North Pole Dinosaurs Lived Short, Hard Lives

The winter holiday season often portrays the North Pole as a cozy fantasyland, but new research on dinosaurs that lived there shows that Arctic life has been tough for millions of years, with North Pole dinos finding it hard to reach their 20th birthday.

The findings, published in the journal Historical Biology, offer a rare look at dinosaur life stages. Fossils from high latitudes better express growth bands that reveal how these animals grew up. Scientists can then analyze them similar to how they study tree rings.

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"We determine growth rates by looking at the number and spacing of the growth bands in a cross section of a femur," co-author Patrick Druckenmiller explained to Discovery News. "We measure the distance of each band from the center of the bone as a proxy for body size. In this case, it's presented as a percentage of total length. Growth banding becomes narrower as the growth rate progressively tapers off later in life."

Following this process, the researchers determined some polar dinosaurs grew rapidly as juveniles, became sexually mature at about age 9, and died at around age 19 (assuming they didn’t bite the dust due to disease, an accident, or for some other reason).

Druckenmiller, curator of Earth Sciences at the University of Alaska Museum, and colleague Gregory Erickson focused their research on Pachyrhinosaurus femur bones excavated from the early Maastrichian (about 65 to 70 million years ago) of Prince Creek Formation in Northern Alaska.

“Pachyrhinosaurus is a member of the horned dinosaur family Ceratopsidae,” Druckenmiller said. "It was a large, probably gregarious, herbivore. Instead of having thick horns over the eyes and nose area (think of the iconic Triceratops) it had large 'bosses,' which are bony growths that give the skull a very thick appearance."

This explain the dinosaur's name: Pachy, meaning "thick and heavy," and rhino, meaning "nose."

This dinosaur was far from being alone in the Arctic, however. The North Slope of Alaska was home to numerous other plant-eating and carnivorous dinosaurs. The most common was a duck-billed dino very similar to Edmontosaurus. The region was also home to a large tyrannosaurid, a few dromaeosaurs, and the human-sized Troodon.

Pachyrhinosaurus would have been preyed upon by the carnivores, but because of its size -- about 26 feet long and weighing around 4 tons -- Druckenmiller suspects few hunters "took on an adult-sized healthy animal."

Animals that would be expected from this area, such as lizards, crocodilians and turtles, have never been found. One reason could be that they had trouble getting to Alaska.

Hendrik Poinar, a McMaster University anthropologist who has also studied North Pole animals, told Discovery News that the Bering Land Bridge, which joined Alaska to eastern Siberia, may have been more of a barrier than a gateway.

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"I think it is increasingly clear that the bridge was indeed a filter more than a bridge," Poinar said. “It certainly was not a freeway, and it makes us think about what ecological function it clearly played over the last several millennia.”

Somehow dinosaurs did make it to Alaska, but they faced "annually freezing winter temperatures," according to Druckenmiller, who explained that scientists determine past climates based on plant remains. The Arctic, however, was somewhat warmer than it is today at certain latitudes.

Nevertheless, he said, "Long, dark winters were probably a major influence on anything that lived there."

Druckenmiller and other researchers hope future studies on North Pole dinosaurs might reveal information about migratory behaviors, overwintering strategies, and dinosaur physiology. The world's largest collection of Arctic dinosaurs is housed within the Earth Science Collection at the University of Alaska Museum in Fairbanks.

Archaeopteryx

Archaeopteryx is a theropod dinosaur that is closely related to birds. It is the first dinosaur who could fly or do something like flying. Archaeopteryx lived in the Late Jurassic in Germany. Archaeopteryx was only 50 centimeters long. It was  size of a raven.


Unlike modern birds Archaeopteryx had small teeth and many other theropod characteristics. It was discovered in 1861. Archaeopteryx is probably a direct ancestor of modern birds.


The body plumage of Archaeopteryx is less well documented and has only been properly researched in the well-preserved Berlin specimen. Thus, as more than one species seems to be involved, the research into the Berlin specimen's feathers does not necessarily hold true for the rest of the species of Archaeopteryx. In the Berlin specimen, there are "trousers" of well-developed feathers on the legs; some of these feathers seem to have a basic contour feather structure but are somewhat decomposed. 




However, in part they are firm and thus capable of supporting flight. Archaeopteryx wings were quite large, which would have resulted in a low stall speed. The first detailed study of the hind wings by Longrich in 2006 suggested that the structures formed up to 12% of the total airfoil. This would have reduced stall speed by up to 6% and turning radius by up to 12%.


Over the years, eleven body fossil specimens of Archaeopteryx and a feather that may belong to it have been found. All of the fossils come from the limestone deposits, quarried for centuries, near Solnhofen, Germany.

Apatosaurus

Apatosaurus means 'deceptive lizard'. You may know it as Brontosaurus. Apatosaurus lived 150 million years ago in North America. This enormous creature was 23 meters long and weighed 25 tons.

Apatosaurus was huge sauropod approaching 23 meters. It reached its maximum size in about 10 years. Its family includes some of the longest creatures ever to walk the earth, including Diplodocus, Supersaurus, Suuwassea. 

It was believed that sauropods like Apatosaurus were too massive to support their own weight on dry land.Apatosaurus was the second most common sauropod in the Morrison Formation ecosystem, after Camarasaurus. It may have been a more solitary animal than other Morrison Formation dinosaurs.

Nathan Myhrvold carried out a computer simulation of the tail, which in diplodocids like Apatosaurus was a very long, tapering structure resembling a bullwhip. This computer modeling suggested that sauropods were capable of producing a whip-like cracking sound of over 200 decibels, comparable to the volume of a cannon.

Large Nest of Juvenile Dinosaurs, First of Their Genus Ever Found

A nest containing the fossilized remains of 15 juvenile Protoceratopsandrewsi dinosaurs from Mongolia has been described by a University of Rhode Island paleontologist, revealing new information about postnatal development and parental care. It is the first nest of this genus ever found and the first indication that Protoceratops juveniles remained in the nest for an extended period.

The findings were reported in the most recent issue of the Journal of Paleontology.

David Fastovsky, URI professor of geosciences, said the bowl-shaped nest measuring 2.3 feet in diameter was found in the Djadochta Formation at Tugrikinshire, Mongolia.

"Finding juveniles at a nest is a relatively uncommon occurrence, and I cannot think of another dinosaur specimen that preserves 15 juveniles at its nest in this way," he said.

The analysis of the 70-million-year-old nest by Fastovsky and his colleagues found that all 15 dinosaurs -- at least 10 of which are complete specimens -- were about the same size and had achieved the same state of growth and development, suggesting they represent a single clutch from a single mother. The discovery also indicates that the young dinosaurs remained in the nest through the early stages of postnatal development and were cared for by their parents.

Protoceratops grew to about 6 feet long and may have taken as long as 10 years to reach full size. Those Fastovsky found in the nest were likely less than one year old when they died.

"I suspect that the preserved animals were rapidly buried by the shifting, accumulating sands that must have constituted the bulk of sedimentation in this setting," he said. "Death likely occurred during a desert sandstorm. My guess is that the initial and present-day dryness contributed significantly to the superb preservation, not just of Protoceratops, but of all the fossils from this unit."

Fastovsky calls Protoceratops "a fascinating and unexpected mass of contradictions." It is an herbivore that lived in a sand sea much like the Sahara Desert and likely bestowed significant parental care on a relatively large number of offspring, perhaps because it lived where mortality was quite high.

A wide variety of theropod dinosaurs lived in Mongolia at the time, some of which, including the notorious Velociraptor, probably ate young Protoceratops'.

"Juvenile Protoceratops mortality may have been rather high, not only from predation but from a potentially stressful environment, and large clutches may have been a way of ensuring survival of the animals in that setting," he said. "Nonetheless, if preservation is any indicator of abundance in life, then during the time represented by the Djadochta Formation, Protoceratops were a very common feature of Mongolian Late Cretaceous desert landscapes."

Madagascar Dinosaur Bone Is Most Massive Osteoderm Ever Found

What more can we learn about long-necked dinosaurs that we don't already know? A Macalester professor and her colleagues have found that Madagascar dinosaurs carried giant, hollow bones in their skin that may have helped them survive the harsh environments they inhabited. This discovery has shed new light on the anatomy and function of these bones in the biggest animals to ever walk on land.

"This is the biggest osteoderm ever found for any backboned-animal," said Curry Rogers, "The fact that it's hollow debunks all sorts of ideas about how these bones functioned in long-necked dinosaurs."

Osteoderms are bones embedded within the skin and are common among reptiles and some mammals. They create the unique pattern on the backs of crocodiles, the armor body covering on armadillos, and the distinctive plates of dinosaurs like Stegosaurus and Ankylosaurus.

Among the long-necked dinosaurs called sauropods, osteoderms are found in one globally distributed subgroup -- the Titanosauria. For more than a century, paleontologists have been trying to figure out how these weird bones were distributed in the skin of the long-necked titanosaurs and what they might have been used for. Were they for protection, like in armadillos and crocodiles? Were they for display? Could they have helped regulate body temperature?

"Knowing something about the lives of these dinosaurs, particularly in the context of the drought-prone paleoenvironment they lived in, tells us that osteoderms may have been important for storing minerals, which allowed Rapetosaurus to survive the rough times," said Curry Rogers.

Instead of the hundreds of interlocking plates in living animals with osteoderms, Rapetosaurus had only a few osteoderms in its skin. This means that they were less likely to serve as protection or as body temperature regulators.

"The discovery of these giant osteoderms provides new insights into what these bizarre structures may have done for the dinosaurs that had them," said Curry Rogers. "It helps us clarify what these Madagascar dinosaurs looked like with their skin on. Our sample also includes both adult and juvenile osteoderms, which tells us how the osteoderms changed over the lifespan of the dinosaur," said Curry Rogers.

In the vicinity of the osteoderm, the skin of Rapetosaurus would have stretched, making it in places up to seven times as thick as an elephant's skin. The bone also hollowed out over the course of the dinosaur's lifespan. So even though it was massive, in the adult dinosaur osteoderms would've actually been fairly lightweight.

Curry Rogers is the lead author of the Nature Communications paper. Her collaborators include Michael D'Emic (University of Michigan and Georgia Southern University), Raymond Rogers (Macalester College), Matthew Vickaryous (Ontario Veterinary College, University of Guelph), and Amanda Cagan, who graduated with a biology degree from Macalester in 2010.

Source: http://www.sciencedaily.com/releases/2011/11/111129125014.htm