swans
more than one lynx is call lynxes
you call them possums if your talking about more than 1
More than one fisherman is fishermen
More than one platypus is two or more platypuses. The plural is not 'platypi'.
Fish
Ants
its just fishermen
Pegasi I think.
Polygamy.
two goats
Vampiresses.
A person who speaks more than one language is called a polyglot.