Rhydon was the first Pokemon ever created!

Rhydon might be Pokemon #112, but he was drawn up before any other Pokemon, even his pre-evolution Rhyhorn. 

Despite being a ground type, Rhydon can be taught water-type moves such as Rain Dance, Whirlpool, and Aqua Tail. 

According to interviews with Ken Sugimori, Rhydon's index number in the game code is 001 in Generation I, precisely because he was the first one coded in. There are also early sketches of Rhydon from Capsule Monsters, the conceptual predecessor to Pokémon.

Rhydon was inspired by many different dinosaurs. Its name can roughly be translated to Rock Lord. According to the game, Rhydron’s drill-horn is capable of crushing un-cut diamonds, and it can knock down buildings with a single strike of its tail. 

(Source)