From Future: Alien Race 1: Taxob-Zhin:
Each of these PDFs introduces a new alien race with complete d20 Modern/Future Statistics and all the background, concepts, and ideas needed to bring the aliens into play in your campaign.
In addition, each Alien Race sourcebook features new rules (i.e. new Advanced Classes, Occupations, Feats, etc.) relating to the particular alien race featured in the sourcebook that can also be applied to the general campaign (with the GM’s permission, of course).