While Walden Pond is a dimple in glacial deposits, Lake Baikal is a trench-like
rift lake similar to Lake Tanganyika.
Like the other unusual rift lake faunas, the thiarid gastropods of Lake Tanganyika evolved in situ in the Tanganyika basin.
However, our current understanding of the African Rift System is that the rift lakes are much younger than Jurassic (Miocene, 5-20 million years ago [M.Y.B.P.]) and were never connected to the ocean but rather were formed by the rifting of the African continent (Baker et al.
hypothesized that this taxon and others from the
rift lakes were from an extinct radiation and, as such, were not related to the currently recognized six families of the Unionida.
The East African Rift system is composed of two main segments, the eastern branch that passes through Ethiopia and Kenya, and a western branch that forms a giant arc from Uganda to Malawi, interconnecting the famous
rift lakes of eastern Africa.