To me, those heads look like they haven't opened yet. Erythronium seed capsules don't have the abrupt shoulders that your pics show:
http://www.efloras.org/object_...
I can't say I have ever observed E. americanum during the seed production. I always assumed leaves are still present. Flora of North America makes no mention, although it does regarding Allium tricoccum. But the FNA isn't very consistent with its descriptions, as it is written by many, many different taxonomy botanists. Also, that would be an incredible find to discover any eastern American Erythronium that is so floriferous.