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RE: Microraptor hanqingi, new species from China.



Alright, fair enough, petrels are squatter than Archaeopteryx. But there are 
bipedal, cursorial, theropods with the bauplan of long legs and long necks and 
small, elevated, halluces that are not fully capable of perching - and they 
also roost in trees. Galliforms like turkeys, I'm thinking of.

I was worried that someone would say petrels can sit in trees because they 
descended from birds that had functioning halluces. It seems illogical to say 
that a morphological character is crucial for a certain function, but that the 
function can be retained even if the character is lost. Let's just take this 
moment to note, there are theropods with no halluces that roost and nest in 
trees. If you don't believe it google image search "petrel tree". The first, 
second, and fourth images prove the point.

I am troubled that you dismiss any comparison between the function of basal 
paravians and modern birds because the former have long necks and legs. In 
reality, this fact is little appreciated, but Microraptor, Anchiornis and 
Xiaotingia have necks roughly as long as their skulls, putting them closer to 
medium - length - necked birds like crows than they are to long - necked forms 
like storks or ducks. The former retain long bony tails, of course, but it's 
not clear that basal paravians would have had important functional differences 
from phasianids like peacocks with much heavier and longer masses of feathers 
on their tails. If turkeys and peacocks aren't close enough to basal paravians 
for you to serve as analogs, then no animal alive on earth today is, so no 
analogs can be cited. 

There is no perfect analog alive today for basal paravians, but the imperfect 
ones we have demonstrate that there is no inviolable rule. No one has 
identified and measured a set of morphologies that correlate with the ability 
to roost in trees in living animals, so this possibility cannot be excluded for 
basal paravians.


________________________________________
From: owner-DINOSAUR@usc.edu [owner-DINOSAUR@usc.edu] on behalf of Tim Williams 
[tijaw
Sent: Thursday, May 24, 2012 9:05 PM
To: dinosaur@usc.edu
Subject: Re: Microraptor hanqingi, new species from China.

K Kripchak <saurierlagen1978@gmail.com> wrote:


> "True" arboreality... If we are leaning toward the notion that "true"
> arboreality arose with the perching pes, no discussion necessary. It's
> what I see as those "pseudo"- arboreal or "near" arboreal critters
> that came before (and were often still around)...


Archaeopterygids, jeholornithids and many small deinonychosaurs might
indeed qualify as incipiently arboreal.  _Jeholornis_ was found with
seeds in its stomach.  Maybe it scaled trunks to get to the seeds far
from the ground, then glided back down.


> Alright... Microraptorans are considered to have been gliders.
> Confuciusnornithids are considered to have been gliders.
> Confuciusornithids are considered to have been "true" arboreal because
> they had a foot morphology that enabled a degree of perching.
> Therefore, Confuciusornithids... gliders... were climbers (had to get
> "up" there somehow) and were "true" arboreal since they had perching
> feet.  Microraptorans... gliders... *may* have been climbers... and
> they couldn't have been arboreal to any degree since the characters
> (pleural) they did possess are ambiguous and they lacked the foot
> morphology to enable perching?


Something along those lines, yes.  But their lack of arboreality in
these theropods is not just due to the pedal morphology.  Their
overall morphology (limb proportions, degree of motion at the joints)
is inconsistent with arboreal behavior.  Spider monkey, my foot.


> It's hard not to interpret the perching foot as being the linchpin for
> arboreality when it is repeatedly referred too during most discussion.
> Sure, they weren't *perfect* hands, or feet, or ungul geometry, or
> limb/digit length ratios, or whatever for grasping branches... But why
> expect animals in transition to have the perfect anything or fully
> functioning whatevers for behaviors or niches they were in the process
> of adapting to


I agree.  Arboreal behavior had to start somewhere.  But IMHO it's
significant that the overall proportions of _Archaeopteryx_,
_Microraptor_ etc are those of a bipedal, cursorial theropod.  They
all had a long neck, a long tail (although generally shorter than the
ancestral condition), and long legs for terrestrial locomotion.


This brings me to the petrel example.  Certain petrels can and do
roost in trees, in spite of the reduced or absent hallux.  The webbed
feet are capable of gripping branches.   My guess is that the anterior
digits toes wrap over the branch.  Cormorants do the same thing, with
rocks and branches.


But petrels, as typical for procellariform birds, have bodies built
for flight and life at sea.  They have short necks, short tails and
short legs.  All neornitheans have the benefit of being descended from
an arboreal, perching bird.  Comparing these advanced birds with
_Archaeopteryx_, _Microraptor_ etc is inappropriate, given just how
different the bauplans are.  It's just as bad as using the juvenile
hoatzin as an analog for tree-climbing behavior in _Archaeopteryx_.


Tinamous are known to roost in trees, in spite of the reduced or
absent hallux.  They don't really perch, and use their tarsi to help
them "sit".  But again, although terrestrial, the bauplan is that of
an advanced modern avian.


> My approach is not opinion-based. My approach is (1) questioning our
> artificial constructs of (a) and (b) based on a different
> interpretation of the available evidence and (2) investigating the
> reasoning behind theories built upon said evidence and constructs.


No, I didn't intend to direct the "opinion-based" barb at you.  I was
thinking more of the recent _Microraptor_-as-a-colugo-like-glider
paper, and similar publications.


> No, no... I understood what you meant by ambiguous.   "Who or whom"
> was insinuating that to us, the characters/traits are ambiguous, but
> if the animal put itself up in a tree, they were anything but.


If an animal habitually spent its time in trees, then th
wouldn't be ambiguous.


> Just like everyone else who lays awake critically thinking about this
> stuff, I'm drawing my own set of conclusions based on our current
> understandings... not just pulling them out of wishes and desires for
> coolness. Although arboreal microraptorans are rather cool :-)


Cool: agreed!  But if we're going to put microraptorans in trees, it
has to be for the right reasons.





Cheers

Tim