Mysterious leaves on cactus/suculent

Can anyone out there help to identify this cactus, and more crucially, to explain the formation of the leaves that sprout from between the thorns? Pics are self-explanatory, and the plant is about one meter tall. This is the only cactus I have ever owned that does this!

 

It's not a cactus, it's an Euphorbia (trigona?). It's completely natural for them
to grow leaves.

 

agreed, euphorbia and trigona is also probably correct. leaves are normal for this one.

 

Thanks to all who responded. Mystery solved! It's so easy when you know how....

 

Leaves shed in late fall. Will grow new ones in the spring/summer months.