(from Greek: παλαιό (palaio)
, "old, ancient"; όν (on)
, "being"; and logos
, "speech, thought") is the study of prehistoric
life forms on Earth through the examination of fossils
This includes the study of body fossils
, tracks (ichnites
, cast-off parts, fossilised faeces
and chemical residues.
Modern paleontology sets ancient life in its context by studying how long-term physical changes of global geography paleogeography and climate paleoclimate have affected the evolution of life, how ecosystems have responded to these changes and have adapted the planetary environment in turn and how these mutual responses have affected today's patterns of biodiversity. Hence, paleontology overlaps with geology (the study of rocks and rock formations) as well as with botany, biology, zoology and ecology – fields concerned with life forms and how they interact.
The major subdivisions of paleontology include paleozoology (animals), paleobotany (plants) and micropaleontology (microfossils). Paleozoologists may specialise in invertebrate paleontology, which deals with animals without backbones or in vertebrate paleontology, dealing with fossils of animals with backbones, including fossil hominids (paleoanthropology). Micropaleontologists study microscopic fossils, including organic-walled microfossils whose study is called palynology.
There are many developing specialties such as paleobiology, paleoecology, ichnology (the study of tracks and burrows) and taphonomy (the study of what happens to organisms after they expire). Major areas of study include the correlation of rock strata with their geologic ages and the study of evolution of lifeforms.
Gorgosaurus (meaning 'fierce lizard') is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, between about 77 and 74 million years ago. Fossil remains have been found in the Canadian province of Alberta and possibly the U.S. state of Montana. Paleontologists recognize only the type species, G. libratus, although other species have been erroneously referred to the genus.
Like most known tyrannosaurids, Gorgosaurus was a bipedal predator weighing more than a metric ton as an adult; dozens of large, sharp teeth lined its jaws, while its two-fingered forelimbs were comparatively small. Gorgosaurus was most closely related to Albertosaurus, and more distantly related to the larger Tyrannosaurus. Gorgosaurus and Albertosaurus are extremely similar, distinguished mainly by subtle differences in the teeth and skull bones. Some experts consider G. libratus to be a species of Albertosaurus; this would make Gorgosaurus a junior synonym of that genus.
Gorgosaurus lived in a lush floodplain environment along the edge of an inland sea. An apex predator, it was at the top of the food chain, preying upon abundant ceratopsids and hadrosaurs. In some areas, Gorgosaurus coexisted with another tyrannosaurid, Daspletosaurus. Though these animals were roughly the same size, there is some evidence of niche differentiation between the two. Gorgosaurus is the best-represented tyrannosaurid in the fossil record, known from dozens of specimens. These plentiful remains have allowed scientists to investigate its ontogeny, life history and other aspects of its biology. (see more...)