Oldest Hairy Microbe Fossils Discovered (weird science)

This microscopic fossil closely resembles a modern tintinnid, a single-celled organism that is a type of plankton. Fossil ciliates including this one were recently identified in a deposit in Mongolia, and they are more than 100 million years older than the previously known fossils of this type. Image credit: Tanja Bosak

This microscopic fossil closely resembles a modern tintinnid, a single-celled organism that is a type of plankton. Fossil ciliates including this one were recently identified in a deposit in Mongolia, and they are more than 100 million years older than the previously known fossils of this type.

Ancient rock deposits, laid down between two massive ice ages, reveal the oldest known fossils for two types of single-celled creatures: Tube-shelled foraminifera and hairy, vase-shape ciliates.

Both closely resemble microbes living today. But the climate they lived in may have been quite different. The fossils appear in limestone deposited on the ocean floor between 635 million and 715 million years ago. This period was marked by two "Snowball Earth" events, when ice may have covered the entire planet.

These fossils date back more than 100 million years earlier than the oldest foraminifera and ciliates previously known. Even so, scientists think these organisms were around much longer, based on changes accumulated in their DNA since they split from close relatives. Some believe these types of single-celled creatures have been around for considerably more than 1 billion years, said Tanja Bosak, a study researcher and assistant professor of geobiology at the Massachusetts Institute for Technology.

"We can't claim we have seen something that is exactly like the modern species," Bosak said. "(But) here we have something that has looked very similar for 700 or more million years."

The fossils have evaded researchers not only because they are so tiny, but also because these deposits do not contain a type of rock that typically preserves fossils, particularly something this small and fragile, she said.

Fossils belonging to foraminifera were found in rocks from Namibia, while ciliates were found in rocks from Mongolia. Both types first appear in layers of rock called cap carbonates, laid down as the world was leaving the earlier snowball state, which occurred 716 million years ago.

Foraminifera, ancient and modern, build protective shells by picking up tiny grains of mineral that they stick to their exterior using a sugary compound. They aren't the only shelled organisms Bosak and her colleagues found. They also discovered amoebas that appeared to be building the same sort of shells.

While this wasn't the first fossil evidence for these amoebas, the nature of their resistant covering was ambiguous in the earlier fossils. The most recent fossils are the first amoebas to show evidence of primitive shell building, Bosak said.

Ciliates, meanwhile, are covered with tiny hairs called cilia. And the fossils found closely resemble modern, planktonic organisms called tintinnids.

Life at the time was quite simple, but it soon became more complex. For instance, the first animal embryos show up after the end of the latest Snowball Earth event, around 635 million years ago.

It's possible the arrival of abundant microbes, particularly the ciliates, may have had some hand in the change, by helping to bump up the amount of oxygen in the atmosphere.

Even after free oxygen dramatically increased in the atmosphere, a change called the Great Oxidation Event, the oxygen level was much lower than it is today. The ciliates lived in the surface waters, then died and sank, taking organic carbon with them and tucking it away in sediments low in oxygen where the organisms would decompose only slowly. The burial of this carbon meant it could not be converted to carbon dioxide by respiration. As a result, oxygen produced by the photosynthesis of other microbes like algae would have built up.
The discovery of these organisms reveals a possible mechanism by which the oxygen levels in the atmosphere increased, allowing life to become more complex, she said.

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The research has been published in articles published online in October and November in the journal Geology, and online in June in the journal Earth and Planetary Science Letters.

| via LiveScience

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Tiny but toothy mammal unearthed

What the animal did with those impressive canines is not exactly clear

An extraordinary looking, mouse-sized, fossil animal is shedding new light on the ancient history of mammals.
With a thin snout, beady eyes and long canines, the creature would have looked remarkably like that fictional sabre-toothed squirrel of Ice Age movie-fame.
But Cronopio dentiacutus is one of the very few mammal specimens to come out of South America from the era when dinosaurs ruled the Earth.
The 100-million-year-old animal is reported in the journal Nature.
It was discovered in sandstone sediments at Cipolletti, Rıo Negro Province, Argentina.
Those ancient river sediments reveal a lot about what the local environment was like in the Late Cretaceous, but scientists are struggling to pin down the details of Cronopio's lifestyle.
The animal displays a host of features that appear to have no parallel among living or extinct mammals, says Prof Guillermo Rougier from the University of Louisville, Kentucky, US.
"The back teeth, the molars, are the kind of teeth that you will find in an insectivore, an animal that eats insects of different kinds, and even very small invertebrates, so perhaps small lizards, which were present in the same place," he told BBC News.
"But we have no idea why he needed such huge canines. Those tusks are a big surprise."
It is possible Cronopio used them to skewer certain insect prey, but it is clear the canines could not have been deployed with much force.

Skulls (G.Rougier)

The slender nature of the snout and the teeth themselves mean that to have bitten down hard, or to have wrestled another creature with its mouth, would have invited almost certain injury.
Cronopio is what is termed a dryolestoid. These were a group of primitive, extinct mammals belonging to the lineage leading to modern marsupials and placental mammals.
They are known mainly from teeth and jaws found in North America and Europe from the Jurassic Period (145-200 million years ago). To now have relatively complete dryolestoid skulls form South America in the form of Cronopio is therefore a boon to scientists trying to study the spread and diversity of mammals through Earth history.
There are so few well-preserved South American mammals from the time of the dinosaurs
"In the northern continents, there is a longer tradition of palaeontology and so they are well represented," observed Prof Rougier.
"In South America, Africa and Australia - not so much work has been done proportionately, and so we know very little; and that's why Cronopio is so important.
"Instead of having a picture that is so heavily biased to what happened in the North, we're starting to get some information about what happened in the southern continents, and fortunately in this case the quality of the specimens is very good."
As to that likeness with Scrat, the acorn-obsessed squirrel in the animated Ice Age features films, Prof Rougier finds the association highly amusing.
"I remember when I saw the movie I thought, 'why have they done this ridiculous animal - there is no such thing?'. And then we find something that kind of looks like it. But it just goes to show - we know so little about the actual diversity of mammals that even some very wild guesses might come through; they might actually be present

 BBC News

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UF researchers discover 20-foot-long crocodile species

University of Florida researcher Alex Hastings displays a pelvic bone of Acherontisuchus guajiraensis, a 60-million-year-old ancestor of crocodiles discovered in northeastern Colombia. (Photo submitted by the University of Florida)

The fossils were found in a coal mine in northeastern Colombia

Sixty-million years ago, in the heat and humidity of Paleocene-era Colombia, a snake so large that researchers named it Titanoboa was the reptile king of its domain.
But it wasn't the only giant reptile hunting for fish in the rivers of northern Colombia.

A new species of enormous crocodile, measured at 20 feet long, has been discovered by University of Florida researchers in the same coal mine that Titanoboa was found.

The creature may have been large enough to give Titanoboa competition for the fish they were both ideally adapted to hunt.

The excavations at the site were led by Jonathan Bloch, associate curator of vertebrate paleontology at the Florida Museum of Natural History; and Carlos Jaramillo, a paleobotanist with the Smithsonian Tropical Research Institute.

Alex Hastings, a UF Ph.D. student in the department of geological sciences, collected the type-specimen for the species. This fossil set will be used as a comparison tool for future finds.

The crocodile, Acherontisuchus guajiraensis, is the latest prehistoric reptile to be found in the Cerrejon coal mine.

It is named after the river Acheron, which in Greek myth is a branch of the river Styx in the underworld.

Bloch described the coal mine as a hot and humid place, where seams of coal spontaneously combust and give off a sulfuric smoke, giving the entire area a very hellish atmosphere.

The Acherontisuchus species was a cousin to modern-day crocodiles, not their direct ancestors, and it dates back 60 million years.

This places the species at the time immediately following the mass extinction event that claimed the dinosaurs, as well as a wide variety of other life on Earth.
cherontisuchus belonged to a group that somehow managed to survive the cataclysm.

"One of the questions about this group was how they were able to survive … what advantages did they have?" Hastings said.

"What this new crocodile really contributes to that is that it is the first evidence of a large-bodied member of this group in a freshwater habitat," he said.

Before now, it was thought that only baby crocodiles would spend any appreciable amount of time in freshwater, and that adults would spend most of their time in a saltwater environment.

Their ability to adapt to multiple environments would have helped this family of crocodiles survive the mass extinction and the lean times that followed it.

Hastings said that their survival depended on taking advantage of multiple resources, rather than just what the ocean provided.

Living in freshwater may also have shielded the species from whatever began to kill off the large marine reptiles of the ocean around the same time as the dinosaurs.

Another rival reptile family, the mosasaurs, began to vanish at this point, so whatever environmental pressure took these creatures may have passed over Acherontisuchus.

Bloch said that the species also is important because each new find tells researchers more about the time period they are from.

He said that the tropics are a very mysterious place when it comes to the fossil record because of the predominantly forested land, which makes it difficult to excavate.

Bloch said this is particularly ironic because a lot of the animal diversity today can be found in the tropics, but we know the least about the creatures that lived there during the Paleocene.

Acherontisuchus' size of 20 feet was based on the larger of two individuals found at the site.

Hastings said that there were certainly larger specimens, as well as smaller. Twenty feet places it at the known upper size of modern specimens, such as the reportedly 21-foot saltwater crocodile captured in the Philippines in early September.

To put this size in perspective, and comparing it to modern specimens, Acherontisuchus probably weighed upward of a ton and grew to be more than half the length of an RTS city bus. It had a wide shelf on the back of its head, giving it a very broad, flat appearance.

Like modern gavial crocodiles, its snout was very long and narrow, filled with pointed teeth, making it ideally suited to hunting fish.

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Largest spider fossil discovered in China

Largest spider fossil has been discovered in volcanic ash in China. The largest spider fossil is believed to be as old as the dinosaur.

Scientists have unearthed the largest spider fossil ever found. The spider, a new species called Nephila Jurassica, with legs spanning 15cm. It was found in a fossil-rich rock formation near Daohugou village in northeastern China. The fossil dates back to the Middle Jurassic, about 165 million years ago, researchers reported in the April 20th Biology Letters. Pic Credit: ZUMA Press/Newscom

The spider, named Nephila jurassica, was discovered buried in ancient volcanic ash in Inner Mongolia, China. Tufts of hairlike fibers seen on its legs showed this 165-million-year-old arachnid to be the oldest known species of the largest web-weaving spiders alive today — the golden orb-weavers, or Nephila, which are big enough to catch birds and bats, and use silk that shines like gold in the sunlight.

The fossil was about as large as its modern relatives, with a body one inch (2.5 centimeters) wide and legs that reach up to 2.5 inches (6.3 cm) long. Golden orb-weavers nowadays are mainly tropical creatures, so the ancient environment of Nephila jurassica probably was similarly lush.

"It would have lived, like today's Nephila, in its orb web of golden silk in a clearing in a forest, or more likely at the edge of a forest close to the lake," researcher Paul Selden, director of the Paleontological Institute at the University of Kansas, told LiveScience. "There would have been volcanoes nearby producing the ash that forms the lake sediment it is entombed within."

Spiders are the most numerous predators on land today, and help keep insect numbers in check. So these findings help us "understand the evolution of the insect-spider predator-prey relationship," Selden said, suggesting that golden orb-weavers have been ensnaring insects and influencing their evolution since the Jurassic Period.

"There were many large or medium-sized flying insects around at that time on which it would have fed indiscriminately," Selden said.

In modern golden orb-weaver species, females are typically much larger than males. This new fossil was a female, suggesting this trend stretches back at least as far as the Middle Jurassic, Selden said — that is, back before the first known bird, Archaeopteryx, or giant dinosaurs such as Brachiosaurus and Diplodocus.

Although this is the largest fossil spider known to date, it is not the oldest. Two species from Coseley, England, Eocteniza silvicola and Protocteniza britannica, both come from about 310 million years ago.

Selden and his colleagues are now investigating other fossil spiders from China, "as well as those from elsewhere in the world — currently Brazil, New Zealand, Australia, Italy and Korea," he said.

The scientists detail their findings online April 20 in the journal Biology Letters.

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