Aucasaurus is a genus of medium-sized theropod dinosaur that lived during the Late Cretaceous period, around 85-70 million years ago. It was first discovered in Argentina and is known for its unique features, such as its extremely reduced arms and almost total lack of fingers. Its skeleton is the most complete abelisaurid skeleton discovered so far, making it an important specimen for paleontologists.
Aucasaurus is significant because it provides valuable insights into the evolution of theropod dinosaurs. It was smaller than its relative Carnotaurus, but more derived in some ways. It was a bipedal predator, meaning that it walked on two legs and had large, sharp claws on its forelimbs for hunting and capturing prey. It is estimated to have measured between 5 and 6 meters in length and weighed between 500 and 600 kilograms. Despite not being very well-known, Aucasaurus is quite famous in the paleontology universe because of its unique features and the completeness of its skeleton.
Discovery and Naming
First Identification
Aucasaurus was first identified in 1999 by a team of scientists led by Jorge Calvo and Bernardo Gonzalez Riga. The fossils were discovered in the Auca Mahuevo site in Patagonia, Argentina. The team initially believed the fossils to belong to a new species of Carnotaurus, another theropod dinosaur. However, upon further examination, they realized that the fossils were distinct enough to warrant their own genus and species.
Etymology
The name Aucasaurus is derived from the Mapuche word “auca,” which means “ancient” or “old,” and the Greek word “sauros,” which means “lizard.” The species name, galtieri, is in honor of Eduardo Galtieri, the former president of Argentina who was in power during the time of the fossils’ discovery. The name is fitting, as Aucasaurus lived during the Late Cretaceous period, approximately 80 million years ago.
Classification
Taxonomic Position
Aucasaurus is a genus of theropod dinosaur that lived during the Late Cretaceous period, approximately 80 million years ago. It belongs to the family Abelisauridae, which is a group of carnivorous dinosaurs that lived in the southern hemisphere during the Late Cretaceous period. The genus contains a single species, Aucasaurus galtieri, which was first discovered in the Rio Limay Formation of Patagonia, Argentina.
Phylogenetic Relationships
Phylogenetic analysis has placed Aucasaurus within the clade Carnotaurini, which also includes the genera Carnotaurus and Majungasaurus. It is believed that Aucasaurus is closely related to Carnotaurus, which is another abelisaurid dinosaur from Argentina. Aucasaurus is also considered to be more derived than Carnotaurus in some ways, such as its extremely reduced arms and almost total lack of fingers.
Overall, Aucasaurus is an important dinosaur that provides valuable insights into the evolutionary history of theropod dinosaurs during the Late Cretaceous period.
Description
Physical Characteristics
Aucasaurus is a genus of medium-sized abelisaurid theropod dinosaur from Argentina that lived during the Late Cretaceous period. It was smaller than the related Carnotaurus, although more derived in some ways, such as its extremely reduced arms and almost total lack of fingers. The type skeleton is complete to the thirteenth caudal vertebra, and so is relatively well-preserved.
Aucasaurus had a large skull with robust jaws and serrated teeth, which it used to tear apart its prey. Its eyes were positioned on the side of its head, giving it good peripheral vision. Its body was covered in scales and it had short, powerful legs that were well-suited for running and hunting.
Size Estimations
Based on the fossils that have been found, Aucasaurus was estimated to be around 5 meters (16 feet) long and weigh approximately 1,500 pounds. This makes it smaller than other abelisaurids and theropods, such as its close relative Carnotaurus, which grew to be about 30 feet long and nearly 3 tons in weight.
Despite its smaller size, Aucasaurus was still a formidable predator and would have been a top predator in its environment. Its speed and agility, combined with its powerful jaws and sharp teeth, would have made it a deadly hunter capable of taking down prey much larger than itself.
Paleobiology
Diet and Feeding Habits
Aucasaurus was a medium-sized abelisaurid theropod dinosaur that lived during the Late Cretaceous period. Based on its skull morphology, it is believed that Aucasaurus was a carnivorous predator. Its teeth were serrated and blade-like, which suggests that it was well-adapted for slicing through flesh. It is likely that Aucasaurus hunted small to medium-sized prey, such as other dinosaurs and mammals.
Locomotion
Aucasaurus had a robust body and powerful legs, which suggests that it was a fast runner. Its hindlimbs were longer than its forelimbs, which is a common characteristic of theropod dinosaurs. Aucasaurus also had a stiff tail, which would have helped it maintain balance while running. It is believed that Aucasaurus was a bipedal dinosaur, meaning that it walked on two legs.
Social Behavior
There is currently no evidence to suggest that Aucasaurus lived in social groups or herds. However, it is possible that juvenile Aucasaurus may have lived in groups for protection. Like other theropod dinosaurs, Aucasaurus likely engaged in intraspecific competition for resources and mates. It is also possible that Aucasaurus engaged in cannibalism, as some other theropod dinosaurs have been known to do.
Paleoecology
Habitat
Aucasaurus roamed the plains of South America during the Late Cretaceous period, specifically during the Santonian to Campanian stage of the Anacleto Formation. The environment during this period was warm and humid, with a mix of forests, rivers, and lagoons. The abundance of water sources and vegetation made it an ideal habitat for many species of dinosaurs, including Aucasaurus.
Contemporaneous Species
During the Late Cretaceous period, Aucasaurus coexisted with a diverse range of species, including other theropod dinosaurs such as Carnotaurus, as well as sauropods, ornithopods, and ankylosaurs. These species likely occupied different ecological niches, with Aucasaurus being a mid-sized predator that likely preyed on smaller herbivorous dinosaurs.
Overall, the paleoecology of Aucasaurus suggests that it was well adapted to its environment and played an important role in the Late Cretaceous ecosystem of South America.
Fossil Record
Fossil Sites
Aucasaurus fossils have only been found in Patagonia, Argentina, specifically in the Rio Limay and Bajo de la Carpa Formations. These formations date back to the Late Cretaceous period, approximately 84-71 million years ago. The fossils were first discovered in 1999 and 2000 by a team of paleontologists led by Luis Chiappe and Jorge Calvo.
Specimen Preservation
The Aucasaurus fossils found in Patagonia are generally well-preserved, with some specimens being almost complete. The fossils include several skulls, vertebrae, ribs, limb bones, and even some skin impressions. The preservation of the fossils has allowed scientists to study the anatomy and behavior of this dinosaur in greater detail.
One notable specimen is the almost complete skeleton of Aucasaurus galtieri, which was discovered in the Rio Limay Formation. The skeleton is missing only a few bones and has provided scientists with valuable information about the anatomy and behavior of this dinosaur. The specimen is currently housed at the Natural History Museum of Los Angeles County.
Overall, the fossil record of Aucasaurus is limited to a few sites in Patagonia, but the well-preserved specimens have provided valuable insights into the anatomy and behavior of this dinosaur.