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...bats by day, and bats, birds, by night.
> So at present it looks like the small pterosaurs outside
> Azhdarchidae died out something like 50 Ma before the big ones. Can hardly
> have had the same cause IMHO.
Outside of catastrophies (which you're not invoking) competition and
predation are the prime causes (most likely) of most extinctions. To say
these forces caused both early and late K extinctions is not a problem. You
seem to believe...but I don't know what you believe. What do you think
could have driven these species into extinction?
>>...but birds have outcompeted bats
> > by day, and bats, birds, by night [...].
> > This is either as a result of an arms race between sensory
> > of vision in birds v. echolocation in bats, or, and this is my feeling,
> > birds can survive in the diurnal predatory environment whereas bats
> May amount to semantics, but I'd rather say "competitive exclusion": birds
> started as diurnal animals and simply didn't get nocturnal (before bats
> evolved at least), but bats (as mammals) started as nocturnal animals and
> were unable to get diurnal because during the day there were too many
> insectivorous birds that ate their food.
Not possible. Many birds' and bats' feeding time overlaps (i.e., at dusk).
In other words, there is a rather fat margin upon which selection could
operate. I mean, it is not as if the birds eat all the insects, right? An
early-riser bat would have access to more insects, leading to more babies.
etc., etc. I think what we are seeing is a kind of niche partitioning:
birds are better competitors at some times, and bats at others. And, I
would be surprised of predation avoidance in birds wasn't part of that
> Predation? There is a bat species
> (is it the false vampire?) that more often than not eats sleeping birds.
Relevance? The bat does this at night, right?
> to mention the owls at night. And I repeat that bats are more
> so they should escape birds of prey _easier_ than birds.
What kind of maneuvers? Can they take off vertically? What are the
> Another explanation, from Pat Shipman: Taking Wing: Bats get sunburn much
> too easily, and bats with heavy sunburn on their wings (a specific example
> is mentioned) can't fly. Don't know if that holds for all bats (after all,
> bat wings are frequently dark brown to black).
Relevance? Melanin. Rise early before sunset, after sunburn time. This is
> But... creatures that grow fast and extend in the periphery before they
> start to fly are totally freed from this problem. No remotely ball-shaped
> pterosaur is known, despite lots of juvenile specimens.
Are you really saying allometry is irrelevant to airworthiness? If not, are
you really saying that juvenile frames are just as airworthy as adult
frames. If not, what?
> I can cite literature (later if needed) about Eocene rheas of apparently
> modern size, whatever else "modern aspect" means.
I would like that ref. And thank you.
> <sigh> Wrong. Jaguars are ambushers _in the jungle hundreds of km away
> the pampa!_ I know many stories in which "the lion" is called "the King of
> the Desert" or is put into a jungle. But I really didn't expect such a
> phenomenon onlist.
I don't know why not. List members have come to expect a gaffed detail such
as this from me, just as they may learn to expect lack of civility from
Pampas grades into jungle. I would be very surprised if lurking cat
predators were not among the reasons why rhea avoid treed areas. But the
puma was the cat I was looking for.
> > for late K pterosaurs? Remote nesting was probably the only available
> > strategy for them. So...
> So what? Maybe that was just what they did. There always were islands, if
> you want such extreme protection.
But predator access to those islands has changed over time--with the
evolution of new/different predators.
> Assuming I've understood what you wrote so far:
> If it had and if we had found that out, we would know that birds could and
> did outcompete pterosaurs, which is the point on which you try to build
> neos outcompeted enantis next (and what about Ichthyornithiformes and
> Hesperornithiformes...). Right? Because we know that *B.* didn't do it,
> while in the current form of your speculation every bird of prey should be
> able to do it, you must do what I wrote above: show why *B.* couldn't have
> done it while falconiforms could have done it, and that K falconiforms
> existed (fossils).
We have no idea what *B* could or couldn't do. Ditto
for falconiforms. How can I possibly do that? You know this is pure
speculation! However, there are some facts to work with. And they favor
1) Most pterosaurs became extinct from causes other than the bolide.
2) No pterosaurs handed over their niche as a gift to rising new species.
3) Something forced them out of their niche.
4) The most likely things to do this is are flying creatures.
5) The most likely flying things to do it were the only ones that
>From these facts and inferences, one can posit a reasonable--if very
difficult to falsify--hypothesis. Simply, speciation and evolutionary
developments affected which creatures occupied which niches. If neornithine
developments had anything to do with this, they may well have also had
something to do with enantiornithine removal. It might even be that
enantiornithines outcompeted pterosaurs early, and neornithines, late. In
any case, chances are that fossils will be informative (ultimately) of
relative diversity and biogeography of these bird clades. Let's just hold
our fire till then.