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Re: flapping from gliding



Nick Longrich wrote:

>There are a number of animals, which I'm not sure whether we profit
>by bringing into the discussion, that leap into the air from the
>water and glide. There are two and four-wing flying fish (are these
>related?) the flying gurnard (I think...) and, unless Iheard wrong,
>some kinds of squid.

The various two- and four-winged flying fishes belong to the same family,
related to needlefishes and halfbeaks which can also glide to some degree.
The "flying gurnard", though, is quite different and is not a glider; it
apparently uses its enlarged pectoral fins for display under water rather
than leaping (certainly the few I have seen did so).   I think you are right
about the squids; certainly some leap from the water using "jet propulsion"
sprays from their siphons.  In "Kon-Tiki" Thor Heyerdahl records them
hitting the raft at night.

>I'd guess they evolved leaping to evade predators, started using the
>pectorals to extend the leap, then enlarged them. And there is one
>powered flier, the hatchetfish, which can beat its pectorals to get
>quite a bit of distance. I don't think that makes it unlikely that
>the hatchetfish evolved along these same lines...

As hatchetfishes apparently do not glide at all and have a very deep sternal
keel they may have evolved flight directly - though it is certainly a
stretch to imagine the early stages in that case!
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