Meet Crocodylus lucivenator, the Crocodile That Hunted Lucy's Kin
University of Iowa
Somewhere between 3.4 million and 3 million years ago, in what is now the Afar region of northeastern Ethiopia, a crocodile sat submerged in shallow water. It was 12 to 15 feet long, weighed somewhere between 600 and 1,300 pounds, and had a peculiar hump in the middle of its snout. When our ancient relatives - members of the species Australopithecus afarensis, the same species as the famous fossil skeleton Lucy - came to the water's edge to drink, this animal was waiting.
That crocodile now has a name. In a study published March 12 in the Journal of Systematic Palaeontology, a research team led by the University of Iowa formally describes the species as Crocodylus lucivenator - Lucy's hunter.
A predator built for ambush
Christopher Brochu, professor in the Department of Earth and Environmental Sciences at Iowa and the study's corresponding author, has been studying ancient crocodiles for 35 years. He first encountered the C. lucivenator specimens during a visit to a museum in the Ethiopian capital Addis Ababa in 2016 and was struck by its unusual combination of physical traits.
The most distinctive feature was a large hump on the snout, similar to what is found on the modern American crocodile but absent in the Nile crocodile that dominates Africa today. The researchers believe the hump served as a sexual display, used by males to attract mates - a behavior observed in some living crocodile species where males lower their heads toward females to show off the structure.
The animal's snout also extended further from its nostrils than other crocodiles of the same era, more closely resembling the elongated snout of modern crocodile species. This combination of traits - the hump, the extended snout, other skeletal peculiarities - set it apart from any previously described species.
121 fossils from a UNESCO heritage site
The team examined 121 cataloged remains, primarily skulls, teeth, and jaw fragments representing dozens of individual animals. All were excavated from the Hadar site in Ethiopia's Afar region, the same area that produced the Lucy skeleton in 1974 and has been a UNESCO World Heritage site since 1980.
Most fossils were fragmentary, requiring the researchers to extrapolate the full skeleton. But one specimen stood out: a jaw with several partially healed injuries suggesting it had fought with another member of its species. Stephanie Drumheller, a teaching associate professor at the University of Tennessee and study co-author, noted that this kind of face-biting behavior appears throughout the crocodile family tree, both in living species and extinct ones. The healing tells us the animal survived the encounter, whether it won or lost.
The only croc on the block
While at least three other crocodile species existed further south in the Eastern Rift Valley during the same period, C. lucivenator appears to have been the sole crocodile in the Hadar ecosystem. And it was the apex predator there - larger than the lions and hyenas that shared the landscape.
Brochu stated plainly that it is a near certainty this crocodile would have hunted Lucy's species. Whether a particular crocodile ever tried to grab Lucy herself is unknowable, but it would have seen her kind and recognized prey.
The Hadar environment during this period was a mosaic of habitats alongside lake and river systems, including open and closed woodlands, gallery forests, wet grasslands, and shrublands. Christopher Campisano, associate professor at Arizona State University and study co-author, noted that the crocodile was one of only a few species that persisted throughout these shifting conditions - suggesting it was a highly adaptable predator.
What the snout hump reveals about evolution
The sexual display theory for the snout hump is plausible but not proven. The researchers base it on analogy with living crocodile species, where similar structures serve reproductive functions. But fossil evidence cannot confirm behavior directly. The hump could have served other functions - perhaps related to thermoregulation, hydrodynamics, or species recognition - that are harder to infer from bone alone.
The extended snout is more straightforward to interpret. It aligns C. lucivenator more closely with the lineage leading to modern crocodiles than with many of its contemporaries, potentially offering clues about when and how the modern crocodile body plan evolved.
Fragments, not complete skeletons
It is worth being clear about what the fossil record provides and what it does not. The 121 specimens are mostly partial - skulls, teeth, jaw pieces. No complete skeleton of C. lucivenator has been found. The size estimates of 12 to 15 feet and 600 to 1,300 pounds are extrapolations based on the skull fragments and comparisons with known crocodile species. These estimates are standard practice in paleontology, but they carry inherent uncertainty.
The claim that it hunted hominins is inferential as well. It is based on the animal's size, its ecological role as an ambush predator in a waterway environment, and its temporal and geographic overlap with A. afarensis. There is no direct fossil evidence - no hominin bone with crocodile tooth marks, for instance - linking the two species in a predatory interaction. The inference is strong, but it remains an inference.
A window into an ancient predator-prey world
The naming of C. lucivenator adds a new dimension to our understanding of the ecosystem in which early hominins evolved. These were not safe environments. The waters that sustained our ancestors also harbored a 1,300-pound ambush predator with a strong bite and patience.
The study, titled "Lucy's Peril: A Pliocene Crocodile from the Hadar Formation, Northeastern Ethiopia," was funded by the U.S. National Science Foundation, the Leakey Foundation, and the University of Iowa. Additional contributing authors include Nathan Platt and Daniel Leaphart from Iowa, Getahun Tekle and Tomas Getachew from the National Museum of Ethiopia, and Jason Head from the University of Cambridge.