Aucasaurus is a genus of medium-sized abelisaurid theropod dinosaur in the tribe Carnotaurini. Its scientific name means “Auca Mahuevo reptile” after the location in Neuquen Province, Argentina where its remains have been found. There is only one known species, A. garridoi; the specific epithet honors Alberto Garrido, who discovered the fossilized remains in 1999. This dinosaur lived 85 to 80 million years ago in South America, during the Cretaceous period. It is a close relative of Carnotaurus, but is considered an even more derived species of abelisaur.
Remains were first found in March of 1999 by a joint expedition between the Museo Municipal Carmen Funes and the Natural History Museum of Los Angeles County. A nearly-complete fossil skeleton was found at the Auca Mahuevo location, which is known for abundant fossils including sauropod eggs. Only part of the tail is missing; it is complete to the thirteenth caudal vertebra. The fossil was similar to Carnotaurus but about thirty percent smaller. The skull was crushed, leading to speculation about how the animal had died.
In June of 2002, paleontologist Rodolfo A. Coria and associates Luis M. Chiappe and Lowell Dingus named this dinosaur Aucasaurus garridoi, having found it different enough from Carnotaurus to warrant its own classification. It is the most complete known abelisaurid, and has therefore been instrumental in the modern scientific understanding of this family’s evolution.
In 2010, Gregory S. Paul reclassified it as a species of Abelisaurus, but no other prominent scientific authorities have agreed with this.
While smaller than its close relative Carnotaurus by about 30%, this animal is still a medium-sized theropod at 20 feet (6.1 meters) in length and has been estimated to weigh up to 700 kilograms. It has many skeletal similarities to its larger relative, but does not possess the distinctive horns that define Carnotaurus. Instead, it has swells on its frontal bones, one ridge above each eye. The snout is also longer and not as deep, causing the fenestrae in its skull to be similarly longer in shape. It did, though, have a shorter and deeper-snouted skull than most theropods. Like other abelisaurs, its teeth are sharp and slender. While no live specimens have been observed, it probably would have round, birdlike pupils similar to those of InGen’s Carnotaurus.
Abelisaurs in general, and carnotaurs in particular, are believed to have been built for speed (though not necessarily for agility). Aucasaurus was no exception, with powerful hind limbs and tail permitting it to run at high speeds. The legs ended with three-toed feet, a fourth toe existing as a vestigial hallux. The three functional toes ended in talons that would assist it in gripping the ground while running. Its arms were not nearly so strong; they were like those of Carnotaurus, to the point of barely possessing fingers at all. The arm is longer in proportion to the body due to the smaller size of Aucasaurus. The hand has four metacarpals, but only two of these ended in fingers; they may not have had claws.
The braincase is similar to that of Majungasaurus, another related genus. It does have a larger floccular process, suggesting it had a wider range of head movements. The ears are also similar to those of Majungasaurus.
Coloration in Aucasaurus is unknown, since no specimens are known to have been created. Its skin is known from partial fossilized remains, and appears similar to Carnotaurus: most of the body seems to have been covered in non-overlapping polygonal scales. The coloration of its skin is not known.
The life stages of Aucasaurus have not been observed. The closely-related Carnotaurus reaches adulthood in, at most, nine or ten years.
Due to a lack of specimens, sexual dimorphism is unidentified in Aucasaurus.
The paleoenvironment in which Aucasaurus lived is believed to have been a warm environment consisting of rivers, lakes, and floodplains. This suggests that it prefers to live near water. The area where the Auca Mahuevo location is found, the Anacleto Formation, is known for abundant titanosaur eggs; this suggests it was a fertile breeding ground, and probably was home to large amounts of plant life.
There is currently no evidence that Aucasaurus was ever bred on Isla Nublar, though its DNA had been recovered as of 2015.
There is no evidence that Aucasaurus was ever bred on Isla Sorna.
Aucasaurus is currently believed to still be extinct, having not been cloned at any point.
Behavior and Ecology
Its close relative, Carnotaurus, is cathermal and active mainly during daylight hours. Aucasaurus may similarly be active periodically throughout the day.
Diet and Feeding Behavior
Aucasaurus was carnivorous, feeding upon other animals. Like Carnotaurus, it was a speedy animal and could have ambushed or pursued prey items. It may have attacked using its jaws to bite prey, or alternatively by ramming or kicking to knock the victim over before moving in for the kill. These behaviors have been observed in Carnotaurus, which is also a known opportunist and will take any advantage it sees when hunting for food.
Its relative Carnotaurus maintains fairly small social groups and is able to be solitary with no real problems as a result. While Aucasaurus lacks the horns that its relative uses for display, it does still possess ridges above its eyes that could be used as display structures.
Like all dinosaurs, Aucasaurus laid eggs to reproduce. The eggs of theropods are similar to those of modern birds, being ovoid in shape to prevent them from rolling away from where they are laid. Eggs belonging to medium-sized dinosaurs typically have incubation periods of at least three months, with larger species having longer duration.
Theropods, and other dinosaurs, typically mate using a cloaca that houses their reproductive organs. Courtship behaviors are only speculative, but the frontal ridges may have been display structures.
While the vocalizations and body language of Aucasaurus cannot be observed due to a lack of specimens, they may be similar to those of Carnotaurus. This carnotaur uses low-pitched roars and howls to assert dominance and warn away rivals, as well as classical jaw-gaping displays with its head lowered similar to a modern bird’s warning posture.
Since Aucasaurus has not been recreated, its ecology is only known from fossils. Its remains were found in an area that is known for titanosaur eggs, suggesting that it could be a predator to hatchling dinosaurs. At least four genera of titanosaurs and one small ornithopod lived in its environment, as well as the theropod Abelisaurus and various other reptiles. It was not an especially larger predator, but still would have shaped its local environment by preying on other animals.
Relationship to Humans
Along with presenting an excellent specimen for abelisaurid research, Aucasaurus has gotten some amount of attention in the Genetic Age. Its genome was reconstructed using ancient DNA found from fossils such as amber by geneticists working under Dr. Henry Wu sometime before 2015. It was not exhibited in Jurassic World, but plans may have been in place for it; the Samsung Innovation Center‘s holoscape interaction included a hologram of Aucasaurus that could be put on display by visitors. The hologram would look, move, and vocalize like the real animal.
Behind the Scenes
The only appearance of Aucasaurus in the films is a brief glimpse of its name and outline on the holoscape featured in Jurassic World‘s online promotional websites. Most fan sites, such as the Jurassic Park Wiki, incorrectly state that it displays the more famous Allosaurus, especially after this dinosaur appeared in Jurassic World: Fallen Kingdom. However, all of the holoscape icons are listed alphabetically, and this icon would be in the wrong place to be Allosaurus. While the text is slightly blurred, a close inspection does reveal it to read “Aucasaurus” in all-caps, and the outline of the dinosaur image is a much closer match for this abelisaurid than an allosaur.