Table 1.

Fusion categories based on bilateral fusion ranks

Fusion categories	Definition	Image
I. Bilateral Distant Non-Fusion	Rank 0 (distant non-fusion) on both sides.	Fig. 1, row 1
II. Bilateral Non-Fusion	Rank 1 (non-fusion) on both sides.	Fig. 1, row 2
III. Partial or Unilateral Fusion	Rank 2 (partial fusion) on one side with: Rank 1 (non-fusion); Rank 2 (partial fusion); or Rank 3 (fusion) on the opposite side OR Rank 3 (fusion) on one side with Rank 1 (non-fusion) on the opposite side	Fig. 1, row 3 shows Rank 2 (partial fusion) on both sides. The 3 asymmetric types are not shown, but all occurred in our sample
IV. Bilateral Fusion	Rank 3 (fusion) on both sides	Fig. 1, row 4