Lucy’s hunter revealed: Giant crocodile terrorized early human ancestors

Now, a University of Iowa-led team has identified that reptile as a previously unknown species. In a study published in the Journal of Systematic Palaeontology, researchers formally describe the crocodile and name it Crocodylus lucivenator, meaning "Lucy's hunter."

A Crocodile From Lucy's Time

The name reflects the animal's place in history. The crocodile lived between 3.4 million and 3 million years ago in what is now Ethiopia, during the same period and in the same region inhabited by Lucy and her species, Australopithecus afarensis.

Discovered in 1974, Lucy became one of the most important fossil finds in human evolution. At the time, her skeleton was the oldest and most complete early human ancestor or relative ever discovered. The find also helped demonstrate that walking upright on two legs, known as bipedalism, evolved before larger brain size.

The newly identified crocodile was an impressive animal, measuring roughly 12 to 15 feet long and weighing between 600 and 1,300 pounds. It was the only crocodile known from the Hadar landscape, an environment that included shrublands, wetlands, rivers, and tree-lined waterways. Researchers believe it was an ambush predator that spent much of its time concealed in the water, waiting for animals to approach for a drink.

"It was the largest predator in that ecosystem, more so than lions and hyenas, and the biggest threat to our ancestors who lived there during that time," says Christopher Brochu, professor in the Department of Earth and Environmental Sciences at Iowa and the study's corresponding author. "It's a near certainty this crocodile would have hunted Lucy's species. Whether a particular crocodile tried to grab Lucy, we'll never know, but it would have seen Lucy's kind and thought, 'Dinner.'"

A Strange and Distinctive Crocodile

Brochu has spent 35 years studying ancient crocodilians. He first examined Crocodylus lucivenator specimens during a visit to a museum in Addis Ababa, Ethiopia, in 2016.

"I was just blown away because it had this really weird combination of character states," Brochu recalls.

One of the crocodile's most unusual features was a prominent hump located in the middle of its snout. Similar structures are found in American crocodiles but not in Africa's Nile crocodiles. Researchers believe the hump may have played a role in courtship displays.

"You see this in some modern crocodiles," Brochu says. "The male will lower his head down a little bit to a female to show it off."

The species also had a snout that extended farther beyond its nostrils than those of other crocodiles living at the time. According to the researchers, this feature more closely resembles the elongated snouts seen in modern crocodiles.

Fossils Reveal Ancient Behavior

To identify the new species, researchers analyzed 121 cataloged fossil remains, including skulls, teeth, and jaw fragments from dozens of individuals. The fossils were recovered from the Hadar Formation in Ethiopia's Afar region.

For decades, Hadar has been one of the most important sites for understanding human origins. In addition to Lucy and other early hominin fossils, the area contains a rich record of ancient wildlife and was designated a UNESCO World Heritage site in 1980.

Most of the crocodile fossils were incomplete, requiring scientists to reconstruct aspects of the animal's anatomy. One specimen, however, preserved evidence of a violent encounter. Several partially healed injuries on its jaw suggest it had fought with another crocodile.

"The fossil record preserves similar injuries in extinct groups as well, so this kind of face-biting behavior can be found throughout the crocodile family tree," says Stephanie Drumheller, teaching associate professor at the University of Tennessee who earned a doctorate at Iowa. "We can't know which combatant came out on top of that fight, but the healing tells us that, winner or loser, this animal survived the encounter."

Top Predator of the Hadar Ecosystem

Although at least three other crocodile species lived farther south in the Eastern Rift Valley, Crocodylus lucivenator appears to have had the Hadar region largely to itself.

"During the Pliocene, Hadar was composed of a variety of habitats alongside its lake and river systems over space and time, including open and closed woodlands, gallery forests, wet grasslands, and shrublands," says Christopher Campisano, associate professor in the School of Human Evolution and Social Change at Arizona State University and a study co-author. "Interestingly, this crocodile was one of only a few species that was able to persist throughout."

The study is titled "Lucy's Peril: A Pliocene Crocodile from the Hadar Formation, Northeastern Ethiopia."

Nathan Platt and Daniel Leaphart from the School of Earth, Environment, and Sustainability at Iowa contributed to the research. Additional co-authors include Getahun Tekle and Tomas Getachew of the National Museum of Ethiopia and Jason Head of the University of Cambridge.

Funding for the research was provided by the U.S. National Science Foundation, the Leakey Foundation, the University of Iowa Office of International Programs, and the College of Liberal Arts and Sciences at Iowa.