This is so easy to answer even I can answer it.
There is only one fish kind. The fish kind before the flood was not sensitive to the salinity of the water. After the flood, the fish kind micro-evolved into many types like the salmon, shark, arowana, and dolphin. But they all still belong to the fish kind because we know that macro-evolution is not possible but micro-evolution is.
So something evolving into 1. in one line of evolution a shark, and 2. another line of evolution a dolphin (sharks are fish, dolphins are mammals) is not macro-evolution?!
ohhhh wait, are you making fun of Noah's Ark? lol I hope so...
Edited by TheNaturalist, : because f*** you, thats why.
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