New research has resolved a long-standing controversy about an extinct 'horned' crocodile that likely lived among humans in Madagascar.
Based on ancient DNA, the study shows that the horned crocodile was closely related to 'true' crocodiles, including the famous Nile crocodile, but on a separate branch of the crocodile family tree.
The study contradicts recent scientific thinking and also suggests that the ancestor of modern crocodiles likely originated in Africa.
The arrival of modern humans in Madagascar between about 9,000 and 2,500 years ago preceded the extinction of many of the island's large animals, including giant tortoises, elephant birds, dwarf hippos, and several lemur species.
One lesser-known extinction that occurred during this period was that of an endemic "horned" crocodile known as Voay robustus.
Early explorers to Madagascar noted that Malagasy peoples consistently referred to two types of crocodiles on the island: a large robust crocodile and a more gracile form with a preference for rivers. This suggests that both types persisted until very recently, but only the gracile form, now recognized as an isolated population of the Nile crocodile (Crocodylus niloticus), is currently found on the island.
Despite nearly 150 years of investigation, the position of the horned crocodile in the tree of life has remained controversial. In the 1870s, it was first described as a new species within the "true crocodile" group, which includes the Nile, Asian, and American crocodiles.
Then, in the early part of the 20th century, it was thought that the specimens simply represented very old Nile crocodiles.
In 2007, a study based on physical characteristics of the fossil specimens concluded that the horned crocodile was actually not a true crocodile, but in the group that includes dwarf crocodiles.