South American Land Mammal Ages

The South American land mammal ages (SALMA) establish a geologic timescale for prehistoric South American fauna beginning 64.5 Ma during the Paleogene and continuing through to the (0.33 Ma). These periods are referred to as ages, stages, or intervals and were established using geographic place names where fossil materials where obtained.

The basic unit of measure is the first/last boundary statement. This shows that the first appearance event of one taxon is known to predate the last appearance event of another. If two taxa are found in the same fossil quarry or at the same stratigraphic horizon, then their age-range zones overlap.

...
Wikipedia