ARK: Survival Evolved

Summary
Survival game with dinosaurs and ancient mammals. Breeding and riding horses available, one unicorn per map Western mod?

Horse Mods
Multiple mods that added realistic horses


 * Realistic horses: MarniiMods: Horses
 * More saddles and horse equipments (jousting and halters): Saddle Emporium (compatible with MarniiMods: Horses)

The Equestrian Land
Caballus Custom Map - The Equestrian Land

Features:
 * An entire map is dedicated to horses with a background story.
 * Majority of dinos are available.
 * Unicorns are breedable.
 * New patterns for Equus.

This mod has its own dedicated page on ARK Wiki.

Tricks & Hacks
Other mods that could be useful:
 * Classic Flyers - to increase speed of flying dinos
 * Stuctures Plus - to improve structures
 * Dino Tracker - to search wild dinos and also your lost dinos