Hello! I just wanted to chime in and say that UMD does not only notify by email. I was accepted via phone in January as a candidate for a fellowship. (Other than UMD, I applied to top-20 schools, but I will be absolutely delighted to go to UMD. My undergrad GPA is not as strong as I'd like, and neither is my GRE subject score, but my other stats are on the higher end.) From my visit to the school, my best guess is that they are letting people know one-by-one or in small waves. They are cutting their program in half this year.
That's all to say, if you haven't heard, don't worry!