Dated phylogeny summarizing the evidence for OC1_Das horizontal transfer and timing of activity in marsupials. Phylogenetic relationships and divergence times between the five marsupials species (short-tailed opossum: Monodelphis domestica, wallaby: Macropus eugenii, eastern barred bandicoot: Perameles gunnii, Tasmanian devil: Sarcophilus harrisii, fat-tailed dunnart: Sminthopsis crassicaudata) are taken from Meredith et al. (2008), Meredith et al. (2009) and Krajewsky et al. (2000). The range of divergence times calculated for the split between the Tasmanian devil and the dunnart (23 to 14 My; dark grey rectangle) is illustrated to show that it overlaps with the timing of OC1_Das activity burst (dashed line at 17 My), derived from our molecular clock approach. The light grey rectangle illustrates the time range during which all OC1 HTs described so far in metazoans took place. See text for more details on our molecular dating of the OC1_Das burst of activity and PCR screening. Products obtained from the PCR screening were cloned and sequenced and are provided in Additional file 4 (122-bp fragments of non-autonomous OC1 in Tasmanian devil and fat-tailed dunnart) and Additional file 5, Additional file 6 and Additional file 7 (empty sites for three OC1_Das copies present in the Tasmanian devil but absent from the dunnart).