Tyrannosaurus rex

[elosha11]

By the time humans die out, there likely will be trillions, perhaps quadrillions of us who have lived upon the planet (and who knows, maybe other planets at some point) from 100,000 years ago to whenever we go extinct. It's mind-boggling to think that at this single moment in time there may be over three times as many humans living as the total number of Tyrannosaurus Rexes who ever existed.

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Naturally I'm highly skeptical of any attempt at estimating the total number of individuals that ever existed for an extinct species. If I'm interpreting the abstract correctly, all the values it mentions has uncertainties of more than two orders of magnitude, so it looks like huge error bars are involved for this total # of individuals estimate.

I don't doubt there were probably way more humans that ever lived than Tyrannosaurus, though.

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New paper on the preferred walking speed of Tyrannosaurus. Their biomechanical model incorporates the interspinous ligaments of the tail, from which they estimated the natural frequency with which they swayed up and down. They were then able to calculate preferred walking speed.

Their estimate (1.28 m/s) is more conservative than many previous estimates of giant theropod walking speed, but more in line with that of many modern terrestrial animals (e.g. humans, ratites, horses, elephants, etc.).

They also have some interesting implications for maximum running speed.

"Minimal sensitivity to muscular and inertial estimates implies that our inverse dynamic approach to constructing a non-rigid tail could be incorporated into more sophisticated hindlimb simulation models, without adding much to the overall uncertainty of the result. This could have implications for maximal running speeds of large taxa like T. rex: maximum running speed was shown to be limited by peak stresses on the limbs, but a compliant tail may serve to reduce these stresses."

royalsocietypublishing.org/doi/10.1098/rsos.201441

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Tyrannosaurus rex Mystery Solved: How Dinosaurs Delivered Bone-Crushing Bites


Tyrannosaurus rex dinosaurs chomped through bone by keeping a joint in their lower jaw steady like an alligator, rather than flexible like a snake, according to a study being presented at the American Association for Anatomy annual meeting during the Experimental Biology (EB) 2021 meeting, held virtually April 27-30.

The research sheds new light on a conundrum that has perplexed paleontologists. Dinosaurs had a joint in the middle of their lower jaws, called the intramandibular joint, which is also present in modern-day reptiles. Previous research has suggested this joint was flexible, like it is in snakes and monitor lizards, helping carnivorous dinosaurs to keep struggling prey in their jaws. However, it has been unclear whether the jaws were flexible at all, or how they could be strong enough to bite through and ingest bone, which Tyrannosaurus did regularly, according to fossil evidence.

“We discovered that these joints likely were not flexible at all, as dinosaurs like T. rex possess specialized bones that cross the joint to stiffen the lower jaw,” said John Fortner, a doctoral student in anatomy at the University of Missouri, first author of the study.


The researchers used CT scans of dinosaur fossils and modern-day specimens to create a 3D computer model of a dinosaur jaw and identify where muscles attach to bone. They then used the model to simulate muscle forces under different biting scenarios. Stars indicate areas where strain was assessed. Credit: Image courtesy of John Fortner, University of Missouri

Fortner and colleagues used CT scans of dinosaur fossils and modern reptiles to build a detailed 3D model of the T. rex jaw. Unlike previous models, their simulations include bone, tendons and specialized muscles that wrap around the back of the jaw, or mandible.

“We are modeling dinosaur jaws in a way that simply has not been done before,” said Fortner. “We are the first to generate a 3D model of a dinosaur mandible which incorporates not only an intramandibular joint, but also simulates the soft tissues within and around the jaw.”

To determine whether the intramandibular joint could maintain flexibility under the forces required to crunch through bone, the team ran a series of simulations to calculate the strains that would occur at various points depending on where the jaw hinged. The results suggest bone running along the inside of the jaw, called the prearticular, acted as a strain sink to counteract bending at the intramandibular joint, keeping the lower jaw stiff.

The team plans to apply their modeling approach to other dinosaur species in order to further elucidate biting mechanics among dinosaurs — and perhaps, help researchers better understand today’s creatures, as well.

“Because dinosaur mandibles are actually built so much like living reptiles, we can use the anatomy of living reptiles to inform how we construct our mandible models,” said Fortner. “In turn, the discoveries we make about T. rex’s mandible can provide more clarity on the diversity of feeding function in today’s reptiles like crocodilians and birds.”

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The Role of the Intramandibular Joint, Symphyseal Tissues, and Wrapping Muscles on Theropod Dinosaur Mandibular Function
John Fortner (University of Missouri)| Alec Wilken (University of Chicago)| Kaleb Sellers (University of Missouri)| Ian Cost (Albright College)| Kevin Middleton (University of Missouri)| Casey Holliday (University of Missouri)

"Sauropsids, unlike mammals, possess an intramandibular joint (IMJ) separating the dentary and postdentary bones, with different lineages either rigidifying (turtles & crocodilians) or maintaining compliance (lepidosaurs & birds) about the joint. IMJ construction and its role on mandibular performance is unclear, impeding our understanding of its function in extinct animals with extreme feeding behaviors like Tyrannosaurus rex. Sauropsids like T. rex pose a particular biomechanical paradox; feeding traces, coprolites, and their robust crania and teeth indicate that they regularly bit through and ingested bone, but their dorsoventrally-tall and mediolaterally-thin hemimandibles, IMJ, and patent mandibular symphyses suggest their mandibles were ill-suited for bone-crushing bites. Extant sauropsids also exhibit wrapping intramandibularis (mIRA) and pterygoideus ventralis (mPTv) muscles, whose effect on mandibular performance and interaction with the IMJ are unknown. Here we model the effect of the IMJ, symphyseal tissue properties, and wrapping muscle orientation on T. rex mandible biomechanical performance in order to give insight into the biomechanical constraints faced by sauropsids, and the link between their mandibular form and function. Joint tissue histology, gross dissection, and iodine contrast data of extant sauropsids were performed to inform model tissue properties, IMJ construction and muscle orientation. We imported a 3D STL model of the T. rex “STAN” and modeled the IMJ by differing material properties of modeled joint tissues to test the influence of linkage materials on mandibular performance. Muscles were mapped onto the model, and their corresponding muscle moments calculated from area centroids, muscle architecture, and volumes. Wrapping mIRA and mPTv muscles were simulated by directing their force vectors to appropriately positioned dummy points using extant sauropsids as a guide. The mandible was then constrained at the jaw joint and in a series of points along the tooth row from rostral to caudal, simulating both unilateral and bilateral bites. We find that while strains are quite high (>6000 µstrains) about the intramandibular joint, mediolateral bending stresses and strain are markedly reduced by the prearticular, which exhibits greater strain than the surrounding bone. Our results suggest the prearticular of T. rex acted as a strain sink to counteract bending about the IMJ and thereby rigidifying the mandible during feeding. We hypothesize that differences in IMJ articulation and prearticular construction may differentially facilitate or impede prearticular streptognathy, and thus intramandibular kinesis about the IMJ, in sauropsids. Forthcoming models will simulate other theropods within and without Tyrannosauridae to test this hypothesis."

www.eventscribe.net/2021/EB2021/index.asp?posterTarget=375632

[Infinity Blade]

Nov 24, 2020 9:33:59 GMT 5 Infinity Blade said:

This is a news report (from University of Wisconsin Oshkosh, which the researchers are from) of an SVP abstract from this year. It pertains to teenage Tyrannosaurus bite force, and indentations on bone apparently suggest a bite force of just under 2,000 lbf (the SVP abstract itself provides estimates for two sets of bite marks, with 5000-6000 N – from indentations on Jane's crania – being the higher of those two).

uwosh.edu/today/90722/chew-on-this-uwo-research-estimates-power-of-teenage-t-rexs-bite/#:~:text=The%20researchers%20estimated%20the%20bite,marks%20attributed%20to%20adult%20T.

This paper has now been published.

Abstract

Background
Bite marks attributed to adult Tyrannosaurus rex have been subject to numerous studies. However, few bite marks attributed to T. rex have been traced to juveniles, leaving considerable gaps in understanding ontogenetic changes in bite mechanics and force, and the paleoecological role of juvenile tyrannosaurs in the late Cretaceous.

Methods
Here we present bite force estimates for a juvenile Tyrannosaurus rex based on mechanical tests designed to replicate bite marks previously attributed to a T. rex of approximately 13 years old. A maxillary tooth of the juvenile Tyrannosaurus specimen BMR P2002.4.1 was digitized, replicated in dental grade cobalt chromium alloy, and mounted to an electromechanical testing system. The tooth was then pressed into bovine long bones in various locations with differing cortical bone thicknesses at varying speeds for a total of 17 trials. Forces required to replicate punctures were recorded and puncture dimensions were measured.

Results
Our experimentally derived linear models suggest bite forces up to 5,641.19 N from cortical bone thickness estimated from puncture marks on an Edmontosaurus and a juvenile Tyrannosaurus. These findings are slightly higher than previously estimated bite forces for a juvenile Tyrannosaurus rex of approximately the same size as BMR P2002.4.1 but fall within the expected range when compared to estimates of adult T. rex.

Discussion
The results of this study offer further insight into the role of juvenile tyrannosaurs in late Cretaceous ecosystems. Furthermore, we discuss the implications for feeding mechanisms, feeding behaviors, and ontogenetic niche partitioning.

peerj.com/articles/11450/#utm_source=Twitter&utm_medium=Social&utm_campaign=11450

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Really sweet paleoart of Sue by Ted Rechlin.



Also, Blue Rhino Studio has another T. rex sculpt.

[Supercommunist]

At risk of sounding like a fanboy, but doesn't it seem that the more we find about tyrannosaurus the more it live up to its crazy hype?

We have a lot of tyrannosaurus fossils which indicate that is was very succesful given that about one in billion animals get preserved.

Young tyrannosaurus seemed to have a pretty good stronghold on the mesopredator niche, given the relative lack of midsized predators. I know dakotaraptor exists but that's just one so far.

We also know tyrannosaurus were very fast and agile for their size while also being much bulkier than many theropods.

I know it seems rather childish to declare one animal better than others, but it does kind of seem that tyrannosaurus was genuinely special.

[spartan]

It's also one of the very few prehistoric giants that gets bigger instead of getting downsized over time.

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Complex neurovascular system in the dentary of Tyrannosaurus

The morphology of the neurovascular canal in the jaw has been analysed in several fossil reptiles, including theropod dinosaurs. However, the details of the neurovascular canal in the dentary of theropods have not been fully elucidated. In this study, we described the well-preserved dentary of Tyrannosaurus rex, analysed the morphology of the neurovascular canal in the dentary using computed tomography techniques, and compared its distribution pattern with other dinosaurs and extant crocodiles. The results show that the neurovascular canal in the dentary of Tyrannosaurus exhibits a rather complex branching amongst the sampled dinosaurs, and that the complexity is comparable to that of extant crocodilians. The complexity of the canal branching is likely related to the high tactile sensitivity of the dentary, suggesting that the jaw tip of Tyrannosaurus may have played an essential role as a sensitive tactile sensor.

www.tandfonline.com/doi/full/10.1080/08912963.2021.1965137

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Tyrannosaurs Suffered from Bone Infections, New Research Shows

Using a CT scanner and a technique called dual-energy computed tomography (DECT), a team of scientists in Germany has identified a bone disease called tumefactive osteomyelitis in the fossilized jaw of a Tyrannosaurus rex.


In 2010, a commercial paleontologist discovered one of the most complete Tyrannosaurus rex skeletons ever found.

The 68-million-year-old skeleton was then sold to an investment banker, who dubbed it ‘Tristan Otto’ before loaning it out to the Museum für Naturkunde Berlin.

In the new research, Dr. Charlie Hamm of Charité University Hospital and colleagues investigated a portion of the Tristan Otto’s lower left jaw.

“DECT deploys X-rays at two different energy levels to provide information about tissue composition and disease processes not possible with single-energy CT,” they explained.

“We hypothesized that DECT could potentially allow for quantitative noninvasive element-based material decomposition and thereby help paleontologists in characterizing unique fossils.”

The CT technique enabled the researchers to overcome the difficulties of scanning a large portion of Tristan Otto’s lower jaw called the left dentary.

On visual inspection and CT imaging, the left dentary showed thickening and a mass on its surface that extended to the root of one of the teeth.

DECT detected a significant accumulation of the element fluorine in the mass, a finding associated with areas of decreased bone density.

The mass and fluorine accumulation supported the diagnosis of tumefactive osteomyelitis, an infection of the bone.

“While this is a proof-of-concept study, noninvasive DECT imaging that provides structural and molecular information on unique fossil objects has the potential to address an unmet need in paleontology, avoiding defragmentation or destruction,” Dr. Hamm said.

“The DECT approach has promise in other paleontological applications, such as age determination and differentiation of actual bone from replicas,” said Dr. Oliver Hampe, a vertebrate paleontologist at the Museum für Naturkunde Berlin.

“The experimental design, including the use of a clinical CT scanner, will allow for broad applications.”

The scientists presented their findings this week at the 2021 Annual Meeting of the Radiological Society of North America.


www.sci-news.com/paleontology/tristan-otto-osteomyelitis-10327.html

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New and already very controversial paper. This paper proposes three species of Tyrannosaurus. The T. rex you all know and love, but also T. regina and T. imperator.

Yeah...

link.springer.com/article/10.1007/s11692-022-09561-5

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Fantastic report on the Tyrannosaurus specimen named "Peter".

A new specimen of Tyrannosaurus rex from the Lance Formation in eastern Wyoming (nicknamed ‘Peter’) is reported herein. The specimen shows taphonomical details including traces on the bones produced by teeth, accompanied by crushed and shattered bones apparently modified during feeding by another T. rex. These record events incurred at the end of the animal’s life or shortly thereafter and may represent extreme osteophagy.

Peter was undoubtedly fed upon, and most likely killed, by another Tyrannosaurus rex. There is especially severe damage to the leg bones (femur and tibia) which can only be due to the jaw mechanics of an animal with an incredible bite force and in the Late Cretaceous Period, the most powerful bite belongs to a T. rex.

www.aucklandmuseum.com/discover/research/trex_peter-scientific-report/abstract

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This paper is a response to Greg Paul's three Tyrannosaurus species paper.

link.springer.com/article/10.1007/s11692-022-09573-1

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Closer examination does not support infection as cause for enigmatic Tyrannosaurus rex mandibular pathologies

Many tyrannosaurid specimens preserve unusual pathologies in the caudal half of the mandible that are of uncertain origin. The two main hypotheses put forth to date both suggest these pathologies are lesions resultant from infection either due to bacteria or protozoans. In light of this controversy, we provide a comparative anatomical study to characterize the pathophysiology of these enigmatic pathologies in order to elucidate their underlying cause. Human individuals that had been subjected to cranial trepanation and specimens of the late Triassic reptile Stagonolepis exhibiting healing fractures provide phylogenetic bracketing for investigating bone surface alterations induced by trauma in dinosaurs. Examination of mandibular pathologies in Tyrannosaurus rex FMNH PR2081 reveals all the characteristics of wound healing in the absence of infection. Additional evidence that refutes the previous hypothesis that these pathologies result from infection by the protozoan, Trichomonas gallinae, is discussed. Behavioral evidence suggests that these pathologies may be wounds induced through intraspecific combat.

www.sciencedirect.com/science/article/abs/pii/S0195667122002178


Looks like the "T. rex infected by protozoans" hypothesis is weakened. I'm going to ask for a full PDF.

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I'm going to ask for a full PDF.

I have it now. If anyone is interested, DM me your email and I'll send it your way.