These two stories were my first purely erotica writings, the first is female only transformation, the second is male only transformation. They both transform one animal part at a time, resulting in a many animal hybrid. (in the male only story there are 5 different animal aspects used in his genitals alone)
What He Wants;
http://iplank.deviantart.com/art/Wha...ants-538340672
Clarity Of Desire;
http://iplank.deviantart.com/art/Cla...sire-540243589
This story is werehorse(male) and werewolf(female)
Be Were;
http://iplank.deviantart.com/art/Be-...253A1455453542
Be Were 2 : Witch Hunt;
http://iplank.deviantart.com/art/Be-...253A1457620426
A pig, two snakes and a giraffe(all female)
Snakes And Ladder;
http://iplank.deviantart.com/art/Sna...=1&ga_recent=1
And for a little less orthodox, female to male, two females transform and merge into a single hermaphroditic canine
A Little Two Familiar part1 : Identical;
http://iplank.deviantart.com/art/A-L...ical-543084923
I also have a series called Beautiful Monsters which each feature a man transforming into a mythical creature- Unicorn, Catoblepas, Chimera, Dragon, Hippocampus, etc, while making out with demi-human mythical creatures, Cowgirl, Faerie, Mermaid, Siren, Gargoyle, Vampire, etc.