Remarkable find by @mcharpentier who then generously showed us this site. First find of this species in Worcester County in 111 years. (Not a typo, one hundred and eleven years!!!) Secondly, this is the first iNat observation in New England under the correct variety. At the species level, the plant is circumpolar and common in Europe and Siberia, with the Western Hemisphere plants only in variety palmatus (hence the common name "western sweet coltsfoot"). It is more common in the US on the west coast. This is state-endangered in Massachusetts as we have the southern most populations in the eastern US, except for a small population in NW Connecticut close to the border with Massachusetts.

A known site for this but still a thrilling day to find this globally rare and declining subspecies in flower. Vegetatively it looks nearly exactly like two other co-occuring species. I've been planning this survey for a few years and finally the time was right. I saw this in a bordering state but close to Massachusetts where I believe this could be found with a serious search effort in the Berkshires. We have some of the same habitat. This is the first New England iNat observation of this species or subspecies.
The flower has only sepals with the petals thought to be modified into the bright yellow staminodes visible in the close-up view.