For generations, crocodiles have been recognized as apex predators, equipped with formidable teeth designed for tearing flesh. However, a recent study published in the journal Current Biology challenges this long-held perception, revealing that some ancient relatives of modern crocodiles were, surprisingly, plant-eaters. This discovery offers new insights into the evolutionary history of these resilient reptiles and highlights their remarkable adaptability.
Researchers analyzed 146 fossil teeth from 16 extinct species closely related to crocodiles. The analysis indicated that at least three separate times in their evolutionary history, groups of ancient crocodiles independently developed adaptations for herbivory – a diet consisting primarily of plants. Understanding how animals adapt their diets over time is crucial for tracking biodiversity and predicting how species might respond to changing environments.
Clues from Fossil Teeth and Analysis Methods
The research team, led by paleontologist Keegan Melstrom from the University of Utah, used a specialized method to measure the complexity of the fossil teeth surfaces. Scientists counted the number of different surfaces on each tooth; a greater number of varying surfaces suggested a greater likelihood that the tooth was used for grinding tough plant material.
Modern carnivores typically have relatively simple teeth—sharp, straight, and with minimal complex surfaces, like those of the Komodo dragon, designed for slicing meat. In contrast, herbivores have teeth with numerous ridges and crevices to expand the chewing surface for breaking down leaves, stems, and branches. Remarkably, some ancient crocodile teeth were found to have up to 20 different surfaces, indicating an intensive chewing process unlike that of modern crocodiles, which generally swallow their prey whole.
Simosuchus: A Unique Snouted Crocodile with a Plant-Based Diet
One particularly striking example is Simosuchus, a tiny crocodyliform with an almost rectangular snout, described as resembling a crocodile whose head was struck by a shovel. The teeth of Simosuchus show similarities to those of marine iguanas from the Galápagos Islands, reptiles known for grazing on algae on coastal rocks. Although Simosuchus was not an aquatic animal, researchers hypothesize it lived near water and may have had a similar plant-eating habit.
Repeated Evolution and Mass Extinction
The study also emphasizes that a plant-based diet didn’t emerge just once in the crocodile lineage. At least three distinct groups independently developed adaptations for herbivory. This suggests that being an herbivore was a successful evolutionary strategy at the time, allowing them to occupy diverse ecological niches.
However, this adaptation didn’t last. Approximately 66 million years ago, the mass extinction event that also wiped out the dinosaurs brought an end to these vegetarian crocodiles. Of the many variations that once existed, only a small number of lineages survived to the present day.
Dietary Flexibility in Modern Crocodiles and a Rich Evolutionary History
Today, around two dozen crocodile species inhabit a variety of habitats, from lakes and rivers to coastlines, and are known as carnivores that prey on fish and other animals. However, research indicates that some modern crocodile species occasionally consume fruits. This finding demonstrates that crocodiles are not simply “living fossils” unchanged since the age of dinosaurs.
As the researchers revealed, the crocodile group has a much more diverse evolutionary history than previously understood. The diversity of tooth shapes and diets in the past provides evidence that crocodiles once occupied a range of ecological niches, from apex predators to plant-eaters, demonstrating their remarkable adaptability throughout their evolutionary journey.
