those are most likely DAZ Studio files. 

http://www.daz3d.com/forums/viewthread/3491/

I don't think Poser has any use for them at all. Maybe for DSON but not sure on that. It seems its an older DS format at that.

Safest bet would be to zip them and store on an archive disk just in case you discover some reason you might need them in the future. But I'm 99% sure you'll never need them if you only use Poser.

 

~Shane