Simplify the following text for a Grade 2 native English-speaking person.
Original: Besides the horse , there are seven other species of genus Equus in the Equidae family . These are the ass or donkey , Equus asinus ; the mountain zebra , Equus zebra ; plains zebra , Equus burchelli ; GrÃ vy 's zebra , Equus grevyi ; the kiang , Equus kiang ; and the onager , Equus hemionus .
Simplified: The old Latin word for horse is equus .