The Gomphotherium land bridge was a land bridge that connected Eurasia to Afro-Arabia between approximately 19 and 15 million years ago (Ma) during the Burdigalian stage of the Early Miocene. More recent analysis found that the Gomphotherium land bridge may have formed slightly earlier, around 20 Ma, which resulted in the Great Old World Biotic Interchange. It is believed that the connection between the Mediterranean and Indian oceans was temporarily re-established during the Langhian stage of the Middle Miocene, before reclosing, and has remained closed to present day. The formation of the land bridge led to an important biotic interchange event known as the Great Old World Biotic Interchange (GOWBI) or the Proboscidean Datum Event, which saw fauna from Eurasia migrating into Afro-Arabia and vice versa. Similar interchanges of have happened occurred throughout the Cenozoic, such and the collision between insular India and Asia. As well as the collision of the Americas, which resulted in the Great American Interchange.
Before the interchange
Isolation of Afro-Arabia
During the Early Cretaceous (Aptian-Albian), Africa became isolated from the rest of Gondwana and Laurasia, spending the rest of the Cretaceous and most of the Cenozoic as an island continent. Mammalian fauna endemic to the continent primarily consisted of Afrotheria (proboscideans, sirenians, embrithopods, hyracoids, and several other groups), metatherians (herpetotheriids), and hyaenodonts (hyainailouroids and several unranked clades).
Proboscideans, the order that contains modern elephants, first evolved in Africa around 60 Ma, during the Selandian stage of the Paleocene; with Eritherium being the earliest known proboscidean, which weighed 3–8 kilograms (6.6–17.6 lb). By the Early Eocene, proboscideans began growing in size. Daouitherium, the earliest known elephantiform, may have weighed 200 kg (440 lb). This would make it the earliest known large mammal within Africa. By the Late Eocene, some taxa began to reach notable sizes such as Barytherium, which could have weighed 2 tonnes (2.0 long tons; 2.2 short tons). Some proboscideans during this time, such as Barytherium and Moeritherium, were semi-aquatic. Elephantimorphs, a clade of proboscideans that includes mastodons and modern elephants, first appeared in the Late Oligocene.
Embrithopods are a enigmatic order of afrotherian mammals that arose in the Early Eocene. The earliest known embrithopod was Stylolophus. Arsinoitheriids were a highly successful group of large herbivores that were widespread in Africa. Arsinoitherium, the most well known taxon, was rhino-like in appearance. The largest species could have stood 1.75 m (5.7 ft) at the shoulders and measured 3 m (9.8 ft) in length. One of its defining features was a pair of enormous horns on its head, which was structured similarly to the horns of modern bovids. Embrithopods were last recorded in latest Oligocene. Within the carnivore guild, hyaenodonts were the dominant carnivores of Africa. Hyaenodonts were consisted of groups such as hyainailouroids, boualitominae, and the Lahimia clade. Hyainailouroids, the most notable group, were one of the three superfamilies of Hyaenodonta, an extinct order of carnivorous mammals, and were thought to have originated from Afro-Arabia, evolving during the Late Paleocene, despite the oldest fossils of hyainailourids being found in Asia. The hyainailourids were ecologically diverse, while hyainailourines were terrestrial predators, apterodontines had otter-like adaptations suggesting they were semi-aquatic predators. Non-mammalian predators included reptiles such as the large madtsoiid Gigantophis and the sebecosuchian Eremosuchus.
Early dispersals
… excerpt ends here. Continue reading the full article.
