Dinosaurs and Other Reptiles from the Mesozoic of Mexico

Jurassic Period Facts

---

Free download. Book file PDF easily for everyone and every device. You can download and read online Dinosaurs and Other Reptiles from the Mesozoic of Mexico file PDF Book only if you are registered here. And also you can download or read online all Book PDF file that related with Dinosaurs and Other Reptiles from the Mesozoic of Mexico book. Happy reading Dinosaurs and Other Reptiles from the Mesozoic of Mexico Bookeveryone. Download file Free Book PDF Dinosaurs and Other Reptiles from the Mesozoic of Mexico at Complete PDF Library. This Book have some digital formats such us :paperbook, ebook, kindle, epub, fb2 and another formats. Here is The CompletePDF Book Library. It's free to register here to get Book file PDF Dinosaurs and Other Reptiles from the Mesozoic of Mexico Pocket Guide.

Reconstruction of the face of Brachiosaurus. The remaining saurishian dinosaurs were theropods, the bipedal carnivores exemplified by Allosaurus. Deciphering the evolutionary relationships of the theropods is difficult due to the often fragmentary nature of theropod fossils. Current thought is that there were several groups of theropods, and that one group, the carnosaurids contained the largest of the carnivores such as Allosaurus. Another theropod group was the coelurosaurids, which containd the birds and smaller carnivores such as ornithomimids, "raptors", and the tyrannosaurs.

The carnosaurs, such as the Jurassic-aged Allosaurus , had long narrow skulls, strong forelimbs, and a variety of horns or knobs projecting from the skull. Allosaurus skeleton displayed at the Cleveland Museum of Natural History.

About the Author

One of the hottest topics of discussion for years was the hypothesis, proposed by Charles Darwin, that birds were descendants of dinosaurs. The shared derived characteristics of birds and dinosaurs include the structure of the hip, egg-laying, as well as a great deal of anatomical similarity.

The discovery of Archaeopteryx , the "first bird" added fuel to this discussion. Archaeopteryx has a skeleton that retains a number of dinosaurian traits such as scales on the neck, teeth in the mouth, a jointed tail, and grasping fingers on the wings. It also has avian characteristics such as hollow bones and flight feathers.

Dinosaurs and Other Reptiles from the Mesozoic of Mexico

Many "dinosaur" specimens have, upon the discovery of feathers, been reassigned to fossil bird species. The discovery of feathers on some dinosaurs has further blurred what was once a clear-cut distinction between birds and dinosaurs. Cladistic analyses have repeatedly shown that birds and some groups of dinosaurs form a well-defined clade. Most paleontologists today feel safe in stating that birds are dinosaurs. Archaeopteryx , once considered the first bird. The fossil is from the Solnhoefen Limestone Jurassic of Germany.

Reconstruction of Archaeopteryx. There have been other fossils interpreted as birds, specifically Protoavis from the Triassic of Texas and Confuscornis from the Jurassic of China. While some paleontologists accept Protoavis as representing a bird that is closer to modern birds than is Archaeopteryx , there is an equally large camp who consider Protoavis as an early dinosaur that had evolved several bird-like adaptations by convergent evolution. Confuciusornis sanctus , the oldest bird with a beak, from Liaoning Province, China. This species retained some of the primitive features seen in Archaeoptyeryx , such as free claws on the wing, along with more advanced features such as the lack of teeth in the bill.

Convert to and from PDF

The consensus view is that the coelurosaurs are the dinosaurian group from which the "avian dinosaurs" evolved. Members of this group include the small predatory dinosaurs such as Compsognathus again a star of the Jurassic Park movies , and Velociraptor. The ornithischian dinosaurs became more significant elements of the dinosaurian faunas during the Jurassic, and especially so during the Cretaceous period.

The ornoithischians are the so-called bird-hipped dinosaurs. However, the resemblance of hip structure between birds and this group is no longer considered evidence for the rise of birds from ornithischians, but as a result of convergent evolution. A major group of ornithischians during the Jurassic was the stegosaourids, exemplified by the genus Stegosaurus , the state dinosaur of Colorado. These quadrupedal animals sported spiked tails and large flat armor plates arrayed along the spine.

Boundaries

These plates functioned for regulation of body heat. Stegosaurus was about 9 meters long and weighed about 2 tons.

Dinosaurios and Lagartos, Oh My! Ancient Creatures of Mexico Given English Touch

Even among dinosaurs it is noteworthy for its incredibly small brain. Stegosaurus in foreground under a gymnosperm tree and a tree fern, with a flying reptile in the background. The ankylosaurs were the armored ornithischians. They appeared in Europe during the late Jurassic and became more abundant during the Cretaceous. Ankylosaurs bore armor and spikes on their backs and may have defended themselves by using their tails which often had armor balls at the tips and by their dense back armor.

Another group of ornithischians was the ornithopods. Among the earliest ornithopods was Camptosaurus , a 17 foot long Jurassic dinosaur from Europe and North America. Camptosaurus reached Australia by the early Cretaceous.

During the Cretaceous the ornithopods became much more diverse. The major geological events of the Jurassic involved the continued separation of the former parts of Pangaea. During this period the northern Atlantic continued to open, with a small connection remaining between North America and Europe. In the southern hemisphere the former parts of Gondwana completely separated, with Antarctica and Australia being the last of the modern southern continents to form.

Great seaways flooded most of the continents, possibly caused by the increased rates of sea-floor formation at the newly forming mid-Atlantic ridge.

Active tectonic plate margins along the then-western coasts of the Americas began or continued the mountain-building that would become the Rocky Mountains in North America and the Andes Mountains in South America. Reconstruction of the continents during the late Jurassic. The Jurassic saw two minor mass extinctions. The first of these occurred about one-third of the way through the period, during the early Jurassic.

At the close of the Jurassic, about million years ago, a second minor mass extinction happened, affecting mostly the ammonoids, marine reptiles, bivalves and certain dinosaur groups such as the stegosaurs and the giant sauropods. Only one stegosaur escaped this extinction, Dravidosaurus , a small stegosaurid restricted to the Cretaceous of India which was an island at that time.

The causes of both of these extinctions are not clear. The Cretaceous period, spanning the time interval from to 65 million years ago, saw the final phases of the opening of the Atlantic Ocean, as well as the northward migration of India toward its collision with Asia during the Tertiary period of the Cenozoic era. The last of the major forms of plant life, the angiosperms, appeared near the beginning of the period. Dinosaurs continued their diversification, with the increasing dominance of the herbivorous ornithischians. The Cretaceous ended with the famous mass extinction that resulted in the extinction of the non-avian dinosaurs, the swimming reptiles, pterosaurs, ammonites and other creatures, nearly three-fourths of all life on Earth in fact.

The bivalves recovered from the Jurassic extinctions and again became major reef-formers in the numerous shallow marginal seas that encroached onto the continents during the Cretaceous. Reconstruction of a Cretaceous seafloor. Note the large ammonite on the right, the belemnites in the center, and the gastropods and bivalves on the seafloor.

Associated Data

Exogyra sp. In this view we see the top of one of the shells. The lower shell was usually quite different in shape.

Ammonites continued their dominance, as did their relatives the straight-shelled belemnites. Modern teleost fish appeared during the Cretaceous and may have competed for the same prey as the ammonites. The teleost fish were apparently stronger and swifter swimmers than the fish of the Jurassic. Some paleontologists speculate that the extinction of ichthyosaurs during the Cretaceous may have been hastened by the rise of these new faster fish that would have been difficult for the ichthyosaurs to catch and eat.

Eubranoceras sp. The specimen is 2.

Baculites , a genus of straight-shelled cephalopods, was particularly abundant in the Cretaceous seas. Note the elaborate suture patterns in the fossil specimen below. Left image Baculites was a straight-shelled cephalopod, about two feet in length, that presumably scavenged the bottom in search of food. Right image, Baculites. Notice the extremely intricate suturing between septa. The plesiosaurs from the Jurassic continued their diversification.

Ichthyosaurs, however, declined during the early Cretaceous before becoming extinct well before the end-of-the-Cretaceous extinction. Both the long-necked plesiosaurs, and the short-necked pliosaurs were present during the Cretaceous. Despite inevitable competition and changes in their diets as new prey evolved, plesiosaurs were doing well up until the extinction at the close of the Cretaceous.

To the list of swimming reptiles we add the mosasaurs, essentially swimming "lizards". These ferocious predators reached lengths to 30 feet 9 meters. Mosasaurs are usually considered relatives of the monitor lizards, although some recent analyses suggest a closer link to snakes is a distinct possibility. Mosasaurs were predators of the Cretaceous seas. Many ammonite fossils have been found that have tooth marks suggesting mosasaurs actively sought and ate ammonites. Some paleontologoists believe that mosasaurs became so successful because they were able to utilize the role in the marine environment that was opened once the ichthyosaurs went extinct.

Mosasaurs apparently gave birth to live young and perhaps had some level of parental care for their young. A mosasaur from the Cretaceous approximately million years old of southern Georgia. The specimen is 26 feet long and almost completely original material. Mosasaur dentition was well-adapted for catching fish, ammonites, and other free-swimming prey. The recurved teeth prevented prey from escaping once caught. Perhaps the greatest change in the terrestrial life of the Cretaceous was the rise and diversification of the flowering plants, the angiosperms. The angiosperms, the last of the seed plant groups to evolve, appeared over million years ago during the the beginning of the Cretaceous.

All members of this group produce flowers. Within the female parts of the flower angiosperms produce a diploid zygote and triploid endosperm.

• Spring Recipes, 2nd Edition: A Problem-Solution Approach
• Recent Advances in Mechanism Design for Robotics: Proceedings of the 3rd IFToMM Symposium on Mechanism Design for Robotics
• Agricultural Finance: From Crops to Land, Water and Infrastructure
• In Black and White: The Life of Sammy Davis, Jr.
• CMOS biotechnology