Dinosaurs evoke prehistoric times. They were fascinating creatures that ruled the world for over 200 million years. Now, they are represented by their descendants, the birds. Among the non-avian dinosaurs, a small-sized species (ca. 1 m in length) named Berthasaura leopoldinae housed at the Museu Nacional/UFRJ (MN 7821-V) from the Cretaceous period (80–90 million years ago), was discovered in sedimentary rocks in Southern Brazil (Cruzeiro do Oeste municipality, Paraná State). Its description and naming were published in the prestigious journal, Scientific Reports in 2021. [1]
The name represents a triple tribute: to Bertha Lutz (1894–1976), biologist, politician and researcher at the National Museum/UFRJ; to the Empress of Brazil Maria Leopoldina (1797–1826), who lived in Paço de São Cristóvão, where the National Museum is today; and to the samba school Imperatriz Leopoldinense, which presented the theme "Uma Noite Real no Museu Nacional" (A Royal Night at the National Museum) during the carnival (2018). Dated back to about 100 million years ago, the skeleton of Berthasaura is one of the most complete theropod dinosaur skeletons in Brazil. An interesting feature is that Berthasaura had no teeth, meaning it is an edentulous dinosaur, the first from Brazil and South America as well (Fig. 1). Its diet would have been similar to that of living birds and turtles. Its fragile bones are embedded in the rock in which the carcass was found (Fig. 2), preventing the examination of the whole skeleton and its morphological adaptations through the paleontologists.
Fig. 1: Life reconstruction of Berthasaura by the Brazilian paleoartist Maurilio Oliveira.
Fig. 2: Sedimentary rock containing Berthasaura’s skeleton (Fig. 2a) recovered from Cruzeiro do Oeste, Southern Brazil and housed in Museu Nacional (specimen MN 7821-V). A cVRT image rendered with CT images shows the bony details in high quality (Fig. 2b).
However, a CT scan, would help to unveil the anatomy of these bones, especially of those hidden in the sedimentary rock. Thereby, the team of paleontologists from the National Museum contacted Clínica Advance in Rio de Janeiro, where a SIEMENS Healthineers CT scanner SOMATOM go.Up was installed. José Augusto Leite, CEO of the Clínica Advance, and his entire technical team, embraced the challenge and performed a CT scan on the Berthasaura (Fig. 3). The scan parameters were advised by Almir Rodrigues Tavares, a biotechnologist at SIEMENS Healthineers.
CT images were taken to create a digital model and 3D printing of each individual bone using a dedicated postprocessing software in paleontology research. It took almost 6 months to complete the whole process. The high quality of the CT images was essential for the success of this undertaking. Formidable aspects of the bone anatomy of Berthasaura were then revealed. The cervical vertebrae, for example, most of them hidden by the sediments, presented highly pneumatic vertebral centra. Pneumatic foramina covering the lateral side of vertebrae are common in extant birds. The avian pneumaticity improves lung ventilation by providing spaces to the air-filled sacs, as well as the necessary lighter skeletons essential for flight.
The femora, tibiae and fibulae of Berthasaura were disarticulated. We were able to digitally segment these bones and to reconstruct the knee. Digital models (Figure 4) revealed remarkably bowed legs, differing from most other dinosaurs that have erected legs, strictly positioned below the pelvis. Instead, the knees of Bethasaura were more similar to extant ostriches, a feature also found in other dinosaurs. Only the left side of the Berthasaura skeleton was exposed from the rock. It was expected that the CT scan would reveal that the right side of the animal had soaked into the rock matrix. In fact, only the left side of the skeleton was preserved. This was demonstrated in three dimensional lifelike images using cinematic volume rendering technique (cVRT) (Fig. 5). It is likely that the animal died with its right side exposed to the atmosphere, being subjected to rain, wind, radiation and decay for some time, whereas the left side remained buried and protected by the ground.
Fig. 3: Specimen MN 7821-V being scanned at Clínica Advance, Rio de Janeiro.
Fig. 4: Digital 3D model of the right femur of Berthasaura created with CT images.
Fig. 5: cVRT images created using a special preset, show the preserved left side of the skeleton on the surface (Fig. 5a), and no signs of right side of the animal soaked in the rock matrix (Fig. 5b). Each individual bone is clearly seen with its distinct outlines (Fig. 5c).
The CT scan also revealed other bones buried below Berthasaura. These bones are elongated and even more pneumatic than Bertha’s bones. These bones belong to flying reptiles that lived together with dinosaurs, the pterosaurs. Pterosaurs were amazing volant reptiles of the Mesozoic Era with remarkably long 4th digits that supported a skin membrane connected to the body. This membrane, the patagium, acted as a wing, analogous to those seen in extant bats, despite the completely different anatomical construction of the wings. The elongated bones found below the skeleton of Berthasaura likely represent an elongated alar phalanx of a pterosaur related to Caiuajara dobruskii, which is quite common in these layers. These findings confirm that pterosaurs and dinosaurs coexisted in the part of Southern Brazil some 80–90 million years ago.
With the acquired CT images, it was possible to suggest an anatomical description of previously unseen parts of the Berthasaura’s skeleton, enabling a better understanding of its body plan and posture. This new information also contributed to a refinement of the position that Berthasaura occupies in the evolutionary tree of theropod dinosaurs. Additionally, a 3D print of the complete Berthasaura skeleton was made possible, which can be used in exhibitions and educational activities promoted by the Museu Nacional/UFRJ. This project further shows the scientific advances that can be achieved through collaborations between the public and private sectors. [2]