Fig. 6

Different hypotheses for the loss of ODAM exon 6 in some but not all proboscideans. a) Loss of ODAM exon 6 based on an ancestral polymorphism in the ancestor of Elephantidae and Mammutidae followed by incomplete lineage sorting of the two allelic variants in Recent and extinct proboscideans. b) One possible scenario for the loss of exon 6 of ODAM based on convergent loss in Mammut americanum and Palaeoloxodon antiquus followed by introgression of the sans exon 6 allele from P. antiquus to Loxodonta cyclotis and Mammuthus primigenius. Other scenarios are also possible based on directions of introgression within Elephantidae that were identified by Palkopoulou et al. [71]