Erm...correct me if I'm wrong but....

Alvin T. Grey

http://www.sciencedaily.com/releases/2010/10/101015185836.htm

<snip>
Yale researcher Nick Longrich discovered a bone with especially large gouges in them. Given the age and location of the fossil, the marks had to be made by T. rex, Longrich said. "They're the kind of marks that any big carnivore could have made, but T. rex was the only big carnivore in western North America 65 million years ago."

Was that correct, taken out of context, or was Albertasaurus, Gorgosaurus et al. extinct by then.

Galvasean

Albertosaurus, Daspletosaurus all lived over 70 million years ago. There is currently no evidence of their time-frame overlapping with Tyrannosaurus rex.

Rubecula

Any ecology with only one predator species in it would be a little strange. T.rex may have been the biggest but to say it was the only one would be pushing believability a bit in my own honest opinion.

Galvasean

Rubecula wrote: »

Any ecology with only one predator species in it would be a little strange. T.rex may have been the biggest but to say it was the only one would be pushing believability a bit in my own honest opinion.

Apparently the huge amount of change a juvenile T. rex went through before becoming an adult meant that Tyrannosaurus of various ages would have occupied a few predatory niches. There were also dromaeosaurs and also troodontids in the area too.

Adam Khor

The idea of a single species of predator occupying several niches is fascinating... but I'm pretty sure there were some other large predators around, we just haven´t found them.

Today, some large, fearsome predators can exclude others from certain areas and even, reduce their numbers or cause their localized extinction; this happened for example in Russia. When tigers are abundant, they cause wolves to become very scarce and even to dissappear from their territory.

Maybe T-Rex was like a tiger in that it would keep other smaller predators out of its territory and so, you are unlikely to find the remains of said predators in T-Rex territory. But it doesn´t mean T-Rex was the ONLY large carnivore in North America. That would be weird IMO.

Alvin T. Grey

http://palaeo.gly.bris.ac.uk/Communication/Lemke/Lemke.html

Guess I was reading this wrong, I thought that Albertasaurus was an older, but still comtemporary of T-Rex (analogous to Ceratasaurus and Alosaurus) both of which went extinct at the KT impact. I thought that Daspleteosauras was older.

And where in the mix Gorgosaurus (a T-rex in a different hat) came in is anyone's guess...

Alvin T. Grey

Galvasean wrote: »

Apparently the huge amount of change a juvenile T. rex went through before becoming an adult meant that Tyrannosaurus of various ages would have occupied a few predatory niches. There were also dromaeosaurs and also troodontids in the area too.

I have a problem with that theory, and not just because JH propounds it. Although Currie and Manning also seem to lean that way. The brain of a Nano-T would have to shift radically in it's skull for it to be a Juvinile T. It's eyes would have to become more binocular.

Animals change as they grow, but they don't change that much.

Adam Khor

Alvin T. Grey wrote: »

http://palaeo.gly.bris.ac.uk/Communication/Lemke/Lemke.html

Guess I was reading this wrong, I thought that Albertasaurus was an older, but still comtemporary of T-Rex (analogous to Ceratasaurus and Alosaurus) both of which went extinct at the KT impact. I thought that Daspleteosauras was older.

And where in the mix Gorgosaurus (a T-rex in a different hat) came in is anyone's guess...

There was a time when paleontologists believed there were Gorgosaurus remains in Hell Creek, but later they were moved to Nanotyrannus.
To my knowledge, Gorgosaurus is actually very similar to Albertosaurus, I think it used to be part of the same genus, and now some paleontologists believe it should be dragged back to Albertosaurus. Either way, it is less related to Tyrannosaurus than Daspletosaurus, Tarbosaurus or Zhuchengtyrannus are.

I wouldn`t be surprised though if an albertosaurine from the latest Cretaceous was found. They seem to have been much faster than tyrannosaurines; would be kind of like the tyrannosaurid version of the cheetah as opossed to the "lion-like" Tyrannosaurus or Daspletosaurus, so I can see them coexisting in the same habitat.

Of course, it would be even cooler to find a completely new kind of giant theropod coexisting with Tyrannosaurus rex, like for example, an abelisaur (Ruben Guzman believes that Labocania is actually a northern abelisaur, found in Mexico's Baja California). He suggests that Labocania may have lived as a scavenger, feeding on the kills of tyrannosaurs. Of course, its all speculation as the remains of Labocania are extremely fragmentary (and some believe its a tyrannosaur itself).

Galvasean

When you compare late Cretaceous North America to the Sahara of the mid Cretaceous, North America seems very lacking in giant predators.

length estimates in brackets, plus possible modern day predator counterpart.

Spinosaurus (50) - grizzly bear
Carcharodontosaurus (40) - lion
Bahariasaurus/Deltadromeus (30) - cheetah
Rogops (20) - hyena/jackal

Yeah, grizzly bears don't live in Africa... but they should!

Alvin T. Grey

Adam Khor wrote: »

There was a time when paleontologists believed there were Gorgosaurus remains in Hell Creek, but later they were moved to Nanotyrannus.
To my knowledge, Gorgosaurus is actually very similar to Albertosaurus, I think it used to be part of the same genus, and now some paleontologists believe it should be dragged back to Albertosaurus. Either way, it is less related to Tyrannosaurus than Daspletosaurus, Tarbosaurus or Zhuchengtyrannus are.

I wouldn`t be surprised though if an albertosaurine from the latest Cretaceous was found. They seem to have been much faster than tyrannosaurines; would be kind of like the tyrannosaurid version of the cheetah as opossed to the "lion-like" Tyrannosaurus or Daspletosaurus, so I can see them coexisting in the same habitat.

Of course, it would be even cooler to find a completely new kind of giant theropod coexisting with Tyrannosaurus rex, like for example, an abelisaur (Ruben Guzman believes that Labocania is actually a northern abelisaur, found in Mexico's Baja California). He suggests that Labocania may have lived as a scavenger, feeding on the kills of tyrannosaurs. Of course, its all speculation as the remains of Labocania are extremely fragmentary (and some believe its a tyrannosaur itself).

It's hard to keep track of all of these tyranosaurids. I remember, and gone are the days, when you had two well known ones. it looks like every man and his doggie (probably called Rex) keeps coming up with other 'cousin' of T-Rex....
As if the family wasn't big enough already. Then, and just as you begin to get your head around it, they go and reclassify the buggers....

/end rant.

Adam Khor

Galvasean wrote: »

When you compare late Cretaceous North America to the Sahara of the mid Cretaceous, North America seems very lacking in giant predators.

length estimates in brackets, plus possible modern day predator counterpart.

Spinosaurus (50) - grizzly bear
Carcharodontosaurus (40) - lion
Bahariasaurus/Deltadromeus (30) - cheetah
Rogops (20) - hyena/jackal

Yeah, grizzly bears don't live in Africa... but they should!

Maybe not grizzlies, but brown bears did live in Africa at one point! (Grizzly bears being a subspecies of the brown bear). And they did coexist with the Barbary lion. Unfortunately, both the Atlas brown bear and the Barbary lion are now extinct.

I don`t think the grizzly is a good counterpart for the Spinosaurus, tho.

Grizzlies are fond of fish, yeah, and they are good swimmers, but they are still land dwelling animals whose diet is composed mainly of vegetable matter.
Spinosaurus on the other hand was exclusively carnivorous (or that's what its fossils tell us) and seems to be very well adapted for a semiaquatic lifestyle. I believe (and this is my personal interpretation, I am no expert of course) that Spinosaurus probably spent a lot of time in the water and fed mostly on large fish (sharks included), crocodiles and sea reptiles, and whatever flying or land animal got within its reach. Like the false gharial (a modern day crocodilian that was once said to be an exclusive fish-eater), it was big enough to eat practically whatever it wanted despite its relatively slender jaws and conical teeth. The exception were probably the giant sauropods like Paralititan.

If this is true, then Spinosaurus would be more similar to a Nile crocodile than to a grizzly bear in many ways, although it would be a much more efficient predator on land. I believe there isn`t really any predator today we could compare it to. Maybe a monstrous cross between a crocodile and a marabou stork?

Galvasean

I do like the theory of the fairly aquatic Spinosaurus, but I don't think it's a real runner unless more of teh skeleton is found.

Oh I forgot to include Sarcosuchus (40) - a big ass crocodile!!!

Rubecula

Galvasean wrote: »

I do like the theory of the fairly aquatic Spinosaurus, but I don't think it's a real runner unless more of teh skeleton is found.

Oh I forgot to include Sarcosuchus (40) - a newt!!!:D:D

Incidentally this reminds me of the weird 'fights' they used to stage in the 1800's in North America when they pitted one wild animal against another. They imported African lions and pitted them against Grizzly Bears. Apparently the Bear won EVERY time.

A bit sick in modern day thought I suppose.

Adam Khor

Rubecula wrote: »

Incidentally this reminds me of the weird 'fights' they used to stage in the 1800's in North America when they pitted one wild animal against another. They imported African lions and pitted them against Grizzly Bears. Apparently the Bear won EVERY time.

A bit sick in modern day thought I suppose.

I guess its because lions aren`t used to face anything like a bear in the wild. They are the top predators in their territory. It's kinda like when Europeans took their huge, powerful hunting dogs to Africa. The dogs never imagined that cats could be dangerous, so they went after leopards every time and got shred to bits.