Tuesday, December 22, 2009

Venomous Dinosaur Discovered in China

ScienceDaily (Dec. 22, 2009) — A group of University of Kansas researchers working with Chinese colleagues have discovered a venomous, birdlike raptor that thrived some 128 million years ago in China. This is the first report of venom in the lineage that leads to modern birds.

"This thing is a venomous bird for all intents and purposes," said Larry Martin, KU professor and curator of vertebrate paleontology at the Natural History Museum and Biodiversity Institute. "It was a real shock to us and we made a special trip to China to work on this."

The KU-China team's findings will be published in the early edition of the Proceedings of the National Academy of Sciences during the week of Dec. 21.

"We think it's going to make a big splash," said Martin.


The article's authors are Enpu Gong, geology department at Northeastern University in Shenyang, China, and researchers Martin, David Burnham and Amanda Falk at the KU Natural History Museum and Biodiversity Institute.


The dromaeosaur or raptor, Sinornithosaurus (Chinese-bird-lizard), is a close relative to Velociraptor. It lived in prehistoric forests of northeastern China that were filled with a diverse assemblage of animals including other primitive birds and dinosaurs.


"This is an animal about the size of a turkey," said Martin. "It's a specialized predator of small dinosaurs and birds. It was almost certainly feathered. It's a very close relative of the four-winged glider called Microraptor."


The venom most likely sent the victim into rapid shock, shrinking the odds of retaliation, escape or piracy from other predators while the raptor manipulated its prey.


"You wouldn't have seen it coming," said Burnham. "It would have swooped down behind you from a low-hanging tree branch and attacked from the back. It wanted to get its jaws around you. Once the teeth were embedded in your skin the venom could seep into the wound. The prey would rapidly go into shock, but it would still be living, and it might have seen itself being slowly devoured by this raptor."


The genus had special depressions on the side of its face thought by the investigators to have housed a poison gland, connected by a long lateral depression above the tooth row that delivered venom to a series of long, grooved teeth on the upper jaw. This arrangement is similar to the venom-delivery system in modern rear-fanged snakes and lizards. The researchers believe it to be specialized for predation on birds.


"When we were looking at Sinornithosaurus, we realized that its teeth were unusual, and then we began to look at the whole structure of the teeth and jaw, and at that point, we realized it was similar to modern-day snakes," Martin said.

Sinornithosaurus is represented by at least two species. These specimens have features consistent with a primitive venom-delivery system. The KU-China research team said it was a low-pressure system similar to the modern Beaded lizard, Heloderma, however the prehistoric Sinornithosaurus had longer teeth to break through layers of feathers on its bird victims.


The discovery of features thought to be associated with a venom-delivery system in Sinornithosaurus stemmed from a study of the anatomy and ecology of Microraptor by the joint Chinese-KU team. They now are seeking to discover if Microraptor may have possessed a similar poison-delivery system.

Friday, December 18, 2009

'Screaming Roadrunner' Ran Circles Around Dinos

By Jennifer Viegas Thu Dec 17, 2009 05:00 PM ET Discovery News

During the Late Cretaceous, Mongolia's Gobi Desert was home to numerous dinosaurs, mammals and lizards. One of the most eye-catching, and possibly ear-splitting, residents was a newly identified bird.

The new species, which lived 71 to 75 million years ago, has been named Hollanda luceria, after the punk/country band Lucero and the Holland family, whose donations helped to support the research.

"Judging from the size of the hindlimb, Hollanda luceria most closely resembled the modern Southern Screamer," project leader Alyssa Bell, a researcher in the Dinosaur Institute at the Natural History Museum of Los Angeles County, told Discovery News.

The modern Southern Screamer's call has been likened to a blaring trumpet and a stadium horn.
For the study, which will appear in the February issue of the journal Cretaceous Research, Bell and her team analyzed the bird's remains, which were originally found in the southern Gobi Desert in 1997.

Previous research on avian anatomy concluded that bones in the third toe reflect how much time the bird spent moving on the ground.

The scientists studied these bones and compared them with those of other birds. Bell said the data "shows that our new bird was most likely a ground-foraging bird like a roadrunner or a chucao, implying that it spent a great deal of its time foraging or hunting on the ground."

Other fossils excavated at the site reveal that the newly identified bird was part of an ecosystem consisting of dinosaurs, such as Protoceratops and Velociraptor, mammals, lizards and other birds, like waterfowl Teviornis and the large, clawed Gobipteryx.

Bell doesn't think H. luceria preyed upon dinosaur eggs, "as they would have been too large for the bird to swallow; however, it probably would have been an active hunter of the small lizards and mammals as well as insects that lived in the environment."

The presence of so much diverse wildlife in the Gobi region during the Late Cretaceous, along with geological studies, suggests that this area was once similar to the Channel Country of central Australia or to the Nebraska Sand Hills.

"Thus, Hollanda's environment would have consisted of sand dunes, which had been stabilized by a covering of vegetation, and a continuous water supply that formed shifting streams and ponds," she said. "This interpretation is very different from early research that saw the Late Cretaceous Gobi as a desert of shifting sand dunes and sand storms."

Gareth Dyke, a paleontologist at University College Dublin, told Discovery News that the new research "is interesting," in part because, "Hollanda has quite an unusual ecology and is also well-preserved."

"It has very long legs compared to other birds known from the time and, from this part of the world, shows that early in their evolutionary history birds had evolved a range of ecological adaptations like fast 'road running,'" he added.

Given the Mongolian bird's connection to a musical group, Bell said Lucero "now joins the ranks of artists such as Mick Jagger, Neil Young, Simon and Garfunkel and Mozart in having a species named after them."

Tuesday, December 15, 2009

Woolly Mammoths Lasted Longer than Previously Thought

ScienceDaily (Dec. 15, 2009) — Extinct woolly mammoths and ancient American horses may have been grazing the North American steppe for several thousand years longer than previously thought. After plucking ancient DNA from frozen soil in central Alaska, a team of researchers used cutting-edge techniques to uncover "genetic fossils" of both species locked in permafrost samples dated to between 7,600 and 10,500 calendar years.

This new evidence suggests that at least one population of these now-extinct mammals endured longer in the continental interior, challenging the conventional view that these and other large species, or megafauna, disappeared from the Americas about 12,000 years ago.

"We don't know how long it takes to pinch out a species," says Ross MacPhee, Curator of Mammalogy at the American Museum of Natural History. "Extinctions often seem dramatic and sudden in fossil records, but our study provides an idea of what an extinction event might look like in real time, with imperiled species surviving in smaller and smaller numbers until eventually disappearing completely."

At the end of the Pleistocene, the geological epoch roughly spanning 12,000 to 2.5 million years ago, many of the world's megafauna, such as giant sloths, saber-toothed cats, dire wolves, stag-moose, and mammoths, vanish from the geological record. Some large species such as Equus caballus, the species from which the domestic horse derives, became extinct in North America but persisted in small populations elsewhere. Because of the apparent sudden disappearance of many megafaunal species in North America, some scientists have proposed cataclysmic explanations like human overhunting, an extraterrestrial impact, and the introduction of novel infectious diseases. The swiftness of the extinctions, however, is not suggested directly by the fossils themselves but is inferred from radiocarbon dating of bones and teeth discovered on the surface or buried in the ground. Current "macrofossil" evidence places the last-known mammoths and wild horses between 13,000 and 15,000 years ago.

But hard remains of animals are rarely preserved, difficult to find, and laborious to accurately date because of physical degradation. Because of this, MacPhee and co-authors Eske Willerslev of the University of Copenhagen in Denmark, Richard Roberts of the University of Wollongong in Australia, and Duane Froese of the University of Alberta in Canada decided to tackle the problem by dating the "last survivors" through dirt. Frozen sediments from the far north of Siberia and Canada can preserve small fragments of animal and plant DNA exceptionally well, even in the complete absence of any visible organic remains, such as bone or wood.

"In principle, you can take a pinch of dirt collected under favorable circumstances and uncover an amazing amount of forensic evidence regarding what species were on the landscape at the time," says Willerslev, director of the Centre for GeoGenetics at the University of Copenhagen. "The use of ancient DNA offers the possibility of being able to sample previous life within the last 400,000 years, freeing us from having to rely on skeletal and other macrofossil evidence as the only way to collect information about species that are no longer with us."

In order to prospect for genetic fossils, the team collected soil cores from undisturbed Alaskan permafrost. Wind-blown Stevens Village, situated on the bank of the Yukon River, fit the bill perfectly. Here, sediments were sealed in permafrost soon after deposition. Two independent methods (radiocarbon and optically stimulated luminescence) were used to date plant remains and individual mineral grains found in the same layers as the DNA.

"With these two techniques, we can be confident that the deposits from which the DNA was recovered haven't been contaminated since these lost giants last passed this way," said Roberts, director of the Centre for Archaeological Science at the University of Wollongong. "It's a genetic graveyard, frozen in time."

Cores collected at Stevens Village offer a clear picture of the local Alaskan fauna at the end of the last ice age. The oldest sediments, dated to about 11,000 years ago, contain remnant DNA of Arctic hare, bison, and moose; all three animals were also found in higher, more recent layers, as would be expected. But one core, deposited between 7,600 and 10,500 years ago, confirmed the presence of both mammoth and horse DNA. To make certain that the integrity of this sample had not been compromised by geologic processes (for example, that ancient DNA had not blown into the surface soils), the team did extensive surface sampling in the vicinity of Stevens Village. No DNA evidence of mammoth, horse, or other extinct species was found in modern samples, a result that supports previous studies which have shown that DNA degrades rapidly when exposed to sunlight and various chemical reactions.

"The fact that we scored with only one layer is not surprising," says MacPhee. "When you start going extinct, there will be fewer and fewer feet on the ground, and thus less and less source material for ancient DNA such as feces, shed dermal tissues, and decaying bodies."

The team also developed a statistical model to show that mammoth and horse populations would have dwindled to a few hundred individuals by 8,000 years ago.

"At this point, mammoths and horses were barely holding on. We may actually be working with the DNA of some of the last members of these species in North America," says permafrost expert Froese, associate professor in the Department of Earth and Atmospheric Sciences at the University of Alberta. "The Yukon Flats includes large shifting river bars with an abundance of high quality forage where large mammals can and could make a living. There may have been a handful of similar sites in Alaska, hosting small remnant populations," says Froese.

"Dirt DNA has lots of exciting potential to contribute to extinction debates in other parts of the world too, as well as a range of archaeological questions," said Willerslev, who also points out that the approach is not restricted to looking back at the past. "We can also use it to make a list of modern species living in any particular location," he said. "This kind of information is really valuable for studies of animals that are hard to detect, and there are some neat forensic applications too."

The new paper is published in the Proceedings of the National Academy of Sciences. In addition to Willerslev, MacPhee, Froese, and Roberts, authors include James Haile, Morten Rasmussen, and Thomas Gilbert of the University of Copenhagen in Denmark; Alberto Reyes, and Simon Robinson of the University of Alberta in Canada; Lee Arnold and Martina Demuro of the University of Wollongong in Australia; Rasmus Nielsen and Kasper Munch of the University of California at Berkeley; Barry Brook, Jeremy Austin, and Alan Cooper of the University of Adelaide in Australia; Ian Barnes of the Royal Holloway University of London in the United Kingdom; and Per Moller of Lund University in Sweden. The research was funded by the Danish National Research Foundation, the Natural Science and Engineering Research Council of Canada, the Alberta Ingenuity Foundation, the Australian Research Council; Discovery Communications, Inc.; the AHRB, and the Arts and Humanities Research Council.