We acquired this one from Harry Luther in the early '90's under parentage name, and it was thought to be a natural hybrid from Mexico. A few were sold to Bill Timm in Florida, and registered as T. Sitting Pretty, (T. streptophylla X paucifolioides). As i recall, T. paucifolioides was a proposed name for the Mexican form of T. circinnata, which later became T. paucifolia.  This Mexican form is different than the Guatemalan form of T. paucilfolia and that is why the name T. paucifolioides  was proposed. Since it was never published, the cross should be listed as T. streptophylla X paucifolia.