Most authors, however, currently favor a distinction between strepsirrhines and haplorrhines. Unfortunately, many of the features that enable such division are related to soft anatomy, so that the classification of fossil 'prosimians' as either strepsirrhines or haplorrhines, albeit favored here, is not always straightforward.
A total of 25 primate genera, corresponding to 7 families (one of plesiadapiforms, 2 of strepsirrhines and 4 of haplorrhines), from up to 116 different localities, are reported (27 from the Eocene, 3 from the Oligocene, 32 from the Miocene, 4 from the Pliocene, 51 from the Pleistocene and one with an undetermined age).