This is a native Ipomoea species collected as seed by a friend in the Northern Territory Australia. The hairy seed were difficult to germinate but eventually I had one germinate and survive. Over the past few years it has gone from strength to strength where i have been able to propagate it. It propagates easily from stem cuttings, rooting at the nodes as seen in the pictures, sending down a root that becomes a storage tuber with time. These cuttings are only a few months old and were in small pots which have restricted their growth. I have not seen it flower yet to fully identify it. It closely matches the description and picture of Kalumburu Yam in The Bush Tucker Field Guide by Les Hiddens, although it was collected closer to Darwin, near Walker Creek.
Hopefully it proves to be a good edible species!
Update: This yam appears to be Ipomoea abrupta after it flowered recently. The flowers open in the morning and have a beautiful delicate scent. I am conducting several interspecific hybrisation experiments with other native species and this species as the pistillate parent.