There is also
pari-ṣkṛta-.
Unfortunately, Mayrhofer could not find any convincing parallels outside Sanskrit. However, there is a general phenomenon in Indo-European, called
s-mobile (the varying presence or absence of a root-initial
s). The Wikipedia entry "
https://en.wikipedia.org/wiki/Indo-European_s-mobile” has a useful summary, as well as some relevant references. (An alternative, but more speculative explanation
would be that in structures like
namaskṛ the
s was reinterpreted as a simplification of earlier
ss (similar to
asi ‘you are’ for expected
as-si, not also the Vedic external sandhi for
-s#st etc.) and that this led to the notion that there is an alternative root form
skṛ-.)