The giant Tyrannosaurus rex pulverised bones by biting down with forces equalling the weight of three small cars, while simultaneously generating world record tooth pressures.
In a new study, US scientists have explained how the fearsome dinosaur could crush bones - a capacity known as "extreme osteophagy" that is typically seen in living carnivorous mammals such as wolves and hyenas, but not in reptiles, whose teeth do not allow for chewing up bones.
The joint Florida State University-Oklahoma State University research team found the prehistoric reptile could chow down with a force more than two times greater than the bite force of the largest living crocodiles - today's bite force champions.
This allowed T rex to drive open cracks in bone during repetitive, mammal-like biting and produce high-pressure fracture arcades, leading to a catastrophic explosion of some bones.
"It was this bone-crunching acumen that helped T. rex to more fully exploit the carcasses of large horned-dinosaurs and duck-billed hadrosaurids whose bones, rich in mineral salts and marrow, were unavailable to smaller, less-equipped carnivorous dinosaurs," study co-author Assistant Professor Paul Gignac said.
The researchers built on their extensive experience testing and modelling how the musculature of living crocodilians, which are close relatives of dinosaurs, contribute to bite forces.
They then compared the results with birds, which are modern-day dinosaurs, and generated a model for T. rex.
From their work on crocodilians, they realised that high bite forces were only part of the story.
To understand how the giant dinosaur consumed bone, they also needed to understand how those forces were transmitted through the teeth, a measurement they call tooth pressure.
"Having high bite force doesn't necessarily mean an animal can puncture hide or pulverise bone, tooth pressure is the biomechanically more relevant parameter," co-author
Professor Gregory Erickson said.
"It is like assuming a 600 horsepower engine guarantees speed. In a Ferrari, sure, but not for a dump truck."
Today, well-known bone crunchers like spotted hyenas and grey wolves have occluding teeth that are used to finely fragment long bones for access to the marrow inside - a hallmark feature of mammalian osteophagy.
Tyrannosaurus rex appeared to be unique among reptiles for achieving this mammal-like ability but without specialised, occluding dentition.
The new study was one of several by the authors and their colleagues that now showed how sophisticated feeding abilities, most like those of modern mammals and their immediate ancestors, actually first appeared in reptiles during the age of the dinosaurs.
What we have in common with puffer fish
Meanwhile, a team of international scientists have found human teeth evolved from the same genes that make the bizarre beaked teeth of the pufferfish.
Published in the journal PNAS, the research has found all vertebrates have some form of dental regeneration potential.
The pufferfish use the same stem cells for tooth regeneration as humans do.
The unique pufferfish beak is one of the most extraordinary forms of evolutionary novelty. This bizarre structure has evolved through the modification of dental replacement.
The beak is composed of four elongated "tooth bands" which are replaced again and again.
However, instead of losing teeth when they are replaced, the pufferfish fuses multiple generations of teeth together, which gives rise to the beak, enabling them to crush incredibly hard prey.The study's authors believe the research can now be used to address questions of tooth loss in humans.
"Our study questioned how pufferfish make a beak and now we've discovered the stem cells responsible and the genes that govern this process of continuous regeneration," said lead author Dr Gareth Fraser, of the University of Sheffield in the UK.
These were also involved in general vertebrate tooth regeneration - including in humans.
"The fact that all vertebrates regenerate their teeth in the same way with a set of conserved stem cells means that we can use these studies in more obscure fishes to provide clues to how we can address questions of tooth loss in humans."
Brain activity recorded on a wristband?
What can we learn about emotions, the brain and behaviour from a wristband?
Plenty, says a prominent MIT engineer whose team have pioneered the use of wearable technology to recognise changes in human emotion.
Professor Rosalind Picard's team have made several new discoveries, including that autonomic activity measured through a sweat response is not as general as previously thought, and carries more specific information related to different kinds of brain activity.
"The skin is purely innervated by the sympathetic branch of the autonomic nervous system," Picard said.
"We can observe increases in sympathetic brain activation by monitoring subtle electrical changes across the surface of the skin."
"Sympathetic" activation occurred when experiencing excitement or stress, whether physical, emotional or cognitive.
In some medical conditions, such as epilepsy, it shows significant increases related to certain areas of the brain being activated.
Wristwatch-like devices can employ sensors for continuous, real-time data gathering.
Picard explained that changes in electrodermal activity occur as the result of atypical activation in deep regions of the brain.
This discovery already has been commercialised for use in seizure monitoring.
Seizures occur when there are abnormal, excessive or synchronous neuronal activity, and could cause convulsions evidenced by violent shaking and loss of control and consciousness.
When someone has recurring seizures, the diagnosis usually is epilepsy.
When some regions of the brain, such as those involved with anxiety, pain, stress and memory are activated during a seizure, they can elicit patterns of electrical changes in the skin.
Picard reported that her group has built an automated machine learning method that can detect compulsive seizures by combining measures of electrodermal activity on the wrist with measures of motion.
The wrist-worn detector was now more than 96 per cent accurate for detecting convulsive seizures.
While they have not demonstrated detection of non-convulsive seizures, 42 per cent to 86 per cent of non-convulsive, complex partial seizures also have significant electrodermal responses.
Picard said other clinical applications for wristband electrodermal monitoring include anxiety, mood and stress monitoring and measuring analgesic responses.
"We know that pain exacerbates anxiety and stress and we are doing more studies to determine how reductions in anxiety and stress could indicate an analgesic response activated by a pain management therapy."