For a long time people thought pterosaurs could only glide and soar, and were not strong enough to flap their wings. In the 20th century, after aeroplanes had been invented, our understanding of flight advanced. English palaeontologists showed that pterosaurs could fly, and Tilly Edinger showed that by the end of the Jurassic, pterosaur brains were more like that of modern birds than of "Archaeopteryx". Recent work has used working model to simulate their flight. The wing membrane was about 1mm thick, with a tough skin and had long fibres reinforcing it. This can be clearly seen in some of the fossils. The structure helped the wings survive the stresses of flight. The larger pterosaurs were mainly soarers, as is the case with birds today.
How pterosaurs moved on the ground has been something of a mystery. It is most likely that they walked on four legs while on the ground, as fossil tracks have been found showing they used both their legs and hands to support them.
Pterosaurs also had special bones. They were extremely light (even more than bird's wings – some were almost as thin as a piece of paper), and some were almost hollow. Tiny holes in the bones are evidence of air sacs which extended into the vertebrae and limb bones, as it does with birds. Also present were supporting struts which made these bones stronger. With these special bones, even the largest of pterosaurs, "Quetzalcoatlus", probably weighed less than 200 pounds.
Pterosaurs were probably egg-layers, and some eggs have been found at pterosaur sites. There is evidence that some species, such as "Pteranodon", had sexual dimorphism (sexes looked different). The skeletons with large cranial (head) crests and small pelvic canals were presumably males. Where several specimens occur at the same location, adults can be distinguished from juveniles. Evidence of tooth wear in "Eudimorphodon" suggests the young were insectivorous, while the adults ate fish. Development took place rapidly in these warm-blooded reptiles, and much of their life-style parallels that of birds. The high energy-level needed for flight explains why both reptilian forms (pterosaurs and birds) developed similar metabolism. In many respects, birds and pterosaurs are good examples of convergent evolution.
Quetzalcoatlus
Quetzalcoatlus was a huge pterosaur, the largest animal ever to fly. It had a 10 to 12 meters wing-span (33/40 feet), but was light in construction (~200 pounds).
"Quetzalcoatlus" had an unusually long neck, and when it stood on the ground it was as tall as a giraffe.
Its fossil record is from the Upper Cretaceous of North America, 70–65.5 million years ago. "Quetzalcoatlus" became extinct at the K/T extinction event.
A college student found the first "Quetzalcoatlus" fossil in Big Bend National Park in Texas. His name was Douglas Lawson, from the University of Texas in Austin. When he was in the park, he saw a bone sticking out of a rock. Since the bone looked hollow, like the bone of a bird, he thought it was part of a flying creature – and he was right. With his professor's help, he kept digging until lots of bones from an arm and wing were found. The rest of the animal's body was missing. Many others have looked for the rest of that huge pterosaur, but it has never been found. Other fossils of "Quetzalcoatlus" have been found, but none are as big as the one Lawson found.
Since "Quetzalcoatlus" was so large, two researchers suggested it was too heavy to fly. This would have been astonishing, because in the whole fossil record there is no flightless pterosaur. It has been thought their mobility on the ground was too poor for them to survive without flight. However, a recent discussion of this idea concluded they probably could fly after all. Another analysis suggested their flight was quite strong. Since we have only a few bones, the question of weight cannot be settled at present.
The feeding habits of "Quetzalcoatlus" (which had a long beak with no teeth) are unknown. This question, and its flight, are still being discussed. The lack of a more detailed skeleton is the main problem in reaching conclusions. Two theories have been proposed.
One idea is that it ate fish, by flying with its jaw in the water, and snapping up fish when it hit them. Texas was largely covered by the Western Interior Seaway at the time. "Of these proposed lifestyles, in-flight piscivory [fish-eating] appears to have gained the most acceptance, with skim-feeding being a frequently suggested foraging method.
The other theory is that it fed on land, partly as a carrion feeder, like vultures and buzzards, and foraged for small animals. This view is gaining ground, because the jaw does not show the adaptations for skimming found in modern birds who catch fish this way.
In flight, it was certainly a soarer, flying on up-currents of air in a warm environment, and its remains come from a site which was far inland in the Cretaceous.
"Quetzalcoatlus" was shown in the movie "When Dinosaurs Roamed America" eating a dead "Triceratops" carcass.
Mozilla (web browser)
Mozilla was a web browser that was made open source. It was developed by Mozilla Foundation. It was the base of Mozilla Firefox.
Fedora (operating system)
Fedora is a distribution (or "distro") of Linux developed by the community-supported Fedora Project and sponsored by Red Hat. It is designed to be safe and is used by companies and governments. Fedora's mission statement is: "Fedora is about the rapid progress of Free and Open Source software."
Linus Torvalds, author of the Linux kernel, says he uses Fedora because it had fairly good support for PowerPC when he used that processor architecture. He became used to the operating system and continues to use it.
"Fedora Core 1" was the first version of Fedora and was released on November 6, 2003, and was codenamed Yarrow. Fedora Core 1 was based on Red Hat Linux 9 and shipped with version 2.4.19 of the Linux kernel, version 2.4 of the GNOME desktop environment, and version 3.1.4 of KDE (the K Desktop Environment).
"Fedora Core 2" was released on May 18, 2004, codenamed Tettnang. It shipped with Linux 2.6, GNOME 2.6, KDE 3.2.2, and SELinux XFree86 was replaced by the newer X.org, a merger of the previous official X11R6 release, which additionally included a number of updates to Xrender, Xft, Xcursor, fontconfig libraries, and other significant improvements.
"Fedora Core 3" was released on November 8, 2004, codenamed Heidelberg. This was the first release of Fedora Core to include the Mozilla Firefox web browser, as well as support for the Indic languages. This release also replaced the LILO boot loader with GRUB. SELinux was also enabled by default, but with a new targeted policy, which was less strict than the policy used in Fedora Core 2. Fedora Core 3 shipped with GNOME 2.8 and KDE 3.3. It was the first release to include the new Fedora Extras repository.
"Fedora Core 4" was released on June 13, 2005, with the codename Stentz. It shipped with Linux 2.6.11, KDE 3.4 and GNOME 2.10. This version introduced the new Clearlooks theme, which was inspired by the Red Hat Bluecurve theme. It also shipped with the OpenOffice.org 2.0 office suite, as well as Xen, a high performance and secure open source virtualization framework. It also introduced support for the PowerPC CPU architecture, and over 80 new policies for SELinux.
The last two cores introduced specific artwork for that version. This is a trend that has continued in later Fedora versions.
"Fedora Core 5" was released on March 20, 2006, with the codename Bordeaux, and introduced the Fedora Bubbles artwork. It was the first Fedora release to include Mono and tools built with it such as Beagle, F-Spot and Tomboy. It also introduced new package management tools such as pup and pirut ("see Yellow dog Updater, Modified"). This release replaced the old LinuxThreads, with the Native POSIX Thread Library.