Sep 17, 2014

Global Warming Changes the Way Sharks Swim

Sharks exposed to ocean water acidified by too much carbon dioxide alter their behavior, swimming in longer spurts than sharks in typical ocean water, particularly during their nighttime wanderings.

The new findings, published in the journal Biology Letters, are troubling, given that one effect of the human consumption of fossil fuels is to make ocean water more acidic. If fossil fuel burning continues as is, sharks may face even more challenges than they do today — when a quarter of species are already at risk of extinction.

"Usually when you expose a fish to some kind of environmental stressor, they usually acclimate to that stressor, and that makes them less vulnerable to that stressor," said study researcher Fredrik Jutfelt, an animal physiologist at the University of Gothenburg in Sweden. "But here, it seemed like this high CO2 [carbon dioxide] continued to be a stressor to these sharks for quite a long time."

Acidifying oceans

The world's oceans absorb carbon dioxide from the atmosphere, a process that decreases the pH (a measure of how acidic or basic a substance is) of ocean water, turning it more acidic. According to the National Oceanic and Atmospheric Administration (NOAA), the pH of ocean surface water has fallen by 0.1 on the 14-point scale since the beginning of the Industrial Revolution. That drop on the pH scale translates to surface water that's 30 percent more acidic than before.

Today, ocean water has a pH of about 8.1, Jutfelt told Live Science, and the atmosphere contains about 400 parts per million of carbon dioxide. If humans continue to load the atmosphere with carbon, this concentration is expected to rise to about 1,000 parts per million by 2100. In that scenario, the pH of ocean water is expected to drop to about 7.7 or 7.8.  The pH scale runs from 0 (most acidic) to 14 (most basic), with a pH of 7 being neutral.

Studies of bony fishes have found that some species react catastrophically to acidified water, while others are quite tolerant, Jutfelt said. But hardly anyone had examined the effects of ocean acidification on sharks and rays, fish known for their cartilaginous bones.

Strange swimming

Jutfelt and his colleague Leon Green, also of the University of Gothenburg, borrowed 20 small-spotted catsharks (Scyliorhinus canicula), from a local aquarium. This small, common bottom-dweller is found throughout the Atlantic Ocean and Mediterranean Sea. They put half of the sharks in tanks filled with typical ocean water with a pH of 8.1, and half in tanks filled with acidified ocean water with a pH of about 7.7 for four weeks.

After this period, the researchers tested the sharks on a variety of physiological responses and behaviors, including their blood pH and oxygen consumption rates. They also took video of the sharks at night, when these nocturnal animals are most active.

Although the CO2-exposed sharks' metabolisms were normal, the researchers found more sodium and bicarbonate ions in their blood, apparently a molecular adjustment made to keep the sharks' blood pH stable in the more-acidic water. Most strikingly, however, was the discovery that the sharks in the acidified water exhibited odd nighttime behavior.

"The control sharks, they would have these many starts and stops throughout the night. They would swim for a few seconds, or up to a minute, maybe, and then stop," Jutfelt said. "But the CO2-exposed sharks, they kept swimming for longer time periods. Some of them swam for an hour continuously."

This continuous swimming behavior could have been a result of altered ion concentrations in the brain, Jutfelt said. Alternatively, the sharks could have sensed that the water was too acidic and kept swimming in hopes of finding better-quality water elsewhere. Surprisingly, Jutfelt said, the sharks kept up this behavior change four to six weeks after first being introduced to the acidified water.

"They don't seem to be able to completely acclimate," he said.

Read more at Discovery News

This Is What Killed Richard III

Forensic analysis of King Richard III’s remains has provided a blow-by-blow account of the English monarch’s final moments, revealing he sustained 11 wounds at or near the time of his death.

Depicted by William Shakespeare as a bloodthirsty usurper, Richard ruled England from 1483 to 1485. He was killed in 1485 in the Battle of Bosworth, which was the last act of the decades-long fight over the throne known as War of the Roses. England’s last king to die in battle, he was defeated by Henry Tudor, who became King Henry VII.

The king’s twisted skeleton was found two years ago under a car park by archaeologists from the University of Leicester.

The skeleton, showing a severe spinal scoliosis, was widely examined by researchers.

The latest investigation, carried out by researchers at the University of Leicester, focused on the king’s final moments.

Modern forensic techniques, including whole body CT scans and micro-CT imaging, were used to examine the 500-year-old skeleton for trauma. The aim was to draw the most likely scenario of Richard’s death and determine which of the king's wounds might have proved fatal.

The researchers identified 11 wounds. Nine were found to the skull, suggesting Richard had removed or lost his helmet, and two to the rest of the skeleton. All injuries were consistent with the types of weapons used in the late medieval period.

"The most likely injuries to have caused the king's death are the two to the (underside) of the skull -- a large sharp force trauma possibly from a sword or staff weapon, such as a halberd or bill, and a penetrating injury from the tip of an edged weapon,” said Guy Rutty, study co-author, from the East Midlands Pathology Unit at the University of Leicester.

Both the head wounds described by Rutty would have caused hemorrhage, injury to the brain or air embolus, leading to death within a short time. Most probably, it was the penetrating injury that went from the base of the skull through to the inner surface of the skull that led to immediate death.

According to the researchers, the head trauma confirms some near-contemporary accounts of the battle, which reported the king abandoned his horse after it became stuck in a mire and was killed while fighting his enemies.

“The injuries are highly consistent with the body having been in a prone position or on its knees with the head pointing downwards,” researchers wrote in the journal The Lancet.

Although it’s not possible to determine the order in which the injuries were inflicted, the researchers made some interpretation on the basis of what's known of medieval armor.

“There were no defensive injuries to the arms or hands suggesting he was still armored at the point of death,” Sarah Hainsworth, professor of materials engineering at the University of Leicester, told Discovery News.

The injuries represent either a sustained attack or an attack by several assailants.

“It is possible that he suffered a simultaneous attack from several assailants,” Hainsworth said.

She noted that at least three weapons were involved in causing injury to the skull. A rondel dagger was most probably used to create a square-shaped injury to the top of the skull, while a number of "shaving type" injuries were caused by a sharp bladed weapon such as a dagger or sword.

Of the two potentially fatal wounds to the base of the skull, one was most likely caused by a pole weapon such as a bill or halberd. The other injury, penetrating through the skull from the base to the inside, was again likely caused by a sword or dagger.

“It is therefore likely that more than one person was involved if each person held one weapon. But we can't say exactly how many people were there or how fast the injuries were sustained,” Hainsworth said.

In addition to the injuries to the base of the skull, the researchers found another potentially fatal wound. It was inflicted to the pelvis, one of the most vulnerable areas to attack in a medieval battle.

But Richard was wearing his armor, so it’s likely he was already dead when a fine-bladed weapon penetrated the right buttock and traversed the right side of the pelvic cavity.

“The most probable mode of injury is after Richard’s armor had been removed,” the researchers said.

Indeed, contemporary accounts of the battle describe Richard’s body as being slung over the back of a horse suffering insults.

“The angle of the injury to the pelvis is highly consistent with such treatment,” the researchers wrote.

The pelvis injury adds to other wounds, such as three face injuries, which were most likely caused after death.

Read more at Discovery News

Weird Little Galaxy Hides a Giant Black Hole

At the heart of a big galaxy lies a big black hole, regions so dense with matter that not even light can escape their gravitational grip. Little galaxies have little black holes -- or so scientists thought.

Consider M60-UCD1, an ultra-compact dwarf galaxy located about 55 million light-years from Earth in the Virgo cluster. Despite its diminutive stance, the galaxy appears to harbor a supermassive black hole, one more fitting in a galaxy 80 times bigger.

The discovery may help resolve a long-standing mystery about ultra-compact dwarf galaxies, which are densely packed, spherical conglomerations of stars.

Scientists suspect these galaxies are the centers of what were once much larger galaxies that were striped of stars by passing neighbors. After the raid, the dense center cluster and its supermassive black hole were all that remained.

“There are quite a few of these ultra-compact dwarf galaxies and people have debated the nature of these objects for a long time. Are they just really, really massive star clusters -- because that’s really what they look like -- or are they the stripped nuclei of galaxies? This one is the first clear case that it is a striped galaxy nucleus,” University of Michigan astronomer Amy Reines told Discovery News.

The discovery also means that the local universe may be teeming with many more supermassive black holes than previous surveys suggest.

“This gives us a whole new home for black holes that we never knew existed before,” Reines said.

M60-UCD1 showed up on astronomer’s proverbial radar screens by an unusual X-ray emission.

“That could be a sign of a weakly accreting, really massive black hole,” said lead researcher Anil Seth, with the University of Utah. “But it also could be a stellar-mass black hole that’s rapidly accreting, or a neutron star.”

“It was an intriguing possibility,” Seth told Discovery News.

Read more at Discovery News

Seeking Earth-Like Alien Worlds in the 'Venus Zone'

Exoplanet hunters have just made it easier to identify alien Venuses, in the hopes that doing so will lead to the discovery of more alien Earths.

A team of researchers has delineated the "Venus Zone," the range of distances from a host star where planets are likely to resemble Earth's similarly sized sister world, which has been rendered unlivably hot due to a runaway greenhouse effect.

The new study should help scientists get a better handle on how many of the rocky planets spotted by NASA's prolific Kepler space telescope are truly Earth-like, team members said.

"The Earth is Dr. Jekyll, and Venus is Mr. Hyde, and you can't distinguish between the two based only on size," lead author Stephen Kane, of San Francisco State University, said in a statement. "So the question then is, how do you define those differences, and how many 'Venuses' is Kepler actually finding?"

The results could also lead to a better understanding of Earth's history, Kane added.

"We believe the Earth and Venus had similar starts in terms of their atmospheric evolution," he said. "Something changed at one point, and the obvious difference between the two is proximity to the sun."

Kane and his team defined the Venus Zone based on solar flux — the amount of stellar energy that orbiting planets receive. The outer edge of the zone is the point at which a runaway greenhouse effect would take hold, with a planet's temperature soaring thanks to heat-trapping gases in its atmosphere. The inner boundary, meanwhile, is the distance at which stellar radiation would completely strip away a planet's air.

The thinking is similar to that behind the "habitable zone" — the just-right range of distances from a star at which liquid water, and perhaps life as we know it, may be able to exist.

The dimensions of these astronomical zones vary from star to star, since some stars are hotter than others. In our own solar system, the Venus Zone's outer boundary lies just inside the orbit of Earth, researchers said.

Future space-based instruments — such as NASA's $8.8 billion James Webb Space Telescope, scheduled to launch in 2018 — will be able to analyze some exoplanets' atmospheres, helping scientists refine the Venus Zone concept, researchers said.

"If we find all of these planets in the Venus Zone have a runaway greenhouse-gas effect, then we know that the distance a planet is from its star is a major determining factor. That's helpful to understanding the history between Venus and Earth," Kane said.

Read more at Discovery News

Sep 16, 2014

770-Pound Colossal Squid a 'Perfect' Specimen

Scientists said Tuesday a female colossal squid weighing an estimated 350 kilograms (770 lbs) and thought to be only the second intact specimen ever found was carrying eggs when discovered in the Antarctic.

The squid had been kept in optimum freezing conditions at the Te Papa museum in Wellington ever since it was brought back to New Zealand from the seas off the frozen continent during the southern hemisphere's summer.

The colossal squid is thought to extend up to 4-5 metres (13-16 feet) from tip to tentacle and weigh up to 500 kilograms. Its relation, the giant squid, can grow a lot longer but is much more spindly.

This specimen, like other octopus and squid species, has three hearts -- one to pump blood around the body and two for its gills (lungs) -- and is estimated to be about 3.5 metres in length.

"This one had two perfect eyes," scientist Kat Bolstad from Auckland University of Technology who led the examination told AFP.

"They have very large and very delicate eyes because they live in the deep sea. It's very rare to see an eye in good condition at all."

Measurements revealed the animal's eye was 35 centimetres (14 inches) in diameter, and confirmed that the specimen was a female.

"We were excited to find that out... as it turns out this one is a female, and it has got some eggs," Bolstad told reporters.

"This was by far the most perfect colossal squid that I have seen."

The only other time scientists anywhere have had the chance to examine an intact colossal squid was in 2008, also at Te Papa, the museum said. That specimen was also female.

Bolstad said the latest specimen was so well preserved the scientists were able to examine it with an unusual level of detail, including the lens on the eyes.

"The fact that we have a specimen in good shape, but that we can get so much information from and still have in good shape, is a win-win," Bolstad said.

Read more at Discovery News

3rd Room of Ancient Greek Tomb Revealed

Archaeologists say they've had a peek inside another room in a monumental ancient tomb in Greek Macedonia that is believed to date back to the era of Alexander the Great.

The ongoing excavations at the Kasta Hill burial mound in Amphipolis -- about 65 miles (104 kilometers) east of Thessaloniki -- have generated excitement and speculation over what (and whom) archaeologists might find inside.

The latest images, released by the Greek Ministry of Culture yesterday (Sept. 14), show an arched, soil-filled room, with some traces of red paint on the limestone walls. The chamber lies beyond beyond the two female statues known as caryatids that were uncovered last week.

The Kasta Hill tomb is enclosed by an enormous wall whose perimeter measures 1,600 feet (490 meters). In August, archaeologists revealed two broken sphinxes at the entrance to the burial complex. Over the past several weeks, they've been removing soil and walls of heavy sealing stones to probe deeper into the tomb. They've discovered mosaic floors, and last week, the team uncovered the wavy-haired caryatids — statues that take the place of columns or pillars — standing guard at the second doorway.

The archaeologists, led by Katerina Peristeri, have said they believe the tomb dates back to the late fourth century B.C. and has the characteristics of a work by Dinocrates, Alexander the Great's chief architect. But excavators are unlikely to find the body of Alexander the Great himself; historical records indicate he was buried in Alexandria, though his body has never been found.

"This is an ongoing excavation; much more will be discovered as the excavation goes forward," Beth Carney, a history professor at Clemson University, told Live Science in an email. Carney, who is not involved in the excavation, said the tomb seems remarkable for its huge circumference and carved portals, but she isn't sure what evidence the archaeologists have for a late fourth century B.C. date.

The date of the tomb could prove important if archaeologists find bones inside that are tough to identify. Archaeologists have quarreled for decades over the identity of a couple buried in the lavish Macedonian tomb at Vergina in northern Greece, near the site of the early capital of the Kingdom of Macedonia. When Greek archaeologist Manolis Andronikos opened the grave (dubbed Tomb II) at Vergina in 1977, he claimed to have found the resting place of Alexander's father, Philip II, a powerful leader in his own right who paved the way for his son's conquests before he was assassinated in 336 B.C. But others have suggested that the tomb actually belonged to Philip III Arrhidaeus, Alexander's (perhaps mentally disabled) half-brother, who was executed in 317 B.C. after a less successful reign.

Read more at Discovery News

Dino-Killing Meteorite Gave Way to Leafy Forests

The meteorite that killed off the dinosaurs 66 million years ago had more of an effect on evergreens and led plants that lose their leaves to dominate forests, reports a new study.

The event wiped out about half of plant species, and fast-growing deciduous trees replaced evergreens, researchers from the University of Arizona report.

"When you look at forests around the world today, you don't see many forests dominated by evergreen flowering plants," said the study's lead author, Benjamin Blonder from the University of Arizona, in a statement. "Instead, they are dominated by deciduous species, plants that lose their leaves at some point during the year."

Blonder and his colleagues studied 1,000 plant leaves fossilized in southern North Dakota, which are stored at the the Denver Museum of Nature and Science.

"There is a spectrum between fast- and slow-growing species," Blonder said. "There is the 'live fast, die young' strategy and there is the 'slow but steady' strategy. You could compare it to financial strategies investing in stocks versus bonds."

Evergreens take more time to build their leaves and last a long time, the researchers reported. Deciduous plants die sooner, but they're able to move more water and acquire carbon faster.

"If you think about a mass extinction caused by catastrophic event such as a meteorite impacting Earth, you might imagine all species are equally likely to die," Blonder said. "Survival of the fittest doesn't apply — the impact is like a reset button. Our study provides evidence of a dramatic shift from slow-growing plants to fast-growing species."

From Discovery News

Schizophrenia Is Actually Eight Genetic Disorders

New research published in the American Journal of Psychiatry suggests that schizophrenia is not a single disease, but rather a group of eight genetically distinct disorders, each of them with its own set of symptoms. The finding could result in improved diagnosis and treatment, while also shedding light on how genes work together to cause complex disorders.

Schizophrenia is classified as a psychotic disorder, one characterized by an inability to discern what is real and not real, to think clearly, have normal emotional responses, and act normally in social situations. As Elyn Saks told us last year, "it's a waking nightmare, where you have all the bizarre images, the terrible things happening, and the utter terror -- only with a nightmare you open your eyes and it goes away. No such luck with a psychotic episode."

Scientists aren't entirely sure what causes it, nor does it manifest identically in all people who have it (leading to the broader diagnosis of being on the 'schizophrenia spectrum'). But links have been made to genetics, social factors (including early development), and neurobiology. The heritability link looks to be particularly promising, however; about 80 percent of the risk for schizophrenia is genetic. Yet scientists have struggled to identify which genes are responsible for the condition.

But a novel approach to analyzing genetic influences on more than 4,000 people with schizophrenia has finally allowed researchers to identify distinct gene clusters that contribute to eight different classes of schizophrenia.

"Genes don't operate by themselves," noted C. Robert Cloninger, MD, PhD, one of the study's senior investigators in a statement. "They function in concert, much like an orchestra, and to understand how they're working, you have to know not just who the members of the orchestra are but how they interact."

Indeed, complex diseases like schizophrenia may be influenced by hundreds or thousands of genetic variants that interact with one another in complicated and dynamic ways, leading to what scientists call "multifaceted genetic architectures." Now, thanks to the work of investigators at the Washington University School of Medicine in St. Louis, the genetic architecture for schizophrenia is starting to take shape.

For the study, Cloninger and his colleagues matched precise DNA variations in people with and without schizophrenia to symptoms in individual patients. In total, they looked at nearly 700,000 sites within the genome where a single unit of DNA is altered (i.e. a single nucleotide polymorphism, or SNP). Specifically, they analyzed the SNPs of 4,200 people with schizophrenia and 3,800 people without it. This allowed them to learn how individual genetic variations interact with each other to produce the illness.

So, for example, hallucinations and delusions were associated with one set of DNA variations, that carried a 95 percent risk of schizophrenia. Another symptom, disorganized speech and behavior, was found to carry a 100 percent risk with another set of DNA.

"What we've done here, after a decade of frustration in the field of psychiatric genetics, is identify the way genes interact with each other, how the 'orchestra' is either harmonious and leads to health, or disorganized in ways that lead to distinct classes of schizophrenia," Cloninger said.

When it comes to schizophrenia and other complex conditions, individual genes have only a weak and inconsistent association (which is why it's often silly to look for single-gene factors). But groups of interacting gene clusters create an extremely high and consistent risk of illness -- in this case, on the order of 70 percent to 100 percent. It's nearly impossible for people with these precise genetic variations to avoid the condition. In all, the researchers found no less than 42 clusters of genetic variations that significantly increase the risk of schizophrenia.

"In the past, scientists had been looking for associations between individual genes and schizophrenia," explained Dragan Svrakic, PhD, MD, a co-investigator and a professor of psychiatry at Washington University. "When one study would identify an association, no one else could replicate it. What was missing was the idea that these genes don't act independently. They work in concert to disrupt the brain's structure and function, and that results in the illness."

According to Svrakic, the key to the study was in organizing the genetic variations and the patients' symptoms into groups. This allowed them to see that particular clusters of DNA variations acted together to cause specific symptoms. Patients were then divided according to the type and severity of their symptoms. Results showed that those symptom profiles corresponded to eight qualitatively distinct disorders based on underlying genetic conditions.

Read more at Discovery News

Sep 15, 2014

Giant Dinosaur Could Fill Fossil 'Black Hole'

A giant dinosaur found in Tanzania once lived during a lush, green period when flowering plants flourished, about 100 million years ago, paleontologists report. The new dino species is a rare find in sub-Saharan Africa, where far fewer dinosaur fossils are discovered than in South America, the researchers said.

Paleontologists discovered the massive fossil in 2007 during fieldwork in the Rukwa Rift Basin in southwestern Tanzania.

Political instability in certain parts of Africa can prevent dinosaur digs, but fossils in this part of the world are also elusive for geological reasons. As the continents drifted apart, Africa did not move as much as the other continents did, leaving its fossils buried instead of pushed up by plate tectonics, said Patrick O'Connor, a professor of anatomy at Ohio University in Athens, Ohio, and one of the researchers on the new study.

Africa also had fewer ideal areas where sediment could quickly bury a creature and begin the fossilization process. Politics and geology, "those two things together account for why we don't know so much about continental Africa as we do about other parts of the world," O'Connor said.

Joseph Sertich, then a graduate student at Stony Brook University in Long Island, New York, and now a paleontologist at the Denver Museum of Nature & Science, was the first to spot the bones in the Rukwa Rift Basin.

"He scrambled into a gully and found the skeleton coming out the cliff surface," O'Connor said.

A careful excavation by local coal miners and paleontologists in 2007 and 2008 suggests that muddy elements had buried the dinosaur's remains — not once, but twice, O'Connor told Live Science. About 100 million years ago, the dinosaur likely died on a muddy floodplain. Mudstone eventually covered its body, but shortly after, a river running through the plain cut away at the mudstone, exposing part of the skeleton and encasing it in sandstone.

A river still runs near the site, and its drainage through the cliff face had begun to uncover the ancient skeleton, O'Connor said.

The researchers recovered about two dozen fossilized bones, enough to determine that they had a new species on their hands, O'Connor said. An analysis of the bones' shapes and features suggest the dinosaur was a titanosaurian, a member of the giant, long-necked and plant-eating sauropod dinosaurs.

The paleontologists named the dinosaur Rukwatitan bisepultus for the Rukwa Rift Basin and its titanosaurian roots — an allusion to the powerful and mythical Greek Titan deities. In Latin, bisepultus means "twice buried," said Eric Gorscak, the study's lead researcher and a doctoral candidate of biological sciences at Ohio University.

"A lot of what we know about titanosaurian evolution and their biology stems from South America, where there's a lot of specimens," Gorscak said. Titanosaurian remains are found on every continent including Antarctica, but "the early evolutionary history outside of South America is fuzzy."

The new finding helps bridge that gap, said Matthew Lamanna, a curator of vertebrate paleontology at the Carnegie Museum of Natural History in Pittsburgh, who was not involved with the study.

Rukwatitan is important because it's "one of the very few Cretaceous-aged dinosaurs known from Africa south of the Sahara Desert," Lamanna told Live Science in an email. "That part of the world is one of the biggest 'black holes' in our understanding of dinosaurs," he said.

Previously, paleontologists found thetitanosaurian Malawisaurus dixeyi in Malawi, but the Rukwatitan fossils are markedly different in shape and size from that specimen and other titanosaurians found in northern Africa, O'Connor said.

Rukwatitan weighed between 10 and 15 tons — about as much as two elephants but not nearly as much as Dreadnoughtus schrani, another type of titanosaurian, discovered in Argentina, that weighed about 65 tons, Gorscak said. He and his colleagues used a computed tomography (CT) scan to view Rukwatitan's bones and its internal structure. Like other titanosaurians and meat-eating theropods — dinosaurs that may have given flight to birds — Rukwatitan's neck bone was hollow and filled with air.

Read more at Discovery News

Ancient Giant Sloth Species Got Huge Fast

An ancient sloth weighing some 5 tons and sporting claws that extended a foot (0.3 meters) is helping to reveal how the slow, furry creatures ballooned in size long ago at a startlingly fast rate, a new study finds.

The massive beast, Eremotherium eomigrans, along with all of the sloth's giant predecessors, went extinct by about 11,000 years ago.

The new study found that some sloth lineages grew more than 220 pounds (100 kilograms) every million years — one of the fastest body growth rates known in the evolution of mammals. The rapid growth rate indicates that several factors in prehistoric times, such as environmental conditions or competition with other animals, may have favored large sloths, the researchers said in a statement.

Other studies have examined sloth growth rates, but accounted for only living species. The researchers incorporated extinct sloths into the equation for the new study to show that the animals grew at an incredibly fast rate over time.

There are six species of sloths living in South America today, which reach a maximum weight of about 12 lbs. (6 kg). However, the fossil record shows a richer diversity, with more than 50 known species that lived between about 2.6 million and 11,700 years ago. In all, the researchers looked at 57 species of sloths that are living or from the fossil record, and examined the average changes in body mass throughout their evolution, the study reported.

"Today's sloths are really the black sheep of the sloth family," study co-author Anjali Goswami, of the University College London earth sciences department, said in a statement. "If we ignore the fossil record and limit our studies to living sloths, as previous studies have done, there's a good chance that we'll miss out on the real story and maybe underestimate the extraordinarily complex evolution that produced the species that inhabit our world."

Nowadays, sloths are vegetarians that live in trees and typically weigh between 8 and 12 pounds (3.5 and 5.5 kg), the researchers said. In contrast, extinct sloths lived in a range of environments, and included ground-, tree- and water-dwelling sloths. Fossilized footprints suggest that some of these ancient sloths walked on their hind legs, and may have also eaten both plants and animals.

Read more at Discovery News