[Buddha-l] Chinese Vinaya Lineages

[Bankei]

It is said the Chinese Bhikkhuni ordination lineage was introduced from Sri
Lanka to China around 433AD. Up to this time the Chinese Bhikkhuni had only
been taking their ordinations from Bhikkhus. Aparently the vinaya lineage of
these Sri Lankan Bhikkhuni was that of the Mahisasaki 'sect'. Currently
Bhikkhuni of the Chinese tradition follow the Dharmaguptaka vinaya.

My questions are:
1) Does anyone know how it was these Sri Lankan nuns were not of the
Theravada lineage? Were there various non-Theravadin groups active in Sri
Lanka at this time?

and

2) How is it that the vinaya in use in China changed from that of the
Mahisasaka to that of the Dharmaguptaka?

Thanks

Bankei