RE: Microraptor also ate fish

[Jason Brougham <jaseb@amnh.org>]

I hate to send this again but some of it was chopped out last time.
 Just for clarity. So long and boring, so sorry!

From: owner-DINOSAUR@usc.edu [owner-DINOSAUR@usc.edu]
 on behalf of Jason Brougham [jaseb@amnh.org]
Sent: Wednesday, April 24, 2013 12:44 AM
To: tijawi@gmail.com; "dinosaur@usc.edu"@listproc.usc.edu
Subject: RE: Microraptor also ate fish

 Now this is a productive debate about Paleontology.

Your points are well made, well supported, succinct, and articulate. 
Thank you. I really want to be as succinct but I will probably fall a little 
short.
 I apologize.

One reason we are all so interested in Microraptor is that, thanks to its 
anatomy, 
its phylogenetic position, and its similarities to other paravian relatives,  
it may 
retain some of the ancestral characters of the ancestors of birds. If so, it 
may be
 a useful model for understanding the transitional forms between the non-flying 
and flying dinosaurs, in any number of aspects of its biology.

As you note, I never said I could prove Microraptor could climb into a tree, I 
said 
we can't rule it out. You are probably annoyed with me for raising hypothetical 
functional possibilities without unambiguous evidence. But is it unscientific 
to 
present a hypothesis, and then discuss with one's peers comparative methods
 to test it? I must reply, with all respect, that you seem to have actually 
committed 
a logical fallacy by categorically calling one of these hypotheses impossible 
on 
a priori grounds. That is where I think scientifically shaky ground and woolly 
thinking entered into this conversation. If I may jokingly exaggerate to make a 
point,
 you are saying that since we never found Amelia Earhart's body there is no way
 she could be dead. Disproving that A = B doesn't prove if Not A then Not B. 
ust because birds with strong halluces often nest in trees doesn't mean diving 
petrels, 
which do not have halluces, can't nest in trees (in fact they do). Thanks to 
observations from actual Zoology, we know for certain that behaviors without 
skelet
ionary 
theory. I am not saying that, if diving petrels were extinct, I could just 
somehow
 tell they climbed trees. But I never claimed certainty, you did. You feel that 
you can say "no way" if the animals are "not adapted for" it without testing 
that
 conclusion, while I do not.

You may retort that analogies are speculative wastes of time. But isn't analogy 
indispensable in evolutionary theory? Didn't Darwin apply the lessons of 
Galapagos finches to apes to help understand all evolution?

Moreover, if we are considering evolutionary sequences, inference from context 
will be relevant. In order for such highly evolved traits as opposed halluces 
to 
evolve, a feedback loop must be established where slight improvements in the 
structure have real survival benefits to the inheritors. Far from there being 
no way,
 it is in fact indisputable that the behaviors must often precede the 
adaptations, or 
else there must be exaptations. As you concede, the gripping of prey by the 
second
 digit which, according to dromaeosaur anatomy could probably flex enough to 
pierce 
its own foot pad, could be just such an exaptation. The fact that, unlike 
Denonychus,
 Microraptor weighs the same as birds like ravens, pheasants, and tinamous that 
roost
 in trees seems to me highly relevant.

>Unless you are arguing that _Microraptor_ could perch like a raven
>(and clearly you aren't), I would say that comparing _Microraptor_ to
>a raven is irrelevant and moot.  _Microraptor_ has no morphological
>traits that are correlated with an ability to climb out on to terminal
>branches the way ravens do.  Yes, _Microraptor_ might have done so.
>Animals often perform functions for which they are not adapted.  But
>I'm trying to keep our inferences about an animal's behavior to a
>soundly scientific footing (so to speak).  In short: What was
>_Microraptor_ actually *adapted* to do?

You say that Microraptor might have done so, but also that this is irrelevant 
and moot? 
If two animals weigh the same, and the question is whether terminal branche
support them, you don't see any relevance? Two animals do not have to have THE 
SAME
 feet in order to hold on to branches. They just need to have feet that can 
grip. 
Do you reject the use of all analogs in comparative zoology and Paleontology? 
Or do you accept that, if a Harbor Porpoise weighing 60 kg can breach the water 
and 
leap into the air, isn't this is one lineof evidence that an ichthyosaur 
weighing 60 kg could
 perform the same maneuver?

What was Microraptor actually adapted to do? What is your answer? No one knows 
what
 Microraptor is adapted to do because there are no four - winged animals with 
functional,
 unfused, finger and toe claws, long bony tails, and feathered integuments 
alive today for 
us to calibrate any correlates. This is why we are all so fascinated by the 
animal. If you 
rely solely on modern morphological correlates, it was adapted to do nothing.

Some measurements, of feather vane asymmetry, wing length and surface area, 
sternum 
size, estimated pectoral muscle mass etc. place Microraptor among powered 
fliers like 
megachiropteran bats. Some wind tunnel tests showed that it was an efficient 
glider and that,
 even thought its leg feathers cut into the induced wind the wrong way, they 
still somehow
 produce lift. That experiment even suggested Microraptor was  adapted to 
quickly tip up to
 land on trunks. Other comparisons to living birds, like ornamental breeds of 
pigeons, suggest 
the leg feathers had no aerodynamic function at all, and that this little thing 
could have spent
 its life darting around in thickets and covering its huge egg clutches with 
its wings. I think all
 of these are real possiblities, and I don't reject any of them a priori.

>This grasping pes may have been exapted in other lineages for arboreal
> perching; but it wasn't there yet.  Not even close, IMHO.

I have photos of two different grouse chicks perching in trees by pinching  
branches - between 
the 2nd and 3rd toe with the left foot, and 3rd and fourth, on the left, in 
both cases. I have 
photos of turke
ave often 
discussed the goats climbing trees. If all goats were extinct you would say 
there was no 
way they could climb trees, because they lack all skeletal correlates for 
climbing, like thumbs. 
But since they are alive we know that one correlate for climbing is being a 
nimble goat!

To repeat, I have never suggested that Microraptor was in the morphological 
category of
'perching' or 'arboreal'. Those two categories are highly derived states in 
true bird evolution.
Instead, I observed that basal birds with body masses low enough (tinamous, 
galliforms, 
anatids) all have many representatives that roost in trees, often at night and 
when brooding 
young. Some birds with NO halluces also nest in trees, and In some cases 
(tinamous with 
estigial halluces and wild turkeys with elevated halluces) their feet even seem 
degenerate 
for perching, so that, if they were extinct, you could go on the DML and argue 
that there was 
"no way" they could get into a tree, let alone with their chicks, since their 
morphology shows 
they were going in the other direction entirely, of being strictly ground birds.

If you look only at unambiguous correlates, how would you know an intermediate 
condition if 
you saw it? If we look at the jaw joint in Morganucodon, would you say that the 
articular and
 quadrate still participate in the jaw joint and that, lacking a purely 
squamosal/dentary jaw joint, 
Morganucodon lacks that correlate for being a Therian and thus has nothing to 
tell us about 
mammal evolution? Or can you see it in context, as a model for how the 
evolutionary stages 
may have progressed, even if it may not be an actual ancestor of true mammals?

>Regarding the manual claws, there is an issue regarding how it is
>difficult to distinguish predation from climbing ability (after all,
>both require gripping).  This leaves scope for exaptation, if a
>predatory manus was co-opted for climbing, which is possible in small
>maniraptorans.  This is an entirely scientific example of
>"uncertainty".

Actually David Hone suggested in h
uld not be brought
 together to grasp prey because of the primary feathers. I was skeptical, so I 
tested it in my precise
 scale model, and found that he was right. To bring the hands together a large 
percentage of the
 length of the primaries strikes the ground. 

-Sullivan, C., Hone, D. W. E., Xu, X. and Zhang, F. The asymmetry of the carpal 
joint and the 
evolution of wing folding in maniraptoran theropod dinosaurs. Proceedings of 
the Royal Society
 B. Published online March 3, 2010. Figure 3

>But if we say that the manual claws or pes could be used for functions
>for which they were clearly not adapted, then we're on shaky ground.
>This is a way that "uncertainty" is mis-used.  The foot of
>_Microraptor_ was *not* adapted for perching.  No amount of discussion
>about wood ducks and ravens will convince me of otherwise.

Agreed. The foot of Microraptor does not have the adaptations of modern 
perching birds.
But its anatomy is tantalizing precisely because we can't exclude the 
possibility that it could 
climb into trees. Not perch, but start on that sequence.

Are you suggesting that Microraptor has LESS gripping ability with the second 
toe than larger 
dromaeosaurs do? I am open to that possibility, has anyone measured that?

Now, you are right if you say that I may be wasting my time imagining the 
lifestyle scenarios of
 Microraptor, Archaeopteryx, Xiaotingia, Anchiornis, Epidexipteryx, and 
Epidendrosaurus, and
that the real ancestral condition, and habits, may be revealed by as yet 
undiscovered animals, 
or may never be revealed. But those taxa grade pretty well into Jeholornis, 
Sapeornis, Confuciusornis 
and so on. They seem to reflect back to the real common ancestor of Paraves, 
which was probably
 small, winged, and just possibly could have climbed into trees to roost as 
basal birds still do.

>I'd say the morphology of _Microraptor_ says "no way".  It has no
>adaptations that correlate with an ability to grasp narrow branches,
>either with its hands or feet (or both together).  If we are going to
>claim
>adapted, and that these behaviors were important to its life habits,
>then I think we're heading in the wrong direction.

Agreed, we must not claim this. But we must remain open - minded to plausible 
hypotheses. 
And we must remember that claims of what Microraptor IS adapted to are also 
speculative 
and must be tested. There is no consensus on what T. rex was adapted to do 
(scavenge or hunt),
nor Alvarezsaurs, nor sauropods, nor sabre toothed tigers. There are just 
leading and minority 
hypotheses.

>... let's not use uncertainty as an invitation for woolly thinking.

Agreed. Let's not claim certainty a priori either. You see, that is why I so 
often resort to real animals 
rather than calculations or theoretical works. If Sokoloff et al. hadn't 
finally buckled down and 
performed surgery on some Starlings, we'd still all be saying that the 
supracoracoideus is an
indispensable adaptation for take off from the ground. Thanks to him we know 
that total loss of the supracoracoideus has disturbingly little effect on take 
off performance. I would have bet my savings 
they couldn't do it, but they did it with seeming ease. That humbled me, and 
made me leery of relying
 on the interpretation of adaptations to predict actual capabilities.

'There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy.'
- Hamlet Act 1, scene 5


>Cheers

>Tim