Tuesday, February 26, 2013
Never get involved in a land war in Asia
and never agree to transcribe 20 hours of meetings from an Australian business meeting.
That's what I've been doing for the last 4 days...utter nightmare. Could NOT understand their accents. Making it worse were the bad audio levels and the fact that a lot of the people preesnt insisted on talking over each other from all around the room except in front of the microphone... I will never transcribe ANYTHING every again.
Anyway, so sorry to be MIA from my blogs.
Sunday, February 17, 2013
Dinosaur show fuels learning, imagination
From SFO Star Advertiser: Dinosaur show fuels learning, imagination
SAN FRANCISCO » About dinosaurs, the old masters, they were never wrong, to paraphrase W.H. Auden if he were writing a poem about the endless fascination kids have with prehistoric beasts. That fascination is part of the reason "Dinosaur Train" is popular among the youngest members of the PBS audience and why the show's fans will enjoy the new special "Dinosaur Train: Submarine Adventure," airing Tuesday.
| ‘DINOSAUR TRAIN: SUBMARINE ADVENTURE’
The PBS special airs at 9 p.m. Tuesday. Repeats 1 p.m. Wednesday and 5 p.m. Thursday.
|
"Dinosaur Train," which premiered in 2009, "stars" Buddy, a curious young Tyrannosaurus Rex whose egg somehow winds up in a nest of Pteranodons (technically flying reptiles — not dinosaurs).
Buddy and his scaly buddies ride the Dinosaur Train around the prehistoric jungles, volcanoes and other settings, learning about species. At the end of each show, a live-action segment with paleontologist Scott D. Sampson helps young viewers learn about the species they have just met with big, unpronounceable names.
"Submarine Adventure" follows the format of the show, but the submarine, of course, gives the dinosaurs a chance to learn about undersea life, including Otto the Ophtalmosaurus — whose speaking voice is disconcertingly reminiscent of Arnold Schwarzenegger's — Shoshana Shonisaurus and Maisie Mosasaurus. By tapping into childhood fascination with dinosaurs, the series and the special teach kids not only about various prehistoric species, but, in a more subtle way, about the diversity of life in the world. Buddy is a welcome member of a blended family.
Friday, February 8, 2013
Fresh Clues In Dinosaur Whodunit Point To Asteroid
From NPR: Fresh Clues In Dinosaur Whodunit Point To Asteroid
Some 66 million years ago, about 75 percent of species on Earth disappeared. It wasn't just dinosaurs but most large mammals, fish, birds and plankton. Scientists have known this for a long time just from looking at the fossil record. If you dig deep enough, you find lots of dinosaur bones. And then a few layers up, they're gone.
But scientists couldn't figure out exactly what had caused this phenomenon. Of course, there were lots of theories.
"Some of them are pretty wacky," says J. David Archibald, an evolutionary biologist at San Diego State University who wrote the book Dinosaur Extinction and the End of an Era. "The really weird ones, of course, are that space hunters came and killed them all off, they died of constipation, mammals ate their eggs."
Then, in 1980, a new theory surfaced.
"It's the one that everybody hears about all the time because it's most dramatic," Archibald says.
Near what is now the town of Chicxulub in the Yucatan Peninsula, an asteroid more than 5 miles across slammed into the Earth. It caused tsunamis and earthquakes, and threw up a cloud of dust that smothered the world.
It sounds like a movie premise, but the Chicxulub impact left behind evidence. It threw up small blobs of black glass that were later found in Haiti. It dusted the world with iridium, an element that is rare on Earth but common in meterorites. It left a barely detectable imprint on the Yucatan Peninsula. Many scientists came to believe that the Chicxulub asteroid alone killed off the dinosaurs — and the public ate it up.
"We have this thing for big glitz and dramatic things," Archibald says. "Instantaneous is better."
But Princeton professor Gerta Keller wasn't convinced. She has her own theories about the mass extinction.
"Vulcanism has played a major role," Keller says.
In the hundreds of thousands of years before the Chicxulub impact, volcanoes in a region of India known as the Deccan Traps erupted repeatedly. They spewed sulfur and carbon dioxide, poisoning the atmosphere and destabilizing ecosystems. Keller says the dinosaurs were already on death's door by the time the asteroid hit.
And there is confusion about when that actually happened.
"If [the impact] is the cause, it had to be precisely at the time of the mass extinction," Keller says. "It can't be before and it can't be afterwards."
Keller's data suggest that the impact happened about 100,000 years before the mass extinction. Previous studies, on the other hand, put it 180,000 years after the dinosaurs died off.
Enter Paul Renne, a geologist from the University of California, Berkeley. To pin down the date, he headed out to the badlands of northeastern Montana.
"It's a region that has yielded a huge number of dinosaur fossils over the years," Renne says. "It's very famous for that."
Renne collected samples of ash that were deposited at the time of the mass extinction just above that treasure trove of fossils. He also obtained some of the glass blobs left by the Chicxulub impact. Measuring the rate of decay of radioactive potassium from these two samples, Renne was able to estimate the age of the impact and the age of the extinction.
"And lo and behold they are exactly the same," Renne says. "The impact clearly occurred right at the extinction level."
His results are published in the journal Science. They reinforce an idea that many scientists have held for years: The Chicxulub asteroid was the straw that broke the dinosaurs' back.
Gerta Keller thinks Renne's method was admirably precise, but she doesn't agree with some of his conclusions. She says his data are contradicted by other samples from Texas where a similar age date shows the Chicxulub impact predates the KT boundary — the point in time between the Cretaceous and Tertiary periods when the dinosaurs are believed to have gone extinct.
Still, there is one thing that Keller and Renne agree on: The asteroid isn't the whole story.
"There were significant extinctions and ecological perturbations going on a million or 2 million years before the impact, so we think that something else was already happening," Renne says. "What caused those things? There is an outstanding candidate — the early eruptions of the Deccan Traps."
The next step will be to find the age of these eruptions.
"We need to be able to place that set of eruptions into a time framework," Renne says.
Then they can better piece together what happened to the dinosaurs — and the rest of the species that went extinct. Renne and Keller will join Archibald and dozens of their colleagues at the Natural History Museum in London at the end of March to talk over their ideas.
"I'm looking forward to rather spirited discussions," Keller says.
Some 66 million years ago, about 75 percent of species on Earth disappeared. It wasn't just dinosaurs but most large mammals, fish, birds and plankton. Scientists have known this for a long time just from looking at the fossil record. If you dig deep enough, you find lots of dinosaur bones. And then a few layers up, they're gone.
But scientists couldn't figure out exactly what had caused this phenomenon. Of course, there were lots of theories.
"Some of them are pretty wacky," says J. David Archibald, an evolutionary biologist at San Diego State University who wrote the book Dinosaur Extinction and the End of an Era. "The really weird ones, of course, are that space hunters came and killed them all off, they died of constipation, mammals ate their eggs."
Then, in 1980, a new theory surfaced.
"It's the one that everybody hears about all the time because it's most dramatic," Archibald says.
Near what is now the town of Chicxulub in the Yucatan Peninsula, an asteroid more than 5 miles across slammed into the Earth. It caused tsunamis and earthquakes, and threw up a cloud of dust that smothered the world.
It sounds like a movie premise, but the Chicxulub impact left behind evidence. It threw up small blobs of black glass that were later found in Haiti. It dusted the world with iridium, an element that is rare on Earth but common in meterorites. It left a barely detectable imprint on the Yucatan Peninsula. Many scientists came to believe that the Chicxulub asteroid alone killed off the dinosaurs — and the public ate it up.
"We have this thing for big glitz and dramatic things," Archibald says. "Instantaneous is better."
But Princeton professor Gerta Keller wasn't convinced. She has her own theories about the mass extinction.
"Vulcanism has played a major role," Keller says.
In the hundreds of thousands of years before the Chicxulub impact, volcanoes in a region of India known as the Deccan Traps erupted repeatedly. They spewed sulfur and carbon dioxide, poisoning the atmosphere and destabilizing ecosystems. Keller says the dinosaurs were already on death's door by the time the asteroid hit.
And there is confusion about when that actually happened.
"If [the impact] is the cause, it had to be precisely at the time of the mass extinction," Keller says. "It can't be before and it can't be afterwards."
Enter Paul Renne, a geologist from the University of California, Berkeley. To pin down the date, he headed out to the badlands of northeastern Montana.
"It's a region that has yielded a huge number of dinosaur fossils over the years," Renne says. "It's very famous for that."
Renne collected samples of ash that were deposited at the time of the mass extinction just above that treasure trove of fossils. He also obtained some of the glass blobs left by the Chicxulub impact. Measuring the rate of decay of radioactive potassium from these two samples, Renne was able to estimate the age of the impact and the age of the extinction.
"And lo and behold they are exactly the same," Renne says. "The impact clearly occurred right at the extinction level."
His results are published in the journal Science. They reinforce an idea that many scientists have held for years: The Chicxulub asteroid was the straw that broke the dinosaurs' back.
Gerta Keller thinks Renne's method was admirably precise, but she doesn't agree with some of his conclusions. She says his data are contradicted by other samples from Texas where a similar age date shows the Chicxulub impact predates the KT boundary — the point in time between the Cretaceous and Tertiary periods when the dinosaurs are believed to have gone extinct.
Still, there is one thing that Keller and Renne agree on: The asteroid isn't the whole story.
"There were significant extinctions and ecological perturbations going on a million or 2 million years before the impact, so we think that something else was already happening," Renne says. "What caused those things? There is an outstanding candidate — the early eruptions of the Deccan Traps."
The next step will be to find the age of these eruptions.
"We need to be able to place that set of eruptions into a time framework," Renne says.
Then they can better piece together what happened to the dinosaurs — and the rest of the species that went extinct. Renne and Keller will join Archibald and dozens of their colleagues at the Natural History Museum in London at the end of March to talk over their ideas.
"I'm looking forward to rather spirited discussions," Keller says.
Wednesday, February 6, 2013
Fossil of new flying reptile from dinosaur age discovered
From NBC News: Fossil of new flying reptile from dinosaur age discovered
Pterosaurs lived among the dinosaurs and became extinct about the same time, but they were not dinosaurs. They are sometimes wrongly called pterodactyls, which actually just describes the first genus of pterosaur discovered by scientists in the 18th century. Small pterosaurs developed during the Triassic Period, about 230 to 200 million years ago. Later, during the Jurassic and Cretaceous periods, more advanced forms of the flying reptiles, like azhdarchids, started evolving.
"These were long-necked, long-beaked pterosaurs whose wings were strongly adapted for a soaring lifestyle," researcher Darren Naish, a paleontologist from the U.K.'s University of Southampton, said in a statement. "Several features of their wing and hind limb bones show that they could fold their wings up and walk on all fours when needed."
The wingspan of Eurazhdarchoindicates it would have been "large, but not gigantic" compared to some of its cousins, Naish said. (The researchers pointed to the example of the giant azhdarchid, Hatzegopteryx thambema, whose bones found in the Romanian town of Hateg show that its wings would have stretched out 36 feet, or 11 meters, during flight.) The discovery brings new evidence to the debate about how azhdarchids lived, the scientists say.
"It has been suggested that they grabbed prey from the water while in flight, that they patrolled wetlands and hunted in a heron or stork-like fashion, or that they were like gigantic sandpipers, hunting by pushing their long bills into mud," Gareth Dyke, a paleontologist from the National Oceanography Center Southampton, said in a statement.
The newly found fossil was uncovered alongside dinosaurs and other terrestrial animals, suggesting that azhdarchids stalked small animal prey in woodlands, plains and scrublands rather than in coastal habitats.
"Eurazhdarcho supports this view of azhdarchids, since these fossils come from an inland, continental environment where there were forests and plains as well as large, meandering rivers and swampy regions," Dyke said.
The findings were detailed online Jan. 30 in the journal PLOS ONE.
Scientists say they've discovered the fossilized bones of a new
type of pterosaur, a flying dinosaur-age reptile, which lived about 68
million years ago and had a wingspan of nearly 10 feet (3-meters).
The skeletal bits of the midsized pterosaur were found in Sebes-Glod
in Romania's Transylvanian Basin, famous for its rich array of Late
Cretaceous fossils, including crocodylomorphs (ancient relatives of
crocodiles), mammals, turtles and dinosaurs like the dwarf sauropod Magyarosaurus dacus and the dromaeosaurBalaur. Scientists dubbed the new reptile Eurazhdarcho langendorfensis and say it belonged to a group of pterosaurs called the azhdarchids.Pterosaurs lived among the dinosaurs and became extinct about the same time, but they were not dinosaurs. They are sometimes wrongly called pterodactyls, which actually just describes the first genus of pterosaur discovered by scientists in the 18th century. Small pterosaurs developed during the Triassic Period, about 230 to 200 million years ago. Later, during the Jurassic and Cretaceous periods, more advanced forms of the flying reptiles, like azhdarchids, started evolving.
"These were long-necked, long-beaked pterosaurs whose wings were strongly adapted for a soaring lifestyle," researcher Darren Naish, a paleontologist from the U.K.'s University of Southampton, said in a statement. "Several features of their wing and hind limb bones show that they could fold their wings up and walk on all fours when needed."
The wingspan of Eurazhdarchoindicates it would have been "large, but not gigantic" compared to some of its cousins, Naish said. (The researchers pointed to the example of the giant azhdarchid, Hatzegopteryx thambema, whose bones found in the Romanian town of Hateg show that its wings would have stretched out 36 feet, or 11 meters, during flight.) The discovery brings new evidence to the debate about how azhdarchids lived, the scientists say.
"It has been suggested that they grabbed prey from the water while in flight, that they patrolled wetlands and hunted in a heron or stork-like fashion, or that they were like gigantic sandpipers, hunting by pushing their long bills into mud," Gareth Dyke, a paleontologist from the National Oceanography Center Southampton, said in a statement.
The newly found fossil was uncovered alongside dinosaurs and other terrestrial animals, suggesting that azhdarchids stalked small animal prey in woodlands, plains and scrublands rather than in coastal habitats.
"Eurazhdarcho supports this view of azhdarchids, since these fossils come from an inland, continental environment where there were forests and plains as well as large, meandering rivers and swampy regions," Dyke said.
The findings were detailed online Jan. 30 in the journal PLOS ONE.
Tuesday, January 29, 2013
Tiny Feathered Dinosaur Found
From News.Discovery.com: Tiny Feathered Dinosaur Found
Reconstruction of Eosinopteryx brevipenna, a new theropod
dinosaur with reduced plumage from the Middle/Late Jurassic of
north-eastern China.
Researchers have discovered a new species of feathered but flightless little dinosaur from the Jurassic period.
Remains of the tiny beast, dubbed Eosinopteryx brevipenna, found in northeastern China suggest it was slightly less than a foot long (30 centimeters) and had a short snout and a short tail. Based on the dinosaur's small wingspan and bone structure, researchers believe it would have been able to run around quite easily, but likely couldn't whip up enough of a wing-beat to fly. The dinosaur also sported toes that would have been suitable for walking along the ground, the researchers added.
This birdlike dinosaur's plumage was much more reduced compared with the feathers on some of its contemporaries, which suggests that feathering was already diversified by the Late Jurassic, adapted to different ecological niches and purposes, the researchers said. (The Jurassic period lasted from about 199.6 million to 145.5 million years ago.)
"This discovery sheds further doubt on the theory that the famous fossil Archaeopteryx — or 'first bird' as it is sometimes referred to — was pivotal in the evolution of modern birds," researcher Gareth Dyke, a senior lecturer in paleontology at the U.K.'s University of Southampton, said in a statement.
"Our findings suggest that the origin of flight was much more complex than previously thought."
Archaeopteryx was long thought by many to have been the earliest bird. Discovered in 1860 in Germany, it is sometimes referred to as Urvogel, the German word for "original bird" or "first bird." But recent findings suggest late-stage Jurassic Archaeopteryx was actually just a relative of the lineage that ultimately gave rise to birds.
The new research was detailed in the Jan. 22 issue of the journal Nature Communications.
Remains of the tiny beast, dubbed Eosinopteryx brevipenna, found in northeastern China suggest it was slightly less than a foot long (30 centimeters) and had a short snout and a short tail. Based on the dinosaur's small wingspan and bone structure, researchers believe it would have been able to run around quite easily, but likely couldn't whip up enough of a wing-beat to fly. The dinosaur also sported toes that would have been suitable for walking along the ground, the researchers added.
This birdlike dinosaur's plumage was much more reduced compared with the feathers on some of its contemporaries, which suggests that feathering was already diversified by the Late Jurassic, adapted to different ecological niches and purposes, the researchers said. (The Jurassic period lasted from about 199.6 million to 145.5 million years ago.)
"This discovery sheds further doubt on the theory that the famous fossil Archaeopteryx — or 'first bird' as it is sometimes referred to — was pivotal in the evolution of modern birds," researcher Gareth Dyke, a senior lecturer in paleontology at the U.K.'s University of Southampton, said in a statement.
"Our findings suggest that the origin of flight was much more complex than previously thought."
Archaeopteryx was long thought by many to have been the earliest bird. Discovered in 1860 in Germany, it is sometimes referred to as Urvogel, the German word for "original bird" or "first bird." But recent findings suggest late-stage Jurassic Archaeopteryx was actually just a relative of the lineage that ultimately gave rise to birds.
The new research was detailed in the Jan. 22 issue of the journal Nature Communications.
Thursday, January 24, 2013
Secret of the Dinosaur Sexes Locked in Bone
From the Smithsonian: Secret of the Dinosaur Sexes Locked in Bone
When Chicago’s Field Museum purchased the Tyrannosaurus rex “Sue” in 1997, the famous and legally-troubled dinosaur was thought to be a female. The key clue was a missing bone.
Like other dinosaurs, T. rex had a row of spike-like bones called chevrons that ran from the base of the tail to almost the tip. Living alligators and crocodiles share this feature, and, decades ago, paleontologist Alfred Sherwood Romer suggested that researchers could distinguish between the skeletons of male and female crocodylians by looking at the placement of the first chevron in the series. In females, the chevron was thought to be shorter and displaced further back from the hips, leaving more room for eggs to pass through her body. Peter Larson, part of the team that excavated Sue but lost her in the prolonged legal battle that followed, extended the same argument to Sue. Since the tyrannosaur’s first chevron was situated further back than in other specimens, Larson proposed, the big T. rex was a female.
When the museum unpacked and reconstructed Sue, though, Sue’s sex came under suspicion. The “missing” chevron was found among the dinosaur’s assorted bones, undermining Larson’s contention. And, as it turned out, the entire comparison was flawed. In a 2005 study of crocodylian chevrons, Gregory Erickson, Kristopher Lappin, and Larson concluded that there is no sexual difference between the first chevrons of male and female crocodylians, nor any detectable dimorphism in tyrannosaurs. At best, the researchers concluded, the “usefulness of chevron anatomy for sexing dinosaurs is tenuous.”
We really don’t know whether Sue was a male or female. The entire episode was just one debate within the long-running attempts of paleontologists to investigate the basic, yet extremely frustrating question of how to properly identify dinosaur sexes. Skeletal differences alone are of almost no help. Every proposed case of sexual dimorphism in non-avian dinosaurs has either been undermined by later studies or is extremely questionable. Either non-avian dinosaurs didn’t show sexual dimorphism in their skeletons, or we have yet to properly detect the differences.
But there actually is a way to identify some female dinosaurs. Medullary bone gives them away. This specific bone tissue was deposited in the long bones of pregnant female dinosaurs, just as it is in living birds. Not all female dinosaurs were developing medullary bone when they died, but the gravid ones were.
Medullary bone can do more than help paleontologists pick out a few females, though. Paleontologists Andrew Lee and Sarah Werning paired the tissue with other histological clues to figure out that most dinosaurs started reproducing while they were still growing, long before they reached skeletal maturity. Dinosaurs lived fast and died young.
Such studies made me wonder if medullary bone could help paleontologists finally detect sexual dimorphism among non-avian dinosaurs. By picking a highly-ornamented species and searching for traces of medullary bone within those dinosaurs, researchers would be able to see whether the females all shared any distinctive anatomical structures or looked just like the males. The process wouldn’t identify all the females, but, if the attempt identified any at all, the investigation might help researchers determine whether there was any conspicuous features to distinguish the sexes.
University of Cape Town histology expert Anusuya Chinsamy and
colleagues have undertaken just such a study, published this week in Nature Communications. Instead of a non-avian dinosaur, though, the researchers picked Confuciusornis sanctus – an early bird preserved by the dozens in the 125 to 140 million year old rock of China.
The avian is a perfect candidate for such a study. Many of these birds are preserved with intact feathers, and their plumage comes in two forms. Some Confuciusornis are preserved with two elongated tail feathers, while others are not. Researchers have debated whether these ornaments are indicators of sexual dimorphism, species differences, individual variation, or simply different molt stages, but bone histology has finally solved the mystery. The Confuciusornis with the long feathers were males, while females lacked the flashy adornments.
A particular Confuciusornis known as DNHM-D1874 yielded the crucial clue. Surrounded by feathers, this articulated skeleton lacked the long tail feathers seen on others. When Chinsamy and colleagues looked at the microstructure of specific bones, they found medullary tissue in the humerus (upper arm bone) and traces in the ulna (a lower arm bone), indicating that the bird had recently finished laying eggs when she perished.
The researchers also sampled the bones of three Confuciusornis preserved with long tail feathers. These specimens didn’t contain medullary bone. While it’s possible that these were females that were not laying eggs around the time of death, the presence of medullary bone in the non-ornamented form and its absence in the ornamented ones is consistent with the idea that the feathers underscore a real sex difference. And since relatively small Confuciusornis have been found with long tail feathers, Chinsamy and coauthors point out, these birds probably started reproducing relatively early in life.
Paleontologists can apply the same technique to non-avian dinosaurs. There are multiple specimens of dinosaurs such as Microraptor and Anchiornis that are preserved with feathers, and the fact that we can detect the color of dinosaur feathers has opened yet another avenue for comparison. Perhaps male and female dinosaurs sported different colors, much like many bird species today. Feathers aren’t a requirement for this kind of study, though – the same technique could conceivably be applied to other non-avian dinosaurs so long as they are known from large enough sample sizes. By breaking into bone, paleontologists may finally be able to discover the secrets of the dinosaur sexes.
References:
Chinsamy, A., Chiappe, L., Marugán-Lobón, J., Chunling, G., Fengjiao, Z. 2013. Gender identification of the Mesozoic bird Confuciusornis sanctus. Nature Communications. 4, 1381. doi:10.1038/ncomms2377
Erickson, G., Lappin, A., Larson, P. 2005. Androgynous rex – The utility of chevrons for determining the sex of crocodilians and non-avian dinosaurs. Zoology. 108, 4: 277-286
Lee, A., Werning, S. 2008. Sexual maturity in growing dinosaurs does not fit reptilian growth models. PNAS. 105, 2: 582-587
Padian, K., Horner, J. 2010. The evolution of “bizarre structures” in dinosaurs: biomechanics, social selection or species recognition? Journal of Zoology. 281, 1: 3-17
Like other dinosaurs, T. rex had a row of spike-like bones called chevrons that ran from the base of the tail to almost the tip. Living alligators and crocodiles share this feature, and, decades ago, paleontologist Alfred Sherwood Romer suggested that researchers could distinguish between the skeletons of male and female crocodylians by looking at the placement of the first chevron in the series. In females, the chevron was thought to be shorter and displaced further back from the hips, leaving more room for eggs to pass through her body. Peter Larson, part of the team that excavated Sue but lost her in the prolonged legal battle that followed, extended the same argument to Sue. Since the tyrannosaur’s first chevron was situated further back than in other specimens, Larson proposed, the big T. rex was a female.
When the museum unpacked and reconstructed Sue, though, Sue’s sex came under suspicion. The “missing” chevron was found among the dinosaur’s assorted bones, undermining Larson’s contention. And, as it turned out, the entire comparison was flawed. In a 2005 study of crocodylian chevrons, Gregory Erickson, Kristopher Lappin, and Larson concluded that there is no sexual difference between the first chevrons of male and female crocodylians, nor any detectable dimorphism in tyrannosaurs. At best, the researchers concluded, the “usefulness of chevron anatomy for sexing dinosaurs is tenuous.”
We really don’t know whether Sue was a male or female. The entire episode was just one debate within the long-running attempts of paleontologists to investigate the basic, yet extremely frustrating question of how to properly identify dinosaur sexes. Skeletal differences alone are of almost no help. Every proposed case of sexual dimorphism in non-avian dinosaurs has either been undermined by later studies or is extremely questionable. Either non-avian dinosaurs didn’t show sexual dimorphism in their skeletons, or we have yet to properly detect the differences.
But there actually is a way to identify some female dinosaurs. Medullary bone gives them away. This specific bone tissue was deposited in the long bones of pregnant female dinosaurs, just as it is in living birds. Not all female dinosaurs were developing medullary bone when they died, but the gravid ones were.
Medullary bone can do more than help paleontologists pick out a few females, though. Paleontologists Andrew Lee and Sarah Werning paired the tissue with other histological clues to figure out that most dinosaurs started reproducing while they were still growing, long before they reached skeletal maturity. Dinosaurs lived fast and died young.
Such studies made me wonder if medullary bone could help paleontologists finally detect sexual dimorphism among non-avian dinosaurs. By picking a highly-ornamented species and searching for traces of medullary bone within those dinosaurs, researchers would be able to see whether the females all shared any distinctive anatomical structures or looked just like the males. The process wouldn’t identify all the females, but, if the attempt identified any at all, the investigation might help researchers determine whether there was any conspicuous features to distinguish the sexes.
A Confuciusornis with long tail feathers. Photo by Laikayiu, image from Wikipedia.
The avian is a perfect candidate for such a study. Many of these birds are preserved with intact feathers, and their plumage comes in two forms. Some Confuciusornis are preserved with two elongated tail feathers, while others are not. Researchers have debated whether these ornaments are indicators of sexual dimorphism, species differences, individual variation, or simply different molt stages, but bone histology has finally solved the mystery. The Confuciusornis with the long feathers were males, while females lacked the flashy adornments.
A particular Confuciusornis known as DNHM-D1874 yielded the crucial clue. Surrounded by feathers, this articulated skeleton lacked the long tail feathers seen on others. When Chinsamy and colleagues looked at the microstructure of specific bones, they found medullary tissue in the humerus (upper arm bone) and traces in the ulna (a lower arm bone), indicating that the bird had recently finished laying eggs when she perished.
The researchers also sampled the bones of three Confuciusornis preserved with long tail feathers. These specimens didn’t contain medullary bone. While it’s possible that these were females that were not laying eggs around the time of death, the presence of medullary bone in the non-ornamented form and its absence in the ornamented ones is consistent with the idea that the feathers underscore a real sex difference. And since relatively small Confuciusornis have been found with long tail feathers, Chinsamy and coauthors point out, these birds probably started reproducing relatively early in life.
Paleontologists can apply the same technique to non-avian dinosaurs. There are multiple specimens of dinosaurs such as Microraptor and Anchiornis that are preserved with feathers, and the fact that we can detect the color of dinosaur feathers has opened yet another avenue for comparison. Perhaps male and female dinosaurs sported different colors, much like many bird species today. Feathers aren’t a requirement for this kind of study, though – the same technique could conceivably be applied to other non-avian dinosaurs so long as they are known from large enough sample sizes. By breaking into bone, paleontologists may finally be able to discover the secrets of the dinosaur sexes.
References:
Chinsamy, A., Chiappe, L., Marugán-Lobón, J., Chunling, G., Fengjiao, Z. 2013. Gender identification of the Mesozoic bird Confuciusornis sanctus. Nature Communications. 4, 1381. doi:10.1038/ncomms2377
Erickson, G., Lappin, A., Larson, P. 2005. Androgynous rex – The utility of chevrons for determining the sex of crocodilians and non-avian dinosaurs. Zoology. 108, 4: 277-286
Lee, A., Werning, S. 2008. Sexual maturity in growing dinosaurs does not fit reptilian growth models. PNAS. 105, 2: 582-587
Padian, K., Horner, J. 2010. The evolution of “bizarre structures” in dinosaurs: biomechanics, social selection or species recognition? Journal of Zoology. 281, 1: 3-17
Sunday, January 13, 2013
Digging for dinosaurs
From NewsLeader.com: Digging for dinosaurs
STUARTS DRAFT — A group of intrepid young archaeologists and paleontologists uncovered a new species of dinosaur at a dig on an Augusta County farm.
Not really. But it was a bit of fun that the Webelos 1 den of Cub Scout Pack 349 indulged in Saturday during a mock archaeological dig organized for the boys to earn their geology badges.
Under a white tent, children and adults were abuzz. The kids, including some younger siblings of troop members, were on their knees and crouched around a 12-foot-by 5-foot perimeter of loosened earth. They scooped, sifted and brushed away dirt.
Andrew Howell, 10, could hardly contain his excitement as he brushed away dirt from a large, spiky fossil.
“It looks like the back of something,” he said. “Maybe a spine with spikes.”
“Wow, yours is big,” said Darrion Johnson, 9, from a few feet away.
“Yeah, it’s huge!” Andrew responded.
Webelos den mother Jaclyn Nahay tried to think of every possible detail to make the educational event as real and fun as possible.
Nahay held up an impressive looking, 2-foot-long model of a fossil that she made out of salt dough, paint and stain. She molded it to like the lower jaw bone of a dinosaur.
She got the idea for how to make the fossils when she came across a website that listed a recipe for making fake human bones.
Nahay adapted it to make the dinosaur fossils for the mock dig. She also made the boys fake passports that listed their scientific credentials, and the countries they have visited for past digs.
The kids made a rope grid to keep track of what they found in each section of the site. They measured, took pictures and recorded their findings in a journal.
“I’m positive these are dinosaur eggs,” said Zachary Furr, 9, as he brushed dirt away from a group of six oval fossils. “(The dinosaur) is like a million years old and had no babies. They didn’t hatch!”
Once uncovered and laid out, the bones will resemble a 10-foot, 7-inch long prehistoric animal, Nahay said.
“I thought it would be fun to make bones that were from different dinosaurs,” she said. “Then it could be a new species that they discovered and then they can name it.”
STUARTS DRAFT — A group of intrepid young archaeologists and paleontologists uncovered a new species of dinosaur at a dig on an Augusta County farm.
Not really. But it was a bit of fun that the Webelos 1 den of Cub Scout Pack 349 indulged in Saturday during a mock archaeological dig organized for the boys to earn their geology badges.
Under a white tent, children and adults were abuzz. The kids, including some younger siblings of troop members, were on their knees and crouched around a 12-foot-by 5-foot perimeter of loosened earth. They scooped, sifted and brushed away dirt.
Andrew Howell, 10, could hardly contain his excitement as he brushed away dirt from a large, spiky fossil.
“It looks like the back of something,” he said. “Maybe a spine with spikes.”
“Wow, yours is big,” said Darrion Johnson, 9, from a few feet away.
“Yeah, it’s huge!” Andrew responded.
Webelos den mother Jaclyn Nahay tried to think of every possible detail to make the educational event as real and fun as possible.
Nahay held up an impressive looking, 2-foot-long model of a fossil that she made out of salt dough, paint and stain. She molded it to like the lower jaw bone of a dinosaur.
She got the idea for how to make the fossils when she came across a website that listed a recipe for making fake human bones.
Nahay adapted it to make the dinosaur fossils for the mock dig. She also made the boys fake passports that listed their scientific credentials, and the countries they have visited for past digs.
The kids made a rope grid to keep track of what they found in each section of the site. They measured, took pictures and recorded their findings in a journal.
“I’m positive these are dinosaur eggs,” said Zachary Furr, 9, as he brushed dirt away from a group of six oval fossils. “(The dinosaur) is like a million years old and had no babies. They didn’t hatch!”
Once uncovered and laid out, the bones will resemble a 10-foot, 7-inch long prehistoric animal, Nahay said.
“I thought it would be fun to make bones that were from different dinosaurs,” she said. “Then it could be a new species that they discovered and then they can name it.”
Subscribe to:
Posts (Atom)