Horses are a big feature in Star Trek V: The Final Frontier. The opening shot is Sybok on his steed:
Later, horses feature prominently in the ground battle on Nimbus III.
Out-of-universe, I always chalked up the horse scenes in this film to William Shatner, given his love of horses and his direction of the film.
But I've always wondered, in-universe, where these horses came from.
Are these animals native to Nimbus III, are they from Earth (the planet was home to a joint colony of the Federation, Romulans, and Klingons), or are they from elsewhere?
Interestingly, the script doesn't call for horses at all, but rather for "odd creatures" with "twisted rhino horns":
2 CLOSER ANGLE - STRANGE HORSE AND RIDER 2
A twisted rhino horn juts from the snout of this odd
creature. The Rider spurs the beast, driving it onward.
His white robes flare out behind him like the wings
of an avenging angel. He rides like a man possessed.
The fact that they didn't go with these particular creatures just confuses the issue. Is there any clarification about the origin of these horse-like animals anywhere?