Digital 3D Models of Theropod Dinosaurs for Approaching Body Mass Distribution and Volume
by: Matías Reolid, Francisco J. Cardenal , Jesús Reolid
Summarized by: Makayla Palm
What data were used? This study picked physical dinosaur models from eight different genera, or groups of dinosaur species, to scan and create 3D computer models. These models were used, alongside measurements collected from previous studies on each genus, in order to infer how these dinosaurs may have hunted, moved, and lived. The eight genera in the study were: Coelophysis, Dilophosaurus, Ceratosaurus, Allosaurus, Carnotautus, Baryonyx, Tyrannosaurus, and Giganotosaurus.
Methods: Each model was scanned by a 3D printer in order to make a digital image. After the eight models were scanned, data on body length, collected in other studies, was added to the models. information was used in order to calculate body mass, volume, and skull length. These calculations were then used to make three ratios: skull length/body length, surface area/volume, and length/mass.
Results: The three ratios calculated, skull length/body length, length/mass, and surface area/volume reveal information about these genera that wouldn’t be easily found by just observing the fossils, such as metabolism, eating habits, and overall roles in the ecosystem. The study first looks at the skull length/body length ratio. The larger a skull the dinosaur had, the larger and more expansive their jaws were. This is directly correlated to a higher demand for energy and higher body mass; a large skull was required to take down enough prey to fulfill energy demands. . If a dinosaur had a smaller skull, it was less equipped to take down larger prey, so this limits the kind of prey it had access to. In the case of Coelophysis, the oldest and smallest genus in the study, its skull/body length ratio infers that its small jaws were suited to smaller prey on land, but also small fish. In contrast, the larger theropods, Tyrannosaurus and Giganotosaurus, had the ability to hunt larger prey because of their large skull/body ratio.
The next ratio observed was the length/mass ratio. This ratio considers differences in body plan that the skull/body length ratio does not. For example, Carnotaurus had a short skull in comparison to the other genera in the study, so it is the outlier in the group. However, the length/mass ratio accounts for its build, which recognizes its ability to hunt larger prey. Similarly, Baryonyx has one of the largest skull/body length ratios, but its long snout shape, similar to modern crocodiles, suggests it fed exclusively on fish and other swimming organisms, rather than large land-living prey. This ratio also sheds light on locomotion possibilities for these theropods. Allosaurus, a mid-size theropod, had longer arms than most other large dinosaurs like Tyrannosaurus. This suggests it may have used its arms when taking down large prey unlike its larger theropod comparisons, which are famous for their seemingly useless arms.
The final ratio observed in this study is the surface area/volume ratio. This was used to study the efficiency of the dinosaurs to release excess heat, which has strong implications for metabolism. If an organism can release heat efficiently, it can have a higher metabolism, because high-metabolism organisms need that heat release. Researchers found that the smaller the dinosaur, the higher heat release, therefore a high metabolism and vice versa. This is consistent with the study’s findings on feeding habits. Coelophysis preyed on smaller organisms, but was probably able to do so more frequently. Tyrannosaurus hunted larger prey, but most likely needed to rest in between for significant periods of time because of its slower metabolism.
Why is this study important? This study allows observations of theropod dinosaurs to be made that would not be possible from studying just the bones. This data strengthens previous ideas about theropod behavior, such as larger dinosaurs need more energy and need to hunt larger prey. Therefore, their body structure is reflective of a creature able to take down the kind of prey it needs. This study also provides new information previously not available because of new data about metabolism and body surface area, such as a surface area/volume ratio, which indicates what dinosaur metabolism may have been.
The big picture: This study of 3D scans of theropod dinosaurs infer information from new data by scanning to scale models. These data allow researchers to compare new measurements like surface area and volume to better understand what dinosaur metabolisms and body plans may have been like, which may confirm or reform what we already know about their roles in their respective environments.
Citation: Reolid, Matías, et al. “Digital 3D Models of Theropods for Approaching Body-Mass Distribution and Volume.” Journal of Iberian Geology, vol. 47, no. 4, 2021, pp. 599–624., https://doi.org/10.1007/s41513-021-00172-1.