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Human arrival 'wiped out' Hawaii's unique crabs

Land crabs unique to Hawaii, as big as a human fist and able to travel huge distances inland, were wiped out by the first human colonists around 1,000 years ago, scientists have deduced.
Fossils have been found at altitudes of 1,000m - unusual for a crab.

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UF researchers link oceanic land crab extinction to colonisation of Hawaii

University of Florida researchers have described a new species of land crab that documents the first crab extinction during the human era.
The loss of the crab likely greatly impacted the ecology of the Hawaiian Islands, as land crabs are major predators, control litter decomposition and help in nutrient cycling and seed dispersal. Their disappearance was caused by the arrival of humans to the islands and resulted in large-scale changes in the state's ecosystem. Researchers said the full impact of the extinction on Hawaii is unknown, but they are certain it led to changes in the diversity of the food web, a continuing concern to conservationists studying species loss in other habitats. The study will be published online May 16 in PLoS ONE.

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Plankton fossils tell tale of evolution and extinction

Scientists studying the fossils of tiny ocean-dwelling plankton, called foraminifera, have uncovered another piece in the puzzle of why species evolve or become extinct.
The issue of whether extinctions and evolution are controlled more by the environment or by the existing diversity of species in an ecosystem is one that scientists have been debating since Darwin's time.
Writing in the journal Science on Friday 15 April, researchers from Imperial College London and Cardiff University say their study of foraminifera, or 'forams', suggests that new species are more likely to evolve when there are fewer species already and that extinctions are more closely linked to a change in environment than they are to the number of existing species.

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Raphus cucullatus
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Title: The end of the fat dodo? A new mass estimate for Raphus cucullatus
Authors: Delphine Angst, Eric Buffetaut and Anick Abourachid

A new mass estimate for the dodo (Raphus cucullatus), based on the lengths of the femur, tibiotarsus and tarsometatarsus, is attempted. The obtained mean mass is 10.2 kg, which is less than previous estimates based on other methods, which ranged from 10.6 to 21.1 kg, and much lower than the 50 lbs reported by a seventeenth-century eyewitness. The new estimated mass, which is similar to that of a large wild turkey, seems more realistic than previous ones and supports the hypothesis that contemporary illustrations of extremely fat dodos were either exaggerations, or based on overfed specimens. Pictures of "fat" dodos may also have been based on individuals exhibiting a display behaviour with puffed out feathers.

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Pictures: Bizarre animals nearing extinction

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Extinction threat for 45 Australian species

Up to 45 rare species of wallaby, bandicoot and other Australian animals could become extinct within 20 years unless urgent action is taken to control introduced predators and other threats, scientists warned Wednesday
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In "Poisoned Present" Tree of Life Gets Slimmer

A study just published in the journal Nature by researchers in France, Spain and Portugal looks for the first time at the effects of climate change on the tree of life (that aggregates species according to their evolution/genetic similarity) to find that the whole of it will be affected. But this is not all bad news because even if the tree is to become "thinner" it keeps its structure as there will be no major losses of biodiversity contrary to what other studies had suggested (this would occur if localised "branches" were totally eliminated).
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Canadians probe what wiped out most life on Earth

Calgary researchers say they've found evidence to support the idea that toxic volcanic ash helped cause the world's largest extinction.
About 250 million years ago, 95% of life in the sea and 70% of life on land was wiped out during the Permian extinction.

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A puzzlingly regular waxing and waning of Earth's biodiversity may ultimately trace back to our solar system's bobbing path around the Milky Way, a new study suggests.
Every 60 million years or so, two things happen, roughly in synch: The solar system peeks its head to the north of the average plane of our galaxy's disk, and the richness of life on Earth dips noticeably.
Researchers had hypothesised that the former process drives the latter, via an increased exposure to high-energy subatomic particles called cosmic rays coming from intergalactic space. That radiation might be helping to kill off large swaths of the creatures on Earth, scientists say.
The new study lends credence to that idea, putting some hard numbers on possible radiation exposures for the first time. When the solar system pops its head out, radiation doses at the Earth's surface shoot up, perhaps by a factor of 24, researchers found.

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During Earth's 4.6 billion year history, there have been many mass extinctions of life that are recognised in the geologic record. Naturally, they have left scientists wondering how these apocalyptic scenarios ever occurred.
Were such extinctions caused by extra-terrestrial objects, such as a massive meteorite, or were they caused by naturally occurring processes that were already present during Earth's evolution? Or, perhaps, mass extinctions resulted from a range of factors that scientists are still trying to link together.

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