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Voay

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Voay is an extinct genus of crocodile that once lived on the island of Madagascar. It existed from the Late Pleistocene through the Holocene periods. The genus contains only one known species, named Voay robustus.

Voay robustus head
Voay robustus head

Its name is taken from the Malagasy word for crocodile. This animal was likely the largest predator to exist in Madagascar in recent times. Understanding Voay helps scientists study how ancient ecosystems functioned on the island.

Researchers have discovered many subfossils of this animal in several locations. These remains include complete skulls, vertebrae, and osteoderms. Osteoderms are bony plates that protect the animal's body.

Voay robustus head
Voay robustus head

Notable finds have been made in places like Ambolisatra and Antsirabe. One of the most striking features of Voay robustus is its skull. It possessed a pair of prominent horns on the posterior, or back, of its head. These horns are actually the posterolaterally extended corners of the squamosal bone. This bone structure is quite different from many other crocodilians.

Voay robustus had several specific physical traits that set it apart. Its snout was shorter and deeper than the snout of the modern Nile crocodile, or Crocodylus niloticus. It also had relatively robust limbs for movement. The osteoderms on its body featured tall keels, which are raised ridges on the bone. These plates were dorsally symmetrical with curved lateral margins. They ran the entire length of the postcranial body.

Voay robustus head
Voay robustus head

These features helped define the unique shape of the animal.

The history of how we classify Voay has changed many times. In 1872, scientists first described the animal and placed it in the genus Crocodylus. Later, researchers noticed it shared certain traits with the Osteolaemus, known as the dwarf crocodile. For example, it had a depressed pterygoid surface that formed a choanal "neck" on the palate. Because it was not close enough to the dwarf crocodile, it was assigned to its own genus, Voay, in 2007.

Voay robustus head
Voay robustus head

This reassignment corrected earlier mistakes caused by poor descriptions of the original fossils.

Recent science has provided even more clarity through paleogenomics. This is the study of very old DNA from fossils. A 2021 study used this method to find that Voay was a sister group to Crocodylus. This means they share a common ancestor. The two groups diverged during the mid-to-late Oligocene epoch.

Voay robustus head
Voay robustus head

This discovery showed that the similarities to the dwarf crocodile were likely due to convergent evolution. Convergent evolution occurs when different species develop similar traits independently.

Voay lived alongside other famous Madagascar animals. It likely became extinct during a major extinction event. This event wiped out much of the endemic megafauna on the island. This group included the elephant bird and the Malagasy hippo.

Voay robustus head
Voay robustus head

Many scientists believe this happened after humans arrived on Madagascar around 2,000 years ago. It is also interesting to note that Nile crocodiles lived in Madagascar at the same time. Some Crocodylus specimens were found to be at least 7,500 years old. This means Voay and the Nile crocodile were contemporaneous.

The presence of both crocodiles created a complex environment. Because Voay shared many similarities with the Nile crocodile, they likely faced interspecies competition. They would have competed for the same resources, such as food and territory. Some researchers once thought the Nile crocodile only arrived after Voay was gone. However, the 7,500-year-old fossils disproved that idea.

Voay robustus head
Voay robustus head

This shows that two different crocodile genera once shared the same island habitat.

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