Dinosaur Dads Took Care of Nest
By Erik Stokstad
ScienceNOW Daily News 18 December 2008
The movie Jurassic Park gave advanced, birdlike dinosaurs a fearsome reputation--swift, intelligent, and deadly. Now it turns out that they had a softer side. Researchers report that males in three species were stay-at-home dads that incubated the eggs in their nests.
There's plenty of evidence to suggest that dinos baby-sat their offspring. A predatory dinosaur called Oviraptor, for example, was discovered in the Gobi Desert in 1993, its fossilized remains protecting a brood of eggs. In addition, dinosaurs' closest living relatives, birds and crocodiles, display nesting behavior: Female crocs guard the eggs, whereas in birds the gender of the stay-at-home-parent depends on the species. But whether male or female dinos had nest duty has remained a mystery.
For the new research, paleontologist David Varricchio of Montana State University in Bozeman compared three species of birdlike dinosaurs--Oviraptor, Citipati, and Troodon--with birds and crocodiles. All three types of dinosaurs were found on nests, and those nests contain large clutches of eggs, as many as 30 each. Varricchio and his colleagues investigated whether they could discern the nesting behavior from the relationship of the clutch size and the animal's body size. Measurements in 433 living birds and crocodiles revealed that, for a given body size, species in which males took care of the nest tended to have the largest clutches. The next-largest clutches were cared for by mothers. Mom-dad partnerships had the smallest clutches. Extrapolated to dinosaurs, the data revealed a pattern of paternal care in the ancient beasts.
Another line of evidence in the paper comes from Gregory Erickson, a biologist at Florida State University in Tallahassee. His studies of dinosaur bone tissue showed that none of the seven specimens associated with nests showed signs of changes associated with egg laying, such as medullary tissue (ScienceNOW, 2 June 2005). That's not sure-fire proof the nest-caretakers were male, he notes, but it's consistent with the hypothesis. The findings are reported in tomorrow's issue of Science.
Richard Prum, an ornithologist at Yale University, says he never expected paternal care in dinosaurs. But with their dinosaur ancestors showing more and more traits once thought to be exclusive to birds, such as feathers, he says the finding makes sense. It also points to a question on the reproductive frontier: Did dinosaurs practice polygamy?
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Blame the Sun for a Cloudy Day?
By Phil Berardelli
ScienceNOW Daily News
17 December 2008
An Australian researcher has linked the sun's magnetic activity to rainfall patterns in his country over the past century. The connection is solid enough that meteorologists might be able to use it to make better long-term weather predictions. But experts remain cautious about the wider implications of the findings.
Scientists have long known that the sun plays a key role in Earth's weather patterns. For example, the number of sunspots on its surface--dark zones of intense magnetic activity--peaks about every 11 years, followed by a period of dormancy. The cycle causes swings in sea-surface temperatures--more sunspots mean warmer oceans, and fewer mean chillier waters--but the effect is small. There's also a 22-year cycle, in which the sun changes the polarity of its magnetic field, but it's unclear how that phenomenon affects Earth.
Now geographer Robert Baker of the University of New England, Armidale, in Australia, has linked solar magnetic activity to Earth's climate--at least regionally. Using sunspot counts and Australian meteorological data, as well as NASA satellite data for more recent years, he tracked sunspots and rainfall in Australia from 1876 to 2006. In this month's issue of Geographical Research, Baker reports that the amount of rainfall in most regions of the country tracked the 22-year magnetic cycle almost exactly. "It was unbelievable," Baker says. At the height of magnetic activity, rainfall across most of the country was plentiful. At the other end of the cycle, many of those same regions experienced severe droughts. The findings are particularly compelling, Baker says, because even though the lengths of the magnetic cycles are not precise and can vary by several years, the rainfall patterns followed them.
So what's behind the connection? Baker thinks it has to do with the amount of ultraviolet (UV) radiation hitting Earth. When the reversing of polarity approaches, he explains, the sun's magnetic field weakens, allowing more UV energy to reach our planet. More UV radiation kills off some of the oceans' plankton, which produce dimethyl sulfide, one of the primary atmospheric chemicals involved in cloud formation, and fewer clouds mean less rainfall.
Based on the 130 years of data, Baker predicts that the current solar cycle, which reached a minimum in 2007, will continue a bit longer. In fact, he says, "there could be a 100-year minimum in solar activity," meaning much of Australia could experience a prolonged drought.
"This could be an important paper," says climatologist John Christy of the University of Alabama, Huntsville. He explains that current climate models don't give the solar effect much weight in general, because scientists think it is overwhelmed by the buildup of greenhouse gases in the atmosphere. But if there's a mechanism by which the sun's variations are tied directly to weather patterns, such as the effect of UV radiation on cloud formation, he says, the sun may have a greater impact than the models are showing. As a result, the models might not be creating an accurate picture for the future.
Solar-terrestrial physicist Mike Lockwood of the University of Southampton in the U.K. says that the paper suggests a previously unknown effect caused by the solar magnetic cycle. "If the connection [between UV radiation and precipitation] proposed here were real," he says, "it would be both highly significant and very illuminating." On the other hand, Lockwood says, the paper contains no statistical tests, and connections such as the one it suggests "can arise readily by chance, even for extended intervals."
Source:Sciencenow
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Researcher discovers new giant toothless pterosaur
The finding is significant because it originated in Brazil and is the only example of the Chaoyangopteridae, a group of toothless pterosaurs, to be found outside China and is the largest one ever discovered.
Mark Witton identified the creature from a partial skull fossil from which he was able to estimate that it would have had a five-metre wingspan - bigger than a family car - and would stand over one metre tall at the shoulder.
He said: “Some of the previous examples we have from this family in China are just 60 centimetres long - as big as the skull of the new species. Put simply, it dwarfs any chaoyangopterid we’ve seen before by miles.”
He has christened the new species Lacusovagus, meaning ‘lake wanderer’, after the large body of water in which the remains were buried. Witton, who belongs to the University’s School of Earth and Environmental Studies (SEES), published his findings in the journal Palaeontology in November.
He was asked to examine the specimen which had lain in a German museum for several years after its discovery in the Crato Formation of the Araripe Basin in North East Brazil, an area well known for the its fossils and their excellent state of preservation. However, he said that this fossil was preserved in an unusual way, making its interpretation difficult.
“Usually fossils like this are found lying on their sides but this one was
lying on the roof of its mouth and had been rather squashed which made even figuring out whether it had teeth difficult. Still, it’s clear to see that Lacusovagus had an unusually wide skull which has implications for its feeding habits - maybe it liked particularly large prey. The remains are very fragmentary, however, so we need more specimens before we can draw any conclusions.”Witton said: “The discovery of something like this in Brazil - so far away from its closest relatives in China - demonstrates how little we actually know about the distribution and evolutionary history of this fascinating group of creatures.”
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