How Fossilized Vomit and Poop Are Rewriting Dinosaur Diets — and Revealed a New Pterosaur

About 110 million years ago in what is now Brazil, a carnivorous dinosaur expelled a foul, compacted mass from its throat. Buried by sediment and mineralized over time, that concretion recently yielded the bones of a flying reptile no scientist had seen before. The discovery—bones preserved inside a fossilized regurgitation—helps show how bromalites (fossilized vomit and feces) can unlock direct, sometimes surprising, evidence about diet, digestion and ecological interactions in deep time.

What the Blob Revealed

Paleontologist Aline Ghilardi and colleagues identified the remains inside the concretion as a new filter-feeding pterosaur, Bakiribu waridza. Though the bones had endured digestion and mechanical damage, jaws and teeth were preserved well enough to indicate a feeding strategy similar to that of the South American pterosaur Pterodaustro—sieving tiny prey from water much like flamingos do today. Ghilardi calls the specimen an exceptional regurgitalite, a type of bromalite that captures a direct predator–prey interaction in a single moment.

Why Bromalites Matter

Bromalites (including coprolites—fossil feces—and regurgitalites) provide unique evidence that skeletons often cannot. They can record: what animals actually ate; the presence of contemporaneous species in the same environment; and clues to internal anatomy and digestive function that soft-tissue fossils rarely preserve. Because many rock formations span millions of years, bromalites can tightly link organisms and food items to the same instant in time—an invaluable window into ancient food webs.

“This was not just a fossil concretion containing a new species of a rare type of pterosaur, but an exceptional ichnofossil, a regurgitalite,” —Aline Ghilardi.

Historical and Recent Examples

Interest in fossilized excretions is far from new. In the 19th century, geologist William Buckland popularized study of coprolites—he even commissioned a table inlaid with 330-million-year-old coprolites that remains on display at Lyme Regis Museum. Modern studies, however, have greatly expanded the scientific value of such finds.

A famous large coprolite attributed to Tyrannosaurus rex contains crushed bone fragments and traces of muscle tissue, showing the predator ingested bone and that digestion could have been relatively rapid. In Europe’s Polish Basin, analyses of Triassic–Early Jurassic bromalites (about 230–200 million years ago) helped researchers reconstruct dietary shifts: opportunistic omnivory among dinosauromorph relatives and early dinosaurs, followed by growing herbivory and carnivory linked to a climate-driven vegetation boom around 208 million years ago.

Digestion, Anatomy and Behavior from Pellets

Sometimes pellets and regurgitates reveal internal anatomy. In 2022 researchers described fish-scale–packed pellets associated with the Jurassic pterosaur Kunpengopterus. These pellets imply a two-part stomach—an acid-secreting front chamber and a more muscular rear section like a bird’s gizzard—supporting inferences about how some pterosaurs processed food despite the absence of fossilized soft organs.

Context Is Crucial

Experts caution that association matters: bromalites found inside an animal’s gut or directly next to a skeleton provide the strongest links between producer and diet. Isolated bromalites require careful taphonomic and geological analysis before confidently assigning a producer. Still, when context is clear, these unusual fossils can reveal predator–prey relationships, digestive physiology, and ecological dynamics unavailable from bones alone.

What may once have been the butt of paleontological jokes is increasingly recognized as a serious line of evidence. As G. Niedźwiedzki put it, the field’s opinion changed rapidly when coprolites began revealing preserved ingredients "that would be almost impossible to find otherwise." Exceptional excreta have become essential clues for reconstructing ancient life.