Present particple can be used in past continuous tense.
Past participle can be used in present perfect tense.
Why do we use 'present participle' in expressing past continuous tense ?
The participles do not have tense themselves-- they carry their names (unfortunately), based on one of their common uses. The tense depends on that of the auxiliary:
Present continuous (I am osculating)-- 'is' is present tense
Past continuous (I was osculating)-- 'was' is past tense.
Future continuous (I will be osculating)-- ('will be' is future 'tense')
As you can see, they all use the 'present participle', which is better called the '-ing form'.
Beware nomenclature; observe function.