The goddess Maariyamman is very ancient
and predates Kannaki legends by some
1000 years. This is evident when we
consider the fact that her worship
is widespread even in North India.
The ancient Maari worship and her legends
are first narrated in the Mahabharatham
epic written in Sanskrit centuries
before the crystallization of Kannaki
legends.
Maari/Ellammaa/Renuka/Mangala worship
is present even in Bengal, Maharashtra, ...
Some aspects of Maari worship:
http://groups.yahoo.com/group/CTamil/message/466
(Please see the links provided therein).