It is Umbereon and a trainer has it somewhere in Rt.212
Araidos
go on Google search and type in how to see certain Pokemon on Pokemon platinum to complete pokedex and click on the one that includes seribi .net in the address the address is in green
It's Umbreon. You can't catch it in the wild but you can get it by levelling up with happiness at night. Trainers with an Umbreon are: Collector Dean (also has an Espeon) found on Route 212 South
Fight trainers, some you need to transfer from other games such as, Pokemon emerald, Pokemon Leafgreen and more. The battle tower is a good place to see transfered pokemon. You have to travel all around to see all the pokemon. It takes time
it is crobat
It is the Pokémon Heracross
It's Heracross. You can catch it in the Safari Zone.
you will get UMBREON by getting eevee to level up with high friendship
That would be Umbreon if you're looking for 168 in the Sinnoh Dex. The trainer who has it in their possession is on the south part of Route 212 - his name is Collector Dean. or you could just grab the Eevee from Bebe in Hearthome City and train it and then level it up at night until it evolves into Umbreon. where abouts
169 is Leafeon, it cannot be caught in the wild in Platinum however its pre-evolved form of Eevee can be gotten by talking to Bebe in Hearthome City then you can take it to the Moss Rock in Eterna Forest and evolve it into Leafeon there.
it has 168 on my game but it varies on your pokemons lvl
Ariados is #168 in the national pokedex, and it is a Bug-Poison type Pokemon.