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Author Topic: Dinosaurs and other prehistoric creatures  (Read 184248 times)

DoomRulz
Mar 13, 2014, 11:08:59 AM
Reply #945 on: Mar 13, 2014, 11:08:59 AM
Q
That would be Cambrian, Silurian, and Devonian-era life you'd be interested in then. Armoured fish, giant orthocones, & sea scorpions were the big guys on the block.


Vertigo
Mar 13, 2014, 06:06:50 PM
Reply #946 on: Mar 13, 2014, 06:06:50 PM
Q
Hmm may I ask you experts for some advices:
I have started to read 3 books about prehistoric life and dinos but when reading in this thread your knowledge is far beyond what i have at the moment, how did you guys and girls manage to learn so much about these time eras and wildlife? Working with it or studied it or just personal interest which lead you to read all books and documentaries you could find?
Advices you have for someone like me who want to learn and become a mini pro at this? :)

Well, in my opinion the best way is to build up your knowledge base in a graded way. If you dived straight in to an academic book, it'll be indecipherable and impenetrable, because they're jam-packed with terminology, descriptors and cladistic groups that wouldn't mean anything to you. If you read something more accessible, you'll be exposed to enough tricky terms that you'll be able to fill in the gaps and figure out what the more advanced works are saying. Here are a few avenues you can pursue for dinosaur research, with their approximate level:

-TV programmes. These vary in quality, but all tend to be very basic - accessible to anyone, rarely offering much in the way of academia. And in many cases, they'll be rife with inaccuracy. Walking With Dinosaurs, for example, was littered with errors and speculation even at the time, and at 15 years old it's been left far behind by modern palaeontology's rapid pace. Planet Dinosaur was based on sound science from what I remember. For the most part, these will just be helping you put together an image of the Mesozoic world, and developing a basic familiarity with the major dinosaur groups.
Every so often they have a piece of very useful information that's hard to find elsewhere (such as the results of the spinosaurid oxygen isotope research in Planet Dinosaur), but you should take everything you learn on these shows with a pinch of salt until you can find a corroborating source.

-Generalist dinosaur books. Non-academic books for adults are quite few and far between, but should provide you with a proper fundamental grounding. Find a good one, re-read it a couple of times, and you'll have a good knowledge base.
I can't really offer you much in the way of recommendation. The last one I read was Paul Barrett's Dinosaurs: A Natural History, but this was in 2002, it'll be hopelessly outdated by now. Things to look for... make sure it's from the last decade at least, and ideally within the last five years. If it has a scaly Velociraptor pictured anywhere, it's a no-go.
I can recommend DK's Prehistoric: The Visual History Of Life On Earth to build up a general knowledge of life's entire history, and an understanding of how the different groups inter-relate. If you're looking for specific information about anything in particular, though, you're out of luck with that one.
One proviso with books. In most cases, they aren't peer-reviewed, and will contain the viewpoint of just one or two experts. As Doom mentioned earlier, every palaeontologist and enthusiast has a different viewpoint, and will disagree on a wide range of subjects (you might even disagree with them yourself as you learn more). Some researchers have highly controversial views that they'll try to convey as proven fact. If there are multiple authors who worked on the book, it should prove more reliable.

-Online resources.
Wikipedia might sound like a cop-out, but the palaeontology sections are brilliantly curated. It's generally very reliable, and absolutely jam-packed with good information, written at a level that you're probably already ready for (I'm listing these avenues as kind of a tiered approach, if you haven't noticed yet). If a question suddenly pops into your mind - "What was Tyrannosaurus' top speed?" "Which animals occupied X ecosystem at Y time?" "Was Michael Crichton right about Z?" - fire up Google and open the relevant Wikipedia page. You'll often find yourself falling down a rabbit hole of time-annihilating information sponging. Similarly, if you hear some tidbit on TV or in a newspaper that piques your interest, fact-check it in Wikipedia to verify its accuracy.
If you come across a word that you're not familiar with (there may be a lot of them on Wikipedia), look it up on Google. This will set you up nicely for more advanced research in the future.
Google's also great for bring up news articles in National Geographic or similar, and the image search is useful if you just have to see a particular fossil for any reason.
Basically... be curious. There's a virtually bottomless well of information at the end of your ethernet cable, and easily found. Wikipedia's usually a better source than most books, because it's curated by multiple authors. Where there's a difference of opinion, both perspectives will usually be detailed.

If you have any question about dinosaur evolutionary relationships, there's just one stop you need to make: thescelosaurus.com. Its cladogram is the best I've ever seen, and lists every remotely viable dinosaur genus. There's a full table for understanding the subdivisions of geological time here. Most of the information here is compiled from ultimate dinosaur tome™ The Dinosauria, a monstrously comprehensive 700-page peer-reviewed academic work which is virtually impenetrable to pretty much everyone.
I do strongly recommend sitting down and taking a flick through Thescelosaurus' clade index, it may be low-tech but I consider it an indespensable resource. You do need a familiarity with the various group names though, which is why I suggest a thorough reading of a generalist adult book first.

-Looking out the window. You can understand a lot about extinct animals by studying living animals which either are related, or occupy a similar ecological niche and body plan. If every palaeontologist did this properly, there question of Tyrannosaurus being an exclusive scavenger would never have been seriously entertained - no living terrestrial vertebrate does it, and even among birds, it's just the vulture, a creature which can travel hundreds of miles with negligible energy expenditure. Anyway, the more you study today's animals, the more you'll understand. Population densities, thermoregulation, energetics, behavioural patterns... a vast amount of it can be transposed to extinct fauna.
Also, if you put a bird feeder in your back garden, you'll have a tiny, highly specialised and successful dinosaur visiting you every day.

-Academic books. If it's written by an active palaeontologist then it's likely to be at this level. Typically, they'll be a tough read, and you'll need quite a broad internal dictionary of technical terms to get through it. But if you build up to it, reading at this level is very attainable. Recent examples I've read and can recommend:

Gregory S Paul's Dinosaurs: A Field Guide. As Doom pointed out, Paul isn't a qualified palaeontologist, and some of his views I strongly disagree with. But this book is extraordinarily comprehensive, with in-depth information about dinosaur biology and ecology, followed by the bulk of the book containing basic information about every viable dinosaur genus (or those he considers viable, I should say). The skeletal diagrams are peerless, and show which parts of the skeleton have been discovered; these diagrams are used for most major species. Even if the early part of the book is impenetrable to you, you might want to pick it up anyway, just for the sake of leafing through the diagrams.
Mark Witton's Pterosaurs: Natural History, Evolution, Anatomy. Alright, this one's not actually about dinosaurs, but it's always helpful to know more about the ecosystems they inhabited; pterosaurs were an important part of that, and occupied niches that remain vacant to this day. I won't say the book brings them to life, it's very stuffily written, but you couldn't ask for anything more comprehensive. More importantly to this topic, this is one of the few academic books which actually explains a lot of its terminology, making it unusually accessible, and a handy stepping-stone for getting into other works.
Matthew P Martyniuk's Field Guide To Mesozoic Birds And Other Winged Dinosaurs. This is quite a short book, and reasonably accessible. It actually focuses more on what most of us would call dinosaurs rather than birds, starting with the most basal example of vaned feathers (and wings) in the oviraptorids. He uses some very unusual cladistics (ever heard of a deinodontid?), but what particularly stands the book apart is that the bulk of it is comprised of illustrations and general information for every relevant species... and the dinosaurs will be considerably birdier than you're accustomed to. Which is not an inaccuracy.
The Dinosauria, which I mentioned earlier, is generally considered the ultimate resource for dinosaur information, but it's at such a high level (and unintuitively presented) that graduates struggle to grapple with it. It's at a level where I can just about understand it, but it's not the kind of thing you can just sit and read.

And one more thing - if you have a question, post it on here. I'm happy to help, and I'd imagine a few other people will be too.



Anyway, that's my advice. Personally, I've been very interested in prehistoric life, evolution and ecology, and particularly dinosaurs, pretty much all my life. I've had a great deal of free time to just sponge up information wherever I can find it, and I've listed some of my favourite sources. At one point I'd intended to study Palaeobiology & Evolution at Portsmouth University when my health picked up, but that's not really on the cards now.


Xenodog
Mar 13, 2014, 08:26:59 PM
Reply #947 on: Mar 13, 2014, 08:26:59 PM
Q
Top notch post as ever Vertigo.  8)

I can recommend DK's Prehistoric: The Visual History Of Life On Earth to build up a general knowledge of life's entire history, and an understanding of how the different groups inter-relate. If you're looking for specific information about anything in particular, though, you're out of luck with that one.
Straight up yes. This is still one of the best dinosaur books on the market.

If every palaeontologist did this properly, there question of Tyrannosaurus being an exclusive scavenger would never have been seriously entertained - no living terrestrial vertebrate does it, and even among birds, it's just the vulture, a creature which can travel hundreds of miles with negligible energy expenditure.
Not entirely. There is also the Brown Hyaena. Whilst the brown hyaena (often unsuccessfully) hunts around 5% of it's prey and also eats Kalahari truffles, tsama melons and ostrich eggs, the bulk of it's diet (over 80%) is simple carrion. But this brings up what I think could be interesting ecological comparisons.
Brown hyaena live in areas with good predator guilds = lots of carrion to appropriate. Did Rex have the same potential? Possibly not, as there doesn't seem to be many sympatric carnivores other than much smaller dromeosaurs. But i think it's been noted how much more lighter young rexes were. It's possible adults could steal a large percentage of their food from their own young.

I should also add I don't think it was one, I just think it's an interesting thing to explore. I of course believe it is both, like the majority of carnivores today, with adaptations that also allow it to find carrion like many carnivores today.

Matthew P Martyniuk's Field Guide To Mesozoic Birds And Other Winged Dinosaurs. This is quite a short book, and reasonably accessible. It actually focuses more on what most of us would call dinosaurs rather than birds, starting with the most basal example of vaned feathers (and wings) in the oviraptorids. He uses some very unusual cladistics (ever heard of a deinodontid?), but what particularly stands the book apart is that the bulk of it is comprised of illustrations and general information for every relevant species... and the dinosaurs will be considerably birdier than you're accustomed to. Which is not an inaccuracy.
I've spoke with the author online, great guy. Also seen some quotes and work of his on display on Montana, in some of the cool dinosaur museums there.

At one point I'd intended to study Palaeobiology & Evolution at Portsmouth University when my health picked up, but that's not really on the cards now.
Oh man, what happened there man?  :-\


Vertigo
Mar 14, 2014, 12:51:33 AM
Reply #948 on: Mar 14, 2014, 12:51:33 AM
Q
Why thank you!

If every palaeontologist did this properly, there question of Tyrannosaurus being an exclusive scavenger would never have been seriously entertained - no living terrestrial vertebrate does it, and even among birds, it's just the vulture, a creature which can travel hundreds of miles with negligible energy expenditure.
Not entirely. There is also the Brown Hyaena. Whilst the brown hyaena (often unsuccessfully) hunts around 5% of it's prey and also eats Kalahari truffles, tsama melons and ostrich eggs, the bulk of it's diet (over 80%) is simple carrion. But this brings up what I think could be interesting ecological comparisons.
Brown hyaena live in areas with good predator guilds = lots of carrion to appropriate. Did Rex have the same potential? Possibly not, as there doesn't seem to be many sympatric carnivores other than much smaller dromeosaurs. But i think it's been noted how much more lighter young rexes were. It's possible adults could steal a large percentage of their food from their own young.

I should also add I don't think it was one, I just think it's an interesting thing to explore. I of course believe it is both, like the majority of carnivores today, with adaptations that also allow it to find carrion like many carnivores today.

How did I not know about the brown hyena? Well spotted. It does sound like it's a bit of a generalist to a degree, I wonder how comparable that diet would be to something like a fox.

With regards to rexy's ecosystem, it did contain a wide variety of herbivores, but most importantly, vast herds of elephant-sized animals (both ceratopsians and hadrosaurs). Because Tyrannosaurus' growth exploded during late adolescence, they'd have to be virtually adult before they could tackle mature examples of those herbivores - a ten-year-old rex probably didn't have the mass or musculature to take them on.
And the trouble is, scavenging the kills of their smaller kin (or other predators such as Acheroraptor) just wouldn't be enough to keep the adults well fed. A 250-kilo Struthiomimus would be a standard kill for a juvenile rex, but for a 6-ton adult, that's like a lion eating a serval - barely enough to keep it fuelled through the day.
The only predator in the ecosystem that could bring down prey suitable for an adult Tyrannosaurus, would be another adult Tyrannosaurus.

That said, I do think rexes may have fulfilled an important ecological function of the vulture: hoovering up any meat left standing around, which otherwise would slowly rot and become a breeding ground for contagion. They were well-adapted for finding a free meal if one happened to be in the area, and could gulp it down bones-and-all.

At one point I'd intended to study Palaeobiology & Evolution at Portsmouth University when my health picked up, but that's not really on the cards now.
Oh man, what happened there man?  :-\

I've had chronic fatigue syndrome for most of my life, and seriously since I was 14. I'd been hoping it would have buggered off by the time I got into my twenties, but eight years into them, it's still there and I still can't do very much. I'm currently struggling with two weekly hours of voluntary work which basically consists of sitting in a room and occasionally talking to people, plus just enough moderate exercise to prevent me degenerating into a porcine lump.

« Last Edit: Mar 14, 2014, 12:53:42 AM by Vertigo »

Sabby
Mar 14, 2014, 01:29:44 AM
Reply #949 on: Mar 14, 2014, 01:29:44 AM
Q
This thread has to have the most intellectually emasculating posts I've seen on this website ._____.


Xenodog
Mar 14, 2014, 10:52:17 AM
Reply #950 on: Mar 14, 2014, 10:52:17 AM
Q
How did I not know about the brown hyena? Well spotted. It does sound like it's a bit of a generalist to a degree, I wonder how comparable that diet would be to something like a fox.
It does eat any carrion and protein it can find, but comparing it to foxes from say, here in Britain from Prof. David MacDonald's early field studies of them (Running with the Fox, if you're interested!) in England, foxes are the greater generalists I'd say. Much less carrion, much more small vertebrates, invertebrates and fruit.
Though the bulk of the good Brown hyaena studies have been done in either the southern Kgalagadi Transfrontier Park, or the Central Kalahari area, both highly arid. It is relatively understudied in the lusher bushveld or lowveld or Botswana or South Africa where it's diet may be different.

With regards to rexy's ecosystem, it did contain a wide variety of herbivores, but most importantly, vast herds of elephant-sized animals (both ceratopsians and hadrosaurs). Because Tyrannosaurus' growth exploded during late adolescence, they'd have to be virtually adult before they could tackle mature examples of those herbivores - a ten-year-old rex probably didn't have the mass or musculature to take them on.
Though haven't there been arguments for possible pack hunting in young rexes? And don''t forget young animals. Juvenile hadrosaurs or ceratopsians would certainly be a large meal - far bigger than struthiomimus  - and yet not out the reach of a young rex.
But again, this is just playing ideas, I'm not serious on adult rex being scavengers!
But thinking about it, taking young prey may provide ecological separation between juvenile and adult rexes to reduce competition that could lead to cannibalism; modern predators today take different ages classes of common herbivores to avoid competition. The different age groups of Rexes could almost act as an entire predator guild itself.

That said, I do think rexes may have fulfilled an important ecological function of the vulture: hoovering up any meat left standing around, which otherwise would slowly rot and become a breeding ground for contagion. They were well-adapted for finding a free meal if one happened to be in the area, and could gulp it down bones-and-all.
Aye, agreed. I think when Jack Horner compared it to a spotted hyaena (ignorantly so, not knowing of their hunting prowess) he on the money: An active predator that scavenges whenever it has the chance.


I've had chronic fatigue syndrome for most of my life, and seriously since I was 14. I'd been hoping it would have buggered off by the time I got into my twenties, but eight years into them, it's still there and I still can't do very much. I'm currently struggling with two weekly hours of voluntary work which basically consists of sitting in a room and occasionally talking to people, plus just enough moderate exercise to prevent me degenerating into a porcine lump.
Really sorry to hear that man.  At least you can always have armchair paleontology!


DoomRulz
Mar 14, 2014, 11:22:25 AM
Reply #951 on: Mar 14, 2014, 11:22:25 AM
Q
With regards to rexy's ecosystem, it did contain a wide variety of herbivores, but most importantly, vast herds of elephant-sized animals (both ceratopsians and hadrosaurs). Because Tyrannosaurus' growth exploded during late adolescence, they'd have to be virtually adult before they could tackle mature examples of those herbivores - a ten-year-old rex probably didn't have the mass or musculature to take them on.
And the trouble is, scavenging the kills of their smaller kin (or other predators such as Acheroraptor) just wouldn't be enough to keep the adults well fed. A 250-kilo Struthiomimus would be a standard kill for a juvenile rex, but for a 6-ton adult, that's like a lion eating a serval - barely enough to keep it fuelled through the day.
The only predator in the ecosystem that could bring down prey suitable for an adult Tyrannosaurus, would be another adult Tyrannosaurus.

That said, I do think rexes may have fulfilled an important ecological function of the vulture: hoovering up any meat left standing around, which otherwise would slowly rot and become a breeding ground for contagion. They were well-adapted for finding a free meal if one happened to be in the area, and could gulp it down bones-and-all.

I first heard your last point mentioned in an episode of PaleoWorld entitled, "The Legendary T.Rex" and Peter Larson and Phil Currie said the same thing. Of course, it featured Jack Horner who seemed (as he does now) hell-bent on proving T.Rex just couldn't have been a hunter, end of story. You'd think they guy's lawyer was eaten by a T.Rex and he has a personal vendetta or something.

All the evidence points to T.Rex being primarily a hunter, the most damning of which is the Triceratops frill with a healed Rex bite mark. At the same time, every top hunter in an ecosystem will scavenge. They all do; it's that simple.

Though haven't there been arguments for possible pack hunting in young rexes? And don''t forget young animals. Juvenile hadrosaurs or ceratopsians would certainly be a large meal - far bigger than struthiomimus  - and yet not out the reach of a young rex.
But again, this is just playing ideas, I'm not serious on adult rex being scavengers!
But thinking about it, taking young prey may provide ecological separation between juvenile and adult rexes to reduce competition that could lead to cannibalism; modern predators today take different ages classes of common herbivores to avoid competition. The different age groups of Rexes could almost act as an entire predator guild itself.

I don't know about juveniles specifically, but I have read about T.Rex in general hunting in packs. I'm not sure I agree because the only animal that shared T.Rex's environment that would warrant pack hunting is Alamosaurus. There's also been speculation by Thomas Holtz of the University of Maryland that T.Rex may have only hunted juvies because the adults were simply too big to go after. In this instance, it's hypothesized that Alamosaurus reached Sauroposeidon proportions. For an animal like T.Rex, when you have ceratopsians and hadrosaurids running about, there's no reason to go after something that big.


Vertigo
Mar 14, 2014, 10:51:25 PM
Reply #952 on: Mar 14, 2014, 10:51:25 PM
Q
With regards to rexy's ecosystem, it did contain a wide variety of herbivores, but most importantly, vast herds of elephant-sized animals (both ceratopsians and hadrosaurs). Because Tyrannosaurus' growth exploded during late adolescence, they'd have to be virtually adult before they could tackle mature examples of those herbivores - a ten-year-old rex probably didn't have the mass or musculature to take them on.
Though haven't there been arguments for possible pack hunting in young rexes? And don''t forget young animals. Juvenile hadrosaurs or ceratopsians would certainly be a large meal - far bigger than struthiomimus  - and yet not out the reach of a young rex.
But again, this is just playing ideas, I'm not serious on adult rex being scavengers!
But thinking about it, taking young prey may provide ecological separation between juvenile and adult rexes to reduce competition that could lead to cannibalism; modern predators today take different ages classes of common herbivores to avoid competition. The different age groups of Rexes could almost act as an entire predator guild itself.

Yeah, I did think about the potential with pack hunting when I was writing my last post. Trouble is, pack hunting is virtually impossible to prove - pretty much the only thing that can do it conclusively is an extraordinary set of footprints. We aren't even certain about Deinonychus' pack hunting, even though it seems obvious given the frequency with which numerous teeth are found in association with the vastly larger ornithopod Tenontosaurus.
My view is, looking at the relationships between big game hunters and their prey, the ideal target tends to be roughly in the region of the weight (or combined weight) of the hunters. This makes sure there's enough to go around. Tyrannosaurus reached a size equivalent to an adult Struthiomimus at just a few years old, so it seems there wasn't a particular need for them to combine arms.

The argument for pack hunting in tyrannosaurids is mainly resting on a fossil site which appears to preserve a 'pride' of Albertosaurus; numerous individuals of wildly varying ages. Currie's even suggested the possibility of the whole family hunting together, with the fast youngsters flushing prey towards the adults.
It's not really a theory I support. Social groups don't necessarily infer group hunting. A good example of this is the great white shark, which in many ways (despite a wholly different environment) is quite analogous to Tyrannosaurus - immensely potent battery of senses, excessive musculature, hunting strategy focused on inflicting massive tissue loss and shock in a single bite. Great whites often travel together, and form groups segregated by age or gender, but they always hunt alone.
My opinion is that Tyrannosaurus (or Albertosaurus at least) formed family groups, with each individual making kills separately. The advantage for the adults would be that having their offspring within their territory, they could protect them against rival adults. Using their extraordinary sense of smell, they could all converge back together when one of them made a kill. Just a theory, anyway.


... Jack Horner who seemed (as he does now) hell-bent on proving T.Rex just couldn't have been a hunter, end of story. You'd think they guy's lawyer was eaten by a T.Rex and he has a personal vendetta or something.

I think Horner's problem is that he's particularly fond of ceratopsians and hadrosaurs, and doesn't take too kindly to anything that saw them as walking lunchboxes.


I don't know about juveniles specifically, but I have read about T.Rex in general hunting in packs. I'm not sure I agree because the only animal that shared T.Rex's environment that would warrant pack hunting is Alamosaurus. There's also been speculation by Thomas Holtz of the University of Maryland that T.Rex may have only hunted juvies because the adults were simply too big to go after. In this instance, it's hypothesized that Alamosaurus reached Sauroposeidon proportions. For an animal like T.Rex, when you have ceratopsians and hadrosaurids running about, there's no reason to go after something that big.

It wouldn't surprise me if nothing touched Alamosaurus once they reached a certain size. It took them many years to reach adulthood (I've read 45 for full size), during most of which they'd be fair game for rexes of various ages. I'd imagine a tiny percentage of them would reach maturity.

« Last Edit: Mar 15, 2014, 05:09:58 PM by Vertigo »

Xenodog
Mar 14, 2014, 11:43:18 PM
Reply #953 on: Mar 14, 2014, 11:43:18 PM
Q
Good comparison of Rex vs. Great white. Also agree it was unlikely a whole family hunted together. Ate, maybe, hunted, no. With modern group hunting predators the youngsters never play a prevalent role. In wolves, pairs (male and female combo) are the significantly most successful because youngsters that form the pack just f*ck everything up.

And on age and maturity...wasn't Sue estimated to be 28?


Vertigo
Mar 15, 2014, 12:16:38 AM
Reply #954 on: Mar 15, 2014, 12:16:38 AM
Q
She is indeed, I meant Alamosaurus in that last paragraph. I'll edit it to make it clear.

« Last Edit: Mar 15, 2014, 05:11:11 PM by Vertigo »

judge death
Mar 15, 2014, 02:55:52 AM
Reply #955 on: Mar 15, 2014, 02:55:52 AM
Q
Thank you so much Vertigo and DoomRulz!

I will try these advices and what you wrote, I see it is the same way in how I learned so much about WW1-2, read everything I can and build up my knowledge and then go further from there.
Will later check out these books and try to find some others as well. Now I will be busy for the closest half year!

I will ask here and ask for help when needed :)

Vertigo: Sad to hear about that, you sound like someone who should have a such job in no time or be a guide or such at a museum, you know probably already more than most in this area :)


Vertigo
Mar 15, 2014, 08:09:12 AM
Reply #956 on: Mar 15, 2014, 08:09:12 AM
Q
Thank you.  :)


DoomRulz
Mar 15, 2014, 04:59:00 PM
Reply #957 on: Mar 15, 2014, 04:59:00 PM
Q
My opinion is that Tyrannosaurus (or Albertosaurus at least) formed family groups, with each individual making kills separately. The advantage for the adults would be that having their offspring within their territory, they could protect them against rival adults. Using their extraordinary sense of smell, they could all converge back together when one of them made a kill. Just a theory, anyway.

Is this sort of behaviour present in modern-day reptiles? My only issue with this is that beyond a certain age, adults would see juveniles as a food source because paternal/maternal instincts would wear out.

... Jack Horner who seemed (as he does now) hell-bent on proving T.Rex just couldn't have been a hunter, end of story. You'd think they guy's lawyer was eaten by a T.Rex and he has a personal vendetta or something.

I think Horner's problem is that he's particularly fond of ceratopsians and hadrosaurs, and doesn't take too kindly to anything that saw them as walking lunchboxes.

Heh, wouldn't surprise me. I think he's also bitter because science journals aren't sucking his cock anymore for discovering Maiasaura.

I don't know about juveniles specifically, but I have read about T.Rex in general hunting in packs. I'm not sure I agree because the only animal that shared T.Rex's environment that would warrant pack hunting is Alamosaurus. There's also been speculation by Thomas Holtz of the University of Maryland that T.Rex may have only hunted juvies because the adults were simply too big to go after. In this instance, it's hypothesized that Alamosaurus reached Sauroposeidon proportions. For an animal like T.Rex, when you have ceratopsians and hadrosaurids running about, there's no reason to go after something that big.

It wouldn't surprise me if nothing touched them once they reached a certain size. It took them many years to reach adulthood (I've read 45 for full size), during most of which they'd be fair game for rexes of various ages. I'd imagine a tiny percentage of them would reach maturity.

Indeed, but here's something I just thought of. With the discovery of Mapusaurus, multiple fossils were found in a bed together suggesting they at least hunted in gangs (but like you said, it doesn't mean they lived together in a unit). Paleontologists have established a predator/prey relationship between it and Argentinosaurus (adults, specifically) so I don't think it's far-fetched to use that as an analogy when describing T.Rex/Alamosaurus. The only difference would be what other herbivores were around during the time of Mapusaurus in Argentina. Like I said, with smaller prey items around, why go after a giant?

Thank you so much Vertigo and DoomRulz!

Cheers! Enjoy the journey :)


Vertigo
Mar 15, 2014, 07:11:22 PM
Reply #958 on: Mar 15, 2014, 07:11:22 PM
Q
My opinion is that Tyrannosaurus (or Albertosaurus at least) formed family groups, with each individual making kills separately. The advantage for the adults would be that having their offspring within their territory, they could protect them against rival adults. Using their extraordinary sense of smell, they could all converge back together when one of them made a kill. Just a theory, anyway.

Is this sort of behaviour present in modern-day reptiles? My only issue with this is that beyond a certain age, adults would see juveniles as a food source because paternal/maternal instincts would wear out.

Well, for starters, Tyrannosaurus is much closer-related to birds than any extant reptile, and even has the beginnings of an avian brain structure. Most birds provide some form of parental care until the offspring is more or less fully grown, but of course no bird takes 18 years to reach full size (and Tyrannosaurus had the physical tools to fend for itself from a young age, unlike most birds).

It also has a higher encephalisation quotient (brain size in relation to what's expected for the body weight) than any non-maniraptoran dinosaur that I know of - nearly double that of a crocodile, I believe, if you use the reptile EQ formula. I'm not particularly well versed in reptile behaviour, they constantly surprise me, but rexy had an unusual and possibly exceptional mental toolbox. Given the animal's potent sense of smell, it could easily recognise specific individuals, and it may have been smart enough to remember familial connections over extended periods.

With the discovery of Mapusaurus, multiple fossils were found in a bed together suggesting they at least hunted in gangs (but like you said, it doesn't mean they lived together in a unit). Paleontologists have established a predator/prey relationship between it and Argentinosaurus (adults, specifically) so I don't think it's far-fetched to use that as an analogy when describing T.Rex/Alamosaurus. The only difference would be what other herbivores were around during the time of Mapusaurus in Argentina. Like I said, with smaller prey items around, why go after a giant?

Yeah, I agree with that. It's not implausible for Tyrannosaurus to gang up to hunt adult sauropods, it's just that it seems unnecessary. Given Alamosaurus' lengthy growth period, I'd imagine there would be at least as many juvenile animals as adults at any one time, which still gives a lone rex plenty of predatory opportunities within that species. Plus, as you say, there are other species which made good targets for Tyrannosaurus.


Predators today take different ages/classes of common herbivores to avoid competition. The different age groups of Rexes could almost act as an entire predator guild itself.

I forget to reply to this bit earlier, but yes, I completely agree. Tyrannosaurus had different specialisations at various ages, and could probably catch its own prey when it was young. Given the absence of any predator between dromie-size and Tyrannosaurus-size in the ecosystem, but plenty of herbivores that fit in the bracket, it seems that young rexes filled the niche.





(New post)

There's an important new tyrannosaurid on the block: Nanuqsaurus hoglundi.

One unusual element is its size - nearly half the length of Tyrannosaurus at 25ft, and the specimen appears to be mature (the skull bones are fused). I'm pretty sure this makes it the smallest known adult tyrannosaurid. It's also very closely related to rexy.

Second thing is the environment. This is an arctic tyrannosaurid, discovered in northern Alaska. During winter months the region became very dark and cold, and it appears the population was isolated by a mountain range (hence the genetic differentiation from southern tyrannosaurids - it's the same with the giant Alaskan Troodon, which was contemporaneous).

Nanuqsaurus' smaller size was probably related to the local conditions - either due to a comparative scarcity of prey, or because it had difficulty hunting in the dark (it's unknown how well tyrannosaurids could see at night). Being lighter meant it could survive on less.
Troodon was specialised for nocturnal predation, so probably grew larger because it had more hours than usual to hunt in optimal conditions.


Some handy illustrations:

Scale bar = 1 metre. A: Nanuqsaurus. B: Tyrannosaurus rex (Sue). C: Tyrannosaurus rex (AMNH 5027 from the American Museum of Natural History). D: Daspletosaurus torosus. E: Albertosaurus sarcophagus. F: Troodon formosus, southern species. G: Troodon, northern species (estimate based on tooth size).

And a superb cladogram detailing the age and relationships of Tyrannosauroidea, including its latest addition. The thick bars delineate uncertainty range of a genus' age, rather than its overall timespan.

« Last Edit: Mar 15, 2014, 11:32:25 PM by Vertigo »

DoomRulz
Mar 17, 2014, 12:50:40 PM
Reply #959 on: Mar 17, 2014, 12:50:40 PM
Q
Forget Nanotyrannus, here's a real pygmy tyrannosaur, lol. A tyrannosaurid that could be bullied by a troodontid; blasphemy I tells ya.



 

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