During the Pliocene epoch some bovins left Africa and entered Europe, where they have evolved into hardy, cold-adapted species. During the Ice Age ancestors of the bison had colonized North America from Eurasia over the Bering Land Bridge in two waves, the first being 135,000 to 195,000 years ago and the second being 21,000 to 45,000 years ago. Below is the list of fossil species that have been described so far listed in alphabetical order that currently do not fit in any of the existing subtribes: Tribe Bovini (Gray, 1821) Genus †Alephis (Gromolard, 1980) †Alephis lyrix (Gromolard, 1980) †Alephis tigneresi (Michaux et al., 1991) Genus †Eosyncerus (Vekua, 1972) †Eosyncerus ivericus (Vekua, 1972) Genus †Jamous (Geraads et al., 2008) †Jamous kolleensis (Geraads et al., 2008) Genus †Probison (Sahni & Khan, 1968) †Probison dehmi (Sahni & Khan, 1968) Genus †Simatherium (Dietrich, 1941) †Simatherium kohllarseni (Dietrich, 1941) †Simatherium shungurense (Geraads, 1995) Genus †Udabnocerus (Burchak-Abramovich & Gabashvili, 1969) †Udabnocerus georgicus (Burchak-Abramovich & Gabashvili, 1969) Taxonomy Majority of phylogenetic work based on ribosomal DNA, chromosomal analysis, autosomal introns and mitochondrial DNA has recovered three distinctive subtribes of Bovini: Pseudorygina (represented solely by the saola), Bubalina (represented today by the genera Syncerus and Bubalus), and Bovina (represented today by the genera Bison and Bos). According to the fossil record and the molecular work, Bubalina and Bovina have diverged from one and another from a common ancestor around 13.7 million years ago in the Late Miocene. The number of taxa and their evolutionary relationships with each other has been debated, mainly as there is several evidence of ancient hybridization events that occurred among the various species of wild cattle, obstructing any evidence of their relationships. Below is the taxonomy of extant genera that are classified as members of the tribe Bovini (more information regarding the species taxonomy is explained more in-depth in their respective subtribe articles): Tribe Bovini (Gray, 1821) Subtribe Pseudorygina (Hassanin & Douzery, 1999) Genus Pseudoryx (Dung et al., 1993) – Saolas Subtribe Bubalina (Rütimeyer, 1865) Genus Syncerus (Hodgson, 1847) – African buffalos Genus Bubalus (Hamilton-Smith, 1827) – Anoas and the wild water buffalos Subtribe Bovina (Gray, 1821) Genus Bison (Hamilton-Smith, 1827) – Bison (might be part of Bos instead) Genus Bos (Linnaeus, 1758) – Taurine and Asiatic cattle Natural history General description Wild cattle are usually massive bovids that are stout-bodied with thick, short legs. Some species can reach impressive body-sizes such as wild