ZBrushCentral

Maya mesh looks like a mess

I would still consider myself very new to both maya and zbrush. I made this dragon thing in maya. Looks to me with my limited knowledge as though its fine. but for some reason when i import it into zbrush it is missing tons of its geometry.
thanks
here is what it looks like
<img src=“http://www.zbrushcentral.com/pixo/atn.gif”>
<img src=“http://www.zbrushcentral.com/pixo/atn.gif”>