Chimera

A Chimera, as understood in the Fullmetal Alchemist series, is a creature synthesized by alchemically "marrying" two or more dissimilar living beings into a new, complete form displaying attributes of its "components". Though a legitimate branch of bio-alchemy, chimeric research has seen very few significant strives in Amestrian history - or at least in recorded history - and has been described as a science built upon countless dead ends and false starts. Still, the production of such fantastical beings is possible with the proper alchemical expertise and skill (as displayed by both Shou Tucker, who had made chimeric alchemy his focus as a State Alchemist, and Cornello, who was able to perform chimeric alchemy with the aid of an incomplete Philosopher's Stone).

Standard chimeras usually appear as hybridized beasts - such as a lion with reptilian features or a monkey with extra appendages - and primarily appear to serve as monstrous guards (as demonstrated by Father Cornello in all his appearances and the Amestrian State Military in the 2003 anime series)

"Successful" human-based chimeras tend to appear the exact same way as when they were still unaltered humans prior to being converted, but can apparently morph and manifest more animal-like aspects if they so wish, and inherit abilities similar to the creature they are combined with (such as heightened senses, strength, speed, etc.), thereby allowng them to use said attributes to their advantage

"Unsuccessful" chimeras, however, suffer large amounts of pain and can barely grasp human languages. They also tend to mostly appear like their animal counterpart, yet still keep characteristics and memories of their human form (for example, Nina Tucker takes the shape more like Alexander than herself, but can still recall Edward and Alphonse).

List of Semi-Human Chimeras by Faction

 * Mr. Shou Tucker's Chimeras (all deceased)
 * Mrs. Tucker (Unknown Creature)
 * Nina Tucker (Dog)
 * Greed's Chimeras (all deceased)
 * Bido (Unknown Lizard)
 * Martel (Snake)
 * Roa (Ox)
 * Dolcetto (Dog)
 * Ulchi (Crocodile)
 * Solf Kimblee's Chimeras (now aligned with Ed)
 * Darius (Gorilla)
 * Heinkel (Lion)
 * Jerso (Toad-like creature)
 * Zampano (Boar-like creature)

In the Anime
The chimeras in the anime vary from those in the Manga; whilst Nina, Mrs. Tucker and Greed's chimeras still appear (and die) in the anime, Shou Tucker himself becomes a chimera, and Kimblee only briefly affiliates with Greed's chimeras (as opposed to his own).