Peter Carrington identified this tiny flower as Sida spinosa, a member of the family Malvaceae

Please click on image to ENLARGE view of tiny Sida spinosa that I don't remember seeing before but which came up voluntarily from fill dirt spread as topsoil on the new parkland adjacent to World Peace Wetland Prairie. I would like to know as soon as possible whether this is native, how invasive it may be, etc. It may already exist on WPWP but I don't think so. If it is allowed to stay, then it will join the WPWP mix, and WPWP volunteers are trying to remove invasive species.

The fill dirt on top of the park is to be dug out. If this and many other volunteer plants on the new park are invasive, the dirt must not be deposited anywhere along the new trail across Pinnacle Prairie or near WPWP.