bats

ifriit: I never said the toes lacked membranes. my point was that without the ability to run on its hind legs alone, as birds and some reptiles can, the proto wings would be useless. if you'll notice, htere are only a handful of mammals besides humans which can walk upright without the aid of their forepaws. (I don't know if hopping should count; if not, then there are none that I know of.)

lucapsa: I've got 2 problems with your hypothesis, too. 1: shrews do not eat small insects. their metabolisms are so fast that they need to eat almost constantlyto keep from starving to death. (so they keep up a constant meal of worms, beetles, etc.) a diet of a few tiny insects at a time would not be enough to keep the shrew/bat alive, especially if it needed to climb back up the tree again between flights. (that is, unless the metabolism had slowed down considerably between the real shrew and the gliding shrew...) also, bats do not eat tiny swarms of insects. for such a diet, the creature would need a huge, wide mouth, like that of the whipoorwill; no modern bats that I know of have such a diet: all either chase moths and mosquitoes around using their sonar, or eat fruit/drink nectar/blood. 2: the gliding squirrel has a long, flat tail used as a rudder; the shrew fhas a skinny, worthless tail, and the bat has almost none at all (it serves only as a prop for the membrane). without the ability such a tail would provide for quick adjusments in mid-flight, the bat may or may not have been able to survive. I don't know.
those links are quite interesting, though I was aware of most of the facts brought forth.
see problem 1.
I think they do use them to eat: perhaps not to catch the animals, but to hold them to their mouths.

Late Cretaceous: you say that there aren't very many predators in New Zealand. perhaps that's why a flightless bat can survive there. I wouldn't take this as proof of any such thing. did any species change? (IE, vegetable to animal . . .) recall that all types of dogs came from one pair of animals, all sparrows from seven birds on the ark, etc. the point being: it's possible that in the isolated environment some MICROevolution took place--population ratio-shiftage is a valid method of changing animal forms (think of the peppered moths). but I don't think there's any evidence of MACROevolution.

lucapsa again: trust me, my intention was not to decieve; thank you for clearing that up for me. however, I htink my point still stands . . .

best of regards,
the_cloaked_crusader

Gee, here all this time I thought beetles were insects. Thanks for correcting me.

The Frumious Bandersnatch

Frumious Bandersnatch: er, note the adjective "small" applied to the insects in question. beetles have a far higher nutritional value than gnats. (we're talking the inch long beetles you find under logs here.)

best of regards,
the_cloaked_crusader

Of course beetles range in size from less than 1 tenth of an inch to several inches. In fact shrews eat anything they come upon and can manage to subdue and small insects are an important part of the diet of many shrews.

http://www.veld.org.za/Melville/mammals.htm
http://www.skullsunlimited.com/scandentia.htm
http://members.vienna.at/shrew/online-frafjord.html

The Frumious Bandersnatch

I have seen slow-motion films of bats catching moths. The bat traps the moth with its wings.

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bandersnatch: er, yes, I assumed as much. but really, would this shrew/bat be able to subsist on the 4-5 skeeters/other small insects it would catch in each gliding session (as opposed to dozens of earthworms/thousands of 1/10 inch beetles)? and considering how long and how much energy it would take to climb up the trees again between flights . . . I don't think the calorie intake would even come close to matching the output.

Gracchus: fascinating. and somehow I don't think a "gliding shrew" would have enough agility/enough wing surface area to accomplish such a feat. bats have grabbing mouths, not "netting" ones.

best of regards,
the_cloaked_crusader

Originally Posted by Gracchus

I have seen slow-motion films of bats catching moths. The bat traps the moth with its wings.

Fascinating. Do you have a reference for that?

Originally Posted by shenzhou

The current majority view is that insect wings evolved from gills. This has a number of advantages over the heat exchange hypothesis such as: gills already had nerves and muscles and so the ability to move,

And because of the blood flow, gills also make excellent heat exchangers, don't they?

JG Kingsolver and MAR Koehl, Aerodynamics, thermoregulation, and the evolution of insect wings: differential scaling and evolutionary change, Evolution, 1985.

This is more the original article on gills and insect wings:
Averof, M and Cohen, SM, Evolutionary origin of insect wings from ancestral gills. Nature, 385: 627-630, Feb. 13, 1997.

Originally Posted by the_cloaked_crusader

bandersnatch: er, yes, I assumed as much. but really, would this shrew/bat be able to subsist on the 4-5 skeeters/other small insects it would catch in each gliding session (as opposed to dozens of earthworms/thousands of 1/10 inch beetles)? and considering how long and how much energy it would take to climb up the trees again between flights . . . I don't think the calorie intake would even come close to matching the output.

Why do you think it would be only 4-5? As thick as mosquito clouds are in the Boundary Waters and gnats in the South, you are off by at least a factor of 10 and probably 100.

Originally Posted by the_cloaked_crusader

lucapsa: I've got 2 problems with your hypothesis, too. 1: shrews do not eat small insects. their metabolisms are so fast that they need to eat almost constantlyto keep from starving to death. (so they keep up a constant meal of worms, beetles, etc.) a diet of a few tiny insects at a time would not be enough to keep the shrew/bat alive, especially if it needed to climb back up the tree again between flights.

This has already been taken care of. Also, have you seen what the food intake of bats is compared to shrews? You are speculating but the evidence is there to test your speculations. It looks to me that your premises are false (as shown by others).

(that is, unless the metabolism had slowed down considerably between the real shrew and the gliding shrew...) also, bats do not eat tiny swarms of insects. for such a diet, the creature would need a huge, wide mouth, like that of the whipoorwill; no modern bats that I know of have such a diet: all either chase moths and mosquitoes around using their sonar, or eat fruit/drink nectar/blood.

That's NOW. Remember, you are looking at the end of a long adaptation chain. We are talking about possible adapatation routes. For you, NO SUCH ROUTE IS POSSIBLE. Notice the "possible". This is what you have to do. As long as such a route is POSSIBLE, you can't claim evolution is impossible.

2: the gliding squirrel has a long, flat tail used as a rudder; the shrew fhas a skinny, worthless tail, and the bat has almost none at all (it serves only as a prop for the membrane). without the ability such a tail would provide for quick adjusments in mid-flight, the bat may or may not have been able to survive.

Bats glide NOW. So the tail is not necessary. A tail is just how the squirrel does it. It doesn't say that is the only way.

but I don't think there's any evidence of MACROevolution.

Macroevolution is speciation. Once you get reproductive isolation, then you are done. Because the only biological REALITY is SPECIES. All those "higher taxa" are simply groups of SPECIES. And yes, speciation -- macroevolution -- has been observed in real time.

In the fossil record, there are series of transitional individuals going across species to species to new genera, family, order, and even class.