Ankheg

The Monsters Know What They're Doing     Dungeons And Dragons original/official source

Monstrosities     Swords & Wizardry original/official source

Angry Golem (web)     D&D 5e original/official source

Pathfinder 1e Bestiary 1     Pathfinder original/official source

All Sorts Of Critters (web)     Pathfinder original/official source

Exotic Encounters     Pathfinder original/official source

Monster Manual     D&D 5e original/official source

Monster Ecology Anthology     D&D 5e (no source link)

Monster Manual 2     D&D 4e (no source link)

MojoBob (web)     D&D 2e original/official source

D&D 2e Monstrous Manual     D&D 2e original/official source

Scruffy Grognard's Monstrous Manual     D&D 2e (no source link)

AD&D Monster Manual     AD&D 1e (no source link)

Iron Falcon Handbook Of Monsters     OSR (no source link)

Lairs And Encounters     Adventurer, Conqueror, King (no source link)