Scientists are studying fossilized feces from 126 million years ago in Spain to better understand the animals that left them behind.
Sandra Barrios de Pedro, a researcher from the Autonomous University of Madrid (UAM), along with scientists from the Mining and Geological Institute of Madrid (IGME), published their findings at Las Hoyas near Cuenca, Spain, in the journal Plos One.
They say the deposits are in "an exceptional state of conservation" and indicate an immense diversity of extinct wildlife.
Fossilized feces – also known as coprolites – provide important information about the diet and feeding habits of the extinct animals that excreted them.
Las Hoyas was once a shallow wetland where microbial mats "formed by cyanobacteria and other microorganisms" grew over "dead animals and their feces, which facilitated the preservation and accumulation of organic debris," says Barrios.
Scientists studied the form, content and chemical composition of the feces and determined that they belonged to a diverse range of aquatic vertebrates, from fish and salamanders to turtles, small sharks and crocodiles. Birds and dinosaurs may have roamed the area during the Cretaceous period.
Las Hoyas has yielded some 2,000 coprolites over the past 30 years, revealing some of "the most varied and extensive sample of the specimens" in the world, Barrios said.
The chemical analysis revealed that the coprolites "belonged mostly to carnivorous animals that ate fish."
In fact, some fossils contained pieces of fish scales and even bone vertebrae and spines, "which shows that most of the inhabitants of the Las Hoyas reservoir were carnivores with ichthyophagous (fish-eating) diets," according to Barrios. Other feces showed that some animals were vegetarian.
Analyzing coprolites is important because "it reveals differences in the effectiveness of the digestive processes of the producers but also helps to know what they ate and how they behaved trophically," concluded the researcher.