A multi-method approach to deciphering the paleobiology of a mosasaur from South Africa
by: Megan R. Woolley, Michael W. Caldwell, Kevin Rey, Romain Amiot & Anusuya Chinsamy
Summarized by: Eli Steingardt is a Philosophy, Politics, and Law major at Binghamton University. Currently, he is a sophomore. He plans to attend law school and advocate in courts on behalf of museums in legal disputes over samples and specimens. In his free time, he plays electric guitar and tutors at Binghamton’s writing center.
What data were used? This study was focused on a tooth discovered as part of a jawbone in South Africa that scientists suspected to have come from a mosasaur called Prognathodon. Mosasaurs were large, aquatic lizards that lived in the Late Cretaceous, between around 95 million years ago and 65 million years ago, when they died along with the non-bird dinosaurs in a mass extinction event caused by an asteroid known as the Cretaceous-Paleogene event. Since mosasaurs lived in marine environments millions of years ago, many different variables–such as depth of the water, the temperature, salt content of the water, and proximity to landmasses–make studying these creatures complex.
What was the hypothesis being tested? Prior to this study, there was a lack of knowledge on the life habits of mosasaurs. The researchers cast a broad net when thinking of hypotheses to test, using many different exploratory tests to try to find something new about the lifestyle and paleobiology of the newly discovered fossil that they suspected belonged to the taxon Prognathodon. Paleobiology is simply anything relating to the study of extinct animals that are in the fossil record. This includes gaining insight into the animals’ growth, ecology, their closest relatives, and painting a better picture of a world that no longer exists.Some data involving the chemical record of other fossil organisms was also obtained to compare their results to.
Methods: Scientists subjected the tooth fragment to some non-destructive analyses in order to learn more about it, like micro-CT scanning in order to make a 3-D image of the tooth and its internal structures. They also performed some destructive analyses, like putting a broken-off piece of the tooth under a Scanning Electron Microscope (SEM). They coated the piece in gold so it would show up clearer under the SEM, then scanned a beam of electrons at it in order to build an image of the interactions between the electrons and the atoms of the sample. The scientists then shot X-rays at the piece in a process called Energy-Dispersive Spectroscopy in order to find out what elements the piece was composed of. The scientists went back to the original tooth, taking small samples and analyzing it for oxygen isotopes, to try to find out how much oxygen was in the tooth, which would tell them about the environment that the animal lived in while it was still alive. Finally, the scientists coated the tooth in resin, cut it into thin slices, and looked at it under a microscope in a process called a histology to study the preserved internal structure of the tooth .
Results: The micro-CT scan showed that the tooth had no root but still had some preserved tissue attachments, which suggests that the tooth had been partially shed from the jaw before death but was still slightly attached by gum tissue when it was buried Under the microscope (figure 4), scientists found that the tooth was poorly preserved, with small scratches and lumps on the tooth. This indicated that the Prognathodon probably preyed on hard-shelled animals, like turtles, whose shells would have scratched the teeth They also noted small spherical structures within the tooth, which researchers described as being clumps of calcium carbonate that typically form in warm, shallow water called ooids (which comes from the Greek word for egg or egg-shaped). The Energy-Dispersive Spectroscopy also indicated the presence of calcium carbonate, supporting the hypothesis that these structures are, in fact, ooids. For the oxygen isotope analysis, the scientists were able to find out the surface temperature of the water that Prognathodon swam in because shifts in percentages of oxygen isotopes tell us indirectly about past water temperature. From there, they were able to determine the amount of oxygen isotopes that the Prognathodon itself took in and therefore could infer its body temperature. They compared the data they collected from the Prognathodon to a shark that lived around the same time, Squalicorax. Since the two animals swam in the same ocean, they could be valid subjects for comparison. The scientists were able to determine that the Prognathodon had a body temperature that was warmer than Squalicorax. Since the Prognathodon was warmer than the shark, it was also probably warmer than the ocean around it.
Why was this study important? Although only one tooth was analyzed, this study remains important. The scientists were able to find out the internal structures of the Prognathodon tooth and hypothesize about the diet (like how it could have eaten turtles) and the body temperature of the animal in life.
Broader implications of this study: This study establishes that a number of tests can be used to determine the diet and body temperature of ancient animals by just using their teeth. Even without the full fossil, teeth can inform us of many different things about the life of the animal. In the future, even partial samples can be used to analyze aspects of ancient animals’ paleobiology, helping to form a more complete picture of their lives.
Citation: Megan R. Woolley, Michael W. Caldwell, Kevin Rey, Romain Amiot & Anusuya Chinsamy (2024) A multi-method approach to deciphering the paleobiology of a mosasaur from South Africa, Journal of Vertebrate Paleontology, 44:6, e2486069, DOI: 10.1080/02724634.2025.2486069