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Re: 11th specimen of Archaeopteryx
I wonder what you guys make of Dececchi and Larsson, 2011, Assessing Arboreal
Adaptations of Bird Antecedents: Testing the Ecological Setting of the Origin
of the Avian
Flight Stroke. PLoS ONE 6(8): e22292.
I don't know if I've seen anyone discuss it on DML.
To summarize, the authors did a very broad comparison of the skeletal
proportions of many types of animals to assess whether paravians had
proportions that correlate with arboreal or terrestrial habitats. They conclude
that their results strongly support the latter and, thus, a terrestrial origin
of birds. I've read the paper at length to try to understand it, and it is not
easy because the large numbers of measurements are aggregated into indices
before being compared. I fear that, though this approach includes more data, it
may water down certain crucial measurements, such as toe anatomy, with
measurements that may be less directly relevant, such as the relative lengths
of hindlimb segments.
Moreover, if I recall correctly, they used a data set for "ground birds" from
Glen and Bennett, 2007, Foraging modes of Mesozoic birds and non-avian theropods
Glen and Bennet did not list the species aggregated in this "Ground - Based"
group, but they did mention the families from which they came, to quote them:
The GB group comprised bird species from the Struthiornithiformes
(Apterygidae, Cassauriidae, Rheidae and Struthionidae), Ciconiformes
(Ardeidae, Burhinidae, Charadridae, Glariolidae, Jacanidae, Scolopacidae,
Spheniscidae), Gruiformes (Otididae, Rallidae) and Galliformes (Phasianidae).
The GB (“ground-based foragers”) category is defined as birds that either
never perch in trees, or at most may roost or spend a small amount of time in
trees with minimal locomotion on branches, particularly narrower ones. All
foraging occurs while the bird is on the ground.
My concern is that this list contains a large number of taxa, including many
galliforms that roost and brood their chicks in trees, and others like Ardeidae
that build large nests in difficult spots high in tree canopies and out on
narrow tree limbs.
We've discussed on the DML before that some "ground birds", like grouse,
turkeys or tinamous (the latter are not on Glen and Bennet's list), almost
invariably roost with their chicks in trees at night, as their characteristic
brooding behavior, as opposed to only a "small amount of time in trees".
Thus I fear that these two papers have had too much confidence in their
categorizations of arboreal bird behavior.
But I will say that I am less persuaded that there was an arboreal origin of
bird flight now than I've ever been. Xu's "four-winged" Microraptor paper in
2003 really was foremost in my mind for many years, but now I am open to the
possibility that the damn thing could have lived on the ground.
On Oct 24, 2011, at 1:20 PM, Matthew Martyniuk wrote:
> On Mon, Oct 24, 2011 at 1:12 PM, Habib, Michael <MHabib@chatham.edu> wrote:
>> Tim's point regarding birds nesting in abrasive plants is well taken, as is
>> Don's comments on Cycads etc. However, I still find myself asking the
>> question: is there any reason we keep trying to put Archaeopteryx (and close
>> relatives) into elevated positions to begin with? Don already pointed out
>> that, at best, we simply cannot exclude some arboreal roosting, etc for
>> Archaeopteryx. We have no evidence that Archie was absolutely confined to
>> terrestrial life, but we have nothing to suggest it was arboreal in any
>> meaningful way, either.
> What about the asymmetrical remiges? If Archie and/or its ancestors
> were not at the very least using WAIR (to get up into high places,
> presumably), why did they evolve? Symmetrical remiges are just as good
> as asymmetrical for brooding nests, display, or any other alternate
> uses of the wings that have been proposed.
Senior Principal Preparator
American Museum of Natural History
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