Tyrannosaurids and Other Big Ancient Predators

[zorkan]

Yes but the tourist trade in North Scotland relies on that one image.

[billy rubin]

certainly not on the weather

[Recusant]

Investigation of the origin of the tyrannosaurids. 

"T. rex's direct ancestor crossed from Asia to North America, new study finds" | Phys.org

Tyrannosaurus rex evolved in North America, but its direct ancestor came from Asia, crossing a land bridge connecting the continents more than 70 million years ago, according to a new study led by UCL researchers.

The study, published in Royal Society Open Science, also found that the rapid growth in size of tyrannosaurids (the group that included the T. rex) as well as a closely related group called megaraptors coincided with a cooling of the global climate following a peak in temperatures 92 million years ago.

This suggests T. rex and its cousins might have been better suited to cooler climates than other dinosaur groups at the time, perhaps due to having feathers or a more warm-blooded physiology.

The international team involved researchers from the universities of Oxford, Pittsburgh, Aberdeen, Arizona, Anglia Ruskin, Oklahoma and Wyoming.

Lead author Cassius Morrison, a Ph.D. student at UCL Earth Sciences, said, "The geographic origin of T. rex is the subject of fierce debate. Paleontologists have been divided over whether its ancestor came from Asia or North America.

"Our modeling suggests the 'grandparents' of T. rex likely came to North America from Asia, crossing the Bering Strait between what is now Siberia and Alaska.

"This is in line with past research finding that the T. rex was more closely related to Asian cousins such as the Tarbosaurus than to North American relatives such as Daspletosaurus.

[Continues . . .]

The paper is open access:

"Rise of the king: Gondwanan origins and evolution of megaraptoran dinosaurs" | Royal Society Open Science

Abstract:

Late Cretaceous Earth was dominated by theropods such as tyrannosauroids and megaraptorans; however, it is unclear how these clades diversified and grew to massive proportions. This study aimed to conduct a biogeographical analysis and test climate as a potential mechanism for the increase in size.

We used published phylogenetic matrices with the R package BioGeoBears to test different biogeographical hypotheses for both clades. We mapped body mass (BM) and body length against known climate data to test this potential hypothesis.

Continental-scale variance did not drive tyrannosauroid biogeography and instead widespread ancestral populations, sympatric speciation and localized extinctions throughout these clades constricted geographic range. Both patterns were supported by statistical analyses. This biogeographical model also indicates the ancestor of the clade Tarbosaurus and Tyrannosaurus was present in both Asia and Laramidia, and therefore the ancestor of Tyrannosaurus came from Asia.

Statistical data illustrated no correlation between Mean Annual Temperature (MAT) and BM but potential climatic shifts may be associated with gigantism in derived megaraptorids and eutyrannosaurians. This biogeographical model implies megaraptorans may have had a cosmopolitan distribution prior to the splitting of Laurasia and Gondwana. Also, gigantism in these clades may be associated with climatic shifts in the Late Cretaceous.

[Recusant]

This one is pretty cool. Based on reexamination of fossils of small dinosaurs, it appears that Tyrannosaurus rex laid large clutches of relatively small eggs rather than smaller clutches of larger eggs--a revision of the hypothesis regarding their reproductive strategy.

"'Vanishingly Rare' Discovery: T. Rex Hatchlings Were Smaller Than a Cat And Born by The Dozen" | ScienceAlert

Jurassic Park was wrong. Again.

In the second movie, hunters find an infant Tyrannosaurus rex and use it to lure the adults into a trap.

But in reality, that baby would have been much smaller, about the size of a cat. And it probably wouldn't have been alone – the nest may have been absolutely crawling with dozens of them.

It likely wouldn't have been very useful as bait either: Its parents probably would have considered losing a baby or two as just part of the process, and wouldn't have cared enough to push a research trailer off a cliff.

So why are we updating our understanding of T. rex's childhood?

In a "vanishingly rare" discovery, paleontologists have found and closely examined fossils of tyrannosaur hatchlings. The remarkable findings are published in the journal Biology – and the implications go way beyond everyone's favorite dinosaur.

"Going through museum collections, my colleagues and I have discovered the first remains of hatchling tyrannosaurs," announced Nick Longrich, paleontologist and evolutionary biologist at the University of Bath in the UK.

[. . .]

Longrich and his team set out to investigate these fragmented fossils gathering dust in storeroom drawers, expecting to find adult specimens of small dinosaurs. Instead, ironically, the work led the team back to the big guys.

One of the small bones appeared to be a third metatarsal – the middle foot bone – of a theropod dinosaur. But on closer inspection, it didn't look like it came from a fully grown animal.

"The surface of the bone was incredibly porous," Longrich says in a video on his YouTube channel.

"And this is the result of all these little microscopic blood vessels creating this dense network of blood vessels. And these nourish the bone as it grows. So they're providing blood to the bone cells as they deposit bone tissue and remodel the bone. And this is typical of an immature dinosaur."

When the bone was compared to others of its era, the researchers realized only one species fit the characteristics they were seeing.

"This is the foot bone of a very, very tiny T. rex. This is the smallest T. rex that we've ever seen," said Longrich.

After that find, the team began to look more closely at other small fossils of bones and teeth, and realized that many could also be attributed to tyrannosaur hatchlings.

[. . .]

The goal of reproduction is obviously to make more of yourself, and in a general sense, organisms use one of two broad strategies to get there.

They either have lots of offspring, quickly and often, so that it doesn't really matter if some (or most) of them don't live very long – there are plenty of backups. Organisms that use this method, such as rodents, are known as r-strategists.

The other method is to have fewer babies, but invest heavily in making sure they survive. These are the K-strategists, and that group includes whales and, of course, us.

[. . .]

[T]he new discovery that tyrannosaur young were small and numerous suggests they had more r-strategist tendencies than we thought.

[Continues . . .]

The paper is open access:

"Hatchlings of Tyrannosaurus rex and the Evolution of Dinosaur Reproductive Strategies" | Biology

Abstract:

Tyrannosaurs were giant predatory dinosaurs that occupied the apex of Late Cretaceous food chains. Little is known about the early life and reproductive ecology of tyrannosaurs due to the extreme rarity of hatchling and juvenile fossils.

We report bones of hatchlings (<1 yr) for Tyrannosaurus rex and Gorgosaurus libratus, weighing ~2.5 kg and ~2.4 kg, respectively, i.e., <0.1% of adult mass. Clutches were likely large. We conservatively estimate ~20 eggs in a small adult T. rex versus ~30 eggs in the largest T. rex, and clutches of ~15 eggs in G. libratus; larger clutches of 50 or even 100 eggs are not impossible.

This suggests an r-selected reproductive strategy. Synchrotron scans reveal Haversian bone remodeling, suggesting that tyrannosaurs moved soon after hatching. Hatchling tyrannosaurs' small size and precociality suggest limited parental care; teeth of hatchlings show wear suggesting that they fed on relatively large vertebrates.

Tyrannosaurs had proportionately larger offspring than most reptiles, but relatively smaller hatchlings than Eumaniraptora and birds, suggesting retention of a primitive reproductive strategy intermediate between that of basal diapsids and birds. Multiple dinosaur lineages evolved large eggs independently, suggesting an evolutionary trend towards increased parental investment.

[Recusant]

This one is pretty cool. Based on reexamination of fossils of small dinosaurs, it appears that Tyrannosaurus rex laid large clutches of relatively small eggs rather than smaller clutches of larger eggs--a revision of the hypothesis regarding their reproductive strategy.

"'Vanishingly Rare' Discovery: T. Rex Hatchlings Were Smaller Than a Cat And Born by The Dozen" | ScienceAlert

Jurassic Park was wrong. Again.

In the second movie, hunters find an infant Tyrannosaurus rex and use it to lure the adults into a trap.

But in reality, that baby would have been much smaller, about the size of a cat. And it probably wouldn't have been alone – the nest may have been absolutely crawling with dozens of them.

It likely wouldn't have been very useful as bait either: Its parents probably would have considered losing a baby or two as just part of the process, and wouldn't have cared enough to push a research trailer off a cliff.

So why are we updating our understanding of T. rex's childhood?

In a "vanishingly rare" discovery, paleontologists have found and closely examined fossils of tyrannosaur hatchlings. The remarkable findings are published in the journal Biology – and the implications go way beyond everyone's favorite dinosaur.

"Going through museum collections, my colleagues and I have discovered the first remains of hatchling tyrannosaurs," announced Nick Longrich, paleontologist and evolutionary biologist at the University of Bath in the UK.

[. . .]

Longrich and his team set out to investigate these fragmented fossils gathering dust in storeroom drawers, expecting to find adult specimens of small dinosaurs. Instead, ironically, the work led the team back to the big guys.

One of the small bones appeared to be a third metatarsal – the middle foot bone – of a theropod dinosaur. But on closer inspection, it didn't look like it came from a fully grown animal.

"The surface of the bone was incredibly porous," Longrich says in a video on his YouTube channel.

"And this is the result of all these little microscopic blood vessels creating this dense network of blood vessels. And these nourish the bone as it grows. So they're providing blood to the bone cells as they deposit bone tissue and remodel the bone. And this is typical of an immature dinosaur."

When the bone was compared to others of its era, the researchers realized only one species fit the characteristics they were seeing.

"This is the foot bone of a very, very tiny T. rex. This is the smallest T. rex that we've ever seen," said Longrich.

After that find, the team began to look more closely at other small fossils of bones and teeth, and realized that many could also be attributed to tyrannosaur hatchlings.

[. . .]

The goal of reproduction is obviously to make more of yourself, and in a general sense, organisms use one of two broad strategies to get there.

They either have lots of offspring, quickly and often, so that it doesn't really matter if some (or most) of them don't live very long – there are plenty of backups. Organisms that use this method, such as rodents, are known as r-strategists.

The other method is to have fewer babies, but invest heavily in making sure they survive. These are the K-strategists, and that group includes whales and, of course, us.

[. . .]

[T]he new discovery that tyrannosaur young were small and numerous suggests they had more r-strategist tendencies than we thought.

[Continues . . .]

The paper is open access:

"Hatchlings of Tyrannosaurus rex and the Evolution of Dinosaur Reproductive Strategies" | Biology

Abstract:

Tyrannosaurs were giant predatory dinosaurs that occupied the apex of Late Cretaceous food chains. Little is known about the early life and reproductive ecology of tyrannosaurs due to the extreme rarity of hatchling and juvenile fossils.

We report bones of hatchlings (<1 yr) for Tyrannosaurus rex and Gorgosaurus libratus, weighing ~2.5 kg and ~2.4 kg, respectively, i.e., <0.1% of adult mass. Clutches were likely large. We conservatively estimate ~20 eggs in a small adult T. rex versus ~30 eggs in the largest T. rex, and clutches of ~15 eggs in G. libratus; larger clutches of 50 or even 100 eggs are not impossible.

This suggests an r-selected reproductive strategy. Synchrotron scans reveal Haversian bone remodeling, suggesting that tyrannosaurs moved soon after hatching. Hatchling tyrannosaurs' small size and precociality suggest limited parental care; teeth of hatchlings show wear suggesting that they fed on relatively large vertebrates.

Tyrannosaurs had proportionately larger offspring than most reptiles, but relatively smaller hatchlings than Eumaniraptora and birds, suggesting retention of a primitive reproductive strategy intermediate between that of basal diapsids and birds. Multiple dinosaur lineages evolved large eggs independently, suggesting an evolutionary trend towards increased parental investment.

[Recusant]

This one is pretty cool. Based on reexamination of fossils of small dinosaurs, it appears that Tyrannosaurus rex laid large clutches of relatively small eggs rather than smaller clutches of larger eggs--a revision of the hypothesis regarding their reproductive strategy.

"'Vanishingly Rare' Discovery: T. Rex Hatchlings Were Smaller Than a Cat And Born by The Dozen" | ScienceAlert

Jurassic Park was wrong. Again.

In the second movie, hunters find an infant Tyrannosaurus rex and use it to lure the adults into a trap.

But in reality, that baby would have been much smaller, about the size of a cat. And it probably wouldn't have been alone – the nest may have been absolutely crawling with dozens of them.

It likely wouldn't have been very useful as bait either: Its parents probably would have considered losing a baby or two as just part of the process, and wouldn't have cared enough to push a research trailer off a cliff.

So why are we updating our understanding of T. rex's childhood?

In a "vanishingly rare" discovery, paleontologists have found and closely examined fossils of tyrannosaur hatchlings. The remarkable findings are published in the journal Biology – and the implications go way beyond everyone's favorite dinosaur.

"Going through museum collections, my colleagues and I have discovered the first remains of hatchling tyrannosaurs," announced Nick Longrich, paleontologist and evolutionary biologist at the University of Bath in the UK.

[. . .]

Longrich and his team set out to investigate these fragmented fossils gathering dust in storeroom drawers, expecting to find adult specimens of small dinosaurs. Instead, ironically, the work led the team back to the big guys.

One of the small bones appeared to be a third metatarsal – the middle foot bone – of a theropod dinosaur. But on closer inspection, it didn't look like it came from a fully grown animal.

"The surface of the bone was incredibly porous," Longrich says in a video on his YouTube channel.

"And this is the result of all these little microscopic blood vessels creating this dense network of blood vessels. And these nourish the bone as it grows. So they're providing blood to the bone cells as they deposit bone tissue and remodel the bone. And this is typical of an immature dinosaur."

When the bone was compared to others of its era, the researchers realized only one species fit the characteristics they were seeing.

"This is the foot bone of a very, very tiny T. rex. This is the smallest T. rex that we've ever seen," said Longrich.

After that find, the team began to look more closely at other small fossils of bones and teeth, and realized that many could also be attributed to tyrannosaur hatchlings.

[. . .]

The goal of reproduction is obviously to make more of yourself, and in a general sense, organisms use one of two broad strategies to get there.

They either have lots of offspring, quickly and often, so that it doesn't really matter if some (or most) of them don't live very long – there are plenty of backups. Organisms that use this method, such as rodents, are known as r-strategists.

The other method is to have fewer babies, but invest heavily in making sure they survive. These are the K-strategists, and that group includes whales and, of course, us.

[. . .]

[T]he new discovery that tyrannosaur young were small and numerous suggests they had more r-strategist tendencies than we thought.

[Continues . . .]

The paper is open access:

"Hatchlings of Tyrannosaurus rex and the Evolution of Dinosaur Reproductive Strategies" | Biology

Abstract:

Tyrannosaurs were giant predatory dinosaurs that occupied the apex of Late Cretaceous food chains. Little is known about the early life and reproductive ecology of tyrannosaurs due to the extreme rarity of hatchling and juvenile fossils.

We report bones of hatchlings (<1 yr) for Tyrannosaurus rex and Gorgosaurus libratus, weighing ~2.5 kg and ~2.4 kg, respectively, i.e., <0.1% of adult mass. Clutches were likely large. We conservatively estimate ~20 eggs in a small adult T. rex versus ~30 eggs in the largest T. rex, and clutches of ~15 eggs in G. libratus; larger clutches of 50 or even 100 eggs are not impossible.

This suggests an r-selected reproductive strategy. Synchrotron scans reveal Haversian bone remodeling, suggesting that tyrannosaurs moved soon after hatching. Hatchling tyrannosaurs' small size and precociality suggest limited parental care; teeth of hatchlings show wear suggesting that they fed on relatively large vertebrates.

Tyrannosaurs had proportionately larger offspring than most reptiles, but relatively smaller hatchlings than Eumaniraptora and birds, suggesting retention of a primitive reproductive strategy intermediate between that of basal diapsids and birds. Multiple dinosaur lineages evolved large eggs independently, suggesting an evolutionary trend towards increased parental investment.