Packera glabella ?

Interesting, although it's also reminds me of Sonchus. Does it bleed white sap when cut ?

I'm leaning towards Sonchus but I don't know the Packera in person, only from pictures.

Thanks for the ideas. The only Packera with similar basal leaves (here) is glabella, but its leaflets are less triangular and the lateral ones are more petiolate. Sonchus leaves are spiny, so this appears to be something different. I'll post back when it flowers, since it should be easy to ID at that time.

What was the answer on the white sap? Sonchus oleracea isn't always particularly spiny. Not saying it is a Sonchus, just that lack of spines isn't definitive.

Floral, the plants are an hour away, and I didn't think to check for sap. The S. oleracea leaves that I've handled in the past had sharp spines, but those were cauline leaves. I've never handled oleracea basal leaves. They do, though, match in general appearance, so you and tofi may be right in suspecting Sonchus.

I handle quite a bit of S oleracea as it is a common weed on my allotment. The basal leaves are quite soft.

And it's not the only species in the genus that is seen.

That's true. I'm just using the one I know best to illustrate the flaws in the prickle theory.