Shemales and futanari are considered females for the purposes of which tagspace they occupy, but are considered separate from males and females for the purposes of specific tags such as "males only" or "yuri" in order to allow those who are into specific genital combinations to more easily find what they're looking for. In the future, please look up the tag definitions before making use of them. It isn't hard.
Please feel free to post in the forums if you'd like new tags added such as "no males," "no females," or "no dickgirls" in order to further aid in specifying genital combinations you and others may be interested in.