 Fossils of birds not clearly assignable to either hummingbirds or a related, extinct family, the Jungornithidae, have been found at the Messel pit and in the Caucasus, dating from 40–35 mya; this indicates that the split between these two lineages indeed occurred at that date.The areas where these early fossils have been found had a climate quite similar to that of the northern Caribbean or southernmost China during that time.The biggest remaining mystery at the present time is what happened to hummingbirds in the roughly 25 million years between the primitive "Eurotrochilus" and the modern fossils.