Monday, April 15, 2013

A conversation with Larry Martin

Jason Brougham has a post at his blog discussing Larry Martin, one of the BAND* leaders and later MANIAC** who passed away in March.  I met Larry at SVP 2002, where my reaction was-

"I had a good discussion with Martin. He's quite a nice guy, it's a shame he's so wrong about almost everything dinobird-related. Seems he officially believes that maniraptorans are birds, but that other coelurosaurs are unrelated. He terms this the "Paulian hypothesis", though it's only similar in thinking of maniraptorans as 2F and preferring the arboreal origin. In his mind, maniraptorans and other birds evolved from a Longisquama-like creature. And like Czerkas believes, some taxa (eg. Scansoriopteryx) are just too hard to place as birds or dinosaurs until a more in depth study is completed. The same old ABSRD arguments were brought up (digit homology, terrestrial theropods, Yixian feathers being collagen, etc.). He referred to both ichthyosaurs and Psittacosaurus as having structures like those found in Sinosauropteryx et al., which is just plain wrong of course. In any case, he does have an interesting eumaniraptoran that will be out soon."

That eumaniraptoran was later named Microraptor gui, btw.  As I recall, he said the leg remiges proved M. gui wasn't terrestrial, therefore birds evolved flight from trees, and therefore birds aren't dinosaurs.  I then said I have no issue with some dinosaurs being arboreal, which I think he was surprised by.
* Birds Are Not Dinosaurs, contrasted with BAD being Birds Are Dinosaurs
** Maniraptorans Are Not In Actuality Coelurosaurs

I feel Jason's post bends over backwards to seem fair, but also that it leaves out Martin's greatest positive influences on paleontology. 

He first writes about Martin being on "our side", which seems to be opposed to creationists, since "He spent his life studying evolution, observing fossils, and we all agreed that dinosaurs and birds were closely related archosaurs."  It seems trivially true that anyone will be on your side about some value or opinion.  Indeed, even evangelical creationists are on "our side" for wishing to teach people the truth, we just disagree on what that truth is.  In any case, as a scientist I think he would have been proud to be against "our side" when it came to heterodox ideas he strongly defended.

Jason believes Martin had a beneficial effect on bird origins research in that BADists "wrote some papers they would not have written unless they felt the need to answer Martin. In the process, progress was made on quantifying the ‘temporal paradox’ issue, and everyone’s hypotheses became more precise and explicit."  But I honestly can't think of many examples where Martin's criticisms directly led to science examining the issue more closely to result in more discoveries, they were mostly just pointed out to be based on fallaceous reasoning or inaccurate interpretation.  If we look at his classic (1983) arguments for BAND, the temporal gap problem had been answered perfectly years earlier by Ostrom (1976).  I don't see Brochu and Norell's (2001) quantification paper as doing more than telling us what we already knew, i.e. the gap between the Tithonian and Aptian is less than between the Tithonian and Triassic.  The arboreal vs. terrestrial rationale actually hindered our side in my estimation, as the BAD response was to double down on the terrestriality of Archaeopteryx and flight origins instead of accepting arboreal theropods could exist, which only occured decades later when scansoriopterygids and microraptorians were found.  These examples can be contrasted with e.g. Jones et al. (2000) instigating research on Longisquama's parafeathers or Burke and Feduccia (1997) instigating research on digital development.

The next argument is that some recent large morphological analyses (e.g. Livezey and Zusi, 2007) have shown Martin was right that convergent evolution could confound cladistic analyses.  I don't think anyone's ever doubted this in principle, as analyses do differ so some must be wrong.  Moreover, the ways such analyses were shown to be confounded were never used by Martin (more characters and taxa, molecular analyses, biogeography, etc.), with his naive falsification and evolutionary scenario alternatives ignored (Makovicky and Dyke, 2001).  Sure Martin (1997) was right(er) than Chiappe that alvarezsaurids are ornithomimosaurs instead of avialans, but it was for all the wrong reasons, so should that really count scientifically?

Finally, Jason says of Martin's 2005 transition to MANIAC that "I have heard few mention that, in this 2004 paper, Martin rather quietly gave up on that view [that dromaeosaurs were only distantly related to birds]."  "... this demonstrates that Martin was open-minded enough to be persuaded by the evidence and to reverse himself on a major part of his hypothesis."  While I do give credit to Martin for finally recognizing this relationship, the details make it look less noble.  First note Martin never actually admitted his quarter century of arguments against Archaeopteryx and Deinonychus being similar were fallaceous, or that this calls into question his entire methodology.  Indeed, he still uses most of them in that very paper, seemingly without realizing his new phylogeny cancels them out (e.g. if maniraptorans are all considered birds, then deriving this whole group from something standard like Ornitholestes eliminates any temporal paradox).  Second, he (as with Feduccia) framed neoflightless maniraptorans as a surprising compromise, when by that time most theropod workers considered it possible if less parsimonious.  The feeling from MANIAC papers is that taxa like Microraptor and Scansoriopteryx have sent everyone back to the drawing board, when BADists have actually been relatively unaffected besides the character distributions in our cladograms.  The impression is an attempt to save face while admitting as little error as possible, which seems distinctly unscientific to me.  Still, I'll say Martin's work was less polemical than Olson's or Feduccia's, the latter's 2013 paper being more unhinged than anything Martin wrote.

Well, that's a lot of criticism of a dead man, but I've never been one to follow the tradition of emphasizing the positive aspects of the deceased while downplaying the negatives.  Yet positives did exist, and I think his greatest legacies in science have yet to be articulated.  Foremost, Larry worked on a LOT besides bird origins.  While I'm not qualified to review e.g. his saber-tooth cat work, his hesperornithine work such as the 1976 osteology of Baptornis was quite good.  He continued such studies until the end of his life, such as his 2011 ornithuromorph predentary paper with Zhou that analysed an often ignored element.  Which brings us to Martin's other great legacy- his students.  I know at least Zhou and Witmer trained under Martin.  Zhou's been instrumental in expanding our knowledge of Jehol bird diversity.  As for Witmer, he has this touching summary on his institutional biography page, which shows my two favorite aspects of his excellent studies are due to Martin-

"I also owe a huge debt to Larry Martin, who got me interested in so many things.  He always encouraged me to look at modern animals along side extinct groups, and this has emerged as my major research paradigm, these nascent ideas later evolving into the extant phylogenetic bracket approach.  And of course it was Larry who introduced me to the previously under-appreciated anatomical system of cephalic pneumaticity, which became my major research focus for a decade and a half.  Although Larry and I are often now pitted as opponents in the fierce debate on avian origins, he has been one of the most important positive influences in my career."

So there are my criticisms and accolades.  But there's one more story I'd like to tell.  Back in October 2004, I decided to write Larry regarding bird origins.  It wasn't meant as a harsh debate, and I wasn't so naive as to think I could do what two decades of published professionals couldn't, but I was intrigued to see where he was coming from and how he would respond to questions and facts that aren't brought up in his papers.  Note this was before his 2005 paper declaring his MANIAC status, but I knew he thought that way due to SVP 2002.  I reproduce the content of this email exchange below, with changes in color and font between Mickey Mortimer and Larry Martin.  I've left out most of the pleasantries preceding and following each actual email, and have formatted them so that e.g. when Martin has four paragraphs, my four paragraphs are responding to them in that order.  While publishing email exchanges without explicit permission is of course frowned on in most instances, I'm hoping my own feelings this is ethical once one party is dead are shared by the community.  I think of Martin's words being like the personal letters of historical scientists that are now public, and it's all scientific exchange matching what he published as opposed to personal details.  So enjoy.  I don't think I've ever read a conversation between a BADist and BANDit, which makes this rather unique.  For all the criticisms I piled on Larry, I don't know many other scientists who would take the time to write such a long and detailed exchange with an unknown undergraduate amateur.  He'll be missed.

I'm an undergraduate at the University of Washington
currently investigating theropod and Mesozoic bird phylogeny.  I heard you
gave a talk the other day where you advanced the hypothesis that
maniraptorans are in actuality birds, and that they are unrelated to
theropods.  I wonder if you could answer a few of my questions.
1. What characters show oviraptorosaurs and dromaeosaurs are birds, while
leaving ornithomimosaurs and tyrannosaurs in Theropoda?
2. What is the sister group of birds + Longisquama in your hypothesis?
3. Do you believe homeotic shifts occur in nature?
Thank you for your time.
I suppose that we could define birds as animals who have or
give evidence of have having an avian wing (primary feathers attached to the
middle digit with the palm extending between the middle and outer digits and
a digit reduction pattern of 2-3-4) all animals with such a wing may
reasonably be supposed to have shared a common volant ancestor.  This brings
dromaeosaurs and oviraptosaurs into the avian fold.  The sister group of
birds and Longisquama (including Longisquama relatives) would probably be
dinosaurs plus many of the more conventional thecodonts.  I am not sure how
crocodilians fit in.  In any case the connection would be very basal within
archosaurs.  Please notice that if dromaeosaurs are secondarily terrestrial
we can expect many reversals of polarity from earlier analysis.  The
frameshift hypothesis was badly crunched by developmental types in a recent
conferance and is only being maintained to preserve a theropod hypothesis
that now fatally flawed.
Accepting your definition of 'bird', why are tyrannosaurs and
ornithomimosaurs excluded?  We have no embryological evidence to know if
they possess digits I-II-III or II-III-IV, and no preserved manual
integument that would tell us if they had primary feathers (no manual
integument has been reported for Pelecanimimus, Dilong, or tyrannosaurids,
though they each preserve integument elsewhere).
What characters do dinosaurs and these 'more conventional thecodonts' share
than Longisquama and birds lack?
Finally, do you mean the particular digital homeotic shift theorized for
theropods was questioned in this recent conference, or the reality of
homeotic shifts as a whole?  In either case, I'd be interested to know the
name of the conference, so that I can examine the references.

Thanks for the reply.  I agree dromaeosaurs and oviraptorosaurs were
secondarily flightless, which indeed leads to reversals of character
polarity from prior analyses. 

Tyrannosaurs are excluded because their hand as restored is not avian,
(they are not maniraptoran), maybe evidence could be provided that they
were once that way, but why worry until there is some reason.  They also
lack a lot of the other cranial features, etc.  Recent description of so
called protofeathers on a tyrannosaurid would seem to be clearly muscle fibers 
or ligaments and is probably better seen as evidence for a lack of feathers.
Ornithomimosaurs (including Mononykus) have derived hands with enlarged
MTCI and a reduced wrist.  I can't see how it relates to the avian hand
and think that they are best compared to compsognathids. I think in terms
of the general story, it makes very little difference where these taxa go. 

If Tyrannosaurs are carnosaurs, we know that at least some carnosaurs have
typical dinosaur rosette scale patterns and this may be a dinosaur
synapomorphy.  They also have interdental plates covered by a 
superdentary bone and this would make them very unlikely birds.  They also
have a long postacetabular ilium, a derived feature found in the earliest dinosaurs and absent from
all of the very early birds.
The conference was the Society of Avian Paleontology and Evolution. 
Essently none of the developmental types thought much of frameshift
although one tried to preserve bird/theropod by postulating a presently 
unknown ancestral six fingered hand.  You have to ask yourself about 
the credibility of an idea that requires a lot of ad hoc new science
to keep it alive. 
I accept your proposal tyrannosauroids lack some maniraptoran characters.
What prevents them from being maniraptoran relatives though?  Branching off
the bird line before maniraptorans developed all of their distinctive
traits?  They do share a lot of characters with maniraptorans, after all.
Regarding Dilong, what features do its supposed feathers have that would
make them less likely to be feathers than the identical structures in
Sinornithosaurus' holotype, or the plumulaceous body feathers of Caudipteryx
and Protarchaeopteryx (besides the fact you know these last three are
maniraptorans; that would be circular reasoning, after all)? 

Check out Ingenia for a maniraptoran example of enlarged mcI, though I admit
no maniraptoran reduces its carpals like ornithomimosaurs.  I agree with you
about Mononykus and other alvarezsaurids being closely related to
ornithomimosaurs.  I even wrote a post to the Dinosaur Mailing List in June
about how they were being put inside Maniraptora and Avialae due to flaws of
most cladistic analyses.  I also agree both groups are close to
compsognathids.  I think ornithomimosaurs+alvarezsaurids could be very
important for your hypothesis, since they show a number of characters you
think of as avian- no supradentary; serrationless teeth with basal
constriction; large sternum; ossified sternal ribs; costal facets on the
sternum; coracoid facets on the sternum; hollow keratinous integument.
Thanks for providing these specific characters.  Tyrannosauroids are almost
universally agreed to be coelurosaurs now, so we don't have to worry about
rosette scale patterns yet.  Velociraptor and Dromaeosaurus possess
supradentaries, so that can't bar tyrannosauroids from being on the bird
line.  If we use the ratio between postacetabular and preacetabular
processes to be an indicator of postacetabular length, the long
postacetabular processes of tyrannosauroids (~120-140%) are comparable to
some maniraptorans (Microvenator- 132%; Ingenia- 128%; Sinornithoides-
146%).  So that can't bar them from being on the bird line either.  Unless
you use a different ratio. 

I completely agree with the latter sentiment.  Unfortunately, the 2004 SAPE
abstracts aren't available yet, so I'll have to wait to see what new data
was presented.  It will be interesting to see how they deal with homeotic
shifts observed in human cervical number, which we can validate since we
know the geneology of the people in question.
please give citations for superdentaries in maniraptorans of any sort!
I think that the position of tyrannosaurs is quite controversal and it
doesn't make any difference to me how they fall out.
I am not convinced that any of the so called protofeathers are real.
Everybody has muscles and just because something is on a bird doesn't mean it's a feather. 
Gladly.  If you ever want confirmation of my statements, just ask.
Currie, 1995. New information on the anatomy and relationships of
Dromaeosaurus albertensis (Dinosauria: Theropoda). Journal of Vertebrate
Paleontology. 15, 576-591.
Barsbold, 1983. Carnivorous dinosaurs from the Cretaceous of Mongolia. Joint
Soviet-Mongolian Paleontol. Expedition Trans. 19, 5-120. 

If tyrannosauroids are stem-birds, they would help us understand bird
evolution a lot.  There's a big gap between Longisquama and dromaeosaurs,
but tyrannosauroids help fill it out.  Besides, if theropods and
maniraptorans are so distantly related, it should be easy to tell them
apart, right?  Even in famous cases of convergence like thylacines vs.
canids, Notoryctes vs. talpids or hesperornithines vs. gaviiformes, the
differences are easy to see if one looks at skeletal details and not gross
This is a very interesting stance I've not seen in the literature.  How do
you reconcile this with the fact Shuvuuia's hollow cylindrical structures
are made of keratin (Schweitzer et al., 1999), and not collagen, actin or
I doubt that any keratin has survived since the Cretaceous.  At least the
mollecular types don't buy into Mary's results.  Evidence that any of these 
structures were hollow is hard to come by.  All of the morphological structure 
is best expained by other interpretations. 
Quite a lot of the anatomy of dinosaurs has been uncertain, for instance
the two decade struggle to get the hand and wrist of Deinonychus correctly

What are the citations for molecular biologists disputing Schweitzer et
al.'s paper, and/or keratin fragments being unable to survive since the
Cretaceous?  Schweitzer et al. state quite plainly "These fibers are seen to
be hollow, both grossly and in microscopic cross section," and photograph an
example in figure 2.  Which alternative explanation is better for clumps of
hollow fibers 200 micrometers in diameter which show smooth outer surfaces,
pithy inner surfaces, plate-like structures at one end, small filaments on
the outer surface, and consisting of microfilaments of 90-95 nanometers?
Agreed.  Even now, there are interesting new possibilities being raised,
like Gishlick's (2002) idea maniraptorans' distal carpal III is fused to the
base of metacarpal III.  As might be expected in e-mail discussions, it
seems a couple questions I'm curious about have got lost with all the
supradentary and keratin information.  Namely-
Why are some (which?) 'thecodonts' more closely related to dinosaurs than to
Given other examples of tetrapod convergence, shouldn't it be easy to tell
maniraptorans from theropods if they are so distantly related?

There has been quite a bit of rethinking of some of the earlier claims and
right at the mommentI think that real evidence of intact Tertiary proteins 
is pretty cutting edge.  Let's say for argumentation that she has keratin tubes, 
what feather structure could they be?  How would it form?
We should have some criteria for thinking something is a feather beyond
finding it on a dinosaur if we intend to show that dinosaurs have feathers.
I think that Roger Sawyer who provided the antigens is going to or has commented on the paper. 
Alan Feduccia probably could give you more commentary. 

Tyrannosaurs are so highly derived that I can't see that they would help much. 
Their wrists, hands, ankles. feet and skulls are all more derived and modified 
than the other tax we have discussed.
Well, these are only supposed to be keratin fragments, not intact keratin.
So that may make it more plausible to you.  If they are keratin tubes, the
feather structure represented would be the rachis and/or barbs.  Prum (1999)
goes into detail about how feathers form ontogenetically and perhaps
phylogenetically as well.
I agree with your statement we need non-circular reasoning if we wish to
show dinosaurs have feathers.  Prum has defined feathers in relation to the
feather follicle, making the first epidermal structure originating from a
follicle homologous to those in living birds the first feather.  I might
just be naive, but it seems to me any epidermal derivitive with a slender
cylindrical base necessitates a follicle to grow from.  So those of
stem-birds (like Confuciusornis and Sinornithosaurus), pterosaurs, and
Longisquama are are potential feathers, if we can establish homology with
birds' feathers.  This latter job is not easy, but is helped by phylogeny
and feather morphology.  As an example of the former, no non-feathered taxa
are closer to modern birds than Confuciusornis or Sinornithosaurus, so their
structures are phylogenetically congruent with homology.  An example of the
latter is the branching observed in the structures of Sinornithosaurus and
Dilong, which is unique to feathers.
Thanks.  I'll ask them. 

This doesn't appear to be true for basal taxa like Dilong.  Besides a few
characters (symmetrical premaxillary teeth in section; fused nasals; nasals
anteriorly convex in transverse section; pneumatic articular; preacetabular
notch on ilium), it looks like a good stem-bird.  Sure, it probably lacked a
true semilunate and other maniraptoran characters, but so did Longisquama.
If I understand Prum's model, his protofeather is none of the above.  It
does not claim homology with any part of a feather other than the collar 
and completely ignores the feather sheath.  It was created directly 
from the dinosaur protofeathers so there is no surprise that it looks like
I certainly don't believe the so called "feathers" in pterosaurs, and I am
amazed that nobody seems to to be upset with spreading feathers everywhere
especially when the majority of dinosaurs can be shown to be covered with scales. 

Why think that these things are feathers when they can't be distinguished
from fossilized muscles found in other organisms.
Notice that Mary's study comes from sediments where we might not expect
ancient preservation while they > are not duplicated where the opportunity
seems better. 

Prum's (1999) stage I feather is homologous to the calamus of modern
feathers, in the sense that it is formed by an undifferentiated follicle
collar.  Sorry for not specifying the calamus last time, I was grouping it
with the rachis in my mind.  Prum and Dyck (2003) describe sheath morphogy
and development in detail.
Though I can't claim to know Prum's thought processes, Prum and Dyck
describe how the model is largely dictated by the developmental mechanisms
of feathers (hierarchical modules), not merely resemblence to
Sinosauropteryx and Beipiaosaurus feathers.  Barbs have to evolve before
rachis because the rachis is just a fusion of barb ridges; barbules have to
evolve after barbs because they are formed by the differentiation of cell
layers in barb ridges; the calamus has to evolve first because the barb
ridges are differentiations of the collar that forms the calamus.  How do
you explain the structure of Longisquama's parafeathers being primitive for
feathers if they have a rachis and a barbless vane (as shown by those
successive magnifications at SVP 2001), when the rachis forms from fused
barb ridges?
Basically every pterosaur worker believes pterosaurs had filamentous
integument.  Why would you doubt it?  I know Feduccia cites Unwin and
Bakhurina (1994) as a contrary view, but they specifically noted such
integument was present in later papers and online communications.  They were
merely saying that the supposed Sordes hairs _figured up till that point_
were internal fibers.  I personally don't think they are feathers, but
that's only because there are so many scaled taxa between pterosaurs and
birds.  Filamentous integument evolved at least twice anyway (birds,
mammals), why not a third time?  And given the standard phylogeny, diapsid
filamentous integument only shows up twice- pterosaurs and coelurosaurs.
Unless you count Longisquama's or Psittacosaurus' structures. 

What specimens would these fossilized muscles be in?  In any case, they can
be distinguished from muscles and collagen (Lingham-Soliar, 2003) in the
following ways.
1. Dinosaur feathers are too long to be collagen fibers.  Even if one were
to hypothesize axial frills on Sinosauropteryx, how do you explain elongate
filaments on left and right sides of dorsoventrally preserved animals (NGMC
91; many Confuciusornis; Eoenantiornis)?  Elongate filaments on areas not
expected to have thick skin or need elongate muscle fibers (skull of
Microraptor; middle of Bewipiaosaurus' ulna)?
2. Dinosaur feathers are mostly perpendicular to the body wall (along ulna,
shoulders, femur of NGMC 91; head and chest of Microraptor; tail and ilium
of Sinosauropteryx), which is compatable with collagen, but not with muscle.
3. Dinosaur feathers are not inside the body wall like the fibers of
ichthyosaurs.  Ichthyosaurs have a very thick body wall, analogous to
cetaceans.  But proposing the body wall of theropods extended as far away
from the bones as seen in NGMC 91 or Eoenantiornis is preposterous.
4. Dinosaur feathers are hollow, unlike collagen.  Even if ichthyosaur
fibers look hollow due to mineralization stages (and you doubt Yixian
dinosaur feathers based on this), the filaments of Shuvuuia are three
dimensional, so cannot be explained in this manner.
5. Dinosaur feathers are suspiciously distributed similar to bird feathers.
There are none on the feet or distal snout.  Elongate feathers are
conveniently on the ulnar side of the lower arm (Beipiaosaurus, NGMC 91) and
distal tail (NGMC 91).  In particular, if they were muscles, we would expect
long tibial fibers on at least some specimens.
6. Dinosaur feathers are sometimes intermixed with vaned feathers, such as
on the head of Microraptor.  This is fairly indisputable proof that whatever
the more simple structures are, they are integument.
7. Dinosaur feathers are made of beta keratin, not collagen, actin or
myosin.  At least in Shuvuuia's case.
8. Why are Yixian lizards, choristoderes, salamanders and psittacosaurs not
covered with these structures?  They should have muscles and collagen, after
How do you explain all of these factors?  I admit they could also be
homologous to turkey bristles (Sawyer et al., 2003), but the data seem to
argue against muscle or collagen.
Specimens from the Djadockhta can preserve keratinous structures, in the
form of claw tips (e.g. Citipati in Clark et al., 1999).  On the other hand,
how many specimens with preserved internal soft tissues have been found
The theory that the rachis is fused barb ridges was rejected some decades
ago and the problems that it had then still aren't resolved. 
Why would you have a calmus if you have nothing else and where does the
feather sheath come in?  
Does Prum actually say that the protofeather is a calamus.  I don't
remember his saying so in any presentation.  I asked him once what part of a 
feather he was talking about, but the collar was all that I got out of it. 
You might try Paul Maderson if you want a critque on his model
of feather development.

Have you read Harris et al. (2002), which shows barb ridges fusing to form a
rachis in figure 4F-J?  Indeed, barb ridges can be induced to fuse to form
rachis if the follicle is split into two (Prum and Dyck, 2003).  Any
Harris MK, Fallon JF, Prum RO. 2002. A Shh-Bmp2 developmental module and the
evolutionary origin and
diversification of feathers. J Exp Zool (Mol Dev Evol) 294:160-176.
Among the more plausible theories is for insulation (it would be comparable
to having fur).  Since the sheath is subsumed by the calamus once the latter
starts developing, and becomes an indistinguishable part of it, one might
assume a feather which is formed completely from the undifferentiated
'calamus setting' of the follicle collar would lack a sheath.  Sheaths would
have evolved only once the follicle collar became differentiated into barb

Prum says stage 1 feathers were formed by an undifferentiated follicle
collar, which is the same way that modern birds form their calamus.
Portions of feathers are only homologous in the sense that homologous
genetic patterns are being expressed at the time they are formed.
Maderson's model seems to contradict the developmental and genetic evidence
in asserting scales and feathers are homologous past the placode stage and
that barbs are formed from frayed scale edges.
Do you have any explanation for why muscle or collagen would exhibit the
eight traits I noted last time in coelurosaur and bird filaments?  They're
listed below in the copy of that message.
Comparison with dinosaurs should be through the common ancestor of the
maniraptorians and birds which according to the cladograms would have an 
avian wing.  If anything else is included as closer to maniraptorians 
than to birds, it would share that ancestor and hence be uninformative. 
If microraptor is a good model the common ancestor would not be bipedal. 

Longisquama has many feather features while protofeathers have essently none.
It also has an avian shoulder girdle. 

Yes, but tyrannosauroids and ornithomimosaurs would be outside the
maniraptoran+birds group, not necessarily have an avian wing (presence of
primaries unknown), and thus be informative.
Sure, but the stem leading to that common ancestor could be bipedal.  We
don't have Longisquama's hindlimbs, after all. 

I suppose I'll bite.  Like Longisquama's structures and bird feathers,
protofeathers are elongate, have a cylindrical base (hence, follicular
development), and a hollow shaft (Shuvuuia).  Pulp caps and sheaths are not
even seen in Yixian bird remiges or retrices, so their apparent absence in
protofeathers is meaningless.  The vanes of Longisquama's structures consist
of a two-layered sheet (since they were filled with sediment; Reisz and
Sues, 2001), so are only superficially similar to a feather vane (which
forms from barb ridges).  I fail to see any feather features parafeathers
have that are absent in protofeathers, let alone many.  Are there any I
Could you be more specific?  Coelurosaurs have slender scapulae and furculae
too, so those characters can't be used to place Longisquama closer to birds
than coelurosaurs.  I can't recall hearing of any other avian pectoral
characters in Longisquama.
Why you resist the one that has a lot of evidence for avian structure and
support the one that does not is more interesting to me than the debate. 
If you want to argue a bipedal ancestor and I would ask why you would even
care?  Than you must go quadrupedal to bipedal to quadrupedal to bipedal.  This seems to be
tedious and should only be pushed because of compelling evidence. 

If tyrannosaurs should turn out to be another secondarily terrestrial
lineage, I don't see how that advances the discussion.

It's exactly the same for me, though of course we have different views
regarding which specimens have a lot of evidence for avian structure and
which have less.  I don't expect to convince you my opinion is correct
(since it's been argued many times in the last couple decades by people with
far more experience) in this debate.  I'm mainly curious why you hold your
position and how you justify it.
But it's only fair I explain why I resist and support what I do too.  In
regards to Longisquama, here are the reasons I don't accept it as feathered.
Reisz and Sues (2000) have shown the supposed sheath is actually an
infilling of sediment.  This is proven by the fact that it covers the vane
corrugations on both part and counterpart, so must be internal.  I have not
heard a defense of why this is wrong from you or anyone else who supports a
feathered Longisquama.
The vane, being formed of two sheets, is unlike a feather vane in everything
except its expanded shape.  I've heard no developmental hypotheses for
changing this into a vane of barbs from you, Maderson or anyone else.  The
fact it can fold or is expanded distally has no relevence if it isn't
Senter (2003) notes the supposed pulp caps are troughs between corrugations
on the middle vane.  He also describes the structures as being tripartite,
with anterior, middle and posterior vanes (the posterior vane narrows
distally until it disappears at midlength, while the middle and anterior
vanes expand to form the distal half.  I don't have the proper photos to
determine if these features are correct, but the fact multiple
interpretations exist certainly makes me weary of accepting Jones et al.'s
view (especially when the latter has proven incorrect in the ways described
above, and in regards to the supposedly separate barbs too- the successively
enlarged photos of the vane edge at SVP 2001 were convincing).
All this leaves in regards to featherlike characters is the narrow base,
which isn't too convincing since protofeathers exhibit it too, and the rest
of Longisquama's anatomy places it outside Sauria (Senter, 2003; 2004).
I've told you why I support protofeathers, with my eight ways they differ
from collagen and/or muscle.  Until you tell me why those are incorrect, we
can't progress on that topic.
When you said Microraptor was quadrupedal, I assumed you meant while
climbing.  While on the ground, you think Archaeopteryx and Confuciusornis
were bipedal, and since the former is so similar to Microraptor, I assumed
you thought it was bipedal on the ground too.  So if we are concerned about
terretrial locomotion only, birds are always bipedal, which is congruent
with ornithomimosaurs or tyrannosauroids being stem birds.  While climbing,
I don't see why small ornithomimosaurs or tyrannosauroids wouldn't use their
hands too.  Hell, with more arm/wrist mobility and perhaps no remiges, it
might have been easier for them than for maniraptorans. 

Here are my thoughts for how it could advance the discussion.
Foremost, I'm trying to understand how you justify separating maniraptorans
from theropods.  I know you'll use the homeotic shift for four-fingered
theropods, so I'm concentrating on the tridactyl ones.  You suggested
postacetabular length and supradentaries, but I showed those characters
don't work.  It's just such an odd concept to believe theropods and
maniraptorans are so distantly related, while being unable to assign some
taxa known from many complete skeletons to either group.  At least back when
you thought maniraptorans were dinosaurs, you had a list of characters that
could be used to separate dinosaurs from birds (hypopubic cup; expanded
tooth roots; four carpals; etc.).  So although you thought the groups were
superficially similar, these details could be used to differentiate them.
But that doesn't seem to be true for your new view.  This confuses me.
Secondly, your entire philosophy of 'not caring' about the relationships of
tyrannosauroids and ornithomimosaurs is confusing.  Finding that
maniraptorans are birds warrants a public talk, but what the next most
closely related group is seems unimportant to you.  There's a huge
morphological gap between Longisquama and birds, and you haven't been able
to give reasons tyrannosauroids and ornithomimosaurs don't fill that gap.
If they are stem birds, it would give us more evidence to use when deciding
what the next most closely related group is.  And I assume that question is
important to you.  This is analogous to my confusion regarding why you or
any other supporter of feathered Longisquama has never tried to figure out
where in Archosauria it goes.  The relationships between archosaurs have
been well resolved for over a decade, I would think such an important taxon
would be worth classifying more precisely.


  1. This is fascinating Mickey - thanks for posting.

  2. A pity we'll never get the answers to some of your questions.

  3. This is a pretty important piece of intellectual history, Mickey. It should be archived.