fecal matters What fossilized dino feces can tell us about their rise to dominance Scientists studied trace fossils called bromalites to reconstruct critical food webs in late Triassic, early Jurassic. Jennifer Ouellette Nov 27, 2024 4:00 pm | 3 Artistic reconstruction of herbivorous, fern-eatingsauropodomorph dinosaurs in the Early Jurassic ecosystem ofSoltykow Credit: Marcin Ambrozik Artistic reconstruction of herbivorous, fern-eatingsauropodomorph dinosaurs in the Early Jurassic ecosystem ofSoltykow Credit: Marcin Ambrozik Story textSizeSmallStandardLargeWidth *StandardWideLinksStandardOrange* Subscribers only Learn morePaleontologists have long puzzled over how the dinosaursoriginally relatively small and of minor importance to the broader ecosystemevolved to become the dominant species some 30 million years later. Fossilized feces and vomit from dinosaurs might hold important clues to how and why this evolutionary milestone came about, according to a new paper published in the journal Nature.Co-author Martin Qvarnstrom, an evolutionary biologist with Uppsala University in Sweden, and his collaborators studied trace fossils known as bromalites, a designation that includes coprolites as well as vomit or other fossilized matter from an organism's digestive tract. As previously reported, coprolites aren't quite the same as paleofeces, which retain a lot of organic components that can be reconstituted and analyzed for chemical properties. Coprolites are fossils, so most organic components have been replaced by mineral deposits like silicate and calcium carbonates.For archaeologists keen on learning more about the health and diet of past populationsas well as how certain parasites evolved in the evolutionary history of the microbiomecoprolites and paleofeces can be a veritable goldmine of information. For instance, in 2021 we reportedon an analysis of preserved paleo-poop revealing that ancient Iron Age miners in what is now Austria were fond of beer and blue cheese.If a coprolite contains bone fragments, chances are the animal who excreted it was a carnivore, and tooth marks on those fragments can tell us something about how the animal may have eaten its prey. The size and shape of coprolites can also yield useful insights. If a coprolite is spiral-shaped, for instance, it might have been excreted by an ancient shark, since some modern fish (like sharks) have spiral-shaped intestines.A tale of two models Excavations in the Late Triassic locality at Lisowice, Poland. The site yielded a large number of coprolites of predators and herbivores. Credit: Krystian Balanda Qvarnstrom et al. were keen to test two competing hypotheses about the dinosaurs' rise to dominance from the Late Triassic Period (237 million to 201 million years ago) to the onset of the Jurassic Period between 201 million to 145 million years ago. "No single hypothesis seems capable of explaining the rise of dinosaurs fully and critical questions about how dinosaurs established their dynasty on land remain largely unanswered," the authors wrote about their research objectives.One hypothesis cites evolutionary competitionthe traditional "competitive replacement" modelas a driving factor, in which dinosaurs were better equipped to survive thanks to superior physiologies, anatomical adaptations, and feeding habits. Alternatively the "opportunistic replacement" model suggests that the dinosaurs were better able to adapt to a rapidly changing environment brought about by random processesvolcanic eruptions, climate change, or other catastrophic events that led to the decline and/or extinction of other species.Qvarnstromand his colleagues focused on 532 bromalites collected from eight sites in the Polish Basin between 1996 and 2017, stored in various scientific collections in Poland. All specimens were photographed and measured, and the team used a number of different techniques to examine the samples. Several bromalites were cut into thin sections and digitally photographed under a microscope. Other samples were scanned with synchrotron microtomography, and the scans were then used for 3D digital reconstructions of the interiors. The team also used chromatography and mass spectrometry to extract and separate plant remains, examining those remains with scanning electron microscopy. Coprolites of herbivorous dinosaurs with numerous plant remains, from the Early Jurassic of Soltykow, Poland. Gregorz Niedzwiedzki, Coprolites of herbivorous dinosaurs with numerous plant remains, from the Early Jurassic of Soltykow, Poland. Gregorz Niedzwiedzki, Large coprolite with fish remains: A coprolite fragment densely packed with fish bones, likely produced by the phytosaur Paleorhinus. Quarnstrm et al, Nature, 2024 Large coprolite with fish remains: A coprolite fragment densely packed with fish bones, likely produced by the phytosaur Paleorhinus. Quarnstrm et al, Nature, 2024 Coprolites of herbivorous dinosaurs with numerous plant remains, from the Early Jurassic of Soltykow, Poland. Gregorz Niedzwiedzki, Large coprolite with fish remains: A coprolite fragment densely packed with fish bones, likely produced by the phytosaur Paleorhinus. Quarnstrm et al, Nature, 2024 They then compared all that data with existing data from fossilized skeletons and footprints, which allowed them to determine which organisms had produced the various bromalites, their feeding behavior, and their relative size and prevalence. This in turn enabled Qvarnstrom et al. to generate food webs from specific periods of time in order to trace how the populations and body sizes of both herbivores and carnivores shifted between the late Triassic and early Jurassic Periods.Their results seem to support the "opportunistic replacement" model, at least in the Polish Basin. It started with the emergence of small omnivorous precursors to the dinosaurs that subsequently evolved into early herbivorous and carnivorous dinosaurs. The rise to dominance of the dinosaurs "occurred against a backdrop of climatic factors that caused shifts in floral communities and might have driven changes in feeding behavior," the authors concluded. The more adaptable dinosaurs were able to feed on a wider variety of food sources, and hence were well adapted to survive."This study advances our understanding of dinosaur diversification and dominance by providing empirical evidence of a mechanism based on random (stochastic) processes," Lawrence Tanner of Le Moyne College in Syracuse, New York, wrote in an accompanying viewpoint. "However, the research is limited in its context and scope, and thus should be seen as a starting point for further work. Using the techniques from this study in other locations would provide a more global context and build a nuanced picture of the connection between Late Triassic environmental disruptions and the ascendancy of the dinosaurs."DOI: M. Qvarnstrom et al., Nature, 2024. 10.1038/s41586-024-08265-4 (About DOIs).DOI: L.H. Tanner, Nature, 2024. 10.1038/d41586-024-03652-3 (About DOIs).Jennifer OuelletteSenior WriterJennifer OuelletteSenior Writer Jennifer is a senior reporter at Ars Technica with a particular focus on where science meets culture, covering everything from physics and related interdisciplinary topics to her favorite films and TV series. Jennifer lives in Baltimore with her spouse, physicist Sean M. Carroll, and their two cats, Ariel and Caliban. 3 Comments Prev story