Aristolochia tanzawana surely represents one of the most spectacular and large-flowered species of the insular Siphisia group.

The slightly lobed foliage (irregular, 4-7 per leaf) is quite a strange feature as it does not seem to occur constantly within cultivated material.

 

From my perception floral characteristics are too close to A. kaempferi  so a taxonomic separation appears not reasonable (plus occuring + intermixing sympatrically), nevertheless further studies are definitely required for a more comprehensive understanding of the infrageneric relationships in the A. kaempferi complex.

 

This particular morph shows many floral characteristics to Aristolochia liukiuensis so in fact, it could turn out to be a special morph of this species with extremely irregularly shaped leaves.