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Re: pterosaurs, bats, flying theropods



--- "Jaime A. Headden" <qilongia@yahoo.com> wrote:
> Michael Habib (mbh3q@cms.mail.virginia.edu) wrote:
> 
> <True, but it is quite likely that bats predate the
> K/T.  Molecular 
> dating suggests a Cretaceous origin, and the fossil
> record does to some
> extent as well, given how early in the Cenozoic
> advanced bats appear
> (including some extant genera in the Eocene). 
> Either Chiropterans have a
> Cretaceous origin, or they underwent a massive
> diversification in the
> Paleocene.>
> 
>   Hey, it happened to the whales in the Eocene, and
> that's with Paleocene
> and Eocene ancestors that are reasonably known. Bats
> may very well have
> their earliest ancestors in the Paleocene, and very
> bat-like archontans
> like colugos (Dermoptera) exist that can be
> purported ancestors with
********************************************************
> little change. We are looking for miracle specimens,
> the special fossil
> that will confirm everything we are preconceived
> about regard bat
> evolution. They are there, and likely the ke
REPLY: actually, what we are seeking, as
paleobiological scholars, are not "miracle specimens"
(a meaningless phrase), nor "the special fossil  that
will confirm everything we are preconceived about
regard[ing] bat evolution". Rather, what is needed are
further, well-preserved specimens of chiropteran
evolution. There is no such thing as a "missing link",
but there are LINKS (plural). Moreover, phylogenetic
systematics is derived from the scientific process:
one may infer, on the basis of available evidence,
what ancestral lineages may (read this word carefully,
Jaime: "may" does not = factuality)have consisted of.
One may use the word "preconceived", but
preconceptions, i.e., hypotheses, are malleable. You
are erecting "straw men" (non-gendered, for those
dissatisfied with gendered English) in order to
reconfirm your lack of cogent hypotheses about
possible end-Cretaceous insectivore mammalians as
possible proto-bats, so to speak.
*******************************************************
> regions will be Fayoum
> (Fayum)-like in geology where we will have that
> special fossil show up. Or
> we could have it and not know.
> 
>   Oh, molecules are not miraculous, and it does
> depend on theories of
> genetic change having a morphological expression,
> and how much a set of
*******************************************************
> genes can express such. Most molecular dates do not
> take into account the
> possibility of Eldredge and Gould's PE, for example,
> or that gene
> evolution may occur at different rates with
> constraints at different times
> in a single lineage.
REPLY: this, too, is a hodge-podge of non-sequitur
sentences, filler space as newspaper editors call it.
Molecular dating is an evolving technique, and the
paleobiologists who have written papers on its
applicability to specific lineages have not, to my
knowledge, used dating to pinpoint evolvability of
clades. A clade will "enjoy" stasis for a period of
time, and analysing this (molecular dating will
provide one with indications, parameters of
deductions) can be done with tracking of habitat
(Niles Eldredge), evolutionary constraints on
subdivided populations (B.S. Lieberman), selections
within clades normalized (George Williams), etc. "Gene
evolution": what do you mean by this vague souvenir
from an echo chamber?. Genomic changes on fitness
landscapes indeed transpire at different rates, at
different times, and molecular dating as a tool of
phylogenetic extrapolations is cognizant of this.
Scientific analysis (e.g., the use of molecular dating
to sort out the evolved clades of "sabre-tooth" cats)
is made up of many facets, including morphogenesis,
ecomorphologies, biomechanics, etc.
I'm afraid that, in the spirit of the season, I cannot
articulate what I think of what you said in one word,
dialogue about scientific ideas should not decompose
like a redox chemical reaction into sandbox politics.
During the past year, brilliant exegeses of
chiropteran evolution have appeared (Kate Jones et al.
have given one a remarkable picture of these taxa). On
several levels, they may have been the
ecomorphological successors of pterosaurs. This is not
to say the chiropterans were mammalian pterosaurs, or
that Cathayornis flew like a bat. Pterodactyloids
were, on the basis of available specimens, likely
agile fliers, perhaps competing with Ichthyornis for
food resources (co-existing taxa, by the way, Jaime,
does not mean they were members of Mr Rogers's
neighbourhood). Some shoreline flying dinosaurs may
have been succeeding in co-opting food niches
dominated by pteranodons. At any rate: by the
Cenozoic, as Gregory Paul has astutely noted, the
feathered dinosaurs were maintaining a uniformity of
body "styles" and in diets, most dinosaurs then (and
now) preferring econiches close to water bodies, due
in the main to post-K/T dinosaurs having feathered
wings and separated modes of locomotion (the hands and
feet, unlike bats, not being needed for collaborative
locomotion). In some regions, to be sure, bats are
dominant flying taxa, large predators enjoying
daylight prowess without the need for echolocation
favoured, as it were, by smaller bats. These large
bats have been seen to attack monkeys (whether they
are eaten or not is not known to me, although eagles
prey on the monkeys), chase off flying dinosaurs.
Moreover, in Europe (and, elsewhere, some bat scholars
have told me), bats do attack and eat nocturnal
migrating dinosaurs in the skies.
While we may not have "special fossil" to coo over, we
do have the awe-full vista of living forms to study.
*******************************************************
> 
>   Cheers,
> 
> =====
> Jaime A. Headden
> 
>   Little steps are often the hardest to take.  We
> are too used to making leaps in the face of
> adversity, that a simple skip is so hard to do.  We
> should all learn to walk soft, walk small, see the
> world around us rather than zoom by it.
> 
> "Innocent, unbiased observation is a myth." --- P.B.
> Medawar (1969)
> 
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