I've seen similar leaf appendages on other aroids, most notably a few meconostigma Philodendrons. The Mickey Mouse Xanthosoma may sometimes show something along this line on leaves. It is the result of an anomalous leaf primordium, which in English means that it is like a "siamese leaf" where there is the full size leaf and then a diminutive one stuck onto it like a siamese twin. This can also show up in aroid blooms where it looks like two blooms fused together, with either one spathe and two spadices or two spathes and a spadix that looks like two fused together. I've seen these on some of my plants from time to time. I've also seen siamese leaves in which there are two half blades on one petiole. All of these arise from similar anomalies in the primordial tissue.
These anomalies usually show up near the junction of petiole and leaf blade, which for a researcher would give a clue as to where the anomalous meristematic tissue (aka "plant stem cells") is located in the developing bud.
Hope this helps,
LariAnn
