[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
FW: Microraptor also ate fish
I was once talking to a doctoral student, now a Professor, about
Microraptor. I implied that it must have lived in trees. He asked why and
I said "come on, the asymmetrical feathers and wings that are so long?" He
said "well, ravens have long wings and asymmetrical primaries and they are
common on steppes. Heck, falcons nest on the ground on the tundra."
The reason I mention it is that Microraptor has huge anatomical
differences from those two animals, but those analogies helped me to
accept that a terrestrial animal can still have long highly aerodynamic
wings. Thus they were useful in informing my armchair opinions.
One thing that irks me a touch about speculation on Microraptor is that we
often construct it in our minds as highly limited and even clumsy. Its
wings encumber it, if it fell in the water it would drown, it can barely
get into a tree or into the air. There are somewhat bumbling animals, and
maybe Microraptor was like a Kakapo. But Maybe it was like a roadrunner,
running and leaping with great vigor and dexterity. Even these ways of
moving are hypotheses, can be supported or contradicted, and they have big
ramifications on evolutionary biology.
Senior Principal Preparator
American Museum of Natural History
(212) 496 3544
On 4/24/13 2:11 AM, "Tim Williams" <firstname.lastname@example.org> wrote:
>Jason Brougham <email@example.com> wrote:
>> 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.
>No worries. BTW, I [snipped] a lot of your text for the sake of
>brevity. I really hope my responses don't give the impression of
>Short response: The point I'm arguing here is the distinction between
>what an animal is *adapted* for and what an animal is *capable* of.
>The former is a subset of the latter, of course. For a fossil taxon,
>adaptations can be inferred based on morphol
>biomechanics. Determining the full potential of the latter (i.e., the
>full range of what an animal is capable of doing) is often impossible
>to approach scientifically.
>For example, what if we wanted to investigate _Archaeopteryx_'s
>ecology based on its morphology. The overall skeletal proportions and
>hindlimb biomechanics indicate that it was a terrestrial cursor. So
>if our hypothesis is that _Archaeopteryx_ was a terrestrial cursor,
>the data support that hypothesis.
>If our hypothesis is that _Archaeopteryx_ was an arboreal animal, then
>the data are not supportive. The lack of arboreal adaptations weighs
>against this hypothesis. Sure, _Archaeopteryx_ might have roosted in
>trees. As you say, many modern birds without obvious arboreal
>adaptations can (and do) roost in trees, such as tinamous, petrels and
>cormorants. But I'm struggling to see how the hypothesis of roosting
>behavior in _Archaeopteryx_ can be upheld scientifically in the
>absence of the requisite adaptations.
>Long response: Read on...
>> 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
>> without unambiguous evidence.
>"Annoyed" is perhaps overstating my reaction. I don't really have any
>emotional investment in this thread, just an intellectual one. ;-)
>> Just 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).
>Yes, I do
> Unless you can demonstrate (a) which morphological traits allow
>petrels to perch in trees, and (b) that _Microraptor_ had these same
>Yes I know I'm being harsh here. But I'm trying to avoid rampant
>speculation about _Microraptor_ behavior simply because this-or-that
>bird can do it. Same for any other non-avialan maniraptoran or basal
>avialan. They weren't crown birds.
>> Thanks to observations from actual Zoology, we know for certain that
>> skeletal correlates are real possibilities we need to acknowledge in
>>evolutionary 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.
>If diving petrels were extinct, I would say that the pedal morphology
>suggests they weren't arboreal. I'd be right.
>> You may retort that analogs are speculative wastes of time.
>That's not really what I said - but it's not far off. :-) I think
>some people too readily resort to modern analogs to explain the
>behavior of fossil taxa. As examples, comparing _Microraptor_ to the
>colugo, or _Archaeopteryx_ to a magpie, or _Epidendrosaurus_ to an
>aye-aye... all these "analogs" have the potential to mislead w.r.t.
>the ecologies of these maniraptorans.
>> But isn't analogy indispensable in evolutionary theory? Didn't Darwin
>>apply the lessons of
>> Galapagos finches to apes to help understand all evolution?
>In broad terms, yes. Again, I'm not rejecting the use of analogs
>outright. I'm just saying we should be *very* judicious about our
>choice of analogs.
>> 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
>> 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
>The trouble is that there is a whole lot of small non-pygostylian
>maniraptorans that clearly weren't adapted for arboreality -
>_Microraptor_, _Archaeopteryx_ and _Jeholornis_ included. If all
>these non-avialan maniraptorans were spending so much time in the
>trees, why did it take so long for maniraptorans to develop any
>arboreal characters? My explanation is simpler: Because they didn't
>spend much time in trees at all. Yes, they might have roosted. But
>how would we know?
>> 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
>I may have given the wrong impression on this one. I think it's
>reasonable that _Microraptor_ ventured in trees, and used its hands
>and feet to grasp trunks and branches. The second toe may indeed have
>been useful in this context. But this is unrelated to an ability to
>roost, because none of the birds you mention uses this kind of pedal
>arrangement for roosting.
>> 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 branches
>>can 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.
>Agreed. But if the two animals don't have the "same feet", you can't
>use them as analogs for how they could have used their feet to grasp
>Show me a modern example of an animal with _Microraptor_-like pedal
>morphology that perches or roosts on narrow branches. If you can't,
>_Microraptor_ did it. Yes, I understand petrels, wood ducks, tinamous
>etc can roost without the aid of a long hallux. But that argument
>alone doesn't cut any ice with me.
>> 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
>> 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.
>_Microraptor_ has the proportions of a terrestrial cursor. It also
>has a few putative scansorial characters. It has a plumage suggestive
>of aerial descents. This leads me to hypothesize that it was an
>animal that spent most of its time on the ground, and occasionally
>ventured into trees.
>> 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 turkeys in trees where the halluces do not touch the
>>branch. We have 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
>Ah, it always comes back to "But goats can climb trees!" :-) Yes,
>goats have certain morphological traits that allow them to climb trees
>(many of these traits are associated with negotiating narrow and/or
>3-dimensional substrates). But unless you can identify these same
>traits in _Microraptor_, goats are utterly irrelevant to how
>_Microraptor_ might have climbed trees.
>Nevertheless, goats don't roost in trees. They are not arboreal. If
>all goats were extinct I would say that, based on morphology, th
>goats were not arboreal, and that tree-climbing was not essential to
>their ecology. I'd be right on both accounts. Whether they did climb
>trees or not is unimportant to me, because it's outside the scope of
>what fossil evidence can tell us.
>> To repeat, I have never suggested that Microraptor was in the
>>morphological category of
>> "perching" or "arboreal" birds. That is obvious, and those last 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,
>> such as In some cases (tinamous with vestigial halluces and wild
>>turkeys with elevated
>> halluces) where their feet are even 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
>> entirely, of being strictly ground birds.
>Excellent point. I wouldn't say there is "no way" they could get into
>a tree. I would say that the morphologies of these birds tell me that
>they are/were terrestrial. In other words, they spent most of their
>time on the ground. I could not rule out roosting; but I can't rule
>out other behaviors too for which there are no apparent adaptations.
>Apparently tinamous "roost" in trees by sitting on their tarsi using
>highly modified scales on the plantar tarsal surface. In any case,
>tinamous and turkeys nest on the ground, don't they?
>> Actually David Hone suggested in his paper that the hands of
>>Microraptor could 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.
>This only applies to small objects, correct? A _Microraptor_ could
>of all four limbs.
>> 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.
>I agree with you here. And so I'll end this voluminous response on a