Elbows of extinct marsupial lion suggest unique hunting style


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Photo by Elsa Panciroli

<i>Thylacoleo</i> hand, containing giant claw.

Drawn by Borja Figueirido from a photograph of a specimen on display in the South Australian Museum

Reconstruction of <i>Thylacoleo</i>.

by Mauricio Ant&oacute;n

Scientists from the Universities of Bristol Málaga have proposed that the long extinct marsupial lion hunted in a very unique way – by using its teeth to hold prey before dispatching them with its huge claws. The marsupial lion, or Thylacoleo carnifex, was a predator in the Pleistocene era of Australia was about the same size as a large jaguar.

It was known to have existed from around two-and-a-half-million years ago until as recently as a few tens of thousands of years ago.

The animal is depicted on native Australian cave art some speculate it still survives as the “QueenslTiger”.

As its name suggests, the marsupial lion has long been presumed to be a cat-like predator, despite lacking large canine teeth – instead it had large, protruding incisors that have been suggested to be canine substitutes.

Thylacoleo was a powerful beast but, as other researchers have noted, it had limbs of different proportions to a lion, suggesting it was not a fast.

It also sported a very large claw on its hand, similar to the dew claw of cats but of a much bigger size, with a bony sheath foisted on a mobile first digit (thumb).

The new study, published in Paleobiology by Christine Janis, a Marie Curie Research Fellow at the University of Bristol (currently on a leave of absence from a professorship at Brown University, USA) with colleagues Borja Figueirido Alberto Martín-Serra from the University of Málaga, Spain looked at the elbow joints of a large number of living mammals.

This showed a strong association between the anatomy of the humerus (upper arm bone) where it articulates with the forelimb the locomotor behaviour of mammals.

Animals more specialized for running (like a dog) have a joint indicating movement limited for back forwards, stabilising their bodies on the ground, while animals more specialised for climbing (like a monkey) have a joint that allows for rotation of the haround the elbow. Modern cats, which (unlike dogs) use their forelimbs to grapple with their prey, have an elbow joint of intermediate shape.

Christine Janis said: “If Thylacoleo had hunted like a lion using its forelimbs to manipulate its prey, then its elbow joint should have been lion-like”.

“But, surprisingly, it a unique elbow-joint among living predatory mammals – one that suggested a great deal of rotational capacity of the hand, like an arboreal mammal, but also features not seen in living climbers, that would have stabilized the limb on the ground (suggesting that it was not simply a climber).”

Christine Janis colleagues proposed that this unique elbow joint, in combination with the huge “dew claw” on a mobile thumb, would have allowed the marsupial lion to use that claw to kill its prey.

In contrast the large incisors were blunt. While Thylacoleo had massive shearing teeth in the back of its jaw, the incisors appear to have functioned better for gripping than for piercing flesh in a killing bite.

They concluded that, unlike a real lion, which holds its prey with its claws, kills it with its teeth, the marsupial lion – unlike any living predator – used its teeth to hold its prey, while it despatched it with its huge claws.



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New species of extinct river dolphin discovered in Smithsonian collection


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Linocut print art by Alexandra Boersma

The skull of <em>Arktocara yakataga</em> on an 1875 ethnographic map of Alaska drawn by William Healey Dall, a broadly trained naturalist who worked for several US government agencies, including the Smithsonian, honored with several species of living mammals, including Dall's porpoise (<em>Phocoenoides dalli</em>). Near the skull of <em>Arktocara</em> is a cetacean tooth, likely belonging to a killer whale (<em>Orcinus orca</em>), collected by Ale&scaron; Hrdli&ccaron;ka, a Smithsonian anthropologist who worked extensively in Alaska, an Oligocene whale tooth collected by Donald Miller, a geologist who worked for the US Geological Survey, collected the type specimen of <em>Arktocara</em>. Donald Orth's dictionary of Alaskan place names, published by the USGS, bookends the image.

James Di Loreto, Smithsonian

The skull of <em>Akrtocara yakataga</em> rests on an 1875 ethnographic map of Alaska drawn by William Healey Dall, a broadly trained naturalist who worked for several US government agencies, including the Smithsonian, honored with several species of living mammals, including Dall's porpoise (<em>Phocoenoides dalli</em>). Near the skull of <em>Arktocara</em> is a cetacean tooth, likely belonging to a killer whale (<em>Orcinus orca</em>), collected by Ale&scaron; Hrdli&ccaron;ka, a Smithsonian anthropologist who worked extensively in Alaska, an Oligocene whale tooth collected by Donald Miller, a geologist who worked for the US Geological Survey, collected the type specimen of <em>Arktocara</em>. Donald Orth's dictionary of Alaskan place names, published by the USGS, bookends the image.

James Di Loreto, Smithsonian

A fossil that has been in the collection of the Smithsonian’s National Museum of Natural History since it was discovered in 1951 is today helping scientists piece together the evolutionary history of whales dolphins, including the origins of the endangered South Asian river dolphin. According to Nicholas D. Pyenson, the museum’s curator of fossil marine mammals, Alexandra Boersma, a researcher in his lab, the fossil belonged to a dolphin that swam in subarctic marine waters around 25 million years ago. It represents a new genus species, which Pyenson Boersma have named Arktocara yakataga.

The researchers reported their findings Aug. 16 in the journal PeerJ. They have also produced a digital three-dimensional model of the fossil that can be explored at http://3d.si.edu/model/usnm214830.

The fossil, a partial skull about 9 inches long, was discovered in southeastern Alaska by Donald J. Miller, a geologist with the United States Geological Survey. It then spent decades in the Smithsonian’s collection. With more than 40 million specimens in the museum’s Department of Paleobiology, “We are always learning new things about the vast legacy built by our predecessors at the museum,” Pyenson said. But earlier this year, he Boersma were captivated by focused their attention on what Boersma calls “this beautiful little skull from Alaska.”

By studying the skull comparing it to those of other dolphins, both living extinct, Boersma determined that A. yakataga is a relative of the South Asian river dolphin Platanista, which is the sole surviving species of a once large diverse group of dolphins. The skull, which is among the oldest fossils ever found from that group, called Platanistoidea, confirms that Platanista belongs to one of the oldest lineages of toothed whales still alive today.

The South Asian river dolphin–a species that includes both the Ganges river dolphin the Indus river dolphin–is of great interest to scientists. It is an unusual creature that swims on its side, cannot see uses echolocation to navigate murky rivers in Nepal, India, Bangladesh Pakistan. Unlike its known ancestors, it lives only in fresh water. But human activities, including the use of fishing nets, pollution disruption of it’s habitat, have decimated the species to only a few thousremaining individuals. The group’s endangered status makes the dolphins difficult to study.

“One of the most useful ways we can study Platanista is by studying its evolutionary history, by looking at fossils that are related to it to try to get a better sense of where it’s coming from,” Boersma said. “Exactly how that once diverse globally widespread group dwindled down to a single species in Southeast Asia is still somewhat a mystery, but every little piece that we can slot into the story helps.”

Based on the age of nearby rocks, the scientists estimate that the Arktocara fossil comes from the late Oligocene epoch, around the time ancient whales diversified into two groups–baleen whales (mysticetes) toothed whales (odontocetes).

“It’s the beginning of the lineages that lead toward the whales that we see today,” Boersma said. “Knowing more about this fossil means that we know more about how that divergence happened.”

Fossils from Platanista‘s now extinct relatives have been found in marine deposits around the world, but the Arktocara fossil is the northernmost find to date. The name of the new species highlights its northern habitat: Arktocara is derived from the Latin for “the face of the north,” while yakataga is the indigenous Tlingit people’s name for the region where the fossil was found.

“Considering the only living dolphin in this group is restricted to freshwater systems in Southeast Asia, to find a relative that was all the way up in Alaska 25 million years ago was kind of mind-boggling,” Boersma said.

Pyenson notes that some conservation biologists argue that the South Asian river dolphin should be prioritized for protection to preserve its evolutionary heritage. “Some species are literally the last of a very long lineage,” he said. “If you care about evolution, that is one basis for saying we ought to care more about the fate of Platanista.”

Chesapeake Testing provided X-ray scanning support for digital-image processing. Materialise provided technical support with 3-D model rendering.



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Twenty-five little bones tell a puzzling story about early primate evolution


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David Haring, Duke Lemur Center

These are fossilized bones found in a coal mine in Gujarat, India. A femur bone from <i>Marcgodinotius</i>, an adapoid, left; a femur bone from <i>Vastanomys</i>, an omomyid, right. A US quarter is shown for size.

Johns Hopkins Medicine

This is a simplified diagram showing evolutionary relationships among primates. NW, new world; OW, old world.

Kenneth Rose, Johns Hopkins Medicine

A cache of exquisitely preserved bones, found in a coal mine in the state of Gujarat, India, appear to be the most primitive primate bones yet discovered, according to an analysis led by researchers from The Johns Hopkins University Des Moines University. Their assessment of the bones, belonging to ancient, rat-sized, tree-dwelling primates, bolsters the controversial idea that primates native to what is now India played an important role in the very early evolution of primates, mammals that include humans, apes monkeys. A description of the research was published online Aug. 7 in the Journal of Human Evolution.

“All other primate bones found so far around the world clearly belong to one or the other of the two primate groups, called clades: Strepsirrhini Haplorhini,” says Kenneth Rose, Ph.D., professor emeritus in the Center for Functional Anatomy Evolution at the Johns Hopkins University School of Medicine. “But many of the Gujarat bones show features that do not clearly belong to one clade or the other.”

According to Rose lead author Rachel Dunn, Ph.D., an assistant professor of anatomy at Des Moines University, this suggests that the little primates represent a very early stage of primate evolution. That idea is counterintuitive, they say, because older primate fossils exist that show more specialized features, but they add that that situation is fairly common in the fossil record.

At the beginning of the Eocene Epoch, about 56 million years ago, the world was warming, encouraging the dispersal of mammals between northern continents. The oldest known primate fossils found appeared around then in North America, Europe northern Asia, but they can already be categorized as either adapoids or omomyids, the most primitive members of Strepsirrhini Haplorhini, respectively. Adapoids were relatives of current day lemurs, lorises bushbabies, while omomyids were more closely related to living tarsiers, monkeys apes.

The newly discovered group of 25 tiny bones, all from somewhere below the neck of the animals, are younger — some 54.5 million years old — but considerably more primitive than the oldest known primate fossil, Teilhardina, which first appears in deposits at the beginning of the Eocene, almost 56 million years old. They are also more primitive than a relatively complete skeleton of the primate Archicebus, found recently in China dated to about 55 million years ago.

Their analysis, Rose says, suggests the Gujarat primates are close descendants of the common ancestor that gave rise to the adapoids omomyids found on the northern continents. But the Gujarat primates date back to a time when what is now India was a drifting lmass — isolated from the northern continents inching its way toward southern Asia.

“These are the best preserved most primitive bones we have from the first 5 million years of primate evolution, but there’s not enough evidence currently for us to figure out when these primates reached India or where they came from,” says Rose. “They are similar enough to the early primates found on the northern continents to indicate that their ancestors migrated between the northern continents what is now India — but in which direction isn’t clear.”

Rose says there are several possible scenarios to explain what they’ve suggested, but all his team can say with high confidence now is that the tiny primates occupied equatorial India prior to its collision with Asia.

Even though the researchers don’t have enough bones to reconstruct a whole skeleton, the bones weren’t embedded in rock so they could be thoroughly examined from every angle, providing insights into the evolution of primate anatomy.

Their analysis is that the Gujarat primates were adapted for climbing the tall dipterocarp trees of ancient rainforests but were less specialized than present-day leaping lemurs or slow-climbing lorises. Their limbs joints suggest more generalized climbing, as in present-day mouse lemurs dwarf lemurs.

Because of such features, Rose his colleagues aren’t sure which clade some of the bones belonged to, suggesting that they represent the most primitive primate anatomy known. But a few of the bones do show the beginnings of features that would later distinguish the clades, like deep grooves where the thigh bone connects to the knee, which helps animals like lemurs to leap. Rose believes it’s possible that differences in hind limb-based movement led to the primates’ divergence into two clades.

Previously discovered teeth jaws of these tiny animals suggest that these primates were also close to mouse lemurs dwarf lemurs in size, about 150 to 300 grams in weight, or 0.5 pounds. Considered together with their generalized anatomy, the small size of the Gujarat primates is likely another primitive trait, with future primates tending to increase in size.

“Considering everything together, we think the most likely scenario is that more primitive primates arrived in what is now India retained their primitive, generalized skeleton, while their relatives on the northern continents continued to evolve,” says Rose. “Hopefully future skeleton finds will make it all clearer.”



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Study highlights serious security threat to many internet users


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UC Riverside

RIVERSIDE, Calif. — Researchers at the University of California, Riverside have identified a weakness in the Transmission Control Protocol (TCP) of all Linux operating systems since late 2012 that enables attackers to hijack users’ internet communications completely remotely. Such a weakness could be used to launch targeted attacks that track users’ online activity, forcibly terminate a communication, hijack a conversation between hosts or degrade the privacy guarantee by anonymity networks such as Tor.

Led by Yue Cao, a computer science graduate student in UCR’s Bourns College of Engineering, the research will be presented on Wednesday (Aug. 10) at the USENIX Security Symposium in Austin, Texas. The project advisor is Zhiyun Qian, an assistant professor of computer science at UCR, whose research focuses on identifying security vulnerabilities to help software companies improve their systems.

While most users don’t interact directly with the Linux operating system, the software runs behind-the -scenes on internet servers, android phones a range of other devices. To transfer information from one source to another, Linux other operating systems use the Transmission Control Protocol (TCP) to package send data, the Internet Protocol (IP) to ensure the information gets to the correct destination.

For example, when two people communicate by email, TCP assembles their message into a series of data packets–identified by unique sequence numbers–that are transmitted, received, reassembled into the original message. Those TCP sequence numbers are useful to attackers, but with almost 4 billion possible sequences, it’s essentially impossible to identify the sequence number associated with any particular communication by chance.

The UCR researchers didn’t rely on chance though. Instead, they identified a subtle flaw (in the form of ‘side channels’) in the Linux software that enables attackers to infer the TCP sequence numbers associated with a particular connection with no more information than the IP address of the communicating parties.

This means that given any two arbitrary machines on the internet, a remote blind attacker without being able to eavesdrop on the communication, can track users’ online activity, terminate connections with others inject false material into their communications. Encrypted connections (e.g., HTTPS) are immune to data injection, but they are still subject to being forcefully terminated by the attacker. The weakness would allow attackers to degrade the privacy of anonymity networks, such as Tor, by forcing the connections to route through certain relays. The attack is fast reliable, often taking less than a minute showing a success rate of about 90 percent. The researchers created a short video showing how the attacks works.

Qian said unlike conventional cyber attacks, users could become victims without doing anything wrong, such as downloading malware or clicking on a link in a phishing email.

“The unique aspect of the attack we demonstrated is the very low requirement to be able to carry it out. Essentially, it can be done easily by anyone in the world where an attack machine is in a network that allows IP spoofing. The only piece of information that is needed is the pair of IP addresses (for victim client server), which is fairly easy to obtain,” Qian said.

Qian said the researchers have alerted Linux about the vulnerability, which has resulted in patches applied to the latest Linux version. Until then, Qian recommends the following temporary patch that can be applied to both client server hosts. It simply raises the `challenge ACK limit’ to an extremely large value to make it practically impossible to exploit the side channel. This can be done on Ubuntu, for instance, as follows:

1. Open /etc/sysctl.conf, append a comm“/net.ipv4/tcp_challenge_ack_limit = 999999999”.

2. Use “sysctl -p” to update the configuration.



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Echo templates aid mental mapping in bats


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Vanderelst et al., <i>eLife</i>, 2016

The artificial bat device in action at St. Andrew's Park, Bristol -- a much leafier environment in comparison to Israel's corridor of boulders.

Vanderelst et al., <i>eLife</i>, 2016

The device in action in a park in Midreshet Ben Gurion, Israel. The echo catchment distances were greater in this corridor of boulders than in the corridor of vegetation in the Royal Fort Gardens, suggesting that bats can use boulders other such landmarks for mapping.

Vanderelst et al., <i>eLife</i>, 2016

A study published in eLife provides new insights on how bats recognise their surroundings to help them build mental maps. Bats have excellent spatial memory, navigate with ease to important locations including roosts foraging grounds. But exactly how these animals recognise such places through echolocation – perception based on soundwaves their echoes – is largely unknown. New research from the Universities of Bristol Antwerp suggests the animals observe remember templates to help form a cognitive map of their environment.

“When we visually recognise places, such as our living room or office, we identify localise the various objects that make up the scene,” says Marc Holderied, PhD, Reader in Biology at the University of Bristol, senior author of the study.

“Echolocation does not allow bats to do this, as the information it provides is more limited. We therefore wanted to discover how these animals recognise their locations differently to those with vision.”

The team proposed that template-based place recognition might underlie sonar-based navigation in bats. This would mean that the animals recognise places by remembering their echo signature, rather than their three-dimensional (3D) layout.

“The viability of a template-based approach to place recognition relies on two properties. One of these is that templates must allow for unique classification in order for places to be recognisable. In other words, they must encode the bat’s specific locations in space to allow it to recognise previously visited places,” says first author Dieter Vanderelst, PhD, from the University of Antwerp, who led the study as a research fellow at the University of Bristol.

To test their hypothesis, the team built an ‘artificial bat’, a device which contained ultrasonic microphones an ultrasonic speaker acting as ears a mouth. Using this device, they collected a large number of echoes from three different locations: the green leafy St. Andrew’s Park Royal Fort Garden in Bristol, the more open stonier landscape of a park in Midreshet Ben Gurion, Israel.

Data were collected at the typical bat-flight heights of about two to three metres. Measurements from each site were gathered stored by a computer integrated into the device. The team then assessed the templates from the data found that the echoes returning from each place were unique enough for them to be used to recognise the location.

“Importantly, our method used the echoes without inferring the location or identity of objects, such as plants trees, at each site. In other words, the data support our hypothesis that bats can recognise places by remembering how they sound, rather than how they appear through the animals’ 3D sonar imaging,” Vanderelst explains.

The research also suggests that the use of prominent landmarks might be an emergent feature of template-based place recognition.

“The prominence of a template’s catchment area reflects how likely it is that the template will be observed stored in a map during exploration. For example, we found the catchment distances to be greater in the Israeli corridor of large boulders than in the corridor of vegetation in the Royal Fort Gardens, suggesting that bats could use the boulders as landmarks for mapping,” Vanderelst adds.

“This leads us to believe that cognitive mapping based on templates would show a natural preference to use such landmarks, as they return stronger more recognisable echo signatures. With these new insights in mind, our aim is to try piece together the entire puzzle of the navigation tendencies capabilities in bats.”



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