Figure 3. L1TD1 has been lost multiple times in eutherian mammals.

A species tree shows the presence or absence of L1TD1 across mammals. Arrows depict L1TD1's genomic locus; black (INADL) and white (KANK4) arrows depict the flanking genes we used to identify syntenic regions, and the blue/green arrow depicts L1TD1. L1TD1's presence in the armadillo genome but not in platypus, opossum, wallaby or Tasmanian devil indicates it was most likely born before the divergence of placental mammals, but after divergence from marsupials (solid branches). L1TD1 function was lost in three lineages (X's, and gray branches); it is present as a pseudogene in megabat and entirely missing from Afrotherian and Cetartiodactylan genomes. The bushbaby L1TD1 gene acquired a novel N-terminal region (depicted in red) through a more recent L1 ORF1p domestication event (red asterisk) that occurred after bushbaby diverged from lemurs (Figure 4B).