It's April, the day after some rain, and in one of my freshly composted garden beds these fruits pop up.
In order to begin identifying these mushrooms I'll need a knowledgeable source. I'm refrencing Common Florida Mushrooms by James Kimbrough, researcher and professor at the Mycology Department in the University of Florida.
With his book, I've narrowed it down to three possible species: Coprinus Floridanus Murr., C. disseminatus, and Panaeolus retirugis Fr.
These caps were between 3-5 cm on diameter which fits the description for all three possible species. Both floridanus and C. disseminatus prefer to grow on decaying wood, P. retirugis prefers "dung or heavily manured soil". Either of these mediums fits the description. These mushrooms came up in a heavily manured garden bed, right up against wood that was salvaged from behind a shed where it had spent several years in contact with fungi and decay.
For further identification I should try and get a spore print to determine spore color, and if seen under a microscope, spore shape. Unfortunately, when I went back out to grab a cap, they had already shriveled up and the caps turned inside out.