Vespersaurus paranaensis represents a fascinating recent addition to the dinosaur fossil record. This small theropod offers unique insights into the diversity of prehistoric life, particularly within ancient desert environments. Its discovery provides a clearer picture of how certain dinosaurs adapted to challenging landscapes.
Discovery and Naming
The story of Vespersaurus began with fossil discoveries between 2011 and 2015 near the town of Cruzeiro do Oeste, located in Paraná State, Brazil. These remains were found at the Cemitério dos Pterossauros site, a location also known for yielding numerous pterosaur skeletons. The dark red sandstones of the Rio Paraná Formation, part of the Paraná Basin, preserved these ancient bones.
Following extensive study, Vespersaurus paranaensis was formally described and named in 2019. The generic name, Vespersaurus, translates to “western lizard,” referencing “vesper,” a Latin word for “evening” or “west.” This name alludes to Cruzeiro do Oeste, which means “Western Cross.” The specific name, paranaensis, acknowledges the Paraná State where the fossils were unearthed.
Numerous partial skeletons of this dinosaur were recovered, including the holotype specimen, MPCO.V 0065d. Footprints resembling those of a functionally one-toed theropod were also found near Cianorte as early as the 1970s, later attributed to Vespersaurus or a close relative.
Physical Characteristics and Unique Adaptations
Vespersaurus was a relatively small theropod dinosaur, estimated to have been about 1 to 1.5 meters (3.3 to 4.9 feet) long, with an estimated body mass of around 11.28 kilograms (24.9 pounds). This size makes it comparable to other small theropods like Noasaurus and Masiakasaurus. As a bipedal carnivore, its overall body plan would have been consistent with that of a small predator.
Its most striking feature, however, was its feet. Vespersaurus possessed a functionally monodactyl foot anatomy, meaning it walked primarily on a single, enlarged third digit. The other toes were significantly reduced or vestigial, indicating they played a minimal role in locomotion. This unique foot structure meant the large third digit bore most of the dinosaur’s weight.
While its teeth were not well-suited for struggling or hard prey, suggesting a more generalist or opportunistic feeding strategy, Vespersaurus is classified as a noasaurid theropod, a group within the larger abelisaurid family.
Ancient Habitat and Lifestyle
Vespersaurus roamed the Earth during the Late Cretaceous period, specifically within the Aptian to Campanian stages. The region where its fossils were found, the Rio Paraná Formation in the Paraná Basin, was once part of the vast ancient Botucatu Desert. This environment was characterized by extensive sand dunes, creating a challenging yet unique ecosystem.
The specialized, functionally one-toed foot structure of Vespersaurus was likely an adaptation to this sandy habitat. Such a foot design could have aided in navigating loose, shifting sands, similar to how modern animals adapt to desert environments. This adaptation would have been beneficial for maintaining stability and moving efficiently across dunes.
As a small theropod, Vespersaurus likely occupied a generalist niche within this desert ecosystem. Its diet would have consisted of smaller animals inhabiting the desert, such as lizards, insects, or even early mammals. Its teeth were not designed for handling large, struggling prey or hard food items, suggesting it was an opportunistic feeder rather than a top predator.