As you can see from these habitat photos taken by Phil Arrowsmith, taken during his recent trip to Madagascar with John Dransfield, that this form looks totally different to these others. It almost looks like it’s another species; “especially with these long petioles” as the description in Palms of Madagascar refers to the “petioles being absent”. So the only way you could tell that this was a form of Dypsis bosseri would be to have it flower and count the stamen !

This is a rare form of Dypsis bosseri which i don't think is in cultivation.