Maximum-likelihood tree (CO1 gene, Tamura-Nei model) with branch lengths of the 10 Mesocrina sequences in the BOLD database. The height of the terminal triangular wedges represents sample number and their horizontal width the genetic variation within the species (where no variation the wedge is a vertical line). Letters represent putative and undetermined Canadian (A, B, D) or Californian (C) species of Mesocrina.