That free (to 3DU members) download is the Ross Rhino character (an excellent freebie from 3DU's Wacky World series) - it includes a Ross.OBJ, not a rhino.RTE, and a WW Rhino.cr2 file plus a full color posed thumbnail PNG - the rhino.rte version comes with a Rhino_for_WW.cr2 and a Rhino_for_WW.rsr that looks like a screenshot of a plain mesh of the other figure in default pose.
I find the the Rhino rte is present in my "vanilla" installs of Poser 5 thru PPro 2010, so I kind of assumed it's part of Poser's legacy content installers - I just don't remember any discussion or instructions mentioning it's existance.
Just an oddity I noticed. I thought someone here might know something specific.
Thanks anyway.