Vertical DNA transfer from endosymbiotic relationship observed in vertebrate species

[Anomalocaris]

That’s what endosymbiotic theory says. However that happened between bacteria, and while endosymbiotic relationships are fairly common between bacteria and even between bacteria and non-vertebrates, this is thought to be a first at the cellular level in a vertebrate species.

Mitochondria has its own DNA and exist in most cells in each vertebrate, The process of mitochondria DNA transfer from one generation of vertebrate to the next occurs outside normal sexual reproduction of the vertebrate, So Mitochrondria appear to fit the definition of vertical gene transfer of endosymbiant in a vertebrate.

In fact it is the vertical DNA transfer of mitochondria that makes possible the genetic dating techniques that showed us our most recent common female ancestor about 100,000 years before the christian god got around to creating her.