Dinosaur skull scans reveal clues about flight—and communication
Riley Black
Nighttime stalkers
Not all bird-like dinosaurs moved like their avian relations, however. Some dinosaurs, the researchers found, moved and likely hunted in ways that run counter to paleontological expectations.
The turkey-size dinosaur Shuvuuia, for example, has long been a mystery to paleontologists. Known for its short arms tipped with large, single claws and toothless or nearly toothless jaws, this genus belongs to a group of bipedal theropods called alvarezsaurs. Bhullar and colleagues were surprised to find that Shuvuuia has an inner ear similar to that in four-legged animals with relatively simple locomotion.
The second Science study may offer insight into Shuvuuia’s odd inner ear. This study looked at both the inner ears and the eyes of dinosaurs to gain insight into the behavior of the extinct animals.
“Both studies complement each other,” says study author and Los Angeles County Museum of Natural History biologist Lars Schmitz—and together they indicate that Shuvuuia truly was an odd dinosaur.
Shuvuuia had long inner ear canals, broadening the range of the dinosaur’s hearing. Schmitz and colleagues propose this dinosaur had excellent hearing, comparable to the auditory ability of modern barn owls. Such precise hearing, combined with Shuvuuia’s large eyes, suggest this dinosaur was active at night.
Precisely what Shuvuuia was hunting is unclear—perhaps small mammals, or social insects like ants. But Schmitz notes that there are many reasons a dinosaur might have evolved to prefer the darker hours. “Body size, foraging style, climate, competition,” all matter, Schmitz notes.
Dinosaur song
The new analyses also led to a greater understanding of how these animals may have communicated with one another. The researchers found that ancestors and early relatives of dinosaurs evolved a longer region of the inner ear called the cochlea, which is associated with hearing high-frequency sounds.
The most likely reason, the paleontologists propose, is that this adaptation allowed adult animals to hear the squeaks and chirps of their hatchlings, similar to the attentive parenting of modern-day alligators and crocodiles. The singing birds of today therefore may trace their vocal abilities to the squeaks that tiny, scaly reptiles made as they hatched over 200 million years ago.
“We gently suggest that modern bird song, in all its mellifluous glory, is a retention in adults of juvenile high-pitched chirps,” Bhullar says.
This wealth of information about dinosaur behavior, gleaned by peering into fossilized skulls, represents the rapidly progressing technologies used to study the prehistoric past.
“I think the availability of modern imaging and rendering techniques is a big factor,” Schmitz says, adding that discoveries about the sensory systems of modern animals can also help paleontologists better examine and understand the anatomy and behavior of long-extinct species, which means even as living animals inform what we know about dinosaurs, the dinosaurs are changing how we see the creatures around us.
Pint-sized Mongolian menace shows dinosaurs loved the nightlife, tooRiley Black
NAT GEO
6/5/2021
It’s a golden age for paleontology: In recent years, scientists have gathered all kinds of clues about the way dinosaurs looked and lived, from awe-inspiring fossil reconstructions to preserved footprints and bite marks on bones. Now, paleontologists are showing that some of the most tantalizing indications of how these extinct animals behaved are enclosed inside their skulls.
It’s a golden age for paleontology: In recent years, scientists have gathered all kinds of clues about the way dinosaurs looked and lived, from awe-inspiring fossil reconstructions to preserved footprints and bite marks on bones. Now, paleontologists are showing that some of the most tantalizing indications of how these extinct animals behaved are enclosed inside their skulls.
© Illustration by Viktor Radermaker Shuvuuia deserti reconstruction
A pair of studies published today in the journal Science details a technique using x-ray imaging to study the preserved inner ears and eye sockets of dinosaurs and other prehistoric reptiles. These scans are allowing paleontologists to learn about aspects of dinosaurs’ lives that might otherwise have been lost to time.
“Inner ear shape has always been linked to the lifestyle and behavior of an animal,” says University of Edinburgh paleontologist Julia Schwab, who was not involved with the research. For instance, human inner ears allow us to hear sounds within a specific range of frequencies, from a leaf falling on a sidewalk to a thunderclap, and the inner ear shape is linked to our bipedal species' sense of balance.
Dinosaur skulls evolved to be thick and protect the brain and associated structures, like the tubular canals of the inner ear, keeping those precious clues intact for tens of millions of years. But those protective bones make it difficult to see the structures encased within. So in one of the studies, led by Yale University paleobiologist Bhart-Anjan Bhullar, the team created a set of scans from 124 archosaurs—a group that includes dinosaurs, other ancient reptiles, crocodilians, and living birds—spanning 252 million years ago through today.
The results offered more detail than the paleontologists hoped. By identifying patterns in the structures of the animals’ inner ears and eyes, the researchers were able to glean new information about what the dinosaurs could see, and what kind of movement their inner ears were tuned for. This provides another way of tracking the evolution of flight in dinosaurs and, by extension, their modern descendants: birds.
What’s more, the results from both studies offer exceedingly rare clues to what dinosaurs might have sounded like. Dinosaur vocalization is notoriously difficult to reconstruct. The sound-producing organs of their bodies generally decay soon after death, and relatively few species had bony features related to sound. But the anatomy of a dinosaur’s inner ear offers some insight into what the animals could hear, and therefore what sounds they might have made.
“Honestly, I never thought that we’d be taking a crack at dinosaur noises,” Bhullar says.
A skull hardwired for flight
For their research, Bhullar and his team examined scans from a wide array of species, including theropods such as Velociraptor and a stubby-armed animal called Shuvuuia; non-dinosaur reptiles, such as pterosaurs; extinct toothed birds, such as Hesperornis; and living birds and crocodiles for comparison.
When the paleontologists looked at scans of sickle-clawed dinosaurs called troodontids that thrived during the Cretaceous period 145 to 66 million years ago, they found that these dinosaurs had similar inner ears to early, flying birds from the preceding Jurassic period, which began 201 million years ago. That was something of a surprise, given most known troodontids were terrestrial dinosaurs that didn’t fly.
But the similarities in the inner ear reveal an evolutionary trait necessary for airborne creatures, raising new questions about how flight evolved.
Bhullar hypothesizes that troodontids, which were about the size of turkeys, inherited ears suited to flight from a more ancient common ancestor with birds—perhaps a flying dinosaur, similar to feathered species such as Anchiornis, that lived 165 million years ago. And an inner ear adapted to the complex movements of flight, helping animals balance while in the air, could have had other uses on the ground.
“I do think that even non-flighted dinosaurs that were closely related to birds were moving around in complex ways,” Bhullar says, such as climbing trees or running up inclines. In dinosaurs closely related to birds, these behaviors may have helped the inner ear develop in such a way that allowed for flight—an activity that requires complex movements and limb control.
A pair of studies published today in the journal Science details a technique using x-ray imaging to study the preserved inner ears and eye sockets of dinosaurs and other prehistoric reptiles. These scans are allowing paleontologists to learn about aspects of dinosaurs’ lives that might otherwise have been lost to time.
“Inner ear shape has always been linked to the lifestyle and behavior of an animal,” says University of Edinburgh paleontologist Julia Schwab, who was not involved with the research. For instance, human inner ears allow us to hear sounds within a specific range of frequencies, from a leaf falling on a sidewalk to a thunderclap, and the inner ear shape is linked to our bipedal species' sense of balance.
Dinosaur skulls evolved to be thick and protect the brain and associated structures, like the tubular canals of the inner ear, keeping those precious clues intact for tens of millions of years. But those protective bones make it difficult to see the structures encased within. So in one of the studies, led by Yale University paleobiologist Bhart-Anjan Bhullar, the team created a set of scans from 124 archosaurs—a group that includes dinosaurs, other ancient reptiles, crocodilians, and living birds—spanning 252 million years ago through today.
The results offered more detail than the paleontologists hoped. By identifying patterns in the structures of the animals’ inner ears and eyes, the researchers were able to glean new information about what the dinosaurs could see, and what kind of movement their inner ears were tuned for. This provides another way of tracking the evolution of flight in dinosaurs and, by extension, their modern descendants: birds.
What’s more, the results from both studies offer exceedingly rare clues to what dinosaurs might have sounded like. Dinosaur vocalization is notoriously difficult to reconstruct. The sound-producing organs of their bodies generally decay soon after death, and relatively few species had bony features related to sound. But the anatomy of a dinosaur’s inner ear offers some insight into what the animals could hear, and therefore what sounds they might have made.
“Honestly, I never thought that we’d be taking a crack at dinosaur noises,” Bhullar says.
A skull hardwired for flight
For their research, Bhullar and his team examined scans from a wide array of species, including theropods such as Velociraptor and a stubby-armed animal called Shuvuuia; non-dinosaur reptiles, such as pterosaurs; extinct toothed birds, such as Hesperornis; and living birds and crocodiles for comparison.
When the paleontologists looked at scans of sickle-clawed dinosaurs called troodontids that thrived during the Cretaceous period 145 to 66 million years ago, they found that these dinosaurs had similar inner ears to early, flying birds from the preceding Jurassic period, which began 201 million years ago. That was something of a surprise, given most known troodontids were terrestrial dinosaurs that didn’t fly.
But the similarities in the inner ear reveal an evolutionary trait necessary for airborne creatures, raising new questions about how flight evolved.
Bhullar hypothesizes that troodontids, which were about the size of turkeys, inherited ears suited to flight from a more ancient common ancestor with birds—perhaps a flying dinosaur, similar to feathered species such as Anchiornis, that lived 165 million years ago. And an inner ear adapted to the complex movements of flight, helping animals balance while in the air, could have had other uses on the ground.
“I do think that even non-flighted dinosaurs that were closely related to birds were moving around in complex ways,” Bhullar says, such as climbing trees or running up inclines. In dinosaurs closely related to birds, these behaviors may have helped the inner ear develop in such a way that allowed for flight—an activity that requires complex movements and limb control.
Nighttime stalkers
Not all bird-like dinosaurs moved like their avian relations, however. Some dinosaurs, the researchers found, moved and likely hunted in ways that run counter to paleontological expectations.
The turkey-size dinosaur Shuvuuia, for example, has long been a mystery to paleontologists. Known for its short arms tipped with large, single claws and toothless or nearly toothless jaws, this genus belongs to a group of bipedal theropods called alvarezsaurs. Bhullar and colleagues were surprised to find that Shuvuuia has an inner ear similar to that in four-legged animals with relatively simple locomotion.
The second Science study may offer insight into Shuvuuia’s odd inner ear. This study looked at both the inner ears and the eyes of dinosaurs to gain insight into the behavior of the extinct animals.
“Both studies complement each other,” says study author and Los Angeles County Museum of Natural History biologist Lars Schmitz—and together they indicate that Shuvuuia truly was an odd dinosaur.
Shuvuuia had long inner ear canals, broadening the range of the dinosaur’s hearing. Schmitz and colleagues propose this dinosaur had excellent hearing, comparable to the auditory ability of modern barn owls. Such precise hearing, combined with Shuvuuia’s large eyes, suggest this dinosaur was active at night.
Precisely what Shuvuuia was hunting is unclear—perhaps small mammals, or social insects like ants. But Schmitz notes that there are many reasons a dinosaur might have evolved to prefer the darker hours. “Body size, foraging style, climate, competition,” all matter, Schmitz notes.
Dinosaur song
The new analyses also led to a greater understanding of how these animals may have communicated with one another. The researchers found that ancestors and early relatives of dinosaurs evolved a longer region of the inner ear called the cochlea, which is associated with hearing high-frequency sounds.
The most likely reason, the paleontologists propose, is that this adaptation allowed adult animals to hear the squeaks and chirps of their hatchlings, similar to the attentive parenting of modern-day alligators and crocodiles. The singing birds of today therefore may trace their vocal abilities to the squeaks that tiny, scaly reptiles made as they hatched over 200 million years ago.
“We gently suggest that modern bird song, in all its mellifluous glory, is a retention in adults of juvenile high-pitched chirps,” Bhullar says.
This wealth of information about dinosaur behavior, gleaned by peering into fossilized skulls, represents the rapidly progressing technologies used to study the prehistoric past.
“I think the availability of modern imaging and rendering techniques is a big factor,” Schmitz says, adding that discoveries about the sensory systems of modern animals can also help paleontologists better examine and understand the anatomy and behavior of long-extinct species, which means even as living animals inform what we know about dinosaurs, the dinosaurs are changing how we see the creatures around us.
By Will Dunham
REUTERS 6/4/2021
Reuters/HANDOUT The fossilized skeleton of the small bird-like dinosaur Shuvuuia deserti
(Reuters) - Under the cover of darkness in desert habitats about 70 million years ago, in what is today Mongolia and northern China, a gangly looking dinosaur employed excellent night vision and superb hearing to thrive as a menacing pint-sized nocturnal predator.
Scientists said on Thursday an examination of a ring of bones surrounding the pupil and a bony tube inside the skull that houses the hearing organ showed that this dinosaur, called Shuvuuia deserti, boasted visual and auditory capabilities akin to a barn owl, indicating it could it hunt in total darkness.
Their study, published in the journal Science, showed that predatory dinosaurs overall generally possessed better-than-average hearing - helpful for hunters - but had vision optimized for daytime. In contrast, Shuvuuia (pronounced shu-VOO-ee-ah) loved the nightlife.
(Reuters) - Under the cover of darkness in desert habitats about 70 million years ago, in what is today Mongolia and northern China, a gangly looking dinosaur employed excellent night vision and superb hearing to thrive as a menacing pint-sized nocturnal predator.
Scientists said on Thursday an examination of a ring of bones surrounding the pupil and a bony tube inside the skull that houses the hearing organ showed that this dinosaur, called Shuvuuia deserti, boasted visual and auditory capabilities akin to a barn owl, indicating it could it hunt in total darkness.
Their study, published in the journal Science, showed that predatory dinosaurs overall generally possessed better-than-average hearing - helpful for hunters - but had vision optimized for daytime. In contrast, Shuvuuia (pronounced shu-VOO-ee-ah) loved the nightlife.
© Reuters/HANDOUT The small bird-like dinosaur Shuvuuia deserti is seen in this 2021 artist's reconstruction
Shuvuuia was a pheasant-sized, two-legged Cretaceous Period dinosaur weighing about as much as a small house cat. Lacking the strong jaws and sharp teeth of many carnivorous dinosaurs, it had a remarkably bird-like and lightly built skull and many tiny teeth like grains of rice.
Its mid-length neck and small head, coupled with very long legs, made it resemble an awkward chicken. Unlike birds, it had short but powerful arms ending in a single large claw, good for digging.
"Shuvuuia might have run across the desert floor under cover of night, using its incredible hearing and night vision to track small prey such as nocturnal mammals, lizards and insects. With its long legs it could have rapidly run down such prey, and used its digging forelimbs to pry prey loose from any cover such as a burrow," said paleontologist Jonah Choiniere of the University of the Witwatersrand in South Africa, the study's lead author
Shuvuuia was a pheasant-sized, two-legged Cretaceous Period dinosaur weighing about as much as a small house cat. Lacking the strong jaws and sharp teeth of many carnivorous dinosaurs, it had a remarkably bird-like and lightly built skull and many tiny teeth like grains of rice.
Its mid-length neck and small head, coupled with very long legs, made it resemble an awkward chicken. Unlike birds, it had short but powerful arms ending in a single large claw, good for digging.
"Shuvuuia might have run across the desert floor under cover of night, using its incredible hearing and night vision to track small prey such as nocturnal mammals, lizards and insects. With its long legs it could have rapidly run down such prey, and used its digging forelimbs to pry prey loose from any cover such as a burrow," said paleontologist Jonah Choiniere of the University of the Witwatersrand in South Africa, the study's lead author
.
© Reuters/HANDOUT Professor Jonah Choiniere of the University of the Witwatersrand is seen holding a 3D printed model of the lagena
"It's such a strange animal that paleontologists have long wondered what it was actually doing," added paleontologist Roger Benson of the University of Oxford in England, who helped lead the study.
The researchers looked at a structure called the lagena, a curving and finger-like sac that sits in a cavity in the bones surrounding the brain and is connected to the part of the ear that lets reptiles and birds keep balance and move their heads while walking. Acute hearing helps nocturnal predators locate prey. The longer the lagena, the better hearing an animal has.
The barn owl, a proficient nocturnal predator even in pitch-black conditions, has the proportionally longest lagena of any living bird. Shuvuuia is unique among predatory dinosaurs with a hyper-elongated lagena, almost identical in relative size to a barn owl's.
The researchers also looked at a series of tiny bones called the scleral ring that encircle the pupil of the eye. It exists in birds and lizards and was present in the ancestors of today's mammals. Shuvuuia had a very wide scleral ring, indicating an extra-large pupil size that made its eye a specialized light-capture device.
The study found that nocturnality was uncommon among dinosaurs, aside from a group called alvarezsaurs to which Shuvuuia belonged. Alvarezsaurs had nocturnal vision very early in their lineage, but super-hearing took more time to evolve.
"Like many paleontologists, I once considered that nighttime in the age of dinosaurs was when the mammals came out of hiding to avoid predation and competition. The importance of these findings is that it forces us to imagine dinosaurs like Shuvuuia evolving to take advantage of these nocturnal communities," Choiniere said.
Benson added, "This really shows that dinosaurs had a wide range of skills and adaptations that are only just coming to light now. We find evidence that there was a thriving 'nightlife' during the time of dinosaurs."
(Reporting by Will Dunham in Washington, Editing by Rosalba O'Brien)
"It's such a strange animal that paleontologists have long wondered what it was actually doing," added paleontologist Roger Benson of the University of Oxford in England, who helped lead the study.
The researchers looked at a structure called the lagena, a curving and finger-like sac that sits in a cavity in the bones surrounding the brain and is connected to the part of the ear that lets reptiles and birds keep balance and move their heads while walking. Acute hearing helps nocturnal predators locate prey. The longer the lagena, the better hearing an animal has.
The barn owl, a proficient nocturnal predator even in pitch-black conditions, has the proportionally longest lagena of any living bird. Shuvuuia is unique among predatory dinosaurs with a hyper-elongated lagena, almost identical in relative size to a barn owl's.
The researchers also looked at a series of tiny bones called the scleral ring that encircle the pupil of the eye. It exists in birds and lizards and was present in the ancestors of today's mammals. Shuvuuia had a very wide scleral ring, indicating an extra-large pupil size that made its eye a specialized light-capture device.
The study found that nocturnality was uncommon among dinosaurs, aside from a group called alvarezsaurs to which Shuvuuia belonged. Alvarezsaurs had nocturnal vision very early in their lineage, but super-hearing took more time to evolve.
"Like many paleontologists, I once considered that nighttime in the age of dinosaurs was when the mammals came out of hiding to avoid predation and competition. The importance of these findings is that it forces us to imagine dinosaurs like Shuvuuia evolving to take advantage of these nocturnal communities," Choiniere said.
Benson added, "This really shows that dinosaurs had a wide range of skills and adaptations that are only just coming to light now. We find evidence that there was a thriving 'nightlife' during the time of dinosaurs."
(Reporting by Will Dunham in Washington, Editing by Rosalba O'Brien)
