Tyrannosaurus sexual dimorphism, yes or no?

[Super Communist]

blogs.smithsonianmag.com/dinosaur/2012/02/intimate-secrets-of-dinosaur-lives/

[Venomous Dragon]

Its common for both reptiles and birds (most animals really), I think its more than likely that they were.

[Anomonyous]

Eh I really doubt it. I don't believe there's much evidence for it.

[Tyrannosaurus]

There is dimorphism, whether it's sexual is mere speculation.

[Anomonyous]

Regarding the wider pelvis, is what would be the passage for eggs actually any larger?
www.bioone.org/doi/abs/10.1671/0272-4634%282007%2927%5B603%3ANEOPSA%5D2.0.CO%3B2
^If you don't care to read all of it, basically what it's saying is that pelvic differences are a unreliable method of inferring the sex of dinosaurs.

[Tyrannosaurus]

That paper said that there was sexual dimorphism in the pelvis, just that it couldn't be used to sex individual specimens. I'm not sure how a Tyrannosaurus would need a wider pelvis, considering how small the eggs are. I wonder if birds have any sexual dimorphism to allow for the eggs to pass? Their hips are quite different though than Theropods.

So what's your theory then on the two morphs, if not sexual dimorphism?

[Anomonyous]

Personally I don't actually know.
Perhaps it's just some individual differences; after all, no 2 tyrannosauruses are alike, the chevron case for example.

[Super Communist]

I wonder if birds have any sexual dimorphism to allow for the eggs to pass?

I am pretty sure only invertebrates and amphibians are the only organisms that have large females due to reproductive purposes alone.

[Venomous Dragon]

Forgive me If I sound like a noob but Have they discounted age? as in first the trex grows in height abd length then gains bulk with age, like plenty of other animals.

[Ultimategrid]

Jun 17, 2012 17:46:37 GMT -5 Super Communist said:

I wonder if birds have any sexual dimorphism to allow for the eggs to pass?

I am pretty sure only invertebrates and amphibians are the only organisms that have large females due to reproductive purposes alone.

Um what about reptiles? Most snakes and some lizards have larger females.
My boa Rosy was almost twice the weight of my friend's male.

[Venomous Dragon]

Jun 17, 2012 23:43:45 GMT -5 Ultimategrid said:

Jun 17, 2012 17:46:37 GMT -5 Super Communist said:

I am pretty sure only invertebrates and amphibians are the only organisms that have large females due to reproductive purposes alone.

Um what about reptiles? Most snakes and some lizards have larger females.
My boa Rosy was almost twice the weight of my friend's male.

Most lizard have larger males only a few have larger females the only one I can think off the top of my head are long nosed leopard lizards and Im pretty sure they think it has more to do with The high cannibalism rate than it does with reproduction.

[Tyrannosaurus]

Jun 17, 2012 18:18:35 GMT -5 Venomous Dragon said:

Forgive me If I sound like a noob but Have they discounted age? as in first the trex grows in height abd length then gains bulk with age, like plenty of other animals.[/quote
Couldn't explain the differences in the skull.

[Anomonyous]

What differences do you speak of?

[Tyrannosaurus]

My mistake, I was remembering a study about skull differences between normal Tyrannosaurus rex and the proposed new species Tyrannosaurus "x". Bakker proposed this new species based on differences in the skull. Somebody had said that T. "x" was just a subadult T. rex, and Larson proved that there's no correlation between age and the skull differences with growth rings. All T. "x" specimens are gracile, however the T. "x" does not include all gracile specimens. There are only three T. "x" specimens known, whereas about half the normal Tyrannosaurus skeletons have been attributed to the gracile morph. I personally think that T. "x" is indeed a separate species, and thus an outgroup irrelevant to this discussion.

The gracile and robust morphs were also proven to be distinct morphs and not growth stages using growth rings.

One piece of evidence though for the robust morph being female is that several of them have healed hip injuries, which Larson attributed to mating.

[Deinobrontornis]

Jun 17, 2012 17:46:37 GMT -5 Super Communist said:

I wonder if birds have any sexual dimorphism to allow for the eggs to pass?

I am pretty sure only invertebrates and amphibians are the only organisms that have large females due to reproductive purposes alone.

Think again! In many bird species, the females are larger than the males. Bald eagle females are 10-25% larger than males. Blue whale and spotted hyena females are also larger than the males.