Which brings up the point that birds may have evolved from flying fish,
because these can gather up a lot of momentum before launching themselves into
the air.

I do hope you are joking. We already know that birds evolved from certain
dinosaurs, and the missing links have been found.

brand new species may have been produced by extra-species matings and the
subsequent fusing of unlike chromosomes.

It happens occasionally, but the two species have to be very closely related.
Insects do not mate with lizards. Two species of lizards might mate & produce a
natural hybrid, which could eventually stabilize into a new species.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"When you come to a fork in the road, take it." Yogi Berra