Austroraptor (Southern Thief) is a genus of unenlagiine dromaeosaurid that lived in the Allen Formation, Argentina, 72 - 66 million years ago, during the Maastrichtian stage of the Late Cretaceous Period. Exceptionally large for a non-avian paravian dinosaur, it was not only one of the largest known land carnivores of the Allen Formation, but also one of the largest dromaeosaurs discovered thus far.
With a length of 5 - 6 meters (16 - 20 feet),[1][2][PhP 1][DN 1]Austroraptor is one of the largest dromaeosaurids known, with only Utahraptor, Dakotaraptor (controversial due to being a possible chimera, a fossil reconstructed with the remains of more than one animal species),[5] and Achillobator approaching or surpassing it in length. On Prehistoric Planet, it is stated that Austroraptor can weigh over 363 kilograms (800 pounds),[PhP 1] aligning with several estimates that give Austroraptor a probable mass of around 300 - 519 kilograms (661.4 - 1,144.2 pounds),[1][2][3] rivaling or exceeding the mass of the heaviest mainland North American grizzly bears.[6]
It is believed that Austroraptor evolved to be unusually big for a dromaeosaur in order to become a larger, more effective predator, allowing it to tackle larger prey.[3]Austroraptor's large size also allowed it to have an edge over the other carnivores it coexisted with, for niche partitioning would not be able to fully prevent hostile encounters with other hunters which may become potential competitors at certain times like droughts, when fishing opportunities for Austroraptor are even harder to come by, which would in turn likely force it into more direct competition with carnivores more suited to hunting on land (it should be noted however that, although Austroraptor was primarily piscivorous based on its various adaptations, it was still likely a competent land hunter).[7]Austroraptor is, in fact, one of the largest terrestrial predators known from the Allen Formation, rivaling the size of two brachyrostran abelisaurs in the area, the (possibly dubious) carnotaurine Quilmesaurus curriei (which is 5.3 meters or 17 feet and 5 inches long), and its smaller relative Niebla antiqua (which is 4 - 4.5 meters or 13 - 15 feet long).
Fishing Adaptations[]
The Austroraptors get ready to take advantage of the increase in fish during summer
“ And with teeth not unlike those of a crocodile, these dinosaurs are very skilled at catching fish. ”
Austroraptor, much like all unenlagiine dromaeosaurs, has a more gracile build and longer legs compared to more recognizable Laurasian eudromaeosaurians like Dromaeosaurus. Its arms, being approximately 46% the length of its femur,[1] are proportionally shorter than those of other dromaeosaurs (indicating that it did not use its arms to handle prey),[7] as well as reduced sickle claws on its feet (it should be noted, however, that the sickle claws were originally meant to be more strongly curved and pointed as indicated by preserved keratin sheaths, but filming constraints unfortunately prevented changes from being made to the animal's digital model).[DN 2]
Most notable of these adaptations are found in the dromaeosaur's skull, which is around 80 centimeters (2 feet, 7 inches) in length.[1] Its snout is low and narrow, filled with teeth that are long, gracile, conical, smooth, almost appear straight when the jaws are closed, and coated with fluted enamel surfaces, resembling the dentition of spinosaurid theropods.[1] While these are ideal for gripping prey, the lack of denticles and serrations render the teeth unable to tear off flesh, meaning that, for prey that it does not intend to swallow whole, Austroraptor must rely on other means to rip its food into smaller pieces.[7] This is demonstrated on the show, where the unenlagiines are seen either swallowing fish whole, or pinning their catch to the ground with one foot so they can pull and tear off the lower half of the fish, leaving the less-desirable upper half behind, unintentionally providing scavenging opportunities for younger, less-experienced individuals.
Overall, these characteristics suggest that Austroraptor lived a primarily piscivorous lifestyle like spinosaurids, fishing in a manner similar to that of herons.[DN 1]
Prehistoric Planet's Portrayal[]
“ For those not yet in their prime, it's a challenging time of year. This young male, still in his juvenile colors, has little hope of securing a place to fish. ”
On Prehistoric Planet, the Austroraptors are designed using a skeletal base made by Dr. Scott Hartman, with their large pygostyles (tail fans) based on the art of David Krentz. Given the size of these tail fans, a lot of considerations were made regarding how the tails of the Austroraptors interacted with parts of the environment they were filmed in (Great Otway National Park in Victoria, Australia), like tree ferns and other plants.[DN 3][PhP 2] Other imperfections in the computer-generated imagery (CGI) of Austroraptor may possibly be attributed to the difficulty of applying the correct shading and highlights in the tree-dense environment of the chosen filming location.
The Austroraptors are depicted with a color scheme of brown and yellowish-white tones, with the brown parts likely inspired by the fact that their lifestyle is comparable to those of grizzly bears. The upper sides of their bodies, the area around their eyes, and their snouts are brown, while their undersides, eyebrows, the rest of their faces, the edges of the wing-like feathers on their short arms, and the edges of their pygostyles are yellowish-white. Interestingly, their eyes are portrayed as having a human-like appearance, with large pupils. Some individuals, particularly those with a deeper shade of brown and slightly more robust builds, also have red patches below and behind their eyes. Dr. Darren Naish, lead consultant of Prehistoric Planet, brings up that this is not a sign of sexual dimorphism, but a trait that is more likely to be seen on some (but not all) adults.[DN 4][DN 5] Subadults appear to still have their juvenile plumage, which comes in a lighter shade of brown with some yellowish-white specks.
Paleoecology[]
Paleoenvironment[]
A swamp forest in the Allen Formation
“ Here in the wetlands of South America, long summer days are fueling a greater feast. These swamps are teeming with animals of all kinds... and hunters are gathering. ”
Austroraptor is known from the Allen Formation in Argentina, South America, a semi-arid environment heavily eroded by winds (partly due to large storms in the region), with landscapes that range from estuaries and tidal flats by the coastal regions to lakes and rivers further inland, providing many fishing opportunities for Austroraptor. On Prehistoric Planet, Austroraptors are shown fishing on the banks of a river running through a lush forest, by a shallow crossing where fish can be caught more easily.[8]
Paleofauna[]
A selection of dinosaurs that lived in the Allen Formation (Austroraptor on the right side, in blue)
Austroraptor, along with two abelisaurs, namely, the similarly-sized Quilmesaurus curriei and its smaller relative Niebla antiqua, are among the largest land carnivores discovered in the Allen Formation. Living alongside these three predatory theropods is the azhdarchid pterosaur Aerotitan sudamericanus, which had a 5-meter (16-foot) wingspan,[9] roughly around the same size as Phosphatodraco. The Allen Formation is also home to five titanosaurs of varying sizes (six if Pellegrinisaurus is confirmed to live in the area), three hadrosaurs (with a fourth potentially dubious one, Willinakaqe), the alvarezsauroid Bonapartenykus, the dog-sized Patagopelta (possibly a parankylosaurian like Antarctopelta),[10][11] at least two ornithuran birds, three snakes, six mammals, several frogs (though only one, Kuruleufenia xenopoides, currently has a name), indeterminate side-necked turtles,[12] and the rhynchocephalian Lamarquesaurus.
“ A ferocious, three foot-long garfish... lunch, for a giant Austroraptor. ”
In the nearby waters of the formation is the plesiosaur Kawanectes (which may or may not be the unidentified elasmosaur species in the sixth and final segment of Freshwater) as well as several fish, with specimen MACN-PV RN 1071 (six incomplete vertebral centra) in Bajo de Santa Rosa determined to be the remains of a gar,[12] much like the ones the Austroraptors are depicted catching on Prehistoric Planet.
Hunting Tactics, Feeding Preferences, and Competitive Behavior[]
Most of Austroraptor's behavior on Prehistoric Planet is based on the observed habits of modern-day herons, bears, crocodiles, and eagles.[DN 1] As with most fishing animals, they are shown relying on ambush, patiently waiting for something to come close, careful not to arouse suspicion or disturb their targets, only striking in sudden bursts once prey is within reach.
Two Austroraptors fighting over their preferred fishing spot
“ For most of the year, they're solitary hunters. But, as the number of fish increases during summer, so does the number of Austroraptors. The biggest try to keep the best fishing spots for themselves. They won't tolerate rivals. ”
While Austroraptors are usually solitary hunters, they take advantage of the increase in fish numbers during summer and congregate around bodies of water to capitalize on this abundant food supply. However, not all fishing spots are equally fruitful, thus making some certain places by the river more advantageous than others. Due to the importance of securing the most ideal fishing spots, the Austroraptors interact very aggressively with each other when it comes to defending their chosen position, attempting to claim the fishing spot of another, or even warding scavengers away from food that they have discarded.
Austroraptor finishes gulping down fish
“ With so much food around, the adults are very wasteful feeders. They often eat only the choicest parts of the fish. And for the youngster, any leftovers will do very nicely... but it's risky. To succeed, he will have to be sneaky. ”
The adult Austroraptors are shown indulging in wasteful eating habits when fish are abundant. They tend to consume only the most desirable portions of the fish, often tearing off and quickly devouring the back half while leaving the front half behind. This behavior results in a significant amount of leftover food on the ground. Young Austroraptors, motivated by the need for sustenance, scavenge these remnants as it presents an opportunity to obtain a meal, even if what they obtain is nothing more but a few scraps. However, they are opportunistic and would take advantage of any situation (e.g. two Austroraptors fighting over an ideal fishing spot) that allows them to acquire more than just leftovers.
While Austroraptor's various fishing adaptations suggest that it was primarily piscivorous, it was still likely able to hunt land-based prey competently, as one study suggests that unenlagiines were better at chasing prey than other dromaeosaurs due to their more gracile physique. Although Austroraptor's very short arms and hands are not very effective in grabbing prey, the same conical shape that allows its teeth to catch and grip slippery fish also make its teeth more resistant to stress, making them effective tools for seizing and attacking larger, struggling prey on land.[7]
Setting Allen Formation, Neuquén, Río Negro, and La Pampa Provinces, Argentina[PhP 2]
Filming Location Great Otway National Park, Victoria, Australia[PhP 2]
In the second segment of Swamps, an Austroraptor is seen snatching a 1-meter (3-foot) garfish out of the river, stomping it down on the ground to rip off and devour only the lower half of the fish. Since it is summer, when many fish are present, a large number of Austroraptors are found gathering all over a shallow river, with some fishing by the banks and others fishing in the middle of the river. One Austroraptor senses a larger, more robust individual with red eye patches sneaking up behind it, intent on taking its fishing spot, and turns around to snarl back at the trespasser. The two individuals hiss and growl at each other before the owner of the fishing spot, being slimmer, is forced to back away.
For the younger ones who have not established their fishing spot nor have enough experience to find a good place to fish, this is a challenging time of year. A young adult male, still in his juvenile colors, attempts to fish from atop a log, but this is suspended too high over the river. Upon seeing the other Austroraptors rip off only the lower half of their catch, the youngster tries to sneak in and grab the discarded upper half of the fish while one of the adults is busy catching and feeding on another fish. Unfortunately, his attempt was not stealthy enough, and the adult notices him and attacks him, forcing the young male to retreat back behind a tree.
“ Bruised and empty handed. But with the adults still feasting around him, there might be another opportunity. Two adults, fighting over the best fishing spot. Time for the youngster to make a move... and time to leave. ”
The youngster then sees two adults fighting over a fishing spot, and, as one adult chases the other into the forest, he sneaks in to steal the latest catch of one of them, a fully-intact garfish lying on the ground. He grabs it and runs off just as the owner of the fishing spot rushes back in to attack him, getting away in a nick of time as the adult slips on the ground.
“ Success, and more than just scraps. A lesson learnt. And when the good conditions return next year, perhaps he'll be able to challenge for a fishing spot of his own. ”
Needing all the food he can get, the young Austroraptor looks around warily one last time before swallowing the entire fish. While he resorts to opportunistic thievery now, perhaps, when fishing season returns next year, he can properly challenge one of the adults for a good fishing spot of his own.
Trivia[]
The second segment of Swamps is the seventh segment to feature intraspecific combat, and is the fourth one to result in the older individual emerging triumphant (assuming that those with the red patches behind their eyes are of greater age).
