"Endler's Poecilia" got into the Aquarium trade via Klaus Kallman of the
New York Aquarium, who got it from the late Donn Eric Rosen, the major
taxonomic expert of the Poeciliidae, to whom I gave it so that he
could name it. Unfortunately he died before naming it. Klaus gave it to
aquarists and added the present common name ("Endler's Livebearer" or
"Endler's Poecilia") with out telling me (as a surprise), and I first
heard about it during a visit to England in the mid-1980's. It was quite
a surprise, but also a disappointment to see how much of the original
color pattern variation has been lost through inbreeding and founder
events. The wild fish are not always "double swordtails", have much more
variable color patterns, and some even have black pectoral fins. But
all have the lovely metallic green spots, though variable in size, shape,
and position. Although highly variable, the wild fish are not quite as
variable as wild guppies, though much more so than P. picta or P. parae--the
closest relatives. You mention their not having the "big triangular veil
tail", but wild guppies never have the veil tail either; veil tails are an
artifact of selective breeding