Giant theropods overview thread

[Deleted]

Sept 17, 2016 21:45:00 GMT 5 spartan said:

Height: 4-5m
Weight: 5000kg

I wonder why they still state such weird figures.

The weight figures are probably just guesses.
Considering the whole animal was estimated to be between
12 and 12.5 meters long and it's around as bulky as Sue I'm
going to say it's probably over 8 tonnes if we use Scott Hartmans method
for estimating weight. 

[Ceratodromeus]

I know i posted the stuff about the Torvosaurus specimen on pages prior, and i think i've got a good idea on the length of the animal now...hopefully any way. Mind you i'm using the reported 52in(132cm) skull which comprises 18% of the body length" off of a website which turns out 8.7m(28.8ft), which seems to be in line with the skeletal in the initial description of T.gurneyi


Thoughts? i feel as if that may be wrong for some reason but who knows

[Deleted]

Sept 21, 2016 1:39:13 GMT 5 Ceratodromeus said:

I know i posted the stuff about the Torvosaurus specimen on pages prior, and i think i've got a good idea on the length of the animal now...hopefully any way. Mind you i'm using the reported 52in(132cm) skull which comprises 18% of the body length" off of a website which turns out 8.7m(28.8ft), which seems to be in line with the skeletal in the initial description of T.gurneyi


Thoughts? i feel as if that may be wrong for some reason but who knows

it seems reasonable.
actually anything at or under 10 meter`s is reasonable for that matter.



a Guy called EoFauna somehow made some 11-12 meter Trovosaurus reconstructions, which seem way off the mark if you ask me.

[Infinity Blade]

It turns out that the theropod Duane Nash was gonna talk about after Microraptor was just Tyannosaurus. Here's his new night stalker rex.

antediluviansalad.blogspot.com/2016/09/night-stalker-rex-part-i-sue-is-built.html

[Deleted]

I hope he didn't really seriously say that Tyrannosaurus was bulkier than ceratopsids and hadrosaurs...if he did then I would have just lost the last of my respect for him. The amount of embellishment I can pick out in the post is cringeworthy, honestly.

[Infinity Blade]

I can't bring myself to believe the idea of Tyrannosaurus not being faster than its prey either. Or the idea of it being that horribly unagile.

[Deleted]

He also swallows the flawed, fat model from Hutchinson et al. (2011). Has he even looked at pictures of featherless birds? They're not that fat. Has he even looked at the lack of spinal curvature in the model's torso? That inflates it's mass a bit since it makes the torso longer than it would have been in life. Scott Hartman's version is much better.

Also, he seems to imply that adult Tyrannosaurus = Sue-sized. Flawed idea. The other adults may be younger, but didn't "B-rex" hit asymptotic growth at roughly ~16 years? The other adult specimens probably weren't gonna grow by a noticeable amount had they been allowed to live to Sue's age.

[theropod]

Mostly I can’t help but wonder if he has even looked at Hartman’s skeletal and tried to understand where the differences lie. Because with properly articulated ribs and trunk vertebrae sue is certainly bulky and will always remain so, but the model based on the mount is way over the top in that regard. Also, does he realize that not all of those "flawed" paleoartworks necessarily portray sue, and that there are other T. rex specimens considerably less robust?

Growth or not, it’s a flawed concept to consider only fully grown dinosaurs adults, and to treat only them as representative. There are tens of mature T. rex specimens, it seems sort of weird all anybody ever talks about when it comes to adult T. rex morphology is sue. I can’t really hold that against Nash’s post though, since he explicitely explains he is only referring to sue, but his own criticism seems to be forgetting about this.

The nocturnal hunting hypothesis is intriguing though, especially, or at least, for large and robust adults.

@broly: B-rex was estimated at 18 (Horner & Padian) to 19 (Erickson et al.) years afaik.

[Deleted]

Sept 25, 2016 23:28:43 GMT 5 theropod said:

@broly: B-rex was estimated at 18 (Horner & Padian) to 19 (Erickson et al.) years afaik.

I remember reading that it "effectively stopped growing at 16+2 years of age" or something like that, though.


Anyway, Tyrannosaurus pretty much reached skeletal maturity at 20 years of age or earlier or so, based on all the scientific literature I could find.

rspb.royalsocietypublishing.org/content/271/1551/1875.short

Though a range of ages (15–25 years) was found for the specimens studied, the seven individuals demonstrate that T. rex reached effectively full size in less than 20 years.

www.nature.com/nature/journal/v430/n7001/full/nature02699.html

T. rex had a maximal growth rate of 2.1 kg d^-1, reached skeletal maturity in two decades

journals.plos.org/plosone/article/asset?id=10.1371%2Fjournal.pone.0026037.PDF
(ignore the obviously obese hutt-like flawed models)

Our results support the inference of an earlier attainment of somatic maturity (growth asymptotes) at around 16–17 years of age compared to the 18–19 years previously estimated from Sue’s histology

[Infinity Blade]

To elaborate on my point about speed: Nash uses bears vs. camels as a case to possibly point out how relative lower leg length can't be used to reliably judge speed in two animals and provided two videos of the two animals running fast to illustrate his point that we cannot be sure that Tyrannosaurus was faster than its prey items. I think he said that, judging from this, he wouldn't be surprised if a bear's short burst speed could match a camel's.

Except looking at two separate videos of two different animals sprinting at max speed may not actually tell you how fast they're going, but rather how quickly they are accelerating. Consider this neat video of a Komodo dragon running down a deer.



As you can see, the Komodo dragon is actually able to give the deer a (literal) run for its money. Is a Komodo dragon as fast as a deer in burst speed? Nope. It can just accelerate rapidly enough to chase one down for a certain period of time.

Also, it's not just proportional distal limb length that suggests that Tyrannosaurus would have been faster than similar sized contemporaneous prey. Tyrannosaurids had more area for leg muscle attachment than did hadrosaurs (according to Greg Paul; this might just apply to the others as well), more proximal insertions for the M. caudofemoralis muscle on the femur than hadrosaurs (increasing stride length; note that ceratopsids also seem to have reduced tails in comparison to other dinosaurs), more tightly appressed and compact metatarsals that formed a functionally single unit (when you think about it, it seems like they'd be better for propulsion than the shorter, less appressed metapodials of its prey) and had a shock-absorbing system (the arctometatarsalian condition).

As for Tyrannosaurus' agility, well, let's just say this. The underlying issue is that it was a long (increasing rotational inertia) biped (must produce more torque to turn). What if I told you a lot of that length (at least half) could be taken out of the equation? Below is a screenshot from Greg Paul's Body and Tail Posture in Theropod Dinosaurs (in The Carnivorous Dinosaurs; ed Carpenter, 2005).



This is Allosaurus' skeleton with the tail lifted dorsally and the neck retracted backward both at max. As you can see with the tail in a more normal horizontal position, the tail comprises approximately half of the theropod's total body length. And since that entire half has now been oriented vertically, it is no longer contributing to rotational inertia, and therefore adversely affecting agility. If we apply this to Tyrannosaurus, who was ~12 meters in length, we end up with an effective length of 6 meters turning around (remember that this 6 meters of theropod is also pneumatized, reducing weight and making it even easier to move around). What else is at least this length (if not longer) and just as massive? A bull African elephant[1], a quadruped that evidently has no issues turning (link). And elephants have columnar legs with not very well developed musculature[2] and lack massive, powerful tail muscles. Tyrannosaurus may have to apply some more torque to turn due to it being a biped, but with its enormous hip; thigh; calf; and caudofemoralis muscles and uncolumnar legs, I'm sure it could do it.

Lastly, how much could Tyrannosaurus really rely on "night stalking"?. For whatever it's worth, here's a screenshot from Kenneth Carpenter's A Closer Look at the Hypothesis of Scavenging versus Predation by Tyrannosaurus rex (in Tyrannosaurid Paleobiology; Parrish et al. 2013); the highlighted segment is of particular interest.



So we have an animal that's not at all particularly adapted to seeing in the dark (the opposite actually), and therefore cannot rely on the cloak of darkness to circumvent its supposed lack of agility. We are once again confronted with the issue that this animal's prey base consisted of megaherbivores that would have been relatively fast and agile for their size. Megaherbivores that could easily kill it. Unless anyone could think of another novel solution to this problem, one that stands up to scrutiny, the only way to solve it is to be relatively fast and agile yourself. To those who suggest otherwise Tyrannosaurus was incapable of this, let me remind you that (quoting Nash himself in a later blog post), "...animals have to make sense. They have to reasonably move through their environment; eat; protect themselves; mate. When you conduct research that points you in the other direction - towards a maladaptive animal ill-equipped to deal with day to day encounters (such as bodies of water) - there is probably something wrong with your scenario."

[1] Macdonald, D. (2001) The New Encyclopedia of Mammals. Oxford University Press, Oxford.
[2] Larramendi, A. (2016) Shoulder height, body mass, and shape of proboscideans. Acta Palaeontologica Polonica 61 (3): 537–574.

[theropod]

Anyway, Tyrannosaurus pretty much reached skeletal maturity at 20 years of age or earlier or so, based on all the scientific literature I could find.

Yeah, well, I’d be careful with that, it’s not really clear what they mean with "effectively". Maybe "effectively full size" was to Horner and Padian within a few tons of maximum size, maybe it was within a few kilograms. Who knows? But the (admittedly somewhat patchy) growth curves and femur length records still support that on average there tended to be quite a bit of growth (in absolute terms) between 18 and 28 years (but as I explained countless times, that doesn’t imply it was the freakin’ same for all individuals, *cough*FrankFang*cough*!).
You might recall this graphic showcasing extrapolated total length (from sue, not that the curve doesn’t base on all the datapoints), which I used when writing about UCMP 118742:

While not overly tight, I think a trend of positive correlation of size with age is still readily apparent here. So firstly, being relatively big relatively earily doesn’t necessarily mean being relatively big later, but also the average 28 year-old would likely be bigger than the average 18 year-old.

[Deleted]

Looks like your average ~28-year old isn't really much bigger than your average ~20-year-old.

[theropod]

Maybe because there are no 20-year olds in there?

In any case the "average" (and only) 28-year-old is quite a bit bigger than the average 18-year-old (which would be about 11m or slightly smaller even).

[Grey]

No one has noticed this abstract talking about the potential size of the giant T. rex phalanx (and the Broome sauropod track) ?

FOOT STRESS SCALING CONSTRAINS ESTIMATES OF MASS FOR
ISOLATED, LARGE SAURISCHIAN DINOSAUR SPECIMENS
SNIVELY, Eric, University of Wisconsin - La Crosse, La Crosse, WI, United States of
America
Tracks and autopodial specimens of sauropod and theropod dinosaurs are
occasionally cited as representing exceptionally large individuals. These specimens
include sauropod tracks of the Broome Sandstone of Western Australia and Plagne in
Southern France, the biggest measuring 1.5 m or more in their largest linear dimension.
Among particularly large fossils of theropods, a Tyrannosaurus rex phalanx (UCMP
137538) is substantially larger than the homologous bone in the next largest specimen. A
common method of first approximating mass of large fossil animals is to cube ratios of
linear size between isolated elements and their homologs from more complete specimens,
and multiply the ratio by a mass estimate for the smaller individual. However, in humans
and elephants body mass scales linearly with surface area of the feet, which maintains
foot stress overall and/or stress from mass distribution between fore and hind limbs.
Squaring ratios of linear dimensions of foot fossils may be a better method of mass
extrapolation than cubing these dimensions.
The large Broome sauropod tracks have been precisely measurable, as clear surface
imprints with discrete anatomical features. Squaring ratios of their digital span to those of
other titanosauriform sauropods yields much lower estimate of body volume than cubing
the ratios, approaching but not exceeding current volumetric estimates of very large
sauropods based on body fossils. Squared-ratio and surface area estimates for the T. rex
phalanx suggest a mass between 11.5 and 14 tonnes, depending on conservative mass
estimates for other specimens.
Although foot areas correlate linearly and precisely with mass in humans, the
squared-ratio/stress-based methods must be part of a larger range of mass estimates
methods for morphologically diverse fossil taxa, especially based on isolated elements.

[Deleted]

I really doubt their estimates for UCMP 137538.

That would make it over 40+% more massive than Sue, the largest among the several tens of known adult individuals, which seems to be a pretty extraordinary claim that needs more evidence to even be remotely close to being parsimonious, and is at odds with how big the UCMP 137538 phalanx seems to be. Didn't Spinodontosaurus show that the UCMP 137538 phalanx was actually similar in size to Sue's, and actually shorter in length? That the ~11-centimeter length figure for Sue's IV-2 phalanx and the ~13-centimeter length of the UCMP 137538 bone don't actually correspond to the same measurement based on how the other measurements for Sue's toe bone match up with it's length figure?

I also don't think such small and variable fragments like individual toe bones (and teeth, looking at you Max Hawthorne) should be used for size estimates. At least a sufficiently-preserved footprint shows a decently good idea of the animal's foot size in life. I know many of you will disagree, but I really think we should not start making full-body size estimates for a lone isolated phalanx.

Also, given that their method seems to be based on humans and elephants, I'm pretty skeptical of said method.