Two new species of enormous dwarf crocodile, measuring up to 12 feet (3.7 meters) in length and with a strong, aggressive attitude, were not ones you would have wanted to encounter during the Early and Middle Miocene.
Between 15 and 18 million years ago, these creatures inhabited areas of Africa. They suddenly appeared to vanish from the scene, which might have been due to rapid environmental changes.
The two new species have been designated Kinyang mabokoensis and Kinyang tchernovi, and while they look similar to today's dwarf crocodiles, these creatures were up to four times larger.
"These were the biggest predators our ancestors faced," says University of Iowa paleontologist Christopher Brochu.
"They were opportunistic predators, just as crocodiles are today. It would have been downright perilous for ancient humans to head down to the river for a drink."
The creatures possessed snouts that were short and deep, with massive, conical teeth, according to the researchers. The nostrils of K. mabokoensis and K. tchernovi would have faced more to the front than those of modern crocodiles, which have nostrils that face directly up.
The two new species were discovered when researchers examined several skull pieces recovered from digs in the East African Rift Valley, which revealed a "very similar" but yet separate pair of crocodile species, according to the researchers.
Instead of hunting for meals in the water, these species would have spent the majority of their time in the forest. The places where they most likely lived and died (parts of what is now Kenya) would have been densely forested at the time.
According to the experts, the most plausible reason for the extinction of the species is a progressive retreat of the woods owing to climate change and less rainfall. Forests gave place to grasslands and mixed savanna woodlands, which were less suitable for the animals.
"Modern dwarf crocodiles are found exclusively in forested wetlands," Brochu explains. "Loss of habitat may have prompted a major change in the crocodiles found in the area."
"These same environmental changes have been linked to the rise of the larger bipedal primates that gave rise to modern humans."
Because it's unclear when the Kinyang crocodiles went extinct, more study will be needed to confirm this theory. Between these huge dwarf crocodiles and present species, there is a gap in the fossil record that would be valuable to fill in.
There's much more to learn about these species in particular — for example, experts aren't sure how many teeth they possessed. Other fossils can now be linked to the species now that it has been recognized.
"They had what looked like this big grin that made them look really happy, but they would bite your face off if you gave them the chance," Brochu adds.
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