Introduction:
Aucasaurus is one of the many genus of, you have guessed it, Abelisauridae. There is so many Abelisaurs that I forgot to count how many there are but surprisingly enough, this dinosaur is the most complete skeleton of any Abelisaurs! While paleontologists did not find many more skeletons of this dinosaur but having the most complete skeleton of any Abelisaurs is more than what any paleontologist can ask and thus making it very well studied dinosaur as well. Let’s not dilly-dally anymore and get to know more about this wonderful dinosaur!!
Discovery:
Aucasaurus was first discovered in 1999, from the Rio Colorado Subgroup, a Late Cretaceous fossil bed groups which consists of Anacleto Auca Mahuevo Formation & Neuquén Basin of Argentina. It was discovered in 1999 but it was not named until 2002 when three paleontologists, Rodolfo A. Coria, Luis M. Chiappe, & Lowell Dingus named it Aucasaurus garridoi.
Aucasaurus meaning ‘Auca Mahuevo lizard‘ after the location in Neuquén Province and garridoi meaning honors Alberto Garrido, who discovered the fossilized remains in 1999. Most interesting quality of the skeleton find we have is that the skull shows damages, not due to fossilization or anything like that but more of a fight with another of it’s own damage. This goes to show that intra-species dinosaur fights did happen and this fella died shortly after the fight. This Aucasaurus may have lost the fight but made history with the completeness of it’s fossil find or else we would not have known so much about this dinosaur!
Biology:
Aucasaurus was very much a medium-sized Abelisaur theropod of all time. I feel like this size range feels the most medium size for a dinosaur. The Aucasaurus measured 5.5 – 6.2m (18 – 20 feet) in length, around 2m (6.5 feet) in height and weighing in around 700 kg. As it is an Abelisauridae, it had to be quite lightweight for it to gain running speeds when hunting as it would have been a pursuit predator with the slender build it has.
As you already know, Abelisauridaes appeared during the Late Cretaceous Period, around 85 – 80 million years ago. And the classification of it in the Abelisaur tree is a lot more complex. It is part of the Abelisauridae family and then it goes down to the Clade, Brachyrostra, which has even has a subfamily called Furileusauria and then another step down to the Tribe called Carnotaurini.
You probably already know who is in the Carnotaurini tribe, I will give you second! You guessed it right, it is Carnotaurus. I hope it was not a hard question. I already have a blog post talking in depth about Carnotaurus and now an Aucasaurus too. Now only one member left from the Carnotaurini tribe, do you wanna guess? It is yours truly, Abelisaurus. Of all the genera in the Abelisauridae family, Abelisaurus falls in the tribe which named after another genus. Now, I gotta make a post about Abelisaurus to complete the tribe!!
I also made another post about another fellow Brachyrostra genus, Ekrixinatosaurus. I also have more posts about other Abelisaur genera like the Majungasaurus, and I do have more posts planned for the Abelisaur family. Do let me know in the comments if I should create a compilation post with all the Abelisauridaes posts I have made.
Unlike most Abelisauridaes, Aucasaurus did not have any sort of horns but rather had a pair of low ridges over the eyes. The skull was also not short or deep-snouted like the most Abelisauridaes like Carnotaurus but rather looking more like a blunt Allosaurus kind. And here is the most weirdest part of all, the hands. The Aucasaurus had 4 beginning finger bones, metacarpals, but the first and the fourth did not have any full fingers, while the second and the third had super short fingers and no claws. Very weird set of hands when compared with other Abelisauridae.
Aucasaurus also had a braincase scan which showed that the brain of Aucasaurus was similar to Majungasaurus and Indosaurus but it had a part of the brain, flocculus, which controls the movement of the body, was much more larger like that of Abelisaurus, which means that it could have had wider range of movements for the head. This goes to show an evidence of evolution.
Not only, Majungasaurus and Indosaurus belonging in the same family tree as well as appearing later in time, it showed that the dinosaur did not spend anymore evolution points for wider range of head movements as they probably did not deem it necessary. Also, they are quite further apart and so they evolved differently than other Abelisaurs.
Aucasaurus does not stop giving because it was the earliest known occurrence of a congenital disorder or birth defect in non-avian theropods. We imagine dinosaurs being these indestructible, perfect and supreme life form, always in the peak form of health but dinosaurs could have had sicknesses, birth defects, cancer and so much more other health problems that we suffer with.
The way we know of its pathology is because 5th and 6th tail vertebrae bone provide evidence of failed segmentation which caused them the two bones which were meant to be separate to be fused and connected into one. And this evidence discovered recently in 2024 and so you never know what you can find even after you have researched it.
The defect may have not caused any problem in it’s day to day life because it did live long enough to become an adult but it maybe caused some inconvenience when making sharp turns when it was hunting prey. But this problem goes to show that dinosaurs are animals like the modern wildlife and not some monsters people think they are.
In 2010, good ol’ paleontologist, Gregory S. Paul thought Aucasaurus was another species of Abelisaurus and not an unique genus of it’s own but later paleontologists discussions made it clear that Aucasaurus is a different species/genus and not an Abelisaurus.
Media:
Aucasaurus, while being thoroughly researched and studied, it does not have much of a presence in the media sphere other than just one appearance in the documentary, Dinosaur Planet. I remember my first introduction to this dinosaur was through this documentary and I found it to be weird and different and my appreciation for the variations of dinosaurs grew and that it was just not only 1 or 2 basic kind of dinosaurs.
Weirdly enough, the documentary called it an Aucasaur, and not Aucasaurus which is odd because that naming is mainly used for family name like saying Tyrannosaur for Tyrannosauridae. Documentaries mainly use that when the creators themselves are not sure which genus they are depicting in the show and that makes this a lot more odd. Aucasaurus in itself is not a family name or a clade name as it is a genus belonging in the Carnotaurini tribe, so yeah!
And that is mainly it for the Aucasaurus, a strange yet complete addition to the increasing number of Abelisauridae. It seems like I am inching my way to completing all of the species profiles for Abelisauridaes. I am thinking of making a list of Abelisauridaes and do let me know if I am missing anything from this post and I hope to see you again in other posts!!
I am surprised as to how there are not many depictions of this dinosaur because not only do we know a lot about this guy but can make an interesting design with an interesting story in documentaries or appearances in games and more. The problem with popular dinosaurs is that it overshadows other genera which are equally as cool as the popular one.
If you ever wanna see my design of Aucasaurus as well as support me in my endeavors is by sharing this with everyone who might be interested in this. And maybe also commission me for some dinosaurs art in Fiverr. I hope to see you again soon in my next post!!
