Colonists Advancing into Africa – Ajnabia
- 演化之聲
- Mar 14
- 4 min read
During the Late Cretaceous, dinosaur faunas in the northern hemisphere (Laurasia) and the southern hemisphere (Gondwana) differed markedly. In Laurasia, herbivorous dinosaurs were dominated by ornithischians such as hadrosaurids and ceratopsians, while tyrannosaurids served as the apex predators. In contrast, Gondwanan ecosystems were characterized by titanosaurian sauropods as the primary herbivores and abelisaurids or megaraptorans as the top predators. These contrasting faunas are generally interpreted as the result of continental breakup, which produced oceanic barriers that limited dispersal between the two landmasses.
The fossil record indicates that during the mid-Cretaceous sauropods largely disappeared from the northern continents, while large ornithopods vanished from Gondwana. However, as new discoveries accumulated, researchers began to notice a different pattern in the Late Cretaceous. Sauropods reappeared in the northern hemisphere, while hadrosaurids appeared in southern continents. Phylogenetic analyses suggest that these animals were not previously undiscovered local lineages, but immigrants that had dispersed across marine barriers and colonized new regions.
In 2020, researchers described the first definitive hadrosaurid known from Africa, discovered in Morocco. This find significantly expanded the known geographic range of duck-billed dinosaurs.
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