Related topics: dinosaurs

Precision and brawn a deadly combination

(Phys.org) —A bizarre, pouched super-predator that terrorised South America millions of years ago had huge sabre-like teeth but its bite was weaker than that of a domestic cat, new research shows.

Elephant tooth evolution rooted in grass

Once they developed a taste for grass, the ancestors of today's elephants swiftly broadened their leaf-only diet and placed their progeny on a new evolutionary track, a study said Wednesday.

X-rays reveal new picture of 'dinobird' plumage patterns

(Phys.org) —The findings came from X-ray experiments by a team from The University of Manchester, working with colleagues at the US Department of Energy's (DOE) SLAC National Accelerator Laboratory. The scientists were ...

Fossils indicate common ancestor for two primate groups

(Phys.org) —Palaeontologists working in Tanzania have discovered the oldest known fossils from two major primate groups—Old World monkeys, which include baboons and macaques, and apes, which include humans and chimpanzees. ...

20 million year-old dwarf koala named after Dick Smith

(Phys.org) —A newly discovered extinct species of koala that lived in the rainforest canopies of northern Australia about 20 million years ago has been named after a famous Australian – Dick Smith.

Bird ancestor reclaims its branch on tree of life

Venerated for 150 years as the forebear of all birds until being relegated two years ago to the common class of winged dinosaurs, the Archaeopteryx was restored to its hallowed branch on the tree of life on Wednesday.

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Paleontology

Paleontology (pronounced /ˌpælɪɒnˈtɒlədʒi/; British: palaeontology; from Greek: παλαιός (palaeos) "old, ancient", ὄν, ὀντ- (on, ont-) "being, creature", and λόγος (logos) "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments (their paleoecology). As a "historical science" it attempts to explain causes rather than conduct experiments to observe effects. Paleontological observations have been documented as far back as the 5th century BC. The science became established in the 18th century as a result of Georges Cuvier's work on comparative anatomy, and developed rapidly in the 19th century. Fossils found in China since the 1990s have provided new information about the earliest evolution of animals, early fish, dinosaurs and the evolution of birds and mammals. Paleontology lies on the border between biology and geology, and shares with archaeology a border that is difficult to define. It now uses techniques drawn from a wide range of sciences, including biochemistry, mathematics and engineering. As knowledge has increased, paleontology has developed specialized sub-divisions, some of which focus on different types of fossil organisms while others study ecology and environmental history, such as ancient climates.

Body fossils and trace fossils are the principal types of evidence about ancient life, and geochemical evidence has helped to decipher the evolution of life before there were organisms large enough to leave fossils. Estimating the dates of these remains is essential but difficult: sometimes adjacent rock layers allow radiometric dating, which provides absolute dates that are accurate to within 0.5%, but more often paleontologists have to rely on relative dating by solving the "jigsaw puzzles" of biostratigraphy. Classifying ancient organisms is also difficult, as many do not fit well into the Linnean taxonomy that is commonly used for classifying living organisms, and paleontologists more often use cladistics to draw up evolutionary "family trees". The final quarter of the 20th century saw the development of molecular phylogenetics, which investigates how closely organisms are related by measuring how similar the DNA is in their genomes. Molecular phylogenetics has also been used to estimate the dates when species diverged, but there is controversy about the reliability of the molecular clock on which such estimates depend.

Use of all these techniques has enabled paleontologists to discover much of the evolutionary history of life, almost all the way back to when Earth became capable of supporting life, about 3,800 million years ago. For about half of that time the only life was single-celled micro-organisms, mostly in microbial mats that formed ecosystems only a few millimeters thick. Earth's atmosphere originally contained virtually no oxygen, and its oxygenation began about 2,400 million years ago. This may have caused an accelerating increase in the diversity and complexity of life, and early multicellular plants and fungi have been found in rocks dated from 1,700 to 1,200 million years ago. The earliest multicellular animal fossils are much later, from about 580 million years ago, but animals diversified very rapidly and there is a lively debate about whether most of this happened in a relatively short Cambrian explosion or started earlier but has been hidden by lack of fossils. All of these organisms lived in water, but plants and invertebrates started colonizing land from about 490 million years ago and vertebrates followed them about 370 million years ago. The first dinosaurs appeared about 230 million years ago and birds evolved from one dinosaur group about 150 million years ago. During the time of the dinosaurs, mammals' ancestors survived only as small, mainly nocturnal insectivores, but after the non-avian dinosaurs became extinct in the Cretaceous–Tertiary extinction event 65 million years ago mammals diversified rapidly. Flowering plants appeared and rapidly diversified between 130 million years ago and 90 million years ago, possibly helped by coevolution with pollinating insects. Social insects appeared around the same time and, although they have relatively few species, now form over 50% of the total mass of all insects. Humans evolved from a lineage of upright-walking apes whose earliest fossils date from over 6 million years ago, and anatomically modern humans appeared under 200,000 years ago. The course of evolution has been changed several times by mass extinctions that wiped out previously dominant groups and allowed other to rise from obscurity to become major components of ecosystems.

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