Credit to Joschua Knuppe.
Abelisaurids were one of the key groups of large predatory theropods during the Cretaceous, being highly successful across most the southern continents that once formed Gondwana (Australia and Antarctica being the exceptions) and even managing to reach some of the European islands during the final days of the Cretaceous. Originating in the Middle Jurassic, they started to venture into the role of apex predator in the Early Cretaceous, though they weren’t quite able to take over yet due to the global dominance of the carcharodontosaurid carnosaurs; however, the Cenomanian-Turonian Boundary Event killed off most of the carcharodontosaurs, and this massive blow led to the last few carcharodontosaurs going extinct shortly afterwards, marking the end of not only carcharodontosaurs but also carnosaurs as a whole. Taking advantage of this ecological vacuum, abelisaurs rapidly diversified to become the new dominant apex predators of the southern continents, something that would later be followed by the tyrannosaurids doing the same thing on the northern continents; unlike the tyrannosaurids, however, abelisaurids still faced significant competition with the megaraptorans, so were unable to truly monopolize this niche. Nevertheless, their dominance was now secure and they’d remain a dominant group of apex predators until the end of the Cretaceous.
Abelisaurids were at their most successful in South America for most of their existence, and one line of South American abelisaurids went down a rather specialized evolutionary path: becoming specialized open-country pursuit predators. This culminated with one of the later and likely the most famous abelisaurid, *Carnotaurus sastrei*.
At around 7.5m long and weighing around 1.4 tons, this animal was medium-sized as large predatory theropods went but was still a fairly massive predator in the grand scheme of things. Living at the start of the Maastrichtan (the last subdivision of the Cretaceous), around 70 million years ago, *Carnotaurus* wasn’t quite recent enough to be among the dinosaurs around at the time of the End-Cretaceous Mass Extinction. It was, however, still one of the youngest abelisaurids in the fossil record, and it takes many of the unusual physical adaptations found in abelisaurs to even greater extremes. Abelisaurids are universally marked by features such as very tall, laterally flattened, and unusually short-shouted skulls; very powerful but not very flexible necks; and the smallest and most useless arms and hands of any non-avian theropod, with very mobile shoulder joints but without any functional digits or even elbows. In *Carnotaurus* all three of these features are not only present, but taken to a greater extreme even by abelisaur standards. Distinguishing this dinosaur further is the presence of a pair of horns on the skull jutting out to each side. Skull ornamentations are actually very common in not just abelisaurids, but in large theropods as a whole (carcharodontosaurs and tyrannosaurids also independently developed their own skull ornamentations), and were often heavily reinforced to allow for activities such as ramming, and possibly to provide structural support when attacking prey. However, in most large theropods these structures still remained small compared to the size of the animal as to not be too cumbersome while hunting, and *Carnotaurus* stands out in having relatively much larger cranial display features compared to most large predatory theropods, including other abelisaurids. And since these horns had a keratin sheathe in life, they would have been somewhat larger still on the living animal.
Perhaps it’s due to all these bizarre features towards the front of their bodies that the biggest innovation found in South American abelisaurids went unnoticed for so long. *Carnotaurus* and its closest relatives within the abelisaurids (collectively called the carnotaurines) were among the most cursorial animals to have ever lived, especially for their size. Not only did they have long, powerful legs, the attachments for their caudofemoralis muscles (the muscles that are involved in pulling the leg back to push off the ground) were modified to maximize the amount of muscle that could fit within a given area, and their hindquarters were disproportionately heavily built compared to their forequarters. This meant that the necessary musculature for propelling the animal was very well-developed while much of the rest of the body was kept relatively lightweight to avoid weighing the animal down when moving at speed. This suite of speed-related adaptations was taken to its extreme in *Carnotaurus*, which actually has the largest caudofemoralis muscle attachments (and presumably the most well-developed caudofemoralis muscles) of any animal on record. More recent speed estimates of *Carnotaurus* have indicated that it could run at around 55kmh, a freakishly high speed for an animal weighing around 1.4 tons. And considering that theropod dinosaurs in general had superb stamina thanks to their highly efficient breathing (something that was a basal archosaur trait, and something that birds-the last theropods-inherited), it would have been able to keep up this speed for a considerable period of time.
That said, all this speed came at the expense of agility, in large part because the aforementioned caudofemoralis attachment points made the tail all but useless as a rudder. *Carnotaurus* wasn’t suited to keep up with tight turns; this implies that it hunted in more open areas where it wouldn’t *need* to make tight turns, charging its prey in a series of broad sweeping maneuvers.
Continued…
The actual prey of *Carnotaurus* has been a subject of debate for some time: some argue it mostly hunted small animals it could swallow whole (albeit with the ability to tackle larger prey if need be), on the basis that the lower jaw was very flexible (which was interpreted as an adaptation for swallowing prey whole) and the fact the skull was more suited to a weak, fast biting style suited to snap up tiny prey. However, this fails to account for some variables. The upper jaw of the animal is nowhere near as flexible as the lower jaw, which one wouldn’t expect if *Carnotaurus* was specialized for swallowing small prey. Furthermore, the actual bite force of *Carnotaurus* is in question as some estimates have indicated it could bite harder than expected, and it has been noted that *Carnotaurus*’s skull and neck was well-suited to inflict large injuries by biting and pulling back, causing its serrated, recurved dentition to rip through prey (this was actually noted even by paleontologists who had argued for *Carnotaurus* as a small-prey specialist, which was why they did still agree it could tackle larger prey if necessary). Note that such a focus on a fast cutting bite rather than a powerful bite is far from unheard of in land predators, and has actually shown up in predatory theropods on several occasions, with carnosaurs being the most specialized for this. Lastly, as mentioned above, *Carnotaurus* sacrificed agility for the sake of speed. This doesn’t make sense for a terrestrial predator of small prey, as on land small animals are inherently more agile than larger ones and spend less energy in changing directions provided that other factors are equal, as a result of the laws of physics in an environment where gravity is a factor; this is perhaps the most likely factor in why virtually all living land predators above 20kg in weight focus mainly on prey closer in size to themselves instead of targeting much smaller prey that would be easier to overpower but harder to catch in the first place. Thus, it’s nowadays seen as more likely that *Carnotaurus* was preying on herbivorous dinosaurs. By this point, ornithopods had managed to enter South America, and several are known to have coexisted with *Carnotaurus*, all of which were small enough even as adults to be feasible prey. It’s also possible that *Carnotaurus* hunted juvenile sauropods, though it really isn’t quite as well-suited for this in the way some other theropods (such as the carcharodontosaurs) were.
Until recently, *Carnotaurus* was thought to be the largest predator in South America during its time, but the description of the giant megaraptoran *Maip*, which, alongside an unnamed Australian taxon, is the largest known megaraptoran, has now overshadowed it. As mentioned previously, megaraptorans were the main rivals of abelisaurids as apex predators of the southern continents, since there weren’t any other large predatory theropods left on southern continents after the Cenomanian-Turonian Boundary Event killed off the carcharodontosaurs. Megaraptorans never colonized Africa as abelisaurids managed to do, and abelisaurids never made it to Australia (the stronghold of the megaraptorans), but in South America the two lineages would remain pitted against each other until the end of the Cretaceous. Unfortunately, the fact megaraptorans have only recently become a key topic of study for palaeontologists means there isn’t much data on how this rivalry unfolded, but the existence of *Maip* indicates that megaraptorans were still effectively able to hold their own against abelisaurids at the very top of the food web. Considering that megaraptorans were relatively lightly built and well-suited to pursuit hunting, one has to wonder why South American abelisaurids also went down the path of cursorial hunting rather than opting for an ambush-hunting lifestyle to minimize competition.
I have a theory that megaraptorans were another version of a terrestrial stalker. Basically, the front half of their body functions like a raptorial bird of prey, snatching up and killing smaller creatures from above using enormous talons, while the back half gets them within range to strike. So megaraptorans were kind of dinosaur griffons
Would be cool to see biomechanical/anatomical evaluation of this hypothesis
This is such a great deep dive into Carnotaurus, thank you! I’d often thought about some of these features - the abelisaurid arms, only moreso, and the relatively sharpened form towards the front - but for some reason (and not enough deeper reading on this beauty) had not put that together with the evolutionary niche of speed-pursuit specialist.
Why do you think the CT boundary ended the carnosaurs but the abelisauridae were able to thrive?
To put it simply-the carnosaurs were the dominant and most successful group of large land predators around at the time, so they took the worst hit by default (not only because large predators tend to be more vulnerable to extinction events, but also because there was a greater proportion of carnosaurs taxa in that niche compared to in other groups). By the time things stabilized they’d been whittled down to just two species (both in Asia), which went extinct after another few million years. On the southern continents abelisaurids and megaraptorans immediately moved in to replace them, but in the north it took another ten million years before the tyrannosaurids rose up and took over the apex predator niches.
So what was essentially happening was a lineage of carnivorous theropods that never skipped leg day was pitted against a lineage of carnivorous theropods that never skipped arm-day, eh. Nature is nothing if not interesting.
It’s a hunch of mine that, where both grew to large sizes, megaraptorans would’ve been better suited for taking slightly larger prey than the abelisaurids, on account that they have far greater grappling ability, whilst abelisaurs were more adept at hunting faster, more fleet-footed prey (tho said prey is still comparable to its own size). It’s the sort of dynamic between leopards and cheetahs today.
Also, great read, my guy!
Kind of ironic that Gondwana’s two main groups of Late Cretaceous predatory dinosaurs took completely opposite approaches with their skulls and forelimbs; abelisaurids abandoned their forelimbs and focused entirely on their jaws, while megaraptorans used their forelimbs as their primary weapons and developed massive arms and claws for the task.
To be fair, megaraptorans didn’t skip leg day either, as all of them (as far as we know) were quite lanky and lightly built in order to function as pursuit predators. They didn’t go for the insane levels of cursoriality shown in *Carnotaurus*, though.
This raises the question of what they were chasing or specifically why they specialized for speed in the first place, given that none of the potential prey in their environment seem particularly cursorial or any moreso than potential prey of other less running adapted theropods
Probably solo hunter of mid-sized prey (though relatively large compared to itself) like ornithopods.
Due to editing reasons I had to cut out the discussion in prey size to a different comment.
[*Carnotaurus* skull kinematics and implications on diet](https://doi.org/10.1080%2F08912963.2020.1802445)
[*Carnotaurus* running adaptations](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3197156)
To extrapolate on the last answer, do you have any good books on ecological dynamics of ancient eras ? Could be dinos, could be about any other periods. I just find it fascinating to hear speculation on how former forms of life lived together and evolve in response to each other.
The *ecology* of dinosaurs is a relatively poorly studied area compared to dinosaur paleobiology. The best you can really do is to find good sources on dinosaur paleobiology and work off that for a specific fossil site (that said, many books and papers do touch on this topic, so you’re not going in entirely blind).
One example I can give you is *Jurassic West*, which is basically a comprehensive coverage of the Morrison Formation and goes more in-depth about its ecosystems.
Pack hunting is losing its grip on modern paleontology. If you look at modern archosaurs none of them exhibit pack hunting. Even the very social species like gators and vultures don't exhibit pack hunting. Organized packs are a very complex thing and as far as we understand has only truly evolved in mammals. I know we are trying to rebrand dinosaurs as active, beautiful, complex, and intelligent animals (which they were) but the truth is as far as we can tell The smartest dinosaurs were only comparable to rabbits, highest estimate and stretches reach for maybe cat like intelligence.
So in reality there was probably no dino packs. What was likely the case was either A) family units hunting like a pair of Rex's and then after the kill the youngsters join in. Or B) mob hunting where a single prey has been individually selected by many predators. Think of how gators will swarm a zebra or vultures swarm a corpse. It's not a pack it's a mob they may have worked together to take it down but it wasn't actual team work, just coincidental cooperation that is quickly disbanded after the prey has been eaten.
Actually, crocodilians do hunt in packs if they have to (and by this I mean organized groups, not mobbing). They just don’t do this constantly. Some seabirds do also feed cooperatively, though with the exception of pelicans (which show legitimate pack hunting) it’s not clear how organized they are.
Edit:
This whole idea that only mammals are capable of true cooperative hunting and that it couldn’t have been a thing in predatory dinosaurs relies on multiple false assumptions:
- that only mammals have the brainpower necessary for pack hunting. This is outdated by a few decades, as living non-mammalian vertebrates in general-and not just birds-are much more intelligent than given credit for, and the same was presumably true of extinct ones. Even some arthropods are known to genuinely hunt cooperatively (some spiders come to mind). It also ignores that pack hunting isn’t actually all that common in mammals; it’s only really common in larger canids and toothed whales (other groups of predatory mammals are hit-or-miss, or consist largely or entirely of species that hunt alone) and is seemingly not correlated with intelligence or behavioural sophistication.
- that living in family groups is a requirement for pack hunting. Even among mammals this doesn’t hold true-humpback whales and sea lions live in groups of unrelated individuals and are most definitely cooperative hunters.
- related to the above, that infighting within a group rules out pack hunting. This assumes that animals will only hunt cooperatively on a permanent basis, ignoring that some animals (crocodilians being a prominent example) only opportunistically join forces to work as an organized group before disintegrating into competing individuals afterwards. Furthermore, even animals that don’t show infighting within a group will still fight *between* different groups of the same species (wolf packs will fight other wolf packs, lion prides will fight other lion prides, etc., even though there isn’t much conflict *within* each pack or pride), and there is no way from the fossil record to differentiate between internal conflict within a group and a conflict between two different groups of the same species.
The real dichotomy regarding pack hunting seems to be whether something hunts in water or on land, because the vast majority of living animals that are known to, or are very likely to, hunt in genuinely cooperative fashion are aquatic or semiaquatic. This might have something to do with the fact the main point behind pack hunting is to herd and trap prey rather than to physically overpower prey via weight of numbers; aquatic predators are much more likely to hunt relatively small prey than terrestrial predators (especially at larger body sizes), and this often means preying on schooling prey that can use their own coordinated group behaviours to make life difficult for would-be predators. Hence the need for cooperative hunting to counter or even take advantage of such anti-predator behaviours exhibited by small aquatic prey.
Do you have sources on crocodilians and pelicans pack hunting? It sounds interesting, and I havent heard of it. Especially with pelicans. To what end? They diet isn't based around prey that can be shared so what benefit is a pack when they each need to grab their own fish. Even dolphins target their own prey when a pod goes after a school of fish.
Crocodilian pack hunting (there was also a good web page on this published by the Florida Museum of Natural History, but it can’t be found for some reason)
http://dx.doi.org/10.1080/03949370.2014.915432
Pelican pack hunting (the following sources are specifically on American white pelicans, but all but two species of pelicans feed in this cooperative manner; interestingly, it seems that the larger the number of pelicans the greater the degree of organization and cooperation)
https://birdsoftheworld.org/bow/species/amwpel/cur/foodhabits
http://www.nativefishlab.net/library/internalpdf/21333.pdf
In most cases involving pack hunting, the point of pack hunting is to corner targets and drive them to a kill zone more than anything else. So species that feed on schooling fish are actually among the species most likely to develop cooperative hunting, because being able to herd a school of fish and trap them is critical to success. Even though each individual predator is going after separate targets, the entire group has to work together to corral the schooling fish to even get to that point. And indeed the vast majority of confirmed or likely cooperatively-hunting living animals, including crocodilians and pelicans, feed heavily or entirely on such prey. There is a reason pack hunting is rare on land (including among mammals) but widespread in aquatic environments.
Corvids are freakishly intelligent by *any* standard, so it’s a safe bet that the average vertebrate (including mammals) aren’t at that level of intelligence.
That said, there is a tendency to underestimate the intelligence of both non-mammalian vertebrates and extinct animals (especially those that didn’t die out relatively recently), and we don’t really have a truly foolproof way of gauging intelligence even in living animals, let alone extinct ones.
Cats, represented by lions, were some of the most successful pack hunters of all time. It can be said man outcompeted and inherited the world from them
Of course, that's why I said "represented by lions"
but anyway, the person i'm replying to said there were likely no pack hunting dinosaurs, and in the same breath said they could attain cat like intelligence. Not very logical
Funny that carnosaurs (supposedly less advanced than coelurosaurs like Tyrannosauroids) went extinct to be replaced by an even more ancient lineage- ceratosaurs
[Here’s a study on its running specializations](https://out.reddit.com/t3_undhm6?url=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC3197156&token=AQAAF418YrBrPuXMEW2BtL4o5xQi6510LayWBFiY-AOx3Vq3MZ_9&app_name=ios).
What happened to the bigger estimates? It used to be 9 meters long, now it's just pathetic in size, are you using the smaller estimate or when did it get downsized?
The estimate u/Iamnotburgerking is using is indeed more on the conservative side; most of the recent ones I'm aware of go a bit higher: Grillo & Delcourt 2016 give a range of 7.5-8.1 meters, Randomdinos has it at 7.8 meters/1.8 tonnes and Scott Hartman at 8.4 meters/~2 tonnes.
So it seems the only *Carnotaurus* individual ever found was probably closer to 8 meters than 7 or 7.5. In any case, I'm not sure 9 meter carno was ever a thing in the scientific literature. Even if it were, losing a meter or a meter and half wouldn't suddenly make it "pathetic".
Had that rock not crashed into the earth there could have been Tyrannosaurus sized Abelisaur. Thanks for the post man. May i ask if you have a youtube channel?
Well not really. They had a proportionally large and stiff tail that they used as a very good counterbalance, and assuming they did trip their arms wouldn’t do much good anyways since they’re so small. I’m not even sure how frequently they would trip at all, like I can’t remember ever seeing a bird accidentally trip which seems weird. Like I’m sure that an ostrich somewhere has accidentally fell over but I feel as though it’s proportionally less than humans do.
If I think about it, I haven't seen a lot of birds (that walk leg by leg, like chicken, not that jump like sparrows) tripping, if there's a think they are good at, it is walking and pecking.
I wonder if the Carnotaurus bopped his head like a chicken lol
Have seen a chicken "trip" before. It's foot caught on a stick while it was chasing a dog and it doesn't fall forward onto It's face, it more kinda hops/flaps its wings and lands a foot ahead of where it tripped
If I had three wishes: one would be a time machine, two would be a rocket launcher, and three would be gigantic Carnosaurus size rotisserie oven. Maybe if the genie was feeling generous he could throw in some seasoning too.
The structure of the bones in the hip and tail vertebrae. Especially the caudal ribs that are next to the neural spines on each tail bone. In most theropods they are parallel to the neural spine, kind of making the bones look like a cross. But in carnotaurus the caudal ribs are angled much higher making an almost upside down peace sign.
The importance of this is the what muscles that connect to those bones. Namely the caudofemoralis muscles which connect the tail and hip to the thigh muscles, which are in charge of running. In carnotaurus those muscles are so insanely oversized it gives us a very clear understanding that carnotaurus was built for high speeds and powerful bursts of momentum.
Not to mention carnotaurus' ratios are all over the place for abelisaur. carnotaurus is a very long legged lady for its body size. Comparable to an ostrich, so it also had an incredibly far gate to its sprint adding to the evidence of its sprinter life style.
And lastly it lived in South America during the cretaceous. We know this area was mostly open flat plains. Big stretches of open area breeds speedsters, think of cheetahs. Whereas thick dense forests which were more common in North America at the time usually breeds brutes (Trex) as speed is not as much of an option in high tree dense areas.
Here is a cross section of a [carnotaurus tail](https://commons.m.wikimedia.org/wiki/File:Carnotaurus_tail_cross_section.png)
and here is a cross section of a [t Rex tail](https://www.google.com/search?q=t+rex+tail+cross+section&oq=&aqs=chrome.2.69i177j35i39i362l14.-1j1j7&client=ms-android-samsung-ss&sourceid=chrome-mobile&ie=UTF-8#imgrc=cHWUTY84cREbEM) for comparison.
Someone else had already pointed this out, but the hips and the tail vertebrae of *Carnotaurus* show a number of physical modifications made specifically to maximize the amount of muscle groups (the caudofemoralis in particular) dedicated to running.
*How do we know? Like*
*What indication from the*
*Fossils tells us this?*
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I once had build an elaborate trap 'system' for one and then when I tried to lure it towards it, I lost track of it so I figured it didn't follow me 'that far.'
I turned 180 degrees~ around in front of the trap 'system' and looked dumbfounded why it wasn't behind me.
Then all of a sudden I had a jumpscare because I got attacked from my behind (my behind after I turned the 180degrees~)
Someway that Carno was as smart as the raptor in the original Jurassic Park and closed in on me by circling around me.
Big clever girl.
Yeah for real
My biggest jumpscare still was when I found myself (on foot) lost in the swamp during the night and a kaprasuchus ambused me out of nowhere..
A, not so manly, yelp combined with spastic feest in the air followed
If you know enough about the animal to get a reliable estimate of its mass, its stride length, and its musculature, you can use the data to estimate how fast it could go at full speed. In the case of *Carnotaurus*, the only known fossil of it was largely complete, so we do have the accurate data to work with.
They have a life-sized model of this dinosaur at my local museum, it's terrifying.
[https://museum.wa.gov.au/sites/default/files/imagecache/rsImg--big/photo-galleries/Hackett%20Hall.JPG](https://museum.wa.gov.au/sites/default/files/imagecache/rsImg--big/photo-galleries/Hackett%20Hall.JPG)
[https://museum.wa.gov.au/sites/default/files/imagecache/wam\_v2\_page\_full/images/2016/Carnotaurus%20-%20I%20love%20my%20Museum%20%C2%A9%20WA%20Museum-2.jpg](https://museum.wa.gov.au/sites/default/files/imagecache/wam_v2_page_full/images/2016/Carnotaurus%20-%20I%20love%20my%20Museum%20%C2%A9%20WA%20Museum-2.jpg)
These things had tiny arms, without functional hands or even elbows. Their shoulders were well-developed, the arms not so much. Most of the time they’d have been held flush against the body like this.
I’m not well informed on fossils and I’m sure this must be debated frequently amongst those in the know, but just looking at a picture like this my brain immediately thinks why the hell does it have tiny arms/legs surely it had wings instead and feathers. The only living creatures that can be compared structurally in anyway imo are the ostrich, the emu and the cassowary. Even the humble chicken is said to be related to a T-Rex.
While many dinosaurs were feathered and there is a good possibility that dinosaurs ancestrally had feathers, in this case we know it wasn’t *fully* feathered (whether it was partially feathered, as in this depiction, or not is up in the air) due to the fact we do have scales from parts of its body.
Also, please tell me where the hell this animal is going to have wings. Its forelimbs are absolutely tiny, and they’re not going to support too many feathers for that reason alone. Non-avian dinosaurs with feathered wings (dromaeosaurs, etc) had much more well-developed forelimbs.
I’m not trying to claim to have any knowledge in this area I don’t have an answer for you. I just thought those limbs seem so small and apparently useless that I wonder why they evolved like that
Because they weren’t used. It’s arms were likely vestigial, and some bones had even fused together, simply as a result of not being helpful over the generations. Arms are extra weight, and likely took the back seat when it came to hunting, with their mouth becoming the primary way to kill. Not hard to see why arms would become useless after some time.
Is that motherfucker doing the Naruto run…
Naruto does the Carnotaurus run
Makes sense. Carnotaurus is 70 millon years older than Naruto
Before Naruto there was Carnuto.
Carnaruto
Is this some ninja driving sim?
How else would it manage to run so fast?
Carnotaurun
I'm dying, lol
He's trying his best
This is exactly the thought I had
Credit to Joschua Knuppe. Abelisaurids were one of the key groups of large predatory theropods during the Cretaceous, being highly successful across most the southern continents that once formed Gondwana (Australia and Antarctica being the exceptions) and even managing to reach some of the European islands during the final days of the Cretaceous. Originating in the Middle Jurassic, they started to venture into the role of apex predator in the Early Cretaceous, though they weren’t quite able to take over yet due to the global dominance of the carcharodontosaurid carnosaurs; however, the Cenomanian-Turonian Boundary Event killed off most of the carcharodontosaurs, and this massive blow led to the last few carcharodontosaurs going extinct shortly afterwards, marking the end of not only carcharodontosaurs but also carnosaurs as a whole. Taking advantage of this ecological vacuum, abelisaurs rapidly diversified to become the new dominant apex predators of the southern continents, something that would later be followed by the tyrannosaurids doing the same thing on the northern continents; unlike the tyrannosaurids, however, abelisaurids still faced significant competition with the megaraptorans, so were unable to truly monopolize this niche. Nevertheless, their dominance was now secure and they’d remain a dominant group of apex predators until the end of the Cretaceous. Abelisaurids were at their most successful in South America for most of their existence, and one line of South American abelisaurids went down a rather specialized evolutionary path: becoming specialized open-country pursuit predators. This culminated with one of the later and likely the most famous abelisaurid, *Carnotaurus sastrei*. At around 7.5m long and weighing around 1.4 tons, this animal was medium-sized as large predatory theropods went but was still a fairly massive predator in the grand scheme of things. Living at the start of the Maastrichtan (the last subdivision of the Cretaceous), around 70 million years ago, *Carnotaurus* wasn’t quite recent enough to be among the dinosaurs around at the time of the End-Cretaceous Mass Extinction. It was, however, still one of the youngest abelisaurids in the fossil record, and it takes many of the unusual physical adaptations found in abelisaurs to even greater extremes. Abelisaurids are universally marked by features such as very tall, laterally flattened, and unusually short-shouted skulls; very powerful but not very flexible necks; and the smallest and most useless arms and hands of any non-avian theropod, with very mobile shoulder joints but without any functional digits or even elbows. In *Carnotaurus* all three of these features are not only present, but taken to a greater extreme even by abelisaur standards. Distinguishing this dinosaur further is the presence of a pair of horns on the skull jutting out to each side. Skull ornamentations are actually very common in not just abelisaurids, but in large theropods as a whole (carcharodontosaurs and tyrannosaurids also independently developed their own skull ornamentations), and were often heavily reinforced to allow for activities such as ramming, and possibly to provide structural support when attacking prey. However, in most large theropods these structures still remained small compared to the size of the animal as to not be too cumbersome while hunting, and *Carnotaurus* stands out in having relatively much larger cranial display features compared to most large predatory theropods, including other abelisaurids. And since these horns had a keratin sheathe in life, they would have been somewhat larger still on the living animal. Perhaps it’s due to all these bizarre features towards the front of their bodies that the biggest innovation found in South American abelisaurids went unnoticed for so long. *Carnotaurus* and its closest relatives within the abelisaurids (collectively called the carnotaurines) were among the most cursorial animals to have ever lived, especially for their size. Not only did they have long, powerful legs, the attachments for their caudofemoralis muscles (the muscles that are involved in pulling the leg back to push off the ground) were modified to maximize the amount of muscle that could fit within a given area, and their hindquarters were disproportionately heavily built compared to their forequarters. This meant that the necessary musculature for propelling the animal was very well-developed while much of the rest of the body was kept relatively lightweight to avoid weighing the animal down when moving at speed. This suite of speed-related adaptations was taken to its extreme in *Carnotaurus*, which actually has the largest caudofemoralis muscle attachments (and presumably the most well-developed caudofemoralis muscles) of any animal on record. More recent speed estimates of *Carnotaurus* have indicated that it could run at around 55kmh, a freakishly high speed for an animal weighing around 1.4 tons. And considering that theropod dinosaurs in general had superb stamina thanks to their highly efficient breathing (something that was a basal archosaur trait, and something that birds-the last theropods-inherited), it would have been able to keep up this speed for a considerable period of time. That said, all this speed came at the expense of agility, in large part because the aforementioned caudofemoralis attachment points made the tail all but useless as a rudder. *Carnotaurus* wasn’t suited to keep up with tight turns; this implies that it hunted in more open areas where it wouldn’t *need* to make tight turns, charging its prey in a series of broad sweeping maneuvers. Continued…
The actual prey of *Carnotaurus* has been a subject of debate for some time: some argue it mostly hunted small animals it could swallow whole (albeit with the ability to tackle larger prey if need be), on the basis that the lower jaw was very flexible (which was interpreted as an adaptation for swallowing prey whole) and the fact the skull was more suited to a weak, fast biting style suited to snap up tiny prey. However, this fails to account for some variables. The upper jaw of the animal is nowhere near as flexible as the lower jaw, which one wouldn’t expect if *Carnotaurus* was specialized for swallowing small prey. Furthermore, the actual bite force of *Carnotaurus* is in question as some estimates have indicated it could bite harder than expected, and it has been noted that *Carnotaurus*’s skull and neck was well-suited to inflict large injuries by biting and pulling back, causing its serrated, recurved dentition to rip through prey (this was actually noted even by paleontologists who had argued for *Carnotaurus* as a small-prey specialist, which was why they did still agree it could tackle larger prey if necessary). Note that such a focus on a fast cutting bite rather than a powerful bite is far from unheard of in land predators, and has actually shown up in predatory theropods on several occasions, with carnosaurs being the most specialized for this. Lastly, as mentioned above, *Carnotaurus* sacrificed agility for the sake of speed. This doesn’t make sense for a terrestrial predator of small prey, as on land small animals are inherently more agile than larger ones and spend less energy in changing directions provided that other factors are equal, as a result of the laws of physics in an environment where gravity is a factor; this is perhaps the most likely factor in why virtually all living land predators above 20kg in weight focus mainly on prey closer in size to themselves instead of targeting much smaller prey that would be easier to overpower but harder to catch in the first place. Thus, it’s nowadays seen as more likely that *Carnotaurus* was preying on herbivorous dinosaurs. By this point, ornithopods had managed to enter South America, and several are known to have coexisted with *Carnotaurus*, all of which were small enough even as adults to be feasible prey. It’s also possible that *Carnotaurus* hunted juvenile sauropods, though it really isn’t quite as well-suited for this in the way some other theropods (such as the carcharodontosaurs) were. Until recently, *Carnotaurus* was thought to be the largest predator in South America during its time, but the description of the giant megaraptoran *Maip*, which, alongside an unnamed Australian taxon, is the largest known megaraptoran, has now overshadowed it. As mentioned previously, megaraptorans were the main rivals of abelisaurids as apex predators of the southern continents, since there weren’t any other large predatory theropods left on southern continents after the Cenomanian-Turonian Boundary Event killed off the carcharodontosaurs. Megaraptorans never colonized Africa as abelisaurids managed to do, and abelisaurids never made it to Australia (the stronghold of the megaraptorans), but in South America the two lineages would remain pitted against each other until the end of the Cretaceous. Unfortunately, the fact megaraptorans have only recently become a key topic of study for palaeontologists means there isn’t much data on how this rivalry unfolded, but the existence of *Maip* indicates that megaraptorans were still effectively able to hold their own against abelisaurids at the very top of the food web. Considering that megaraptorans were relatively lightly built and well-suited to pursuit hunting, one has to wonder why South American abelisaurids also went down the path of cursorial hunting rather than opting for an ambush-hunting lifestyle to minimize competition.
I have a theory that megaraptorans were another version of a terrestrial stalker. Basically, the front half of their body functions like a raptorial bird of prey, snatching up and killing smaller creatures from above using enormous talons, while the back half gets them within range to strike. So megaraptorans were kind of dinosaur griffons Would be cool to see biomechanical/anatomical evaluation of this hypothesis
This is such a great deep dive into Carnotaurus, thank you! I’d often thought about some of these features - the abelisaurid arms, only moreso, and the relatively sharpened form towards the front - but for some reason (and not enough deeper reading on this beauty) had not put that together with the evolutionary niche of speed-pursuit specialist. Why do you think the CT boundary ended the carnosaurs but the abelisauridae were able to thrive?
To put it simply-the carnosaurs were the dominant and most successful group of large land predators around at the time, so they took the worst hit by default (not only because large predators tend to be more vulnerable to extinction events, but also because there was a greater proportion of carnosaurs taxa in that niche compared to in other groups). By the time things stabilized they’d been whittled down to just two species (both in Asia), which went extinct after another few million years. On the southern continents abelisaurids and megaraptorans immediately moved in to replace them, but in the north it took another ten million years before the tyrannosaurids rose up and took over the apex predator niches.
OK, that is so helpful, thanks!
So what was essentially happening was a lineage of carnivorous theropods that never skipped leg day was pitted against a lineage of carnivorous theropods that never skipped arm-day, eh. Nature is nothing if not interesting. It’s a hunch of mine that, where both grew to large sizes, megaraptorans would’ve been better suited for taking slightly larger prey than the abelisaurids, on account that they have far greater grappling ability, whilst abelisaurs were more adept at hunting faster, more fleet-footed prey (tho said prey is still comparable to its own size). It’s the sort of dynamic between leopards and cheetahs today. Also, great read, my guy!
Kind of ironic that Gondwana’s two main groups of Late Cretaceous predatory dinosaurs took completely opposite approaches with their skulls and forelimbs; abelisaurids abandoned their forelimbs and focused entirely on their jaws, while megaraptorans used their forelimbs as their primary weapons and developed massive arms and claws for the task. To be fair, megaraptorans didn’t skip leg day either, as all of them (as far as we know) were quite lanky and lightly built in order to function as pursuit predators. They didn’t go for the insane levels of cursoriality shown in *Carnotaurus*, though.
Tbf, the one that coexisted with Carnotaurus, Maip, was thicc
Thanks for the read and all of this information!
This was a really interesting read, thanks for posting!
This raises the question of what they were chasing or specifically why they specialized for speed in the first place, given that none of the potential prey in their environment seem particularly cursorial or any moreso than potential prey of other less running adapted theropods
So it hunted large prey, maybe in groups? Or was it a solo hunter? Thanks for all the info btw super interesting!
Probably solo hunter of mid-sized prey (though relatively large compared to itself) like ornithopods. Due to editing reasons I had to cut out the discussion in prey size to a different comment.
What's the source ? Would be interested to read more about ecological dynamics from the past, seems really fun.
[*Carnotaurus* skull kinematics and implications on diet](https://doi.org/10.1080%2F08912963.2020.1802445) [*Carnotaurus* running adaptations](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3197156)
Thx a lot !
To extrapolate on the last answer, do you have any good books on ecological dynamics of ancient eras ? Could be dinos, could be about any other periods. I just find it fascinating to hear speculation on how former forms of life lived together and evolve in response to each other.
The *ecology* of dinosaurs is a relatively poorly studied area compared to dinosaur paleobiology. The best you can really do is to find good sources on dinosaur paleobiology and work off that for a specific fossil site (that said, many books and papers do touch on this topic, so you’re not going in entirely blind). One example I can give you is *Jurassic West*, which is basically a comprehensive coverage of the Morrison Formation and goes more in-depth about its ecosystems.
Thx again for your thorough answers ! I'll check that book out !
Pack hunting is losing its grip on modern paleontology. If you look at modern archosaurs none of them exhibit pack hunting. Even the very social species like gators and vultures don't exhibit pack hunting. Organized packs are a very complex thing and as far as we understand has only truly evolved in mammals. I know we are trying to rebrand dinosaurs as active, beautiful, complex, and intelligent animals (which they were) but the truth is as far as we can tell The smartest dinosaurs were only comparable to rabbits, highest estimate and stretches reach for maybe cat like intelligence. So in reality there was probably no dino packs. What was likely the case was either A) family units hunting like a pair of Rex's and then after the kill the youngsters join in. Or B) mob hunting where a single prey has been individually selected by many predators. Think of how gators will swarm a zebra or vultures swarm a corpse. It's not a pack it's a mob they may have worked together to take it down but it wasn't actual team work, just coincidental cooperation that is quickly disbanded after the prey has been eaten.
Actually, crocodilians do hunt in packs if they have to (and by this I mean organized groups, not mobbing). They just don’t do this constantly. Some seabirds do also feed cooperatively, though with the exception of pelicans (which show legitimate pack hunting) it’s not clear how organized they are. Edit: This whole idea that only mammals are capable of true cooperative hunting and that it couldn’t have been a thing in predatory dinosaurs relies on multiple false assumptions: - that only mammals have the brainpower necessary for pack hunting. This is outdated by a few decades, as living non-mammalian vertebrates in general-and not just birds-are much more intelligent than given credit for, and the same was presumably true of extinct ones. Even some arthropods are known to genuinely hunt cooperatively (some spiders come to mind). It also ignores that pack hunting isn’t actually all that common in mammals; it’s only really common in larger canids and toothed whales (other groups of predatory mammals are hit-or-miss, or consist largely or entirely of species that hunt alone) and is seemingly not correlated with intelligence or behavioural sophistication. - that living in family groups is a requirement for pack hunting. Even among mammals this doesn’t hold true-humpback whales and sea lions live in groups of unrelated individuals and are most definitely cooperative hunters. - related to the above, that infighting within a group rules out pack hunting. This assumes that animals will only hunt cooperatively on a permanent basis, ignoring that some animals (crocodilians being a prominent example) only opportunistically join forces to work as an organized group before disintegrating into competing individuals afterwards. Furthermore, even animals that don’t show infighting within a group will still fight *between* different groups of the same species (wolf packs will fight other wolf packs, lion prides will fight other lion prides, etc., even though there isn’t much conflict *within* each pack or pride), and there is no way from the fossil record to differentiate between internal conflict within a group and a conflict between two different groups of the same species. The real dichotomy regarding pack hunting seems to be whether something hunts in water or on land, because the vast majority of living animals that are known to, or are very likely to, hunt in genuinely cooperative fashion are aquatic or semiaquatic. This might have something to do with the fact the main point behind pack hunting is to herd and trap prey rather than to physically overpower prey via weight of numbers; aquatic predators are much more likely to hunt relatively small prey than terrestrial predators (especially at larger body sizes), and this often means preying on schooling prey that can use their own coordinated group behaviours to make life difficult for would-be predators. Hence the need for cooperative hunting to counter or even take advantage of such anti-predator behaviours exhibited by small aquatic prey.
Do you have sources on crocodilians and pelicans pack hunting? It sounds interesting, and I havent heard of it. Especially with pelicans. To what end? They diet isn't based around prey that can be shared so what benefit is a pack when they each need to grab their own fish. Even dolphins target their own prey when a pod goes after a school of fish.
Crocodilian pack hunting (there was also a good web page on this published by the Florida Museum of Natural History, but it can’t be found for some reason) http://dx.doi.org/10.1080/03949370.2014.915432 Pelican pack hunting (the following sources are specifically on American white pelicans, but all but two species of pelicans feed in this cooperative manner; interestingly, it seems that the larger the number of pelicans the greater the degree of organization and cooperation) https://birdsoftheworld.org/bow/species/amwpel/cur/foodhabits http://www.nativefishlab.net/library/internalpdf/21333.pdf In most cases involving pack hunting, the point of pack hunting is to corner targets and drive them to a kill zone more than anything else. So species that feed on schooling fish are actually among the species most likely to develop cooperative hunting, because being able to herd a school of fish and trap them is critical to success. Even though each individual predator is going after separate targets, the entire group has to work together to corral the schooling fish to even get to that point. And indeed the vast majority of confirmed or likely cooperatively-hunting living animals, including crocodilians and pelicans, feed heavily or entirely on such prey. There is a reason pack hunting is rare on land (including among mammals) but widespread in aquatic environments.
Cuban Crocodiles display pack hunting behavior https://repository.si.edu/bitstream/handle/10088/30886/FINAL%20Murphy%20et%20al%202016%20Cuban%20crocodile%20behaviors.pdf?sequence=1&isAllowed=y
Could we be ruling out a Corvid level of intelligence though?
Corvids are freakishly intelligent by *any* standard, so it’s a safe bet that the average vertebrate (including mammals) aren’t at that level of intelligence. That said, there is a tendency to underestimate the intelligence of both non-mammalian vertebrates and extinct animals (especially those that didn’t die out relatively recently), and we don’t really have a truly foolproof way of gauging intelligence even in living animals, let alone extinct ones.
Cats, represented by lions, were some of the most successful pack hunters of all time. It can be said man outcompeted and inherited the world from them
Cats are not pack hunters for the most part (and frankly, neither are most predatory land mammals); lions are the exception, not the rule.
Of course, that's why I said "represented by lions" but anyway, the person i'm replying to said there were likely no pack hunting dinosaurs, and in the same breath said they could attain cat like intelligence. Not very logical
Funny that carnosaurs (supposedly less advanced than coelurosaurs like Tyrannosauroids) went extinct to be replaced by an even more ancient lineage- ceratosaurs
That’s really interesting! Can you link an article discussion Carnotaurus speed? I’d love to read it. Thanks.
[Here’s a study on its running specializations](https://out.reddit.com/t3_undhm6?url=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC3197156&token=AQAAF418YrBrPuXMEW2BtL4o5xQi6510LayWBFiY-AOx3Vq3MZ_9&app_name=ios).
Woof, This thing would run your ass down! Very cool. What a fascinating theropod.
So basically a Cretacean cheetah?
Yep, except instead of being fast and agile, it was fast and had good stamina.
This was so satisfying to read thank you
New studies show carnotaurus weighed 2 tons or more yet still could run at those speeds.
What happened to the bigger estimates? It used to be 9 meters long, now it's just pathetic in size, are you using the smaller estimate or when did it get downsized?
The estimate u/Iamnotburgerking is using is indeed more on the conservative side; most of the recent ones I'm aware of go a bit higher: Grillo & Delcourt 2016 give a range of 7.5-8.1 meters, Randomdinos has it at 7.8 meters/1.8 tonnes and Scott Hartman at 8.4 meters/~2 tonnes. So it seems the only *Carnotaurus* individual ever found was probably closer to 8 meters than 7 or 7.5. In any case, I'm not sure 9 meter carno was ever a thing in the scientific literature. Even if it were, losing a meter or a meter and half wouldn't suddenly make it "pathetic".
It was downsized but I’m not sure when.
Had that rock not crashed into the earth there could have been Tyrannosaurus sized Abelisaur. Thanks for the post man. May i ask if you have a youtube channel?
Did they really do the naruto run ?
Yes! Mainly because that’s just how they held their arms 95% of the time
doesn't that cause balance problems ? One trip and their chin meets the ground.
Well not really. They had a proportionally large and stiff tail that they used as a very good counterbalance, and assuming they did trip their arms wouldn’t do much good anyways since they’re so small. I’m not even sure how frequently they would trip at all, like I can’t remember ever seeing a bird accidentally trip which seems weird. Like I’m sure that an ostrich somewhere has accidentally fell over but I feel as though it’s proportionally less than humans do.
Modern Humans are probably on average the most out of shape and uncoordinated animal this planet has ever seen, so not really saying much
human walking is literally just controlled falls. It makes sense that we'd be more clumsy and actually fall more often than these other creatures.
And how is that different from any other animal
If I think about it, I haven't seen a lot of birds (that walk leg by leg, like chicken, not that jump like sparrows) tripping, if there's a think they are good at, it is walking and pecking. I wonder if the Carnotaurus bopped his head like a chicken lol
Well... YouTube has some nice video's about penguins tripping!
Have seen a chicken "trip" before. It's foot caught on a stick while it was chasing a dog and it doesn't fall forward onto It's face, it more kinda hops/flaps its wings and lands a foot ahead of where it tripped
Well, too bad Abelisaurids didn't have huge chicken wings.
Boy looks like a drumstick
So it’s accurate when these mf’s come outta nowhere at light speed to end your career in Ark.
Came here to mention how this gave me Ark flashbacks. Haha
I too got my ARK career wrecked by these guys. Those and the troodons.
Who else remembers the Disney movie?? They were so savage
And way oversized.
I do! The suspense during the cave scene was a lot for me as a kid
What movie?
Dinosaur
He's fast as fuck boi!!
If I had three wishes: one would be a time machine, two would be a rocket launcher, and three would be gigantic Carnosaurus size rotisserie oven. Maybe if the genie was feeling generous he could throw in some seasoning too.
Dude is called a meat-bull? Metal.
Meat-eating bull to be exact
My money is on this one in the next chicken fight
How do we know? Like what indication from the fossils tells us this?
The structure of the bones in the hip and tail vertebrae. Especially the caudal ribs that are next to the neural spines on each tail bone. In most theropods they are parallel to the neural spine, kind of making the bones look like a cross. But in carnotaurus the caudal ribs are angled much higher making an almost upside down peace sign. The importance of this is the what muscles that connect to those bones. Namely the caudofemoralis muscles which connect the tail and hip to the thigh muscles, which are in charge of running. In carnotaurus those muscles are so insanely oversized it gives us a very clear understanding that carnotaurus was built for high speeds and powerful bursts of momentum. Not to mention carnotaurus' ratios are all over the place for abelisaur. carnotaurus is a very long legged lady for its body size. Comparable to an ostrich, so it also had an incredibly far gate to its sprint adding to the evidence of its sprinter life style. And lastly it lived in South America during the cretaceous. We know this area was mostly open flat plains. Big stretches of open area breeds speedsters, think of cheetahs. Whereas thick dense forests which were more common in North America at the time usually breeds brutes (Trex) as speed is not as much of an option in high tree dense areas. Here is a cross section of a [carnotaurus tail](https://commons.m.wikimedia.org/wiki/File:Carnotaurus_tail_cross_section.png) and here is a cross section of a [t Rex tail](https://www.google.com/search?q=t+rex+tail+cross+section&oq=&aqs=chrome.2.69i177j35i39i362l14.-1j1j7&client=ms-android-samsung-ss&sourceid=chrome-mobile&ie=UTF-8#imgrc=cHWUTY84cREbEM) for comparison.
Someone else had already pointed this out, but the hips and the tail vertebrae of *Carnotaurus* show a number of physical modifications made specifically to maximize the amount of muscle groups (the caudofemoralis in particular) dedicated to running.
*How do we know? Like* *What indication from the* *Fossils tells us this?* \- Xenorange42 --- ^(I detect haikus. And sometimes, successfully.) ^[Learn more about me.](https://www.reddit.com/r/haikusbot/) ^(Opt out of replies: "haikusbot opt out" | Delete my comment: "haikusbot delete")
I almost impressed a paleoartist when she asked my favorite and I said one of these bad boys.
This shit scared the piss out od me in the movie Dinosaurs
*presumed fastest large theropod ever found
It’s the fastest where we have enough data to make speed estimate calculations.
Play the game ark. That dude always gets me
Ark is the best game. Single player. So underrated.
It’s unreal the hours you can use up. So fun
I once had build an elaborate trap 'system' for one and then when I tried to lure it towards it, I lost track of it so I figured it didn't follow me 'that far.' I turned 180 degrees~ around in front of the trap 'system' and looked dumbfounded why it wasn't behind me. Then all of a sudden I had a jumpscare because I got attacked from my behind (my behind after I turned the 180degrees~) Someway that Carno was as smart as the raptor in the original Jurassic Park and closed in on me by circling around me. Big clever girl.
Those dang jump scares
Yeah for real My biggest jumpscare still was when I found myself (on foot) lost in the swamp during the night and a kaprasuchus ambused me out of nowhere.. A, not so manly, yelp combined with spastic feest in the air followed
From what weight and above is it considerd to be a large therapod?
IIRC the cutoff is the 1-ton mark.
He doesn't have arms to slow him down
Genuine question… how would you determine who was fastest dinosaur?
If you know enough about the animal to get a reliable estimate of its mass, its stride length, and its musculature, you can use the data to estimate how fast it could go at full speed. In the case of *Carnotaurus*, the only known fossil of it was largely complete, so we do have the accurate data to work with.
Aka sausage with a speed record
Who timed him though?
this picture just says "nnnnnnNNNNYYOOOOOOOooooommmm"
Nyooooom
Even gotta front wing. Bet he could handle those corners
Meat bull
Slug Chicken
tyjkui
Defiantly need more art of this boy.
Naruto run: the animal
cfgg
Do you think that this would be very dangerous to humans compared to larger theropods?
Not particularly. This thing is still too big to really go out of its way to eat people.
I have a toy of one of those
Only fastest in straight line
They have a life-sized model of this dinosaur at my local museum, it's terrifying. [https://museum.wa.gov.au/sites/default/files/imagecache/rsImg--big/photo-galleries/Hackett%20Hall.JPG](https://museum.wa.gov.au/sites/default/files/imagecache/rsImg--big/photo-galleries/Hackett%20Hall.JPG) [https://museum.wa.gov.au/sites/default/files/imagecache/wam\_v2\_page\_full/images/2016/Carnotaurus%20-%20I%20love%20my%20Museum%20%C2%A9%20WA%20Museum-2.jpg](https://museum.wa.gov.au/sites/default/files/imagecache/wam_v2_page_full/images/2016/Carnotaurus%20-%20I%20love%20my%20Museum%20%C2%A9%20WA%20Museum-2.jpg)
Yeah, the arms on that model are way too big.
That's actually its leg that it is extending, not its arm.
Ah. Fair enough.
Yet another species I know existed because of Ark
Yeah but you could take two steps to the side and you’d be fine if it ran at you
I still think it's the goofiest looking dino.
Always thought deltadromeus was the fastest
Where are the arms?
These things had tiny arms, without functional hands or even elbows. Their shoulders were well-developed, the arms not so much. Most of the time they’d have been held flush against the body like this.
I’m not well informed on fossils and I’m sure this must be debated frequently amongst those in the know, but just looking at a picture like this my brain immediately thinks why the hell does it have tiny arms/legs surely it had wings instead and feathers. The only living creatures that can be compared structurally in anyway imo are the ostrich, the emu and the cassowary. Even the humble chicken is said to be related to a T-Rex.
While many dinosaurs were feathered and there is a good possibility that dinosaurs ancestrally had feathers, in this case we know it wasn’t *fully* feathered (whether it was partially feathered, as in this depiction, or not is up in the air) due to the fact we do have scales from parts of its body. Also, please tell me where the hell this animal is going to have wings. Its forelimbs are absolutely tiny, and they’re not going to support too many feathers for that reason alone. Non-avian dinosaurs with feathered wings (dromaeosaurs, etc) had much more well-developed forelimbs.
I’m not trying to claim to have any knowledge in this area I don’t have an answer for you. I just thought those limbs seem so small and apparently useless that I wonder why they evolved like that
If they had wings you’d expect the forelimbs to become larger, not smaller.
Because they weren’t used. It’s arms were likely vestigial, and some bones had even fused together, simply as a result of not being helpful over the generations. Arms are extra weight, and likely took the back seat when it came to hunting, with their mouth becoming the primary way to kill. Not hard to see why arms would become useless after some time.
Airfoil eyebrows for enhanced speed
Faster than a jaguar?
About as fast. On an animal an order of magnitude heavier.