Millions of years ago, giant dwarf crocodiles roamed part of Africa with a liking to our human ancestors.
In a new study, researchers led by the University of Iowa announced the discovery of two new species crocodiles 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 western Africa.
But the giant dwarf crocodiles were much bigger – hence their name – than their modern relatives. Dwarf crocodiles rarely exceed 4 or 5 feet in length, but ancient forms measured up to 12 feet and were probably among the fiercest threats to any animal they encountered.
“They were the biggest 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 perilous for ancient humans to head down the river for a drink.”
The new species are called Kinyang mabokoensis and Kinyang chernovi. They had short, deep snouts and large conical teeth. Their nostrils opened slightly upwards and forwards, not directly upwards as in modern crocodiles. They spent most of their time in the forest, rather than in the water, waiting to ambush prey.
“They had what looked like this big smile that made them really happy, but they’d bite your face off if you gave them the chance,” Brochu said.
Kinyang lived in the Rift Valley of East Africa, in parts of present-day Kenya, during the early to mid-Miocene, a time when the region was largely covered in forest. Yet, from the end of a period called the Miocene climatic optimum around 15 million years ago, both species seemed to disappear.
Why did they disappear? Brochu thinks climate change leads to less rainfall in the region. Reduced rainfall has led to a gradual retreat of forests, giving way to grasslands and mixed wooded savannahs. The landscape change affected Kinyang, which researchers say likely preferred forested areas for hunting and nesting.
“Modern dwarf crocodiles are found exclusively in forested wetlands,” says Brochu, who has studied ancient and modern crocodiles for more than three decades. “The loss of habitat 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 acknowledges that what caused the Kinyang to die requires further testing, as researchers are unable to pinpoint when the animals went extinct. Additionally, there is a gap in the fossil record between Kinyang and other lineages of crocodiles that appeared about 7 million years ago. The new arrivals included 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 study was published in The anatomical file.
Christopher A. Brochu et al, Miocene Giant Dwarf Crocodiles of Kenya and Crocodylid Faunal Dynamics in the Late Cenozoic of East Africa, The anatomical file (2022). DOI: 10.1002/ar.25005
University of Iowa
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