One recent user edited in races included in WotC's Plane Shift: Zendikar supplement.
Another user contends that those aren't official races.
Rather than individual editors unilaterally deciding on the in-/exclusion of these races, can we hash it out here?
Please make your best arguments for and against Zendikar-race inclusion. Highest-voted answer should prevail, in my opinion, for the purposes of the linked question.