The tipping point:' First T. rex mass death site in southern US, found in Utah, strengthens evidence

[Grim Reaper 6]

In a groundbreaking discovery of the first T. rex mass death site in the southern U.S., announced Monday by the Utah Bureau of Land Management, scientists found evidence of pack-like behavior among the famous ancient predator in the Grand Staircase-Escalante National Monument. This discovery should be the tipping point for reconsidering how these top carnivores behaved and hunted across the northern hemisphere during the Cretaceous.” “This discovery should be the tipping point for reconsidering how these top carnivores behaved and hunted across the northern hemisphere during the Cretaceous.

https://www.msn.com/en-us/news/us/the-tipping-point-first-t-rex-mass-death-site-in-southern-us-found-in-utah-strengthens-evidence-of-pack-behavior/ar-BB1fPGP0?rt=1&ocid=Win10NewsApp&referrerID=InAppShare

 

Edited April 20, 2021 by Manwon Lender

[the13bats]

Your link is not what you desire it to be.

[Grim Reaper 6]

26 minutes ago, the13bats said:

Your link is not what you desire it to be.

Thank you my brother, I corrected it in the nick of time!!!!!!

[Silver]

42 minutes ago, Manwon Lender said:

Thank you my brother, I corrected it in the nick of time!!!!!!

Damn, I missed it!

[Silver]

Obviously these bods know more than I do, but I read years ago that so-called "elephant graveyards" did not really exist, and were caused by corpses drifting together by weather forces, such as floods. Obviously they have thought of this. Though there is no reason for them not to hunt in packs, lions do, bears don't.

[Wepwawet]

Natural predator traps, such as the La Brea tar pits, can give a false impression of predator numbers and if there are groups of them. However, if you get a bunch of animals found together as the result of flooding, it's more likely that they all dead in a bunch because they lived in a bunch and were victims of the same event.

The work Currie has done on T. rex and Tarbosaurus bataar seems good, to me anyway, and while there is no definitive proof, and probably never will be, I don't see any overiding reason not to think that they hunted in packs. There is one aspect that may point to T. rex and it's cousins having greater intelligence than they are credited with, and that is that their primary prey animal, hadrosaurs, over the course of their evolution evolved to having ever larger brains in relation to their body size. Both tyranosaurs and the ornithopods that hadrosaurs evolved from, appear at about the same time, and, it seems to my unprofessional eye, engage in a "brains race", with the hadrosaurs having to keep up with the ever increasing intelligence of the animal that wants to eat them. Over the course of their evolution, the brain of hadrosaurs grew to be twice the size in relation to it's body size, and were by far potentially the brainiest ornithischians. The big unknown is the internal structure of the tyranosaur brain. They outwardly look like many other large theropods, bar oversized head and undersized arms, but that is convergent evolution. Something like a Carcarodontosaurus looks similar to a tyranosaur, but is more primitive, while tyranosaurs are a branch of coelurosaurs, the majority of whose members were maniraptors, with brains, even if not "Jurrasic Park" type door opening brains.

[SHaYap]

Crocs aren't exactly pack hunters, but it does look like they are though... 

~

[Grim Reaper 6]

1 hour ago, Wepwawet said:

Natural predator traps, such as the La Brea tar pits, can give a false impression of predator numbers and if there are groups of them. However, if you get a bunch of animals found together as the result of flooding, it's more likely that they all dead in a bunch because they lived in a bunch and were victims of the same event.

The work Currie has done on T. rex and Tarbosaurus bataar seems good, to me anyway, and while there is no definitive proof, and probably never will be, I don't see any overiding reason not to think that they hunted in packs. There is one aspect that may point to T. rex and it's cousins having greater intelligence than they are credited with, and that is that their primary prey animal, hadrosaurs, over the course of their evolution evolved to having ever larger brains in relation to their body size. Both tyranosaurs and the ornithopods that hadrosaurs evolved from, appear at about the same time, and, it seems to my unprofessional eye, engage in a "brains race", with the hadrosaurs having to keep up with the ever increasing intelligence of the animal that wants to eat them. Over the course of their evolution, the brain of hadrosaurs grew to be twice the size in relation to it's body size, and were by far potentially the brainiest ornithischians. The big unknown is the internal structure of the tyranosaur brain. They outwardly look like many other large theropods, bar oversized head and undersized arms, but that is convergent evolution. Something like a Carcarodontosaurus looks similar to a tyranosaur, but is more primitive, while tyranosaurs are a branch of coelurosaurs, the majority of whose members were maniraptors, with brains, even if not "Jurrasic Park" type door opening brains.

I think that this maybe the most conclusive evidence to date on the subject. Hopefully when they are finished with the investigation there will be some great papers written on the subject. While there will always be skeptics, I think this find will eventually turn the theory in fact more or less in my opinion.

“Traditional excavation techniques, supplemented by the analysis of rare earth elements, stable isotopes and charcoal concentrations convincingly show a synchronous death event at the Rainbows site of four or five tyrannosaurids. Undoubtedly, this group died together, which adds to a growing body of evidence that tyrannosaurids were capable of interacting as gregarious packs.”

Thanks for your participation in the thread and the knowledge you have added to it.

[Wepwawet]

1 hour ago, third_eye said:

Crocs aren't exactly pack hunters, but it does look like they are though... 

~

I understand the point, and they certainly do live in a group, but not in a pack, as we understand the term. There are though some major differences between crocs and T. rex. Crocs, let's say Nile crocodiles as they are the ones that most of us associate with crocs and their behaviour, live together by default rather than necessity. They are restricted to the river, and will naturally congregate at places were prey come to the river. It's rather like a predator trap. Basically you could say that  crocs are "lazy" in that they sit waiting for prey to come to them. T. rex was a mobile hunter, pack or individual, and is analagous to a big cat, whether lion or tiger being the point of contention. Their lifestyles would have been very different to that of a croc, a very primitive animal in comparison, and the evidence shows that T. rex chased after hadrosaurs, some of whom lived and bore the scars, and in one case a dislodged T. rex fang in the base of it's tail. Intelligence is another factor, crocs don't need great intelligence to live as they do, and their Reptile Encephalization Quotient is at the base level of 1.0, which means they are right at the level they need to be for their body mass. On the other hand, the T. rex REQ is around 7.8, which indicates a vast difference in potential intelligence, it's the equivalent between a cat and us. The question arises then as to why T.rex needed this amount of brain power, to sit waiting for prey at a place were they always turn up eventually, or to actively hunt. Does T. rex need this amount of brain power to hunt as an individual, maybe, as there is no great difference between a lion and a tiger other than that one is a pack hunter and the other an individual. A tiger has the same brain as a lion. But dinosaurs, including living ones, are not the same as mammals in this.

So the question is why did T.rex need brain power far above other dinosaurs, apart from it's more brainy smaller coelurosaur cousins, and why did it's main prey, hadrosaurs, need to engage in a "brains race", while, for instance, triceratopsians, herd animals living at the same time as the herd living hadrosaurs, were not very smart at all. I would contend that hadrosaurs needed to get smart not to avoid a solitary T. rex, but a pack of them. Though I'll admit that this is something that will probably elude us, and the question, T. rex, lion or tiger, will remain. Currie, btw, did not discuss hadrosaur intelligence in his book, that's just my personal take on this, rightly or wrongly.

Edited April 20, 2021 by Wepwawet

[SHaYap]

2 hours ago, Wepwawet said:

Though I'll admit that this is something that will probably elude us, and the question, T. rex, lion or tiger, will remain.

If feathered? 

I'm still leaning with the idea of t Rex being more like the monitor lizards, or hyenas, not quite primarily predator and happily a scavenger. If the population of giants were littering the landscape of the day, just one carcass will feed plenty, pack or pride. 

~

[Wepwawet]

45 minutes ago, third_eye said:

If feathered? 

I'm still leaning with the idea of t Rex being more like the monitor lizards, or hyenas, not quite primarily predator and happily a scavenger. If the population of giants were littering the landscape of the day, just one carcass will feed plenty, pack or pride. 

~

I think feathered as a juvenile, though the feathers will be more like the filaments seen on it's distant relative Yutyrannus, not veined feathers. At adult size it's too big to need a covering, unless it was active in the same type of environment as Yutyrannus, and it's equally feathered ornithopod prey. Adult hadrosaurs don't show signs of being feathered, as "mummified" skin impressions show, and as they were about the same body mass as a T. rex, I think it's safe to say that a covering on an adult T. rex would be counterproductive, though I would not rule out some gaudy "mohican" for display purposes.

I would say that T. rex. like most carnivores, took it's food when and where it could, and that will involve scavenging. But now the nitty gritty arguments about whether it was primarily a scavenger or a hunter. Let's take Horner because of his comments about the eyes of T. rex, calling them "beady little eyes", and then others pointing out that T.rex had a superb sense of smell. Together a picture can be painted of an animal with "poor vision" though a great nose, therefore it fits the bill as a scavenger. But there are problems with this. T. rex has eyes that do look "beady" in it's oversized head sitting on a large body, but it has the largest eyes of any land animal, and their size in relation to the animals overall size is not relevant. Would an obligate scavenger need what was probably superb vision, not I would say for a land bound animal, a vulture, yes.

Sense of smell is a bit more ambiguous. I would imagine that a herd of hadrosaurs could be smelt from some distance with just a mediocre sense of smell, so I don't know why it would need such a good sense, but then wolves have a great sense of smell and are primarily hunters. Maybe there are environmental factors at play, I don't know.

How much food will an active warm blooded animal such as a T.rex need, perhaps proportionally as much as a lion, so needing a full belly every three or four days. Could the death rate of hadrosaurs by natural means supply the needs of T. rex, and added to that, what was the ratio of hunter to prey, Bakker suggested that it was about same in the time of T.rex to the African savanna today. I doubt lions could survive just by scavenging, and the same with hyenas. Modern cold blooded reptiles have far less need to find food on a daily basis, or even on a monthly basis for the likes of crocs or Komodo dragons.

There is also the issue of T. rex being the only large theropod in it's range during it's existance as a species, and until 2015 with the discovery of the large maniraptor Dakotaraptor, there was nothing even approaching T. rex in size. Dakotaraptor might have caused problems for juvenile T. rex, but not adults. So far only one example of Dakotaraptor has been found, minus it's head so we cannot tell what it might have eaten, small ornithopods and other maniraptors I would guess, unless it was a pack hunter and took down hadrosaurs, not an impossibe scenario. Otherwise we have this population of large herd animals and, without further information on Dakotaraptor, seemingly only T. rex as their predator.

If T. rex was an obligate  scavenger, as some believe, or even spent some time scavenging, what was acting as the natural predator of these herds of hadrosaurs, and other large ornithiscians, sauropods having gone extinct in that part of the world long ago. I would say that on the basis of what we know at this time, if T. rex did not act as the apex predator, and as primarily a predator, we would have a serious imbalance of nature with nothing controlling an ever exapanding population of hadrosaurs and other large ornithiscians.

Another factor in determining if T. rex were a hunter is the already mentioned wounds to hadrosaurs, from which they survived. The speed of any dinosaur is always a topic with widely ranging views, but going on the current thinking, T. rex may have managed 25mph. The average hadrosaur may have managed 30mph, some estimates go up to 35mph. What do they need to run from if not their primary predator, T. rex, and that the wounds found on fossils are at the tail end does indicate a stern chase with the T. rex just managing to get it's teeth on the tail. I see an analogy with lions getting up behind a wildebeest and just managing to rake their claws down it's rump before it escapes.

And finally, there is, IMO, the growth rate of T. rex to be taken into consideration. T. rex had just about exactly the same rate of growth as us. Comparatively slowly up until about 13-14, then a sudden massive increase until they reached their full size at about 18. This rapid rate of growth is going to need massive amounts of food, teenagers whether T,rex or humans, don't change. I really don't believe that they could have sustained themselves by scavenging, and needed to hunt, again and again and again. At the start and early stages of this growth spurt, could a T.rex have taken down a hadrosaur by itself, I would say not as it just is not tall and bulky enough. Certainly fast enough though, fast enough, and intelligent enough, to drive hadrosaurs towards the adult T.rex ambush? who knows.

Yeah, reading this it sounds like a copy and paste from a wiki article, but it's not, so may be inaccurate accurate here and there.

[SHaYap]

6 minutes ago, Wepwawet said:

Yeah, reading this it sounds like a copy and paste from a wiki article, but it's not, so may be inaccurate accurate here and there.

Outside of the classroom nobody can say for certain one way or another, t Rex population was widespread across many terrain and climate conditions, wouldn't surprise me if they adapted specifically and regionally too. 

I still wonder how far north of the Arctic they actually roamed. 

~

[Wepwawet]

9 minutes ago, third_eye said:

Outside of the classroom nobody can say for certain one way or another, t Rex population was widespread across many terrain and climate conditions, wouldn't surprise me if they adapted specifically and regionally too. 

I still wonder how far north of the Arctic they actually roamed. 

~

I don't think T.rex appeared further north than Montana, and north of that we get Albertasaurus. Yutyrannus lived in what became northern China and Siberia, which was cold back then, though not as cold, though there are tens of millions of years separating Yutyrannus and T. rex. Tarbosaurs lived in what became Mongolia, which was even back then a bit of a desert. There is a bit of an issue in that animals living in colder and more mountainous regions tend not to get fossilized due to lack of swamps and slow flowing silty rivers, so there is a huge gap in the already huge gap in knowledge. We actually know so little that I think if we could go back we would get a huge surprise and throw all our present ideas and books out the window, to the amusement of troodondids studying us, but that might be fiction.

[Wepwawet]

6 hours ago, Wepwawet said:

 Intelligence is another factor, crocs don't need great intelligence to live as they do, and their Reptile Encephalization Quotient is at the base level of 1.0, which means they are right at the level they need to be for their body mass. On the other hand, the T. rex REQ is around 7.8, which indicates a vast difference in potential intelligence, it's the equivalent between a cat and us.

 

Oops, too high on the REQ. I have two sets of info in my mind, one states 7.8, the other is a variable set of figures more a little short of 3.0. Even so, T.rex was not "stupid", no animal is, except us.

Encephalization quotients are difficult to accurately gauge, with discrepancies between members of the same species, and with dinosaurs, arguments about how much of the brain case was filled with brains, and how much by "padding". This is the prime reason why widely different results are obtained, and confusion caused.