A team of paleontologists from the Netherlands, Canada and the United Kingdom has examined the wear marks on the teeth of several species of mosasaurs, large aquatic reptiles from the Late Cretaceous epoch that filled a range of ecological niches within marine ecosystems.
Life reconstruction of Gavialimimus almaghribensis hunting a school of teleosts. Image credit: Tatsuya Shinmura.
Mosasaurs were a group of large predatory marine reptiles that inhabited all of the world’s oceans during the Late Cretaceous epoch, between 90 and 66 million years ago.
These creatures went extinct during the end-Cretaceous extinction event which killed non-avian dinosaurs and 75% of life on the planet.
Although their relationship to other reptiles is not completely certain, mosasaurs appear to be closely related to a group known as monitor lizards.
Most mosasaurs had two bladelike, serrated ridges on the front and back of the tooth to help cut prey.
“Mosasaurid reptiles were large, predominantly marine squamates, and one of only a few groups of squamates that became fully aquatic,” said Dr. Femke Holwerda, a paleontologist at Utrecht University and the Royal Tyrrell Museum of Palaeontology.
“During the final c. 30 million years of the Cretaceous period, mosasaurs rapidly evolved a wide array of morphologies, and occupied a range of ecological niches in marine ecosystems around the globe.”
“By the end of the Cretaceous they were firmly established as a group, often hypothesized as apex predators in most ecosystems they inhabited.”
Holwerda et al. apply three-dimensional dental microwear texture analysis to provide quantitative dietary constraints for type-Maastrichtian mosasaurs, and to assess levels of niche partitioning between species. Image credit: Holwerda et al., doi: 10.1038/s41598-023-42369-7.
In their research, Dr. Holwerda and colleagues focused on mosasaur species that lived in what is now the southeastern part of the Netherlands and northeastern Belgium during the Maastrichtian age of the Cretaceous period, between 68 and 66 million years ago.
Currently, five such species are recognized: the large (over 10 m long) Mosasaurus hoffmanni and Prognathodon saturator; the intermediately-sized Prognathodon cf. sectorius and Plioplatecarpus marshi; and the diminutive (3 m long) Carinodens belgicus.
“We were curious whether different species of mosasaurs around Maastricht were really getting in each other’s way in their choice of food, or whether this was not so much of a problem,” Dr. Holwerda explained.
“In the absence of data on stomach contents of the Maastricht mosasaurs, we therefore looked at minute scratches on their teeth.”
“We made casts of the mosasaur teeth in silicone rubber and put them in the 3D scanner,” said Dr. Anne Schulp, an paleontologist at Utrecht University, the Natuurhistorisch Museum Maastricht and the Naturalis Biodiversity Center.
“This technique had already been used in dinosaurs, but we were the first to look at the teeth of mosasaurs in the same way.”
The team’s results indicate that these mosasaurs did not exhibit neatly defined diets or strict dietary partitioning.
“Instead, we identified three broad groups: (i) mosasaurs Carinodens belgicus and Plioplatecarpus marshi plotting in the space of modern reptiles that are predominantly piscivorous and/or consume harder invertebrate prey, (ii) Prognathodon saturator and Prognathodon sectorius overlapping with extant reptiles that consume larger amounts of softer invertebrate prey items, and (iii) Mosasaurus hoffmanni spanning a larger plot area in terms of dietary constraints.”
“With this research, some missing pieces of the puzzle from the long-gone latest Cretaceous world are found,” Dr. Schulp said.
“We wish to understand diversity better. And that is made easier for us because the animals studied all come from the same rocks, and therefore the same period.”
“So instead of describing just one species, we look at the ecosystem as a whole.”
The findings were published in the journal Scientific Reports.
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F.M. Holwerda et al. 2023. Three-dimensional dental microwear in type-Maastrichtian mosasaur teeth (Reptilia, Squamata). Sci Rep 13, 18720; doi: 10.1038/s41598-023-42369-7
