Green swordtail was created in 1848.

= Xiphophorus is a genus of freshwater fish in family Poeciliidae of order Cyprinodontiformes. The type species is X. hellerii, the green swordtail.=

A Swordtail is a type of fish that has a sword shape on their tail. Males have them but females don't.

Swordtail is not a mammal, it's a fish although it gives birth. Another example like Swordtail is Guppy. Guppy gives birth but it's a fish.

A swordtail is a tropical fish and a goldfish is not. The swordtail would need a higher temp. than the goldfish. Depending on where you live it probably wouldn't survive the winter.