The leona is not a jarana because its strings are plucked, not strummed. In son jarocho music, a jarana is an instrument that is strummed.
In this video, you can see the plucking of the leona, not the strumming, because it is not a jarana.
http://www.youtube.com/watch?v=DCmI8YybpKA
In this video you can see a strumming instrument (jarana), and a plucked instrument (requinto), of son jarocho music.
http://www.youtube.com/watch?v=b39R__VC7O4&NR=1
Here is a list of son jarocho instruments:
http://www.lauderiaestanzuela.com.mx
Of course, you can also strum a requinto and a leona, and pluck a jarana, but it is not a common practice.
source:
I'm mexican.