Like Pokémon Diamond & Pearl, Pokémon Platinum is set up so that if you have one of the 5 GBA games inserted into your DS, changes appear to the Wild Pokémon. Most of the time in some areas it's just like say a Level 2 Staravia in Lake Verity. However, there are a fair few Pokémon that are exclusive to this method. So for you to catch them all, you will need the respective game plugged into the 2nd slot of the DS while you play. Below is the list;

Ruby in the GBA Slot

Nat No.	Pic	Name	Type 1	Type 2	Location
#273		Seedot			Route 203 Route 204 Route 210 (South) Eterna Forest
#274		Nuzleaf			Route 210 (South) Route 229
#303		Mawile			Iron Island
#335		Zangoose			Route 208 Route 210 (South)
#338		Solrock			Lake Verity Lake Acuity Lake Valor Mt. Coronet Spring Path Turnback Cave

Sapphire in the GBA Slot

Nat No.	Pic	Name	Type 1	Type 2	Location
#270		Lotad			Route 203 Route 204 Route 205 (North) Route 212 (South)
#271		Lombre			Route 212 (South) Route 229
#302		Sableye			Iron Island
#336		Seviper			Route 208 Route 210 (South)
#337		Lunatone			Lake Verity Lake Acuity Lake Valor Mt. Coronet Spring Path Turnback Cave

Emerald in the GBA Slot

Nat No.	Pic	Name	Type 1	Type 2	Location
#204		Pineco			Route 203 Route 204 Route 210 (South) Route 229 Eterna Forest
#213		Shuckle			Route 224
#216		Teddiursa			Route 211 Lake Acuity
#217		Ursaring			Acuity Lakefront Route 216 Route 217

FireRed in the GBA Slot

Nat No.	Pic	Name	Type 1	Type 2	Location
#010		Caterpie			Route 204 Eterna Forest
#011		Metapod			Eterna Forest
#023		Ekans			Route 212 (South)
#024		Arbok			Great Marsh
#058		Growlithe			Route 201 Route 202

LeafGreen in the GBA Slot

Nat No.	Pic	Name	Type 1	Type 2	Location
#013		Weedle			Route 204 Eterna Forest
#014		Kakuna			Eterna Forest
#027		Sandshrew			Wayward Cave
#028		Sandslash			Route 228
#037		Vulpix			Route 209 Route 214

Any Pokémon Game in the GBA Slot

Nat No.	Pic	Name	Type 1	Type 2	Location
#094		Gengar			Old Chateau (Room with Eyes on Wall)