Derivation of (A) marsupial and (B,C) eutherian ancestral karyotypes from the predicted ancestral therian karyotype. (A) The predicted ancestral marsupial karyotype was formed by fusions of the predicted therian chromosomes. (B) Inversions, fusions and fissions led to (C) the previously predicted ancestral eutherian karyotype . T – Therian, M- Marsupial. Chromosomes have been colour-coded to reflect homology with human chromosomes (refer to key in Figure 6).