Monday, February 16, 2009

Until the 1980s, there was ongoing controversy (occasionally reflected in cryptozoological literature) over whether dinosaurs had a single ancestor or many different ones. In the current view, it appears that Richard Owen had it right in 1842 when he invented the name Dinosauria (“terrible reptiles”), based only on three known fossil genera that he thought had one common ancestor. The defining characteristic of the Dinosauria is now considered to be (along with a few other minor skeletal characteristics of the femur, humerus, ankle, and foot) a ball-andsocket joint at the hip, like the mammals, that supports the body weight and allows for an erect, bipedal gait in certain types. As a group, they flourished for 160 million years, from the Late Triassic to the end of the Cretaceous (225–65 million years ago). The most primitive dinosaur yet found is the 3-foot-long Eoraptor, discovered in northwestern Argentina in 1991.

Not all huge fossil reptiles were dinosaurs. The flying pterosaurs, the marine plesiosaurs and mosasaurs, the diapsids Tanystropheus and Champsosaurus, the mammal-like therapsids— none of these are classed with the dinosaurs.

The Superorder Dinosauria is subdivided into two orders, the Saurischia and the Ornithischia.

The Saurischia included carnivorous, bipedal therapods such as Tyrannosaurus and the herbivorous, long-necked sauropodomorphs such as Apatosaurus. They had in common elongated necks, long second fingers, and skeletal cavities housing air-filled sacs connected to the lungs. It was this type of dinosaur that survived extinction at the end of the Cretaceous in the form of Birds.

The Ornithischia included dome-headed and horned cerapods (such as Iguanodon and Triceratops) and the armored thyreophorans (such as Stegosaurus and Ankylosaurus). They shared key characteristics of the jaws and teeth that enabled them to chew plants efficiently.

Giganotosaurus may have been the largest carnivorous animal that ever lived on land. A theropod dinosaur from the Early Cretaceous of Argentina that was first described in 1995, it was at least 42 feet from nose to tail tip. Vertebrae from a related species yet unnamed that was discovered in Patagonia in 2000 indicate an even greater length of 45 feet. The largest Tyrannosaurus rex was only 40 feet long.

At 110–120 feet, the herbivorous sauropod Seismosaurus of the Late Jurassic of New Mexico is the longest land vertebrate yet discovered, weighing in at 33 tons. Its tail alone was about 50 feet, and its head and neck were nearly that length. The Cretaceous sauropod Argentinosaurus of Patagonia may also have attained this size, though it is only known from vertebrae and limb bones. In late 1999, some vertebrae from a possibly even larger sauropod were discovered in southern Patagonia; preliminary estimates gave it a length of 167 feet.

Different species of dinosaurs went extinct throughout the Mesozoic, not just at the end of the Cretaceous. For example, more time elapsed between the death of the last Stegosaurus and the hatching of the first Tyrannosaurus than between the extinction of the last dinosaur and the birth of the first modern human.

There is no unambiguous evidence for dinosaur fossils after the Cretaceous-Tertiary boundary. Dinosaur teeth mixed with mammalian bones in Paleocene deposits have been found in the Hell Creek Formation in Montana, but it’s not clear whether they had originally come from earlier, dinosaur-bearing levels. Redeposition of older fossils into younger sediments by rivers or streams is not uncommon.

Surviving dinosaurs are not a zoological impossibility, especially in areas that have been geologically stable for the past 60 million years (such as Africa). Large dinosaurs that are coldblooded (ectothermic) would have a better time surviving in hot, equatorial regions than warmblooded (endothermic) animals with high metabolic rates. Ectotherms also require only 10 percent of the amount of food taken in by full endotherms. However, determining dinosaur energetics and thermal biology without living models is, at best, a speculative endeavor.

The two major types of African dinosaur in this section are the Mokele-Mbembe, which might be a surviving sauropod, and the Em ela- Ntouka, which some think might be a ceratopsian survivor such as Monoclonius. Both are known by many different local names. The others in the list are much less documented.

Mystery Dinosaurs

Em ela-Ntouka;


Mokele-Mbem be;

Partridge Creek Beast;


Silwane Manzi.


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