Millions of years ago, giant dwarf crocodiles roamed parts of Africa with a fondness for our human ancestors.
In a new study, researchers led by the University of Iowa have announced the discovery of two new crocodile species that roamed East Africa between 18 and 15 million years ago before mysteriously disappearing. The species, called giant dwarf crocodiles, are related to the dwarf crocodiles currently found in Central and West Africa.
But giant dwarf crocodiles were much larger – hence their name – than their modern-day relatives. Dwarf crocodiles rarely exceed 4 or 5 feet in length, but the ancient forms measured up to 12 feet and were probably among the most ferocious threats to any animal they encountered.
“They were the largest predators our ancestors faced,” says Christopher Brochu, a professor in the Iowa Department of Earth and Environmental Sciences and corresponding author of the study. “They were opportunistic predators, just like crocodiles are today. It would have been downright dangerous for ancient humans to head to the river for a drink. “
The new species are called Kinyang mabokoensis And Kinyang Chernovi. They had short, deep muzzles and large conical teeth. Their nostrils opened slightly upward and forward, not directly upward as in modern crocodiles. They spent most of their time in the forest rather than in the water, waiting to ambush their prey.
“They had what looked like a big smile that made them really happy, but they would bite your face if you give them the chance,” Brochu said.
Kinyang lived in the East African Rift Valley, in parts of present-day Kenya, during the early Middle Miocene, a time when the region was largely forested. Yet, since the end of a period called the Miocene Optimal Climatic, about 15 million years ago, both species seemed to be disappearing.
Why did they disappear? Brochu believes that climate change has led to a decrease in rainfall in the region. The reduction in rainfall has led to a gradual withdrawal of forests, giving way to mixed forested grasslands and savannahs. The change of landscape influenced Kinyangwhich researchers say they likely preferred wooded areas for hunting and nesting.
“Modern dwarf crocodiles are found exclusively in wooded wetlands,” says Brochu, who has been studying ancient and modern crocodiles for more than three decades. Habitat loss may have caused a major change in the crocodiles found in the area.
“These same environmental changes have been linked to the rise of large bipedal primates that gave rise to modern humans,” adds Brochu.
Brochu recognizes what caused the Kinyang death requires further testing, as researchers are unable to accurately determine when the animals went extinct. Additionally, there is a gap in the fossil record between KInyang and other crocodile lineages that appeared about 7 million years ago. Among the new arrivals were relatives of the Nile crocodile currently found in Kenya.
Brochu has examined the specimens on several visits since 2007 to the National Museums of Kenya, Nairobi.
The research was funded by the US National Science Foundation, the National Geographic Society, the Leakey Foundation, the Wenner Gren Foundation for Anthropological Research, the Fulbright Collaborative Research Program, the Boise Fund of the University of Oxford, the Specialist Group of Crocodiles of the IUCN, the University of Iowa, the Karl und Marie Schack-Stiftung Fund and Vereinigung von Freunden und Förderern der Goethe-Universität Frankfurt and the Ministerio de Universidades de España.
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Materials provided by University of Iowa. Original written by Richard C. Lewis. Note: The content can be changed by style and length.