Photograph (c) Julius T. Csotonyi (csotonyi.com)

About 15 feet tall and 40 feet long, Tyrannosaurus rex, whose name means "king of the tyrant lizards," is one of the largest known land predators to ever roam the Earth.

By Denise Chow
LiveScience

Male and female dinosaurs may have shared the responsibility of incubating their offspring, but how to determine which parent was involved remains a mystery, according to a new study that re-examines the idea that the brooding behavior of modern birds may predict similar behavior in their dinosaur ancestors.

Modern birds are thought to have evolved from theropods, a group of carnivorous dinosaurs that include such recognizable predators as the Velociraptor and Tyrannosaurus rex.

In research published in the journal Science in 2009, scientists examined the way existing birds incubate their eggs, claiming that only male theropods took part in incubation. But the study, which compared the size of male and female birds with the size and number of eggs that were laid, omits some important factors, said Geoff Birchard, a professor in the department of environmental science and policy at George Mason University in Fairfax, Va., and co-author of the new study. [Image Gallery: Dinosaur Daycare]

"They looked at the number of eggs and how big they were, and said they could figure out whether mommy incubated, daddy incubated, or both did," Birchard told LiveScience. "The problem is, the biology behind it is a little bit off."

Birchard and his colleagues repeated the 2009 study using more data from living bird species. They determined that comparing the size of the birds with the clutch size — which is determined by multiplying the number of eggs laid in a nest by the volume or mass of the eggs — could not effectively determine whether it was the male or female guarding the eggs.

"Our analysis of the relationship between female body mass and clutch mass was interesting in its own right, but also showed that it was not possible to conclude anything about incubation in extinct distant relatives of the birds," study co-author Charles Deeming, a researcher at the University of Lincoln in the United Kingdom, said in a statement.

Part of the problem is that birds do not all exhibit the same brooding behavior.

"There's a huge amount of variation with birds," Birchard said. "With certain bird types, two parents are always involved, but with some bigger birds, only the daddy is incubating the eggs. With dinosaurs, overall, there's a huge amount of variety, too."

And whether the actions of modern birds can be used to predict the behavior of dinosaurs is also a source of debate.

"There are great differences of opinion about it," Birchard said. "There's a long time gap between dinosaurs and the origin of birds, so it's an awful long time for us to say what's being done with birds was also being done with dinosaurs. We use this kind of inference sometimes, but birds are also a very unique group."

The findings of the new study were published online Tuesday in the journal Biology Letters.

Follow Denise Chow on Twitter @denisechow. Follow LiveScience @livescience, Facebook and Google+. Original article on LiveScience.com.

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Luis Rey

Scientists have found the crouching posture of birds, which allows them to hold their wings high, likely took off after flight evolved.

By Charles Choi
LiveScience

Birds can hold their wings high because of the strange way they crouch, and now scientists say the origins of this folded posture may provide insight into the evolution of their flight.

Birds stand and walk in an unusually crouched way, with the femur, or thighbone, held nearly horizontally — unlike humans, whose legs stand vertically. Birds’ crouched stance helps support their balance and movement by ensuring the center of gravity lies above the feet. Birds’ bipedal, or two-legged, stance reflects their dinosaur heritage — dinosaurs evolved a bipedal posture early in their evolution, about 235 million years ago.

The crouch seen in birds is quite different from the sprawling posture seen in the closest living relatives of birds, the crocodilians. Birds and crocodilians belong to a diverse menagerie of creatures known as the archosaurs, which also include all dinosaurs and the extinct flying reptiles known as pterosaurs. The first archosaurs, which appeared about 250 million years ago, resembled modern crocodiles. Although the archosaurs, like modern crocodiles, were four-legged animals with long, heavy tails, they had longer limbs than crocodiles’ to make it easier for them to live and move on land. [Avian Ancestors: Images of Flying Dinosaurs]

Scientists disagree on how birds evolved to crouch. Some researchers contend this shift happened gradually in a group of dinosaurs known as coelurosaurs, which included tyrannosaurs and raptors. Others suggest this change occurred more suddenly, beginning with the few immediate dinosaur ancestors of birds and the origin of flight.

The dino crouch
To help resolve this debate, scientists explored the bird family by analyzing 3-D computer models of 17 archosaurs spanning about 250 million years of evolution. These included living birds, such as chickens; what may be one of the first birds, Archaeopteryx; the four-winged, feathered dinosaur Microraptor; two-legged predators, such as Velociraptor and Tyrannosaurus; and crocodiles, the closest living, albeit still distant, relatives of birds.

John Hutchinson / Nature

Scientists looked at the bird family by analyzing 3-D computer models of 17 archosaurs spanning about 250 million years of evolution. Here, the digitized fossil skeletons and CT scan data from a basal dinosaur (a) and a basal bird (b) in different views, revealing how body proportions evolved.

"We basically started from a simple digital 'shrink wrap' of the whole skeleton," said researcher Vivian Allen, a biomechanist at the Royal Veterinary College in Hatfield, England. "From this, we expanded the 'shrink wrap' to match how much flesh we think existed around the different parts of the skeleton. This was based on both detailed reconstruction of the muscular anatomy of each animal and on what we have measured from CT scans of their living relatives."

Paleontologists had agreed for years that the crouch seen in birds evolved as their tails became shorter, shifting the center of gravity of certain dinosaurs progressively forward as those creatures became more birdlike. This forced the legs to become less vertical and more crouched to keep the center of gravity balanced over the feet. [Paleo-Art: Stunning Illustrations of Dinosaurs]

"Non-avian dinosaurs and archosaurs in general all have this very large, muscular heavy tail, that obviously represents a significant amount of mass on the back of the animal," Allen told LiveScience. "So as you move along the evolutionary lineage of birds, this is reduced in progressively more birdlike dinosaurs and, eventually, is basically lost, or reduced to a small stump. It seems very intuitive to suggest that this loss of the tail, loss of this huge mass towards the back of the animal, would be the main thing responsible for more birdlike dinosaurs and birds themselves having more mass concentrated towards the front of the animal."

Dinosaur forelimbs
Unexpectedly, the researchers found the evolution of this crouch was more linked with their fronts than with their backs.

"Our results suggest enlargement of the forelimbs was more important to the forward shift in center of mass than loss of the tail," Allen said.

"The tail is the most obvious change, if you look at dinosaur bodies," said researcher John Hutchinson, an evolutionary biomechanist at the Royal Veterinary College in Hatfield. "But as we analyzed and reanalyzed and punishingly scrutinized our data, we gradually realized that everyone had forgotten to check what influence the forelimbs had on balance and posture, and that this influence was greater than that of the tail or other parts of the body."

Since the forelimbs of the ancestors of birds eventually became the wings of birds, these findings may provide insight into the origin of bird flight.

"One of the interesting things that our work shows is that birds could not have evolved these large forelimbs, these wings, without also having to make significant changes to the anatomy and function of their hind limbs," Allen said. "Which makes total sense, when you think about it — everything is attached to the same body, so why wouldn't changing one thing affect the others? But still, it was cool to find that, and to have some actual numbers and stats to back it up."

As to when and how quickly the center of gravity changed position in dinosaurs, the researchers found some merit to both sides of the argument. "There were gradual changes early on in dinosaurs, but we were amazed by how much the increase in forelimb size began altering the center of mass just before when flight may have first evolved in early birds and their closest relatives," Allen said.

Changes in body shape influence how animals balance, "and both shape and balance are important for flight," Hutchinson told LiveScience. For instance, if the center of gravity is close to the wings, "then stable flight, such as gliding, is theoretically possible," Hutchinson said.

Some of the crouching "seems to have started just a bit before when flight seems to have evolved," Hutchinson said. "But it didn't really take off until after flight evolved."

Dinosaur ancestors of birds may have evolved enlarged forelimbs "for reasons other than powered flight, such as prey capture or negotiating complex terrain," Hutchinson noted. [In Photos: Amazing Birds of Prey]

Allen noted that the researchers analyzed only a few relatives of birds. The researchers next plan to scan fossils of more specimens to build computer models of their skeletons and "try and get a clearer picture of what was going on in this really interesting sequence of anatomical evolution," Allen said.

In addition, instead of looking at one or a few aspects of each specimen at any given time — such as its mass, posture, skeletal proportions and muscular anatomy — the scientists hope to analyze every aspect of each specimen together simultaneously in predictive computer simulations that animate their bodies. Such models would help reveal how these extinct animals stood and moved, and how that changed over time.

"Developing techniques for looking at lots of complex data at the same time — computer simulations of how the extinct animal worked as a mechanism — that's definitely the way to go in the future," Allen said.

"It's just hard," she continued. "The maths are hard, and the computing requirements are very high. But we're getting there. What with very, very fast computers being increasingly dirt cheap and the technical skills of researchers getting increasingly very good, there are definitely some very exciting possibilities in the near future of extinct animal mechanics studies."

Allen, Hutchinson and their colleagues, Karl Bates and Zhiheng Li, detailed their findings online Wednesday in the journal Nature.

Follow us @livescience, Facebook and Google+. Original article on LiveScience.com.

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Jay Im / University of Calgary

A University of Calgary dinosaur researcher examines a clutch of dinosaur eggs.

By Stephanie Pappas
LiveScience

Dinosaurs laid eggs, of that there is no doubt. But what scientists haven't been as clear on is whether they brooded over their eggs like birds or buried them like crocodiles.

Now, a new study finds that at least one dinosaur took a birdlike approach to hatching eggs. Troodon was a small, meat-eating dinosaur that grew to be about 8 feet (2.4 meters) long. The dinosaurs date back to the Late Cretaceous, about 75 million years ago, and they apparently incubated their eggs much like modern birds.

Most birds sit on their eggs to warm them, but crocodiles and their relatives completely bury their nests. The difference between the two shows up in the eggshells: Croc eggs have many pores to allow for air and water exchange, lest the eggs suffocate in their closed, humid nests. Bird eggs exposed to the air have fewer pores, because their eggs would be more in danger of drying out. [Image Gallery: Dinosaur Daycare]

University of Calgary dinosaur researcher Darla Zelenitsky and Montana State University paleontologist David Varricchio studied Troodon egg clutches from Canada and Montana, examining the fossilized shells for signs of burial. They compared the porosity of the eggshells with that of eggshells from modern-day crocodiles, birds that nest by burying their eggs in mounds, and birds that nest by brooding, or sitting on their eggs. 

They found that porosity varied across the dino eggshell, suggesting the dinosaur laid its eggs almost vertically in sand or mud, but didn't bury the eggs completely. The adult would have had direct contact with the upper portions of these partially buried eggs, Varricchio said.

"There are similarities with a peculiar nester among birds called the Egyptian plover that broods its eggs while they're partially buried in sandy substrate of the nest," Varricchio said in a statement.

The plover, a wading bird, nests by laying its eggs in warm sand and then sitting on the nest with a wet belly, cooling the eggs from above.

The findings demonstrate that birdlike behavior evolved in theropods, the caste of bipedal dinosaurs related to today's birds, Zelenitsky said in a statement. The researchers reported their findings in the spring issue of the journal Paleobiology.

Previous studies have found that dinosaurs were doting parents. In 2008, Zelenitsky and her colleagues reported in the journal Science that dinosaur daddies sat on nests while dino moms went out to snag meals. Another study published this month in the journal Nature found that dinosaur embryos wiggled and kicked in their eggs before hatching.

Follow Stephanie Pappas on Twitter and Google+. Follow us @livescience, Facebook and Google+. Original article on LiveScience.com.

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D. Mazierski

An artist's impression of an embryonic Lufengosaurus, showing the dinosaur's growing skeleton.

By Stephanie Pappas
LiveScience

Embryonic dinosaurs kicked and wiggled in the egg, a new discovery of a baby-dino-bone bed suggests.

The bones, all from not-yet-hatched embryonic dinosaurs, are among the oldest dinosaur-embryo fossils ever found. What's more, the embryo fossils came from separate nests and the dino embryos were at different stages of development when they died — two discoveries that will enable researchers to study how dinosaurs developed before hatching.

"It tells us quite a bit about early embryonic stages and changes that occur in the embryonic life of these animals — something we haven't really seen before," said study researcher Robert Reisz, a paleontologist at the University of Toronto.

In addition to discovering evidence of in-egg kicking, the researchers found that the embryos, which probably belonged to the long-necked Lufengosaurus, grew faster than the embryos of any birds or mammals alive today. [See Images of the Tiny Dino Embryos]

Tiny-bone find
Timothy Huang, a chemist at National Chung Hsing University in Taiwan and an amateur archaeologist, discovered the embryonic bones about three years ago in Yunnan Province, China. The bone bed has an area of about 3 square feet (1 square meter) and a thickness of about 4 to 8 inches (10 to 20 centimeters). In this small patch, the researchers eventually uncovered more than 200 itsy-bitsy bones.

A. LeBlanc

A cross-section of an embryonic dinosaur femur found in Yunnan, China. The honeycomb-like area is bone tissue with large spaces for blood vessels, indicating rapid growth of the bone.

A geological analysis of the spot revealed that slow flooding probably smothered the eggs, which seem to have been laid in a colonial nesting site. After the flood, the embryos and eggs rotted and fell apart, leaving a mound of disarticulated bones. The bones date to the Lower Jurassic period, or between 199.6 million and 175.6 million years ago. That makes them just as ancient as the oldest known embryos ever found, which were discovered at a nesting site of long-necked Massospondylus dinosaurs in South Africa. 

It was a boon for science that the dino embryos had fallen apart, instead of fossilizing inside their eggs, Reisz told LiveScience.

"People are extremely possessive and fond of their embryos inside their eggs — imagine us asking them to take pieces out and do the sections on them and cut them, and essentially do damage to them," he said. "These bones are completely disarticulated, and we have a lot of them — so it's not unreasonable to be able to take a few and cut them, and see what their internal anatomy is like."

Credit: Phil Gilston

Lufengosaurus grew to be about 20 feet (6 meters) in length.

How baby dinos grew
The bone bed contained spinal bones, limb bones, shoulder blades and even a few fragments of skull, but Reisz and his team focused their analysis on the most prevalent and best-preserved bones: femurs, or thigh bones. These little leg bones ranged from 0.5 to 0.9 inches (12 to 22 millimeters) in length, shorter than matchsticks.

The bones were porous, filled with cavities that would have once allowed blood to flow to the growing tissue. The size of the cavities is determined by how fast the animal grows — which made researchers realize these embryos got big quickly.

"They grow very fast — faster than we expected, and faster than most other dinosaurs that have been studied this way," Reisz said.

The fast growth rate makes sense, given that Lufengosaurus grew to 20 feet (6 meters) in length.

The researchers also found an asymmetrical thickening in the femurs associated with muscle action on the bone. The finding suggests the little dinos were kicking and twitching inside their eggs.

The team also discovered evidence of organic material — probably collagen, part of the connective tissue that forms ligaments and tendons. If the material isn't too deteriorated, it could be compared to collagen in living animals, thus providing a new way to look at relationships between modern creatures and the extinct dinosaurs, Reisz said.

"We're setting a new benchmark as to what can be done in dinosaur embryology," Reisz said. He and his colleagues will report their findings Thursday in the journal Nature. An upcoming goal, Reisz said, is to give the embryos their first dental exam.

"One of the things we may try in the near future is to look at the embryonic teeth themselves," he said. "They're very cool."

Follow Stephanie Pappas on Twitter and Google+. Follow us @livescience, Facebook and Google+. Original article on LiveScience.com.

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J.A. Peñas - SINC

An artist's impression of the egg-laying of the sauropod Ampelosaurus.

By LiveScience staff

Researchers in northeastern Spain say they've uncovered hundreds of dinosaur egg fossils, including four kinds that had never been found before in the region. The eggs likely were left behind by sauropods millions of years ago.

Eggs, eggshell fragments and dozens of clutches were nestled in the stratigraphic layers of the Tremp geological formation at the site of Coll de Nargó in the Spanish province of Lleida, which was a marshy region during the Late Cretaceous Period, the researchers said.

"Eggshells, eggs and nests were found in abundance and they all belong to dinosaurs, sauropods in particular," the study's leader, Albert García Sellés from the Miquel Crusafont Catalan Palaeontology Institute, told Spanish news agency SINC this week.

"Up until now, only one type of dinosaur egg had been documented in the region: Megaloolithus siruguei," Sellés added. His team found evidence of at least four other species: Cairanoolithus roussetensis, Megaloolithus aureliensis, Megaloolithus siruguei and Megaloolithus baghensis. Megaloolithus eggs are thought to be associated with sauropods, long-necked dinosaurs that were among some of the largest to roam the planet.

The Coll de Nargó area is considered one of the most important dinosaur nesting areas in Europe, the researchers said, adding that their study shows it was used by several dinosaurs from the Late Campanian age (around 71 million years ago) to the Late Maastrichtian age (around 67 million years ago).

"We had never found so many nests in the one area before. In addition, the presence of various oospecies (eggs species) at the same level suggests that different types of dinosaurs shared the same nesting area," Sellés said, adding that the dinosaur eggs could help scientists determine the date of future findings at the site.

"It has come to light that the different types of eggs are located at very specific time intervals," Sellés explained to SINC. "This allows us to create biochronological scales with a precise dating capacity. In short, thanks to the collection of oospecies found in Coll de Nargó we have been able to determine the age of the site at between 71 and 67 million years."

The findings are published in the March issue of the journal Cretaceous Research.

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Cas Liber

A hypsilophodon skeletal cast at the Melbourne Museum. Ancient crocociles noshed on young hypsilophodon dinosaurs, researchers have found.

By Charles Choi
LiveScience

Crocodile-like beasts may have nibbled on young dinosaurs some 75 million years ago, according to scientists who analyzed bite marks on dinosaur bones.

The findings suggest the rivalry between the reptiles started early in life, the researchers say.

Bites from living crocodylians such as alligators and crocodiles are often seen on the bones of their prey and scavenged bodies. Scientists can use these to identify bite marks on fossils from crocodyliforms, the reptiles to which modern crocodylians belong.

Research investigating crocodyliforms from the age of dinosaurs has often focused on the largest such reptiles feeding on equally giant dinosaurs. Now, paleontologists have direct evidence of a small crocodyliform biting juvenile dinosaurs.

Scientists unearthed these fossils in the Grand Staircase-Escalante National Monument in southern Utah.

Boyd CA, Drumheller SK, Gates TA (2013) Crocodyliform Feeding Traces on Juvenile Ornithischian Dinosaurs from the Upper Cretace

CT scans show puncture marks and embedded croc teeth in a juvenile dinosaur bone.

"This area is very hot and arid in the summer and cold in the winter," said researcher Clint Boyd, a vertebrate paleontologist at the South Dakota School of Mines and Technology. "Most of the area is dominated by massive, cliff-forming rock outcrops."

Back when the reptiles were alive, their environment was warm and wet, dominated by rivers and floodplains and lush with bushes and trees. Dinosaurs in the area included duck-billed hadrosaurs, horned ceratopsians such as Triceratops and predatory relatives of T. rex. The area also holds an especially diverse assembly of crocodyliforms, including the gigantic alligatoroid Deinosuchus riograndensis. [Paleo-Art: Stunning Illustrations of Dinosaurs]

The researchers unearthed 75-million-year-old fossils of at least three members of a kind of small, two-legged herbivorous dinosaur known as a hypsilophodontid. On the right thighbone of one, the researchers found a conical tooth embedded that was just 2.5 millimeters wide (a little less than one-tenth of an inch), and similarly tiny puncture marks were seen on a left shoulder bone.

"I was very surprised to find such clear feeding traces on such small bones," Boyd told LiveScience. "It shows the importance of carefully evaluating all the fossils collected from an area, and not assuming that some fossils won't be important just because they are very small or not completely preserved."

It remains uncertain how large the crocodyliform that made the marks was. However, the dinosaurs in question probably weighed about 28 to 46 pounds (13 to 21 kilograms); and living crocodylians 3 to 6 feet (1 to 1.8 meters) long are known to take down prey that big.

"Usually people tend to focus on the dangers that big, adult dinosaurs were having to deal with, but this study shows that even though dinosaurs were the dominant animals during the Cretaceous, they still had to worry about predators as soon as they were born," Boyd said.

The researchers will continue to study fossils from many time periods to look for additional traces of crocodyliform feeding, such as at an approximately 33-million-year-old locality in Badlands National Park in South Dakota.

Boyd and his colleagues Stephanie Drumheller and Terry Gates detailed their findings online Wednesday in the journal PLOS ONE.

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rancisco Gascó under the direction of Mike Taylor and Matt Wedel

Plant-eating dinosaurs called sauropods had the longest necks in the animal kingdom. Here an adult Brontomerus mother.

How did the largest of all dinosaurs evolve necks longer than any other creature that has ever lived? One secret: mostly hollow neck bones, researchers say.

The largest creatures to ever walk the Earth were the long-necked, long-tailed dinosaurs known as the sauropods. These vegetarians had by far the longest necks of any known animal. The dinosaurs' necks reached up to 50 feet (15 meters) in length, six times longer than that of the current world-record holder, the giraffe, and at least five times longer than those of any other animal that has lived on land.

"They were really stupidly, absurdly oversized," said researcher Michael Taylor, a vertebrate paleontologist at the University of Bristol in England. "In our feeble, modern world, we're used to thinking of elephants as big, but sauropods reached 10 times the size elephants do. They were the size of walking whales."

Amazing necks

To find out how sauropod necks could get so long, scientists analyzed other long-necked creatures and compared sauropod anatomy with that of the dinosaurs' nearest living relatives, the birds and crocodilians.

"Extinct animals — and living animals, too, for that matter — are much more amazing than we realize," Taylor told LiveScience. "Time and again, people have proposed limits to possible animal sizes, like the five-meter (16-foot) wingspan that was supposed to be the limit for flying animals. And time and again, they've been blown away. We now know of flying pterosaurs with 10-meter (33-foot) wingspans. And these extremes are achieved by a startling array of anatomical innovations." [ Image Gallery: 25 Amazing Ancient Beasts ]

Among living animals, adult bull giraffes have the longest necks, capable of reaching about 8 feet (2.4 m) long. No other living creature exceeds half this length. For instance, ostriches typically have necks only about 3 feet (1 m) long.

When it comes to extinct animals, the largest land-living mammal of all time was the rhino-like creature Paraceratherium, which had a neck maybe 8.2 feet (2.5 m) long. The flying reptiles known as pterosaurs could also have surprisingly long necks, such as Arambourgiania, whose neck may have exceeded 10 feet (3 m).

The necks of the Loch Ness Monster-like marine reptiles known as plesiosaurs could reach an impressive 23 feet (7 m), probably because the water they lived in could support their weight. But these necks were still less than half the lengths of the longest-necked sauropods.

Sauropod secrets

In their study, Taylor and his colleagues found that the neck bones of sauropods possessed a number of traits that supported such long necks. For instance, air often made up 60 percent of these animals' necks, with some as light as birds' bones, making it easier to support long chains of the bones. The muscles, tendons and ligaments were also positioned around these vertebrae in a way that helped maximize leverage, making neck movements more efficient.

In addition, the dinosaurs' giant torsos and four-legged stances helped provide a stable platform for their necks. In contrast, giraffes have relatively small torsos, while ostriches have two-legged stances. [ Image Gallery: Animals' Amazing Headgear ]

Sauropods also had plenty of neck vertebrae, up to 19. In contrast, nearly all mammals have no more than seven, from mice to whales to giraffes, limiting how long their necks can get. (The only exceptions among mammals are sloths and aquatic mammals known as sirenians, such as manatees.)

Moreover, while pterosaur Arambourgiania had a relatively giant head with long, spear-like jaws that it likely used to help capture prey, sauropods had small, light heads that were easy to support. These dinosaurs did not chew their meals, lacking even cheeks to store food in their mouths; they merely swallowed it, letting their guts break it down.

"Sauropod heads are essentially all mouth. The jaw joint is at the very back of the skull, and they didn't have cheeks, so they came pretty close to having Pac Man-Cookie Monster flip-top heads," researcher Mathew Wedel at the Western University of Health Sciences in Pomona, Calif., told LiveScience.

"It's natural to wonder if the lack of chewing didn't, well, come back to bite them, in terms of digestive efficiency. But some recent work on digestion in large animals has shown that after about 3 days, animals have gotten all the nutrition they can from their food, regardless of particle size.

"And sauropods were so big that the food would have spent that long going through them anyway," Wedel said. "They could stop chewing entirely, with no loss of digestive efficiency."

What's a long neck good for?

Furthermore, sauropods and other dinosaurs probably could breathe like birds, drawing fresh air through their lungs continuously, instead of having to breathe out before breathing in to fill their lungs with fresh air like mammals do. This may have helped sauropods get vital oxygen down their long necks to their lungs.

"The problem of breathing through a long tube is something that's very hard for mammals to do. Just try it with a length of garden hose," Taylor said.

As to why sauropods evolved such long necks, there are currently three theories. Some of the dinosaurs may have used their long necks to feed on high leaves, like giraffes do. Others may have used their necks to graze on large swaths of vegetation by sweeping the ground side to side like geese do. This helped them make the most out of every step, which would be a big deal for such heavy creatures.

Scientists have also suggested that long necks may have been sexually attractive, therefore driving the evolution of ever-longer necks; however, Taylor and his colleagues have found no evidence this was the case.

In the future, the researchers plan to delve even deeper into the mysteries of sauropod necks. For instance, Apatosaurus , formerly known as Brontosaurus, had "really sensationally strange neck vertebrae," Taylor said. The scientists suspect the necks of Apatosaurus were used for "combat between males — fighting over women, of course."

Taylor and Wedel detailed their findings online Feb. 12 in the journal PeerJ.

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Dr. Diying Huang

A mating pair of strashilids, fossil insects from the Jurassic that resemble modern aquatic flies.

By Stephanie Pappas
LiveScience

A group of Jurassic insects thought to have been parasites of feathered dinosaurs were falsely accused, new research finds. Instead, the tiny creatures were aquatic flies, similar to some still living today.

The findings don't change the reality that dinosaurs really did have lice and other parasites, Nanjing Institute of Geology and Paleontology researcher Diying Huang and his colleagues write in the Thursday issue of the journal Nature. Huang and his colleagues had previously discovered dino-fleas 10 times the size of the ones that plague mammals today.

But insects known as the strashilids had been wrongly identified as bloodsuckers, Huang and his colleagues now conclude.

The itsy-bitsy insects, only a few millimeters long, have grasping back legs and what appeared, in fossilized specimens, to be a sucking beak. These remains made scientists think strashilids belonged to an extinct group of dinosaur parasites. But researchers had only discovered a handful of these Jurassic insects.

Now, Huang and his colleagues have examined 13 new specimens of strashilids from 165 million years ago, found in Inner Mongolia. Two of these specimens even preserve males and females having sex. [See Images of the Fossil Flies Having Sex]

The new look at these ancient insects reveals that only male strashilids had grasping back legs, an indication that these limbs were used to hang on to females during sex, not to cling to dinosaur feathers during feeding. What's more, both sexes had vestigial mouthparts, suggesting the short-lived adults didn't feed at all. The insects also had large, membranous wings.

An examination of the insects' genitalia matched them to a modern group of flies, the Nymphomyiidae. These flies have feathery wings and live along rapidly moving streams. Like the Jurassic insects, adults of the present-day flies keep some vestiges of their larval selves. The ancient flies, in particular, often hung on to their abdominal gills, an unusual feature among insects, the researchers report.

Researchers suspect that these flies probably shed their wings toward the end of their lives and returned to the water to mate as their last act. The fossils of flies engaged in the act, which reveal wingless males gripping wingless females, support that theory.

Actual dino-parasites from the Jurassic were larger than strashilids, measuring about 0.7 inches (17 millimeters) in length for species such as Pseudopulex jurassicus and Pseudopulex magnus. In one way, ancient fleas were less scary than modern versions, however — a 2012 study in the journal Nature found that Jurassic bloodsuckers probably couldn't jump. 

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O. Sanisidro

Though the plant-eating dinosaur Ampelosaurus was among the largest to walk the Earth, it was equipped with a puny brain.

By Charles Choi, contributor, LiveScience

An advanced member of the largest group of dinosaurs ever to walk the Earth still had a relatively puny brain, researchers say.

The scientists analyzed the skull of 70-million-year-old fossils of the giant dinosaur Ampelosaurus, discovered in 2007 in Cuenca, Spain, in the course of the construction of a high-speed rail track connecting Madrid with Valencia. The reptile was a sauropod, long-necked, long-tailed herbivores that were the largest creatures ever to stride the Earth. More specifically, Ampelosaurus was a kind of sauropod known as a titanosaur, many if not all of which had armorlike scales covering their bodies.

Sauropod skulls are typically fragile, and few have survived intact enough for scientists to learn much about their brains. By scanning the interior of the skull via CT imaging, the researchers developed a 3-D reconstruction of Ampelosaurus' brain, which was not much bigger than a tennis ball.

"This saurian may have reached 15 meters (49 feet) in length; nonetheless its brain was not in excess of 8 centimeters (3 inches)," study researcher Fabien Knoll, a paleontologist at Spain's National Museum of Natural Sciences, said in a statement. [ Gallery: Stunning Illustrations of Dinosaurs ]

The first sauropods appeared about 160 million years earlier than this fossil.

"We don't see much expansion of brain size in this group of animals as they go through time, unlike a lot of mammalian and bird groups, where you see increases in brain size over time," researcher Lawrence Witmer, an anatomist and paleontologist at Ohio University, told LiveScience. "They apparently hit on something and stuck with it — expansion of brain size over time wasn't a major focus of theirs."

For years, scientists have wondered how the largest land animals ever lived with such tiny brains. "Maybe we should flip that question on their end — maybe we shouldn't ask how they could function with tiny brains, but what are many modern animals doing with such ridiculously large brains. Cows may be triple-Einsteins compared to most dinosaurs, but why?" Witmer said.

heir computer model also revealed the ampelosaur had a small inner ear.

"Part of the inner ear is associated with hearing, so the fact it had a small inner ear means it probably wasn't all that good at hearing airborne sounds," Witmer said. "It probably used a kind of hearing we don't think much about, which depends on sounds transmitted through the ground."

The inner ear is also responsible for balance and equilibrium, Witmer said.

"Given what we know about its inner ear, Ampelosaurus probably didn't put a real premium on rapid, quick jerky eye or head movements, which makes sense — these are relatively large, slow-moving, plant-eating animals," he said.

Knoll and his colleagues had previously developed 3-D reconstructions of another sauropod, Spinophorosaurus nigeriensis. In contrast to Ampelosaurus, Spinophorosaurus had a fairly developed inner ear.

"It is quite enigmatic that sauropods show such a diverse inner ear morphology whereas they have a very homogenous body shape," Knoll said. "More investigation is definitely required."

Currently scientists are debating whether sauropods held their heads near the ground, grazing on low vegetation, or high up like giraffes to browse on high leaves. "It could be that learning more about the inner ear could tell us what sauropod neck posture was like," Witmer said.

The scientists detailed their findings online Jan. 23 in the journal PLOS ONE.

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Sydney Mohr

New research suggests male oviraptor dinosaurs would shake their tail feathers to woo potential female mates (reconstruction of such dino-wooing shown here).

By Charles Choi
LiveScience

Feathered dinosaurs might have used muscular tails to shake tail feathers and lure the opposite sex, researchers say.

Scientists analyzed 75-million-year-old fossils of feathered, two-legged dinosaurs known as oviraptors retrieved during expeditions to the Gobi Desert in Mongolia. Although oviraptors were members of the meat-eating theropods, making them relatives of such fearsome predators as T. rex and Velociraptor , most oviraptors had beaks that lacked teeth.

"There are good reasons to think they had gone vegetarian," researcher Scott Persons, a vertebrate paleontologist at the University of Alberta in Canada, told LiveScience. "They were odd ducks, strange dinosaurs," said Persons, who presented the study results at the Society for Vertebrate Paleontology's annual meeting in November, but only this week were they published in a scientific journal.

Past research had revealed oviraptors often had eye-catching bone crests on their heads. "Now we know there was something funny going on at the other end, too," Persons said.

Scott Persons

A series of five fused bones at the end of the tail of the oviraptor Nomingia.

Oviraptor tails were short, but were made of many tailbones, with many points between these vertebrae where they could flex. Persons and his colleagues found oviraptor tailbones also had many projections onto which muscles could attach. Computer models estimating the size of these muscles based on oviraptor skeletons suggest these muscles were quite large. [ Paleo-Art: Stunning Illustrations of Dinosaurs ]

"Their tails were not only very, very flexible, but quite muscular," Persons said. "They could not only move them sinuously to strike a pose, but also hold it to do a muscular dance with the tail."

Unusually, at the very end of the tail, "in some oviraptors, the last few vertebrae were actually fused together to become one solid, ridged, bladelike structure," Persons said. "The only other kind of animal where you see that are modern-day birds, where it's called a pygostyle, which serves as an anchor point for a big fan of tail feathers."

Modern-day birds use pygostyles to help them fly, "but oviraptors were not flying animals — they had feathers, but they didn't have big broad wings," Persons said. "What else are pygostyles used for? Peacocks and turkeys use their tail feathers for courtship displays."

Scott Persons

Digital models of the tailbones and musculature of an oviraptor. Three stages of reconstruction are shown in views from the side and top: a) the tailbones modeled off skeletal measurements; b) a key muscle, the m. caudofemoralis longus, modeled over the digital skeleton; c) the full muscle reconstruction.

Past research has suggested that dinosaurs may have first evolved feathers for show, not flight. Persons and his colleagues found that at least four known oviraptor species separated by 45 million years had pygostyles.

"I think like peacocks, oviraptors were strutting their stuff by shaking their tail feathers to show off," Persons said. "Between the crested head and feathered-tail shaking, oviraptors had a propensity for visual exhibitionism."

Although feathers on dinosaur forearms might have served as stabilizers that helped them steer, that may not have been the case for any tail plumes. "Flightless birds such as ostriches and emus don't have big tail-feather fans, and birds that do have big tail-feather fans such as peacocks and turkeys don't try to use them to run at all, but just keep them tucked in except when fanned out for display."

In the future, Persons and his colleagues want to see if such tails were typically found in one sex or the other. "Maybe they were larger in males, as we see in modern-day birds," Persons said. "The problem there is that the tip of the tail is one of the rarest parts of a fossil skeleton to find, so it might be hard to discover evidence of these sexual differences."

Persons and colleagues Philip Currie and Mark Norell detailed their findings in Friday's issue of the journal Acta Palaeontologica Polonica.

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