(it does no good to evolve from animal A to animal B if there are no other animal B's to mate with, so all morphological/genetic change has to be within certain limits for sexual species, which may explain why polyploidy isn't observed in animals).
Polyploidy is observed in animals, a good example is the
Xenopus family of frogs which has species which are diploid, tetraploid, octoploid and dodecaploid. Polyploidy is also inferred historically for a number of lineages, i.e. modern teleost fish have clear evidence of multiple whole genome duplications compared to mammals.
TTFN,
WK
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