for display ;-).
In the tradition of TetZoo, let me suggest those strange tail 'feathers' were actually the blades of the first helicopter, Epidexipteryx having achieved the marvel of a fully rotating element larger than a flagellum. Clearly, more work will have to be done to determine if this is the case. :-)
Thanks for comments, and to Dartian for lovely words :)
Zhang et al. say that Epidexipteryx is a subadult: it's Epidendrosaurus/Scansoriopteryx that's juvenile.
Could someone explain what characters suggest scansoriopterygids are the sister clade to avians? As you mentioned, the pubis not being retroverted is a bit odd. I wonder more about the lack of true feathers however, given purportedly more basal lineages (Deinonychosauria and Oviraptorosauria) clearly had true feathers. Epidexipteryx, while not an adult, is probably close enough to an adult that more than downy feathers on its arms should be preserved.
Perhaps, especially if the clade were dinosaurian aye-ayes, the proto-wing feathers were secondarily lost due to being an obstruction when probing. However, I can't help shake the suspicion they are basal to Maniraptora.
Well, you are correct, but the basic underlying premise of my paper on the subject, and my proposal for an amendment to the ICZN (which, interestingly, was not addressed in their proposed amendment of this year) was basically to point out that I don't see why the authors should have to suffer just because the ICZN took longer to get with the electronic publishing program than the publishers did. Publishers basically got on the DOI program as a means of "locking down" advance electronic publications to validate them, and it seemed (and still seems) to me that the publishers get to define what is a "publication" more than the ICZN does. Certainly, I fully understand that the ICZN is trying to ensure much-needed forms of stability, permanency, and universality in order to create stable taxa, and I know that they have contemplated these issues long and hard -- but they meet less frequently and move far more slowly that the world of publishing has when it comes to the incorporation of electronic media into the concept of "publishing." In every case of which I am aware (I'd be interested in exceptions, if anyone knows of any!), every DOI-registered electronic "pre-print" has been followed, in relatively short order, by actual paper publication of the identical material, so I am quite convinced that these should count as much as any other publication. I have nothing against the Czerkases and "Scansoriopteryx" or any particular allegiences to Zhou et al. for Epidendrosaurus; I was simply trying to make a case based on the concepts involved.
The ICZN is still taking comments and suggestions on their new proposal, so if any or all of you feel strongly about this matter one way or another, please let them know!
Oh, come on. There are clear analogs in extant birds.
Chris Taylor wrote:
Nope. The current rules make Scansoriopteryx the correct name (first in print on paper) and even the proposed amendments to the rules for electronic publications (which wouldn't be retrospective anyway) wouldn't support Epidendrosaurus as the correct name (advance online publications don't advance the publication date unless they themselves independently fulfill the requirements for online publication).
I'd just like to point out that availability, while printied date is relevant, is important in establishing date of publication. I cannot place an earlier date than availability on my book, and have any taxonomic work therein be retroactively applied. This is the argument that has been leveled at the Czerckas', with all due respect given them in the fine image quality of their work. But were I to publish a book and place a date on it from a year back, with taxonomic data in it, my book CANNOT apply retroactively, and it appears that the Czerckases did in fact publish a date and then did not release their volume for nearly a month after that date, as according to their own website and the sales that they, exclusively, offered for the book. It was never available before from anyone else but them. As such, their date is off by several weeks.
Well, so much for this guy. As we all had, I see you had a field day with this one, and it certainly makes a topic most befitting for TP.
It is also nice if Scansoriopteryx would win out as it seems it would, for what would be more apt to name in honor of Heilmann?
As a side note, what is it with the blue Stage 2-fuzz? And blue feathers in general?
True blue is very VERY hard to achieve in avian feathers (as a structural color, a lot of feathers are simply not physically suited for it), and significant amounts of it do not appear in the plumage of anything that is not hefty and well able to take care of itself (think Indian Peacock), or lived in habitat where blue provided camouflage, until far far up in the neornithine tree.
It is certainly not unviable, but the conditions necessary for it to arise are not trivial and also seem to require a good deal of chance judging from all we actually know and about anything we can infer with a reasonable amount of certainty. Also remember that in feathers, as soon as you can have true blue, you can have green. (Interestingly, IIRC sky-blue structural color is also not exactly commonplace as well as for the most part phylogenetically very constrained among the Lepidoptera)
In short, I have not seen anything that would justify extensive blue feather color in such small forest-dwelling animals as this earlier than 70 Ma-ish (Cuculiformes might go back that far). Paleo-artists might want to take note of this.
Blue bare skin is rather easy though. Bluish slate grey plumage is also very easy to evolve. The right melanin in the right dilution will entirely do that trick. And as the basic kit for this is present at least since the late Ediacaran, blue-grey color will pop up as frequently as it indeed does.
But the brilliant blue as per the first reconstruction (moreover as downy fuzz), or BBC's sky-blue Iberomesornis?
Not parsimonious at all.
All the best,
Eike
Makes one wonder what spin Feduccia and his followers will say about this specimen to contort it out of the Dinosauria--maybe the propubic pelvis?
Another thought:
Is it possible the the propubic pelvis in Epidendrosaurus/Scansoriopteryx became retroverted during ontogeny? How many embryonic/juvenile maniraptorans/avialans do we have that might shed light on this?
It is true that blue feathers are not common in Ratites and Galloanseres, but actually they are widespread otherwise. Families like Columbidae, Musophagidae, Rallidae, Cuculidae Coraciidae, Alcedinidae, Momotidae, Trogonidae, Trochilidae and Psittacidae come to mind immediately. Blue feathers ara also widespread within Passeriformes, both oscines and suboscines. So clearly blue structural colour has evolved independently a large number of times among both large and small birds. As a matter of fact the diminutive Blue Wrens (Maluridae) contain some of the bluest birds in existance.
I must say I don't see any particularly compelling reason that this would not have been possible during the first half of avian history.
Display doesn't have to mean sexual display. Perhaps we're looking at a dinosaurian coati or ring-tailed lemur that roamed about in packs, tails up, and ventured into the trees for protection or to find food. There might have been specific plume color patterns for different ages. Dominance may even have prompted hormonal surges that further altered plume color with the next molt.
But of course, this stuff doesn't fossilize and a thing with a duck's bill is not therefore a duck.
I like your Dinosaurs. They are great!
Before feathered dinosaurs were known, birds were usually defined by having feathers. Why don't we simply use Aves to be "everything descended from the first thing to get feathers" (assuming they only evolved once, of course). Why couldn't dromaeosaurs be considered birds - I bet most people seeing a live one would think "a flightless bird" rather than "a reptile".
William Miller wrote:
"Before feathered dinosaurs were known, birds were usually defined by having feathers. Why don't we simply use Aves to be "everything descended from the first thing to get feathers" (assuming they only evolved once, of course). Why couldn't dromaeosaurs be considered birds - I bet most people seeing a live one would think "a flightless bird" rather than "a reptile"."
William, you confuse a few things, perhaps unintentionally:
1) You need to be able to define "feather" to associate it in the fossil record, or to infer its prescence if unknown (aka, quillknobs in some animals).
2) You confuse "bird" with "feathered animal", and you confuse "bird" with a definition of Aves, as well as Aves and "bird" even without the definition. This is a lot of lumping of identities to tie feathers to some broad avian, birdy, or Aves concept
The first reconstruction image, with it's outspread arms and short boned tail, reminds me of a (young) siamang/gibbon/orangutan/bonobo more than anything. Could it have been a part-time gliding arboreal vertical climber? This would make the tail feathers functionally more significant. Any clear sign of presence or absence of glide membrane/feathers on forelimbs? An open tropical rainforest (no lianas) might allow such a niche. Any frugivory or foliavory or predatory carnivory indicated?
(Fascinating post!)
Avians were diagnosed by feathers; that's not the same as definition.
The history of actual definitions of Aves is here: TaxonSearch: Aves. Note that the first definition is from 1986--before then, it had never been defined.
I'd also like to note that I disagree with the authors of that page in overriding the original definition, as a crown group. Aves was also diagnosed by many things other than feathers: toothless beaks, hard eggshells, flight, tridactyly, bipedality, endothermy, etc. Each of these arose at a different time. The only group which possesses all of them is the crown group, which is therefore the best sense for the name.
(Also, "bird" is arguably a separate word from "avian".)
Well, everybody knows that the bird is the word!
But..But.. This was in the NEWS! I thought that meant we couldn't post about it? Isn't that too pedestrian?
Jaime: I ws suggesting "bird" (well, "class Aves", but I think bird = a member of Aves) should be defined as "feathered animal", not confusing the two.
Why wouldn't this make sense?
I'm not fond of the crown group because it seems bizarre to say things like enantiornithines weren't birds.
The post is now up as promised and Corwin Sullivan will be around on the Musings to answer questions over the next few days.
Is it possible the animal's tail got shorter as it grew? Or is that nonsense?
In my large-scale analysis of theropods (in preparation), Scansoriopterygidae are placed sligtly more basal than Avialae: they're basal paravians, sister-group of Eumaniraptora (Avialae+Deinonychosauria). This different position explains more the "incisivosaur-like" skull and the absence of some pelvic features widespread among basal avialans, dromaeosaurids and troodontids (in particular the scapular, ischial and pubic features).
In my blog, I suggested an alternative and very heterodox interpretation of Scansoriopterygids: given the absence of evidence for remiges in Epidexipteryx, is it possible that the "feather impressions" seen in the forelimb of the "Scansoriopteryx heilmanni specimen" are not feathers, but a different tegument: it is interesting to note that in remige-bearing maniraptorans, the remiges are inserted on the second finger, whereas in Scasoriopteryx these impression are close to the hyper-elongated third finger. This very long lateral finger is similar to the pterosaurian fourth digit. So, it is possible that the "feather impressions" of Scansoriopteryx were remnant of a patagium. In my opinion, the presence of this structure may explain the elongation of the lateral digit in these small theropods better than the Aye-Aye hypothesis.
Is it too heterodox? Remember that the maniraptoran "bauplan" is not only an orthogenetic trend toward birds, and that the evolution of a patagium occurred many times in tetrapod evolution. As stated Thomas Holtz: "Theropod paleobiology, more than just bird origins!".
If I'm wrong or incorrect somewhere in my comment, I apologise.
> "So, it is possible that the "feather impressions" of Scansoriopteryx were remnant of a patagium".
- Well done, Andrea Cau.
'Nuff said!
Leo
Tim Morris:
Well, tadpoles have tails while adult anurans do not. But that analogy only goes so far, and I can't think of any amniote examples of significant post-birth tail reduction.
But were I to publish a book and place a date on it from a year back, with taxonomic data in it, my book CANNOT apply retroactively, and it appears that the Czerckases did in fact publish a date and then did not release their volume for nearly a month after that date, as according to their own website and the sales that they, exclusively, offered for the book. It was never available before from anyone else but them. As such, their date is off by several weeks.
True, but as Jerry Harris showed, the likely actual available date of the Czerkas book was still prior to the printed release of the Epidendrosaurus paper.
As I commented over at my own site, I think that the proposed ICZN rule that advance online pre-prints not affect the publication date is more than a little unfortunate, and I'm more or less inclined to support Jerry Harris on this one. Of course, there's always the chance that the amendment could change before it becomes official if enough people argue against it. The problem, I suppose, is that some journals (e.g. Molecular Phylogenetics and Evolution) put pre-prints online before the formatting process is even complete, which makes it difficult to judge how they are supposed to relate to the finished product.
Would surprise me.
A couple.
The main reason is that, under phylogenetic nomenclature, if something isn't a bird, it doesn't need to be a reptile. In fact, nothing is a reptile (unless we define Reptilia in such a strange fashion that birds are reptiles, too).
No.
First, it's way too tiny for that. You know what 20 cm are? The maximum distance between the tips of your thumb and your middle finger.
Second, the shoulder girdle, pelvic girdle, wrists, ankles, fingers and so on make all that completely impossible. The necessary freedom of movement just isn't there.
Tropical rainforests did not exist in the Cretaceous.
No. Also, fruits would have been limited to ginkgo fruits; angiosperm trees didn't exist yet.
Yes, and this is what happens in Confuciusornis and Enantiornithes -- but not to that extent. A part of the tail probably is missing in the break.
I think it's bad idea for a couple pragmatic reasons.
First, it will include various critters that have traditionally been considered non-birds (potentially including tyrannosaurs, depending on how you define "feather"). This causes more confusion than a definition that yields a more traditional content. (I dislike the crown group definition for the same reason.)
Second, feathers don't fossilize too well. We could easily end up with forms near the base of Aves we can't tell if they're birds or not because we can't tell if they were feathered or not.
"a part-time gliding arboreal vertical climber?
"it's way too tiny for that. You know what 20 cm are? The maximum distance between the tips of your thumb and your middle finger."
Hmm.
"Rhacophorus nigropalmatus, commonly known as Wallace's Flying Frog ... With a body length of 80-100 mm (males are smaller than females), it is one of the largest species of Rhacophorus."
http://en.wikipedia.org/wiki/Rhacophorus_nigropalmatus
"The smallest ... flying squirrels ... (Petaurillus) of northern Borneo and the Malay Peninsula; their bodies are just 7 to 9 cm long and their tails 6 to 10 cm."
http://www.britannica.com/EBchecked/topic/211703/flying-squirrel
- I don't at this point have an opinion on the "gliding" thing either way, but I'm not sure that the "too small" argument is working.
Okay, I really want to restore this little bastard for my blog. But there are some stumbling blocks--help me out, folks!
1) What the heck is the membraneous structure? Were the feathers arranged in "rows?" Should I just put "chick fuzz" all over the body?
2) What about the tail break? Given the length of Scansoriopteryx's tail, I'd think a long tail should be present in this new animal.
3) Should I give it a long third finger?
Thanks, guys! Mostly, I'm concerned about the feather structure.
Thank you! Thank you! Thank you! I'm so glad you covered this one to clarify what the journalists constantly screw up so badly. I even have a rant on the subject... Bad science reporting needs to be stopped.
I would like to point out to anon that at least flying frogs and snakes are parachuters, not gliders. They develop means only to retard their descent. While flying snakes have been known to cover horizontal distances well enough, they have to leap out to do it, and not all such snakes do that. Gliding, passive flying, and powered flying are on a sort of continuum, but even with those fronds, Epidendripteryx doesn't look even remotely capable of gliding, parachuting, or whatever. A recent paper revised the idea of even Longisquama being able to do anything in the air with its "appendages", given that while there is no evidence of them being paired, even if they were they lack the aerodynamic ability to retard descent very well, especially since they are "slotted" along their length until you reach the expanded tips.
Thus it seems these tail "feathers" appear to be display ornaments.
The long display tailfeathers would probably function for display -- as would bright colours, strong teeth, lager size, etc.
But when I saw the photo, the first thing I thought was that the tailfeathers would be very good for steering in the air during long jumps among branches or even trees, either to move this way or that, or to maintain a straight flight and compensate for the fact that a marmoset sized critter isn't really very aerodynamic.
"I would like to point out to anon that at least flying frogs and snakes are parachuters, not gliders. ... Gliding, passive flying, and powered flying are on a sort of continuum ... it seems these tail "feathers" appear to be display ornaments."
Agreed. I just wanted to point out that the small size in and of itself doesn't appear to contradict gliding/parachuting.
What DDeden proposed seems to have been an ape- or howling monkey-like grip-based climber, and that's something Epide[i]xipteryx is too small for.
(And as mentioned, Rhacophorus parachutes instead of gliding.)
Slotted??? Aren't they just wrinkled? And lens-shaped in cross-section?
I'm not that confident that the "ETFs" are necessarily homolog with feathers - let's say on the level of the feather follicle - given that there are other even branched elongate avian integuments - the beard bristles of the wild turkey (see e.g. the study Sawyer et al. 2003) - which appear to be no high-level feather homologs.
And considering the model of Prum (1999) or Prum & Brush (2002, 2003): The series of evolutionary steps leading to feathers may not be as simple and straight as the outlined five stages. Assuming a hair- or bristle-like follicular ("stage I") or non-follicular appendage you could imagine a subsequent evolution of differentiation processes in the respective zone of the basal collar that do not result in a branched appendage and/or a phase in the development of an only distally branched appendage in which a long calamus-like tube is shaped.
Ref: Sawyer et al. 2003 in Mol Dev Evol 297B:27-34; http://dx.doi.org/10.1002/jez.b.17
David,
Voigt et al., in a recent Naturwissenschaften here, argue that the structures are flat, hollow, apparently in a single row. They argue that IF the structures were paired, and arranged in a "wing", the structures formed into a plane can only overlap at the tips, with the caudally deflected distal ends overlapping, but the main shafts, being narrower, cannot form a functional planform without putting slots between the segments. This is nonviable as an aerial planform, even in a glider, although it MIGHT be useful in a parachuter. But that's only IF the structures were paired; there is no evidence for that at all in any of the specimens.
Err, the link did not come through. Try this, or paste this -- http://www.springerlink.com/content/365408287l2v655x/ -- into your browser.
Oh, the slots are between the "parafeathers", not in them. I see. Thanks for the link.
@Karl:
"...the pubis not being retroverted is a bit odd."
There is a reason why certain types, particularly fliers, retroverted the pubis from the ancestral angle, and why they sometimes proverted them again (in addition to any balance-related reasons, which I now consider secondary). The angle in Epidex. looks particularly odd in the light of the cladogram the authors gave, which I don't think reflects reality much - and you don't need to believe it either. See Bull et al. (1997), Naylor et al., (2001), and Springer et al. (2008) for "When cladograms go bad". Beware especially of Springer's Ecological Vicars. They're the worst. They lurk in the trees and ambush you - and don't look to bootstrapping to rescue you!
"I wonder more about the lack of true feathers however, given purportedly more basal lineages (Deinonychosauria and Oviraptorosauria) clearly had true feathers. Epidexipteryx, while not an adult, is probably close enough to an adult that more than downy feathers on its arms should be preserved."
There is no reason why flight feathers need to be preserved. There are plenty of fossils preserved in much the same sort of way as this that nonetheless had flight feathers that allowed the animal to fly well. Not that this flew *well* as such, but extreme tail shortening in dinobirds is closely associated with flight. Not all fliers had short tails but I know of no explanation other than flight that can explain extreme tail shortening in bipedal dinobirds. You can bet Epidex. had big enough flight feathers on its arms. I'd just like to know where the squashed flower/afro comb style things were on the body. As far as I can see the paper doesn't indicate this. And of course, Deinonychosauria and Oviraptorosauria weren't more basal:
http://www.geocities.com/strangetruther/parlogram01.gif
John Jackson wrote:
"There is no reason why flight feathers need to be preserved. There are plenty of fossils preserved in much the same sort of way as this that nonetheless had flight feathers that allowed the animal to fly well. Not that this flew *well* as such, but extreme tail shortening in dinobirds is closely associated with flight. Not all fliers had short tails but I know of no explanation other than flight that can explain extreme tail shortening in bipedal dinobirds. You can bet Epidex. had big enough flight feathers on its arms. I'd just like to know where the squashed flower/afro comb style things were on the body. As far as I can see the paper doesn't indicate this."
It is not enough to state that something is not true, or that something is true; you must demonstrate this fact by removing the improbability of your being false. In this case, most certainly, there is a reasonable chance you are incorrect in arguing there were "flight feathers" on the arms of Epidendripteryx. However, in at least one possibly syntaxic specimen, Scansoriopteryx heilmanni's holotype, the arm is indicated with filamentous integument, and there is no evidence of any pennaceous feathers anywhere. Epidendrosaurus ningchengensis similarly preserves portions of the body covering, even the tail feathers, but nothing else. It is possible that the lack of feathers preserved elsewhere is an artifact of preservation, but it stretches incredulity to assume that the arm was feathered when there are specimens that contradict this. One must disprove THOSE specimen's relevance to this subject to even begin arguing that feathered arms were present.
---
As for the cladistic stuff: Put out a contradictory and comparable analysis, or walk away from this argument. This is true of all other analysts, and they know it. Think that Senter and Xu and Holtz will not produce their own analyses with refinement to arrive at different results? They do not take any one analysis at face value, but they don't dismiss an analysis based on supposed "cladistic jitters" as you seem to do.
"3) Should I give it a long third finger?"
I say yes. The supplementary information provides measurements for the preserved manual phalanges and metacarpals. This shows there are five bones which are roughly the same length (the smallest is 89% of the longest). This also happens in Scansoriopteryx, due to the elongate phalanges III-1 and III-2, but not in Archaeopteryx or other coelurosaurs. From my comparisons, the two phalanges toward the bottom loosely associated with an ungual are III-2 (14 mm) and III-3 (13.5 mm), while the phalanx articulated with an ungual is II-2 (12.4 mm). Metacarpals II (13 mm) and III (13.4 mm) are crossed over each other towards the top, while the short phalanx preserved on the upper left is II-1 (7.6 mm), and metacarpal I is also preserved (5.1 mm). These correspond almost exactly to proportions in Scansoriopteryx (except a slightly shorter mc I and II-1), but cannot be matched to manual elements of any other coelurosaur.
This is interesting. It's always been a bit of a puzzle to me how flat scales could convert into round feather shafts. A strap-like featherish structure that later, perhaps, developed a furled shaft would fill in that gap a little.
Fascinating creatures, and an excellent posting.
I have no opinion on whether or not Epidendripteryx had flight feathers, though the lack of any evidence of them would tend to place the burden of proof on anyone suggesting it did. However I think Jaime is wrong to attach much significance to the absence of flight feathers in Scansoriopteryx and Epidendrosaurus - these were young juveniles, and since we don't know their development patterns, could easily be the equivalent of downy chicks in modern birds.
I sympathise greatly with William's view that many of these organisms maybe ought to be treated AS birds. While we lack enough evidence to be certain in many cases, I am fairly sure that if a Velociraptor or Oviraptor were alive today we would treat them as flightless birds - possibly bearing the same kind of relation to neornithes as a platypus does to eutherians. While do accept that Aves does not necessarily equate to what we usually mean by Birds, I do think that when coming up with definitions careful consideration should be given to what was originally intended when the taxon name was created. Though I haven't researched the detail I assume that Aves was originally intended to refer to birds. Therefore I would suggest that Aves should refer to birds, including extant birds, and extinct creatures which would be treated as birds if alive today - and if the definitions being used don't cater for that, then the problem lies with the definition.
Regarding definitions; crown-based definitions are in my opinion truly awful, I can think of no exceptions (though I am open to being shown otherwise). Node-based ones make more sense, but also have serious issues.
David refers to phylogenetic nomenclature - well I think I have made my views on that very clear in the past. :)
And may I take this opportunity to wish a speedy demise to the Phylocode.
Mark Lees (putting on helmet and body armour in anticipation of the responses to this, unless you all ignore me)
'There are lies, damn lies, and cladistics'
Fine -- but how short this one's tail really was, as opposed to there being something missing in the break, is the very question.
Agreed -- if only those, and not Sinosauropteryx and Ornitholestes and Allosaurus, were alive, in any case.
Agreed. (Especially because aves is the Latin word for "birds".)
At the same time, the definition should ensure that animals that have traditionally not been considered birds should be kept outside. (Article 10.1 of the PhyloCode: current and historical usage must be taken into account when crafting a definition.) I think Achillobator should be kept outside, and this most likely keeps Velociraptor and Microraptor out, too.
Crown-group definitions are a subset of node-based ones: every node-based definition in which all (internal) specifiers are extant automatically applies to a crown-group.
The only coherent argument that has yet been made for the "convention" to give all well-known names to crown-groups was made by K. de Queiroz in the December 2007 issue of Systematic Biology. It's a fairly good argument, too, even though it still doesn't quite convince me. You should read it.
Because I was describing the status quo. To the best of my knowledge, all people who work on nonavian dinosaurs use phylogenetic nomenclature these days. :-|
I got the last word in that thread, because you didn't come back... and as you just demonstrated (by contrasting "crown-based" and "node-based" definitions), you still don't understand the basic terms of phylogenetic nomenclature well enough to be able to have a qualified opinion, frankly.
You have fallen among the scientists. This leaves you two choices: Either you present a demonstrably better method for reconstructing phylogenetic trees. Or you go here. Of course, the same holds for Mr Jackson.
David, I was under the impression that even if we disagreed we would be civil. I guess that's not so any more, since the link you suggested that John Jackson and I go to is entitled "shut the f**k up". I am not impressed. Have you ever heard of the concept of disagreeing without being disagreeable.
I do know that "aves is the Latin word for 'birds'" - the point I was making is that I while I assume it to be so, I have not checked if its first use as a modern scientific name for a class specified any other limits than simply 'birds'. I have no reason to think it did, I was just cautiously admitting I had not checked.
You state that I was "contrasting "crown-based" and "node-based" definitions" - if my comment gave that impression (I don't think it does, but I an see that it could be read that way), that was a mistake. I was not intending to contrast these, merely to state that I think the former has even bigger issues than the latter.
With reference to the last thread we debated on, you state "you didn't come back..." - that's right, I didn't. As I stated at the time I thought we had rather diverted the thread from it's topic and were hogging it. To be honest I also got very tired of having to address your nitpicking and misinterpretation of much of what I said. I was coming to the conclusion that your debating strategy centred around deliberately misinterpreting my comments, so as to deflect from the actual issues. If you viewed having the last word as some kind of victory, all I can say is if it means that much to you, you go ahead and think that.
You state that you don't think I am "able to have a qualified opinion" - odd - do you behave this way every time you don't agree with someone? For what it's worth, your view on whether or not I am qualified to have an opinion is a matter of indifference to me.
"You have fallen among the scientists." - what does that mean? Is it a suggestion that I some how fail to make the grade as a scientist? If your opinion mattered to me I would be offended - but as it is, you go ahead and think what you like. For the record while I never tried for a PhD, I do have a MSc, and work in applied (not academic) science. I was going to go on about my record and work, but that's just being defensive and I don't think I have to justify myself against your petty remarks.
I was tempted to join in the name calling - but this is Darren's blog (and an excellent one) so not really an appropriate place for us to argue. David, if you do respond to this I'm am not likely to reply, since I suspect I may write something I'll regret and share some of my extensive knowledge of obscure English expletives.
Mark Lees
I consider that website a joke. I was asking you what your point is if you don't present an alternative to cladistics. What other method of phylogenetics is there? What do you suggest?
Now this is an incredible accusation. I may of course have made misunderstandings; if so, please clear them up. But to claim that anyone without a, like, political agenda would ever deliberately misinterpret something boggles the mind!!!
I don't. What did you think? I'm disappointed that you didn't continue the discussion till one of us was proven wrong. I'm disappointed that you let me have the last word.
You gave me the impression that you quite simply don't know what you're talking about, and I made the mistake of not making the present tense explicit. Of course I think you're able to learn! If I'm wrong and you do know what you're talking about, show me, and I'll gladly eat my words. So far, though, you seem to confuse basic concepts...
Simply that you need to support your claims with evidence. That's all.
And for the record, while I won't try to provoke you, I find the large English expletive vocabulary interesting :-)
YAWWC! Yet Another Weird and Wonderful Creature [you have brought to my attention]... that deserves its own documentary/show. Thanks, Darren!
But what I'm wondering now is - could it lose those ETF's readily, to escape, if grabbed from behind?
(Maybe some'll be found fossilised as isolated shed clumps?)
Other ideas, (just for fun):
ETF's were a lure - dabbled into water or protruded through foliage to attract would-be predators as prey (maybe the ribbons were coloured/styled/moved so as to look like giant earthworms, or edible snakes, or munchy myriapods, or...)
ETF's were for defense - rigid, sharp-edged, and deployed in a porcupine-reminiscent backward-rushing butt-wiggling 'slice-and-dice' mode.
Well... Truth can be stranger than fiction...
@Jaime:
My point is that the observations we make of this specimen are best explained by flight feathers being present. It isn't definite - we've all been surprised by how certain species have turned out in the last few years - but I don't think I was implying any certainty. I think it's fairly clear that the absence of clear flight feather traces doesn't mean much in this fossil of Epidexipteryx. There clearly are long strands of something hanging off Scansoriopteryx' arms. They too don't look much like pristine feathers in their current state, but they do look like the feathers of a bird that's been under a dustbin lid in my garden for a few weeks - at least as far as apparent structure is concerned. They are also rather sparse and feint of course but I can forgive that after so much time. I can't think why there would be long non-flight-feather type fibres hanging off a forelimb like that. It certainly doesn't stretch incredulity to prefer the notion that the arm was feathered, and I don't think it stretches incredulity even to assume it. We shouldn't be misled by Confuciusornis, whose flight feathers were abnormally robust and suitable for leaving fossil traces.
"As for the cladistic stuff: Put out a contradictory and comparable analysis, or walk away from this argument."
If I complain about a cladogram because I don't trust cladograms produced in that way, there's no point in my producing a slightly different one produced in a similar way. I have however produced a phylogeny produced in a different way.
PS - How much do you want for your picture of an 'ovi skull with egg'?
@Mike Lee:
I think it's an important aspect of this whole area of discussion that while cladists claim some kind of scientific high ground, they never listen to the advice of scientists etc from other fields (and of course they hate hearing ideas that clash with their own, for the usual reason that some people hate to see anyone think, look, or behave differently: it casts their own veracity into doubt).
I don't think we'll ever change cladists, partly because it's very hard to disprove simply and vividly, ideas about past events, and partly because it's just a form of entertainment - it never really matters if the ideas are wrong. The strategy I now prefer is to bypass the palaeontologists - go straight from the fossils and the experts in specialist fields to the public. Some palaeontologists have useful insights - for example Mickey Mortimer's suspicion is interesting - that Expidexipteryx should be given a long third finger. Which brings me to David Marj. Even he can be useful sometimes - about the age of the Daohugou for example. Nonetheless, you have my sympathies!
I don't think we'll ever change cladists
Change them into what? And what definition of 'cladist' are you talking about?
"Change them into what?"
Into transformed cladists of course, ha ha!
I'd say we have a typical juvenile male jay basilisk here, if not for the fact the tail is much too short, juvenile male jay basilisks don't have display feathers, and the feet are all wrong. The basilisks, being descended from dromaesaurids, have a curved talon on the inner toe, which can range from small and slightly curved as in canary basilisks, to large and strongly curved as in wolf basilisks.
But what really kills the possibility it's a juvenile male jay basilisk is the fact jay basilisks are products of my imagination. :)
Michael S. Y. Lee is someone else :o)
I agree that we can't simply assume that flight feathers are automatically preserved in the Daohugou Bed (after all, NGMC 91 from similar sediment looks weird, if you know what I mean). But why do you think those of Confuciusornis were "abnormally robust"? I've never seen that mentioned or implied anywhere.
What way?
For the record, thank you once again for the booklet by Sir Peter Medawar on science theory that you sent me several years ago. None of the ideas in it were news to me (or contrary to the theory or practice of cladistics, in spite of what I remember had been your implications), but the examples, and the way the ideas are summarized, are beautiful and useful. Will you attend the SVP meeting in Bristol next year?
Nah. That's what the principle of parsimony is for: if you can't disprove competing falsifiable hypotheses, the ones that require the smallest number of extra assumptions must be considered, at the very least, the starting point for further investigation. Where else would you start? The maximally munificent hypothesis?
The traditional approach to phylogenetics (think Romer or Carroll in vertebrate palaeontology) is to do "cladistics with three characters" in one's head, use the resulting poorly resolved tree to come up with a scenario, and to then use that scenario to resolve the tree. Any such scenario consists of tons of extra assumptions. That's why we do cladistics with 300 or 400 or 500 characters today and then use the result to decide which scenarios are most parsimonious.
I wouldn't call that a suspicion. I'd call that a well-founded and easily testable hypothesis (even though testing it could amount to a lot of work -- but easy work, just measuring lots of bones basically).
AAAARRRRGH!!! :-)
Are we glad its eyes have rotted away! :-)
David said . . .
I thought pointing out the great age of the remains would be over doing it. I mean, even if such creatures actually existed in the real world, and the phenomenon that powers their paralyzing stare did work, you've still got the problem of finding someone powerful enough and experienced enough to actually bring the animal back to life. Just as well Jay Basilisks are imaginary, removes a great temptation from many a callow and unwise mind. :)
LOL, just in case anyone was wondering if feathered dinos are still controversial, at least in the little details, check the comments count on this post!
Thanks for posting this because, let's face it, Epidexipteryx is all over the news right now (I'm proud to be able to pronounce that one) and I don't trust that I'm getting the real story until I read it here. LOL
So kind, thanks. Is Epidexipteryx really all over the news? I thought something else was. If I was American I know who I'd be voting for (clue: not McCain). Good luck America, our lives are in your hands pretty much.
For the record, the president of the Society for Vertebrate Paleontology endorsed Obama in her speech after the banquet at the conference two weeks ago and got lots of applause, and no disapproval that I noticed. Quelle surprise. How fitting that the terrestrial Cretaceous and Cenozoic seems to vote for Obama, too -- Obama might win Montana...
American academics and public sector workers tend to be democrats while private sector and small business owners tend to be republicans but the individualists and free thinkers tend to be libertarians.
That's why I'm glad I'm Canadian and I don't have to vote right now. ;)
That's why I'm glad I'm Canadian and I don't have to vote right now. ;) "The News" for me is a little less mainstream than the election.
For a very small value of "tend".
David
Yes, unfortunately.
Why unfortunately? It's bad enough that you can look an American in the face and tell with high probability what party they usually vote for.
David
If you can do that with just a face, knowing our ethnic mixture and conceptual biases across roughly 2,500 miles of country and multiple climates and environemts as well as attitudes, you must be one hell of a psychologist.
Around 90 % of those Americans that are counted as "black" have (if at all) been voting Democratic ever since Democrats and Republicans switched places. (Sometimes 88, sometimes 97 as in the current polls, but always such extremely high percentages.)
Likewise, though by a considerably smaller margin, people counted as "Hispanic" vote Democratic, except in southern Florida, where most "Hispanics" are people who fled from Cuba and vote Republican.
That leaves a yet smaller but still comfortable Republican margin among people counted as "white non-Hispanic".
That's what I mean.