This is an omoplata setup from the leg lasso guard by pushing your leg through while breaking the opponents posture. This is a variation to the omoplata from lasso guard by inverting.
Samir Chantre shows his version of a triangle choke from Spider/Lasso guard. It is important to cut your calf muscle across the opponents neck and not over their back to break their posture.
Here is the triangle choke from spider guard shown by world champion Demian Maia of Brasa.