Guest Blog Post by Anne Betterman and Felix J. Augustin
Sometimes, the smallest marks on a fossil bone can tell us some of the most interesting stories. In our recent study, published in Fossil Record, we investigated “bioerosion” – traces left by organisms during feeding and other activities – on fossil bones from Upper Cretaceous deposits of Haţeg Basin in Romania. These traces gave us a new perspective on what happened to animal remains and on how the ancient ecosystem of Haţeg Island functioned.
Although bioerosion can provide important information about ancient ecosystems, it is still rarely studied in detail. Precious few previous studies had documented bioerosion from the Haţeg Basin, the principal area for fossils from Haţeg Island, but only from a limited number of bones and localities. We therefore wanted to figure out how common and widespread bioerosion was across the Haţeg Basin, and whether differences in taphonomy, local fauna, and depositional environments influenced its occurrence.
To investigate this, the extensive Upper Cretaceous vertebrate fossil collection of the University of Bucharest was inspected. We discovered numerous new examples of bioerosion on dinosaur and turtle remains, coming from several different localities and geological formations. This allowed us to compare traces from different parts of the Haţeg Basin and from different depositional environments.
What stood out to us most was how widespread these traces turned out to be. We found evidence of bioerosion across a larger geographical and temporal range than previously recognized. Even more striking was the similarity between different environments, including braided and meandering river systems and floodplains, as well as generally well drained and more poorly drained environments.
It appears that despite these environment-related differences, the overall patterns of carcass decomposition were remarkably consistent. This suggests that similar processes may have affected carcasses on Haţeg Island both across different environments and throughout millions of years.
The traces also provide information about the organisms that interacted with the carcasses, and which most often fail to be preserved on their own. We documented several types of bioerosion, including grooves, pits and boreholes. Some of these traces were probably produced by multituberculate mammals, skin beetles or termites, revealing that a range of organisms fed on the carcasses of different dinosaurs and turtles after their death.
These findings provide valuable insights into the functioning of the ecosystem of Haţeg Island, as death and decomposition are important ecological processes. Once an animal died, its carcass became a resource for other organisms. The traces preserved on fossil bones provide a rare record of these interactions, which usually remain cryptic.
With this research, we hope to add another layer to our understanding of ancient Haţeg Island. By looking beyond the spectacular dinosaurs and paying attention to the marks left on their bones, we can develop a more complete picture of how this Late Cretaceous ecosystem functioned.
In the end, our study shows that fossils can represent much more than just the remains of individual animals. A small groove, pit or borehole found on them may record an ecological interaction that took place millions of years ago. These seemingly “boring” traces are therefore anything but boring – they can help us understand not only how animals lived on Haţeg Island, but also what happened after they died.
Original source:
Bettermann A, Csiki-Sava Z, Bocherens H, Augustin FJ (2026) Not only boring issues: bioerosion on bones from the Upper Cretaceous of the Haţeg Basin (Romania) and the implications for carcass decomposition on Haţeg Island. Fossil Record 29(2): 675-705. https://doi.org/10.3897/fr.29.189421
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