The two mentioned are the most common.
On the google books link it mentions Sonchus oleraceus has a slender spine that is long and hairy.
I can see something on the spine which looks black.
We don't know which species the other 3 are, (Sonchus erzincanicus is in one location only and rare).
https://thefloatingtroubadour....
Keys to some on efloras ..
http://www.efloras.org/florata...
Sonchus tenerrimus and S. palustris could be two more ..
http://www.revolvy.com/main/in...
