Figure 1

Ray patterns of C. briggsae and C. elegans. Ventral views of a) C. elegans and b) C. briggsae male tails. Anterior to the left. Left side up. Bilateral pairs of rays are numbered from anterior to posterior. a) C. elegans pattern in which ray 3 is separate from all other rays. This pattern is referred as a 2(1)3+3 pattern. b) C. briggsae pattern in which ray 3 is clustered with rays 4 – 6. This pattern is referred to as a 2/4+3 pattern. In this pattern ray 3 may be either free (right side) or fused with ray 4 (left side). The 2(1)3+3 pattern is ancestral to the Elegans-group, a monophyletic clade that includes C. elegans and C. briggsae [34].