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Re: BATS, BIRDS, PTEROSAURS, ECHOLOCATION & SIGHT



From: "michele b" <michelebnz@yahoo.com>
Sent: Thursday, March 01, 2001 7:28 AM


> I am not sure if I missed something, but is there any
> evidence that some pterosaurs might have had
> echolocation capabilities to a greater or lesser
> degree?  Or is this ruled out by fossil evidence?

If pterosaurs had echolocation, there must have been some kind of selective
pressure to favour development of a sound-based system over a visual one,
assuming that the immediate ancestors of pterosaurs had reasonable vision.
With dolphins, an acoustic system works better underwater than a visual one,
so that's one likely selective pressure. With bats, the dominance of birds
in the aerial environment presumably resulted in an acoustic system being
one possible solution to exploiting a nocturnal niche not occupied by birds.

What pressure would pterosaurs have had to develop an acoustic system?
During the day, a visual system would probably have been better - given that
it would, presumably, be well-developed already. If pterosaurs roosted in
caves or dense forests where visual acuity is less effective, it could have
led to the development of basic "clicks" like oil birds and Rousettus
megabats. Who knows, but it seems unlikely that a sophisticated echolocation
system would have developed where a visual system was just as effective.

Adam Britton