Mapping the march of the mouse

Murine species originating in southern Asia were given the opportunity to spread into Africa and Europe roughly 11 million years ago, in a period known as the Miocene, as a result of the continental drift. The route of that dispersal has been difficult to define because of the poor fossil record in the Middle East. “This part of the world remains terra incognita to palaeontologists,” says Raquel López-Antoñanzas of France’s Université de Montpellier.

To rectify this, López-Antoñanzas and her team have been sifting through sediments collected at various sites in Lebanon. One such search yielded a few tiny teeth. Based on their distinctive shape, the researchers soon realized they were dealing with a new species, which they dubbed Progonomys manolo. “We later realized that this was, in fact, one of the oldest species of murines ever found out of Asia, with the data suggesting that it is 10.5–11 million years old,” she says. 

These are the first representatives of this ancestral genus ever to be discovered in the region, offering striking evidence of the route travelled by the earliest rodents. 

“This study is an important addition to our understanding of the route and timing of the spread of mice throughout the Old World,” says palaeobiologist Lawrence Flynn of Harvard University in the USA, who was not involved in the study. “From these Miocene age roots, there exploded the tremendous radiation of living mouse species of Eurasia and Africa.” 

Notably, the teeth suggest an omnivorous diet, rather than the plant-based diet favoured by many modern rodents, indicating that this early species was more generalized than its specialist contemporary descendants.

López-Antoñanzas now hopes to profile these and other murine fossils in greater detail to more accurately reconstruct the history of these mammals, including their spread and adaptation to new environments.

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