How can Zangoose and Serviper be related (according to the Pokedex)?

Question

All I noticed was that Zangoose has long claws and Serviper has long fangs.

Comments

Which entry stated that they were related?

Answer 1

Zangoose and Seviper, much like real life mongooses and snakes, are bitter enemies, and abhor each other in every possible way. It is this bitter rivalry, not their physical appearance or capabilities, that relates them.