Assertion: burro's horse | /r/AtLocation | north america
Facets:
value: prior to their mysterious disappearance
type: TEMPORAL
Source sentences:
text: Conventional theories postulate that horses introduced by the Spanish more than 500 years ago were a different species than those horses who existed in North America prior to their mysterious disappearance approximately 10,000 years ago.
text: The fact is they are nearly identical to the horse that existed in North America 57 million years ago.