Alligators, birds and dinosaurs, new study


This 2013 video from Florida in the USA is called Ninja Gator! Alligator climbs fence.

From the University of Maryland in the USA:

Alligator study reveals insight into dinosaur hearing

March 18, 2019

Summary: A biologist finds alligators build neural maps of sound the way birds do, suggesting the hearing strategy existed in their common ancestor, the dinosaurs.

Alligators are not descendants of dinosaurs, but from early archosaur ancestors of both dinosaurs and crocodiles.

According to most paleontologists, birds are indeed descendants of dinosaurs.

To determine where a sound is coming from, animal brains analyze the minute difference in time it takes a sound to reach each ear — a cue known as interaural time difference. What happens to the cue once the signals get to the brain depends on what kind of animal is doing the hearing.

Scientists have known that birds are exceptionally good at creating neural maps to chart the location of sounds, and that the strategy differs in mammals. Little was known, however, about how alligators process interaural time difference.

A new study of American alligators found that the reptiles form neural maps of sound in the same way birds do. The research by Catherine Carr, a Distinguished University Professor of Biology at the University of Maryland, and her colleague Lutz Kettler from the Technische Universität München, was published in the Journal of Neuroscience on March 18, 2019.

Most research into how animals analyze interaural time difference has focused on physical features such as skull size and shape, but Carr and Kettler believed it was important to look at evolutionary relationships.

Birds have very small head sizes compared with alligators, but the two groups share a common ancestor — the archosaur — which predates dinosaurs. Archosaurs began to emerge around 246 million years ago and split into two lineages; one that led to alligators and one that led to dinosaurs. Although most dinosaurs died out during the mass extinction event 66 million years ago, some survived to evolve into modern birds.

Carr and Kettler’s findings indicate that the hearing strategy birds and alligators share may have less to do with head size and more to do with common ancestry.

“Our research strongly suggests that this particular hearing strategy first evolved in their common ancestor,” Carr said. “The other option, that they independently evolved the same complex strategy, seems very unlikely.”

To study how alligators identify where sound comes from, the researchers anesthetized 40 American Alligators and fitted them with earphones. They played tones for the sleepy reptiles and measured the response of a structure in their brain stems called the nucleus laminaris. This structure is the seat of auditory signal processing. Their results showed that alligators create neural maps very similar to those previously measured in barn owls and chickens. The same maps have not been recorded in the equivalent structure in mammal brains.

“We know so little about dinosaurs,” Carr said. “Comparative studies such as this one, which identify common traits extending back through evolutionary time add to our understanding of their biology.”

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What a young Tyrannosaurus rex ate


This video says about itself:

T-Rex: Attack of the Dinosaur | Walking with Dinosaurs in HQ | BBC

The mother Tyrannosaurus breaks her fast to provide a kill to feed her young. Even though they are small and vulnerable, the young T-Rex‘s already have a fierce competitive streak.

Broadcast in 1999, Walking with Dinosaurs set out to create the most accurate portrayal of prehistoric animals ever seen on the screen.

From the University of Wisconsin Oshkosh in the USA:

Teenage T. rex was already chomping on prey

March 11, 2019

New research from the University of Wisconsin Oshkosh indicates that even as a teenager the Tyrannosaurus rex showed signs that it would grow up to be a ferocious predator.

In a study published last week in the peer-reviewed journal Peerj — the Journal of Life and Environmental Sciences, UWO scientists reported evidence that a juvenile T. rex fed on a large plant-eating dinosaur, even though it lacked the bone-crushing abilities it would develop as an adult.

While studying fossils from an Edmontosaurus — a plant-eating Hadrosaurid or duck-billed dinosaur, UWO vertebrate paleontologist Joseph Peterson noticed three large, v-shaped, bite marks on a tail bone and wondered, “Who made these?”

Peterson knew that T. rex — a member of the meat-eating dinosaur suborder known as Theropoda — was “a likely culprit.”

“We suspected that T. rex was responsible for the bit marks, because in the upper Cretaceous rock formation, where the hadrosaur was discovered, there are only a few carnivorous dinosaurs and other reptiles in the fossil record. Crocodile fossils are found there, but such a crocodile would have left tooth marks that are round rather than the elliptical punctures we found on the vertebra,” Peterson explained.

“There also were small Velociraptor-like dinosaurs, but their teeth are too small to have made the marks. Finally, an adult T. rex would have made punctures that would have been too large! That’s when we started considering a juvenile tyrannosaur.”

To test the hypothesis, Peterson and geology student Karsen Daus, of Suamico, coated the fossil with a silicon rubber to make a silicone peel of the puncture marks.

They found that the dimensions of the “teeth” better matched a late-stage juvenile T. rex (11 to 12 years) than an adult (approximately 30 years).

“Although this T. rex was young, it really packed a punch,” Peterson said.

“This is significant to paleontology because it demonstrates how T. rex — the most popular dinosaur of all time — may have developed changes in diet and feeding abilities while growing,” he said. “This is part of a larger, ongoing research initiative by many paleontologists to better understand how T. rex grew and functioned as a living creature over 65 million years ago.”

Most theropod feeding traces and bite marks are attributed to adults; juvenile tooth marks rarely have been reported in the literature, he added.

“We really are in the ‘Golden Age’ of paleontology,” Peterson said. “We are learning more now than we ever thought we would know about dinosaurs. And, we’re learn more about how they grew up.”

Small dinosaur discovery in Victoria, Australia


This 11 March 2019 video about Australia says about itself:

New wallaby-sized dinosaur identified from fossils found along Victorian coast

Fossilised jawbones found in rocks along Victoria’s Gippsland coast have been identified as belonging to a new species of plant-eating dinosaur the size of a wallaby that would have roamed the land between Australia and Antarctica.

Galleonosaurus dorisae is just the second dinosaur of its type to be identified from the 125-million-year-old rock platforms south-east of Melbourne — and the fifth from along the Victorian coastline.

Millions of years ago, this area was a lushly forested rift valley with a 4,000-km chain of volcanoes to the east, said palaeontologist Matthew Herne of the University of New England.

From the Cambridge University Press in England:

New wallaby-sized dinosaur from the ancient Australian-Antarctic rift valley

March 11, 2019

A new, wallaby-sized herbivorous dinosaur has been identified from five fossilized upper jaws in 125 million year old rocks from the Cretaceous period of Victoria, southeastern Australia.

Reported in the Journal of Paleontology, the new dinosaur is named “Galleonosaurus dorisae,” and is the first dinosaur named from the Gippsland region of Australia in 16 years. According to Dr Matthew Herne, a Postdoctoral Fellow at the University of New England, NSW, and lead author of the new study, “the jaws of Galleonosaurus dorisae include young to mature individuals — the first time an age range has been identified from the jaws of an Australian dinosaur.”

Galleonosaurus was a small-bodied herbivorous dinosaur within the large family called ornithopods. “These small dinosaurs would have been agile runners on their powerful hind legs,” explained Dr Herne.

The name Galleonosaurus dorisae refers to the shape of the upper jaw, resembling the upturned hull of a sailing ship called a galleon, and also honours the work of Dr Doris Seegets-Villiers, who produced her PhD thesis on the palaeontology of the locality where the fossils were discovered.

Galleonosaurus is the fifth small ornithopod genus named from Victoria, which according to Dr Herne, “confirms that on a global scale, the diversity of these small-bodied dinosaurs had been unusually high in the ancient rift valley that once extended between the spreading continents of Australia and Antarctica.” Small ornithopods appear to have thrived on the vast forested floodplain within the ancient rift valley.

At the time of Galleonosaurus, sediments were shed from a four thousand km long massif of large, actively erupting volcanoes that once existed along the eastern margin of the Australian continent. Some of these sediments were carried westward by large rivers into the Australian-Antarctic rift valley where they formed deep sedimentary basins. However, as these sediments washed down the rivers of the rift valley the bones of dinosaurs, such as Galleonosaurus and other vertebrates, along with the logs of fallen trees, became mixed in. According to Dr Herne, “this land has now vanished, but as ‘time-travellers’ we get snapshots of this remarkable world via the rocks and fossils exposed along the coast of Victoria.”

The new article shows that Galleonosaurus dorisae is a close relative of Diluvicursor pickeringi; another small ornithopod named by Dr Herne and his team in 2018, from excavations along the Otway coast to the west of the Gippsland region. Interestingly, “the jaws of Galleonosaurus and the partial skeleton of Diluvicursor were similarly buried in volcanic sediments on the floor of deep powerful rivers,” explained Dr Herne. “However, Galleonosaurus is about 12 million years older than Diluvicursor, showing that the evolutionary history of dinosaurs in the Australian-Antarctic rift had been lengthy.”

The jaws of Galleonosaurus were discovered by volunteers of the Dinosaur Dreaming project during excavations near the town of Inverloch. The most complete jaw and the key specimen carrying the name Galleonosaurus dorisae was discovered in 2008 by the seasoned fossil hunter Gerrit (‘Gerry’) Kool, from the nearby town of Wonthaggi. Gerry and his wife Lesley have been instrumental in organizing the Dinosaur Dreaming excavations along the Victorian coast for 25 years.

Prior to discovery of Galleonosaurus dorisae, the only other ornithopod known from the Gippsland region was Qantassaurus intrepidus, named in 1999. However, Qantassaurus had a shorter more robust snout than that of Galleonosaurus, explained Dr Herne, who added, “we consider that these two, similarly-sized dinosaurs fed on different plant types, which would have allowed them to coexist.”

The new study reveals that the ornithopods from Victoria are closely related to those from Patagonia in Argentina. “We are steadily building a picture of terrestrial dinosaur interchange between the shifting Gondwanan continents of Australia, South America and Antarctica during the Cretaceous period,” added Dr Herne.

These are exciting times for dinosaur research, explained Dr Herne: “Using advanced techniques, such as 3D micro-CT scanning and printing, new anatomical information is being revealed on dinosaurs such as Galleonosaurus dorisae. These techniques are helping us to delve deeper into the mysterious world of dinosaur ecology — what they ate, how they moved and how they coexisted — and their evolutionary relationships with dinosaurs from other continents.”

Big Tyrannosaurus rex, why its small arms?


This 11 March 2019 video says about itself:

Why did T. rex have small arms? | Natural History Museum [in London, England]

Tyrannosaurus‘s tiny arms are often joked about. But were their surprisingly muscular limbs actually more useful than they’re given credit for?

Museum scientist Kieran Miles explains some of the theories for what these famous dinosaurs may have used their disproportionately small appendages for.

Dinosaurs, gradual decline or sudden extinction?


This July 2016 video says about itself:

Experience the Disaster that Wiped Out Dinosaurs

When the dinosaur-killing asteroid struck Earth, most of the impact energy was directed outwards and upwards into space. Only 1% of the force traveled down into the ground, but it was enough to ring the planet like a bell and wipe out species around the globe. Only those creatures able to seek shelter from the intense heat on the surface survived.

From Imperial College London in England:

Dinosaurs were thriving before asteroid strike that wiped them out

March 6, 2019

Dinosaurs were unaffected by long-term climate changes and flourished before their sudden demise by asteroid strike.

Scientists largely agree that an asteroid impact, possibly coupled with intense volcanic activity, wiped out the dinosaurs at the end of the Cretaceous period 66 million years ago.

However, there is debate about whether dinosaurs were flourishing before this, or whether they had been in decline due to long-term changes in climate over millions of years.

Previously, researchers used the fossil record and some mathematical predictions to suggest dinosaurs may have already been in decline, with the number and diversity of species falling before the asteroid impact.

Now, in a new analysis that models the changing environment and dinosaur species distribution in North America, researchers from Imperial College London, University College London and University of Bristol have shown that dinosaurs were likely not in decline before the meteorite.

Lead researcher Alessandro Chiarenza, a PhD student in the Department of Earth Science and Engineering at Imperial, said: “Dinosaurs were likely not doomed to extinction until the end of the Cretaceous, when the asteroid hit, declaring the end of their reign and leaving the planet to animals like mammals, lizards and a minor group of surviving dinosaurs: birds.

“The results of our study suggest that dinosaurs as a whole were adaptable animals, capable of coping with the environmental changes and climatic fluctuations that happened during the last few million years of the Late Cretaceous. Climate change over prolonged time scales did not cause a long-term decline of dinosaurs through the last stages of this period.”

The study, published today in Nature Communications, shows how the changing conditions for fossilisation means previous analyses have underestimated the number of species at the end of the Cretaceous.

The team focused their study on North America, where many Late Cretaceous dinosaurs are preserved, such as Tyrannosaurus rex and Triceratops. During this period, the continent was split in two by a large inland sea.

In the western half there was a steady supply of sediment from the newly forming Rocky Mountains, which created perfect conditions for fossilising dinosaurs once they died. The eastern half of the continent was instead characterised by conditions far less suitable for fossilisation.

This means that far more dinosaur fossils are found in the western half, and it is this fossil record that is often used to suggest dinosaurs were in decline for the few million years before the asteroid strike.

Co-author Dr Philip Mannion, from University College London, commented: “Most of what we know about Late Cretaceous North American dinosaurs comes from an area smaller than one-third of the present-day continent, and yet we know that dinosaurs roamed all across North America, from Alaska to New Jersey and down to Mexico.”

Instead of using this known record exclusively, the team employed ‘ecological niche modelling’. This approach models which environmental conditions, such as temperature and rainfall, each species needs to survive.

The team then mapped where these conditions would occur both across the continent and over time. This allowed them to create a picture of where groups of dinosaur species could survive as conditions changed, rather than just where their fossils had been found.

The team found habitats that could support a range of dinosaur groups were actually more widespread at the end of the Cretaceous, but that these were in areas less likely to preserve fossils.

Furthermore, these potentially dinosaur-rich areas were smaller wherever they occurred, again reducing the likelihood of finding a fossil from each of these areas.

Tyrannosaur evolution, video


This 3 March 2019 video says about itself:

The Rise of the Tyrannosaurs

The discovery of a new tyrannosaur, Moros intrepidus, has revealed how these iconic animals went from small, agile predators to the massive, bone-crushing T. rex.

Small tyrannosaur relative discovery in Utah, USA


This 21 February 2019 video says about itself:

Moros intrepidus: North America’s Tiny Tyrannosaur

“Diminutive, fleet-footed tyrannosauroid narrows the 70-million-year gap in the North American fossil record”

From North Carolina State University in the USA:

New species of tiny tyrannosaur foreshadows rise of T. rex

February 21, 2019

A newly discovered, diminutive — by T. rex standards — relative of the tyrant king of dinosaurs reveals crucial new information about when and how T. rex came to rule the North American roost.

Meet Moros intrepidus, a small tyrannosaur who lived about 96 million years ago in the lush, deltaic environment of what is now Utah during the Cretaceous period. The tyrannosaur, whose name means “harbinger of doom,” is the oldest Cretaceous tyrannosaur species yet discovered in North America, narrowing a 70-million-year gap in the fossil record of tyrant dinosaurs on the continent.

“With a lethal combination of bone-crunching bite forces, stereoscopic vision, rapid growth rates, and colossal size, tyrant dinosaurs reigned uncontested for 15 million years leading up to the end-Cretaceous extinction — but it wasn’t always that way,” says Lindsay Zanno, paleontologist at North Carolina State University, head of paleontology at the North Carolina Museum of Sciences and lead author of a paper describing the research. “Early in their evolution, tyrannosaurs hunted in the shadows of archaic lineages such as allosaurs that were already established at the top of the food chain.”

Medium-sized, primitive tyrannosaurs have been found in North America dating from the Jurassic (around 150 million years ago). By the Cretaceous — around 81 million years ago — North American tyrannosaurs had become the enormous, iconic apex predators we know and love. The fossil record between these time periods has been a blank slate, preventing scientists from piecing together the story behind the ascent of tyrannosaurs in North America. “When and how quickly tyrannosaurs went from wallflower to prom king has been vexing paleontologists for a long time,” says Zanno. “The only way to attack this problem was to get out there and find more data on these rare animals.”

That’s exactly what Zanno and her team did. A decade spent hunting for dinosaur remains within rocks deposited at the dawn of the Late Cretaceous finally yielded teeth and a hind limb from the new tyrannosaur. In fact, the lower leg bones of Moros were discovered in the same area where Zanno had previously found Siats meekerorum, a giant meat-eating carcharodontosaur that lived during the same period. Moros is tiny by comparison — standing only three or four feet tall at the hip, about the size of a modern mule deer. Zanno estimates that the Moros was over seven years old when it died, and that it was nearly full-grown.

But don’t let the size fool you. “Moros was lightweight and exceptionally fast,” Zanno says. “These adaptations, together with advanced sensory capabilities, are the mark of a formidable predator. It could easily have run down prey, while avoiding confrontation with the top predators of the day.

“Although the earliest Cretaceous tyrannosaurs were small, their predatory specializations meant that they were primed to take advantage of new opportunities when warming temperatures, rising sea-level and shrinking ranges restructured ecosystems at the beginning of the Late Cretaceous,” Zanno says. “We now know it took them less than 15 million years to rise to power.”

The bones of Moros also revealed the origin of T. rex’s lineage on the North American continent. When the scientists placed Moros within the family tree of tyrannosaurs they discovered that its closest relatives were from Asia. “T. rex and its famous contemporaries such as Triceratops may be among our most beloved cultural icons, but we owe their existence to their intrepid ancestors who migrated here from Asia at least 30 million years prior,” Zanno says. “Moros signals the establishment of the iconic Late Cretaceous ecosystems of North America.”

The research appears in Communications Biology, and was supported in part by Canyonlands Natural History Association. Lecturer Terry Gates, postdoctoral research scholar Aurore Canoville and graduate student Haviv Avrahami from NC State, as well as the Field Museum’s Peter Makovicky and Ryan Tucker from Stellenbosch University, contributed to the work.