Fossil study reveals dogs evolved with climate change

Old dogs can teach humans new things about evolution. In Nature Communications a new study of North American dog fossils as old as 40 million years suggests that the evolutionary path of whole groups of predators can be a direct consequence of climate change.

Two early dogs, Hesperocyon, left and the later Sunkahetanka, were both 
ambush-style predators. As climate changes transformed their habitat, 
dogs evolved pursuit hunting styles and forelimb anatomy to match 
[Credit: Mauricio Anton]

"It's reinforcing the idea that predators may be as directly sensitive to climate and habitat as herbivores," said Christine Janis, professor of ecology and evolutionary biology at Brown University, who worked with lead author Borja Figueirido, a former Brown Fulbright postdoctoral researcher who is now a professor at the Universidad de Malaga in Spain. "Although this seems logical, it hadn't been demonstrated before."

The climate in North America's heartland back around 40 million years ago was warm and wooded. Dogs are native to North America. The species of the time, fossils show, were small animals that would have looked more like mongooses than any dogs alive today and were well-adapted to that habitat. Their forelimbs were not specialized for running, retaining the flexibility to grapple with whatever meal unwittingly walked by.

But beginning just a few million years later, the global climate began cooling considerably and in North America the Rocky Mountains had reached a threshold of growth that made the continental interior much drier. The forests slowly gave way to open grasslands.

Pups of the plains

Did this transition affect the evolution of carnivores? To find out, Figueirido and the research team, including Jack Tseng of the American Museum of Natural History in New York, examined the elbows and teeth of 32 species of dogs spanning the period from ca. 40 million years ago to 2 million years ago. They saw clear patterns in those bones at the museum: At the same time that climate change was opening up the vegetation, dogs were evolving from ambushers to pursuit-pounce predators like modern coyotes or foxes -- and ultimately to those dogged, follow-a-caribou-for-a-whole-day pursuers like wolves in the high latitudes.

"The elbow is a really good proxy for what carnivores are doing with their forelimbs, which tells their entire locomotion repertoire," Janis said.

This is a skeleton of a 30-million-year-old fossil dog, Archaeocyon, in the 
American Museum of Natural History canid collection. The earliest dogs, 
going back 40 million years in North America, were animals no larger 
than a Chihuahua or a common house cat today 
[Credit: © AMNH/D. Finnin]

The telltale change in those elbows has to do with the structure of the base where the humerus articulates with the forearm, changing from one where the front paws could swivel (palms can be inward or down) for grabbing and wrestling prey to one with an always downward-facing structure specialized for endurance running. Modern cats still rely on ambush rather than the chase (cheetahs are the exception) and have the forelimbs to match, Janis said, but canines signed up for lengthier pursuits.

In addition, the dogs' teeth trended toward greater durability, Figueirido's team found, consistent perhaps with the need to chow down on prey that had been rolled around in the grit of the savannah, rather than a damp, leafy forest floor.

Not an 'arms race' of limbs

The study, with some of Janis' prior research, suggests that predators do not merely evolve as an "arms race" response to their prey. They don't develop forelimbs for speedy running just because the deer and the antelope run faster. While the herbivores of this time were evolving longer legs, the predator evolution evident in this study tracked in time directly with the climate-related changes to habitat rather than to the anatomy of their prey species.

After all, it wasn't advantageous to operate as a pursuit-and-pounce predator until there was room to run.

"There's no point in doing a dash and a pounce in a forest," Janis quipped. "They'll smack into a tree."

If predators evolved with climate change over the last 40 million years, the authors argue, then they likely will have to continue in response to the human-created climate change underway now. The new results could help predict the effects we are setting in motion.

"Now we're looking into the future at anthropogenic changes," Janis said.

Source: Brown University [August 18, 2015]

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Divers raise wreckage of Confederate warship

After 150 years at the bottom of the Savannah River, the armored skeleton of the Confederate warship CSS Georgia is being raised to the surface one 5-ton chunk at a time.

In a Friday, Aug. 14, 2015 photo provided by the US Navy, Chief Warrant Officer 3, Jason Potts, on scene commander for Task Element CSS Georgia, supervises as a piece of casemate, made of railroad ties and timber, which served as the outer layer of armor for CSS Georgia, is raised from the Savannah River in Savannah, Ga. Navy divers are working in conjunction with archaeologists, conservationists, Naval History and Heritage Command and the U.S. Army Corps of Engineers in a project directed by Naval Sea Systems Command Supervisor of Salvage and Diving to salvage and preserve CSS Georgia [Credit: MC1 Blake Midnight/US Navy via AP]

Navy divers who began working in late June to recover cannons, unexploded shells and other artifacts from the riverbed finally started midweek on their last major task — retrieving an estimated 250,000 pounds of the Civil War ironclad's armored siding.

The CSS Georgia was scuttled by its own crew to prevent Gen. William T. Sherman from capturing the massive gunship when his Union troops took Savannah in December 1864. Still classified as a captured enemy vessel by the Navy, the remains of the Confederate ironclad are being salvaged as part of a $703 million deepening of the Savannah harbor for cargo ships.

"The historical significance is evident in everything we do," Chief Warrant Officer 3 Jason Potts, the Navy's on-scene commander, said Wednesday as his crew prepared to start raising the first of three giant slabs of armor.

The CSS Georgia was a crude example of the first armored warships designed during the Civil War to stand up to cannon and artillery fire. Its 1,200-ton frame was built using three layers of timber topped with 24-foot strips of railroad iron.

In a Friday, Aug. 14, 2015 photo provided by the US Navy, from left to right, Parker Brooks, left, Jim Jobling, center, and James Duff, archaeologists assigned to the CSS Georgia project, examine a piece of casemate, made of railroad ties and timber, which served as the outer layer of armor for CSS Georgia, in Savannah, Ga. Navy divers are working in conjunction with archeologists, conservationists, Naval History and Heritage Command and the U.S. Army Corps of Engineers in a project directed by Naval Sea Systems Command Supervisor of Salvage and Diving to salvage and preserve CSS Georgia [Credit: MC1 Blake Midnight/US Navy via AP]

Having sections of the Georgia's armor for study should reveal more about how the Confederacy compensated for the South's lack of an industrial base when it came to building ships and other war machines.

"A lot of these ironclads are built by house carpenters, they're not built by shipwrights," said Jeff Seymour, historian and curator for the National Civil War Naval Museum in Columbus. "So what are the construction techniques? They vary from ship-to-ship."

The Georgia proved so bulky its own engines were too weak to propel it against the Savannah River's currents. The Confederates anchored the ironclad off Old Fort Jackson as a floating gun battery. It was sunk without ever firing a shot in combat.

After months of preparation work by underwater archaeologists, Navy divers from the Virginia Beach-based Mobile Diving Salvage Unit 2 arrived in late June.

Their first task was to raise 132 unexploded shells — both cannonballs and rifled shells shaped like large bullets — found scattered across the wreckage site. Using a crane mounted on a barge, they also pulled up four cannons weighing 1,000 to 10,000 pounds apiece.

Other artifacts soon emerged from 40 feet or more of water: a flywheel, a pump and sections of the steamship's boiler. Perhaps most impressive, the Georgia's propeller was recovered intact and still attached to the long shaft that turned it.

"We don't just simply want to bring it all back to the surface," Potts said. "We want to bring it back intact. So we go to the maximum effort to make sure we don't rip these things apart on the way up."

The three large sections of the Georgia's armored casemate, however, proved too heavy to raise without cutting them down into smaller pieces. They're being separated into about 20 total chunks, each measuring about 4 feet by 24 feet and weighing roughly 5 tons.

After a century and a half, Potts said, most of the ship's wooden hull has rotted away. But the railroad iron remains essentially glued together by mud and silt from the riverbed. The crew uses a crane-held tool with a long, flat blade to slide between the iron strips and pry apart chunks of the armor.

A web of slings is then attached to the slab of armor to ensure its weight is evenly distributed as the crane lifts it from the river.

With river currents typically limiting divers to less than three hours underwater each day, Potts estimates it will take his team nearly a month to raise all of the armored siding. That's at a rate of roughly one 5-ton chunk per day.

All artifacts from the CSS Georgia are being sent to the Conservation Research Laboratory at Texas A&M University in College Station, Texas, for cataloging and preservation. The Navy hasn't said where those artifacts will ultimately reside.

Author: Russ Bynum | Source: Associated Press [August 17, 2015]

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Paleobotanists identify what could be the mythical 'first flower'

Indiana University paleobotanist David Dilcher and colleagues in Europe have identified a 125 million- to 130 million-year-old freshwater plant as one of earliest flowering plants on Earth.

A large intact specimen of the fossil, Montsechia. Usually only small fragmentary
 pieces of the fossil are found [Credit: David Dilcher]

The finding, reported Aug. 17 in the Proceedings of the National Academy of Sciences, represents a major change in the presumed form of one of the planet's earliest flowers, known as angiosperms.

"This discovery raises significant questions about the early evolutionary history of flowering plants, as well as the role of these plants in the evolution of other plant and animal life," said Dilcher, an emeritus professor in the IU Bloomington College of Arts and Sciences' Department of Geological Sciences.

The aquatic plant, Montsechia vidalii, once grew abundantly in freshwater lakes in what are now mountainous regions in Spain. Fossils of the plant were first discovered more than 100 years ago in the limestone deposits of the Iberian Range in central Spain and in the Montsec Range of the Pyrenees, near the country's border with France.

Also previously proposed as one of the earliest flowers is Archaefructus sinensis, an aquatic plant found in China.

"A 'first flower' is technically a myth, like the 'first human,'" said Dilcher, an internationally recognized expert on angiosperm anatomy and morphology who has studied the rise and spread of flowering plants for decades. "But based on this new analysis, we know now that Montsechia is contemporaneous, if not more ancient, than Archaefructus."

He also asserted that the fossils used in the study were "poorly understood and even misinterpreted" during previous analyses.

"The reinterpretation of these fossils provides a fascinating new perspective on a major mystery in plant biology," said Donald H. Les, a professor of ecology and evolutionary biology at the University of Connecticut, who is the author of a commentary on the discovery in the journal PNAS. "David's work is truly an important contribution to the continued quest to unravel the evolutionary and ecological events that accompanied the rise of flowering plants to global prominence."

Illustrations based on fossilized remains show long- and short-leaved forms 
of the plant and a single seed [Credit: Oscar Sanisidro]

The conclusions are based upon careful analyses of more than 1,000 fossilized remains of Montsechia, whose stems and leaf structures were coaxed from stone by applying hydrochloric acid on a drop-by-drop basis. The plant's cuticles -- the protective film covering the leaves that reveals their shape -- were also carefully bleached using a mixture of nitric acid and potassium chlorate.

Examination of the specimens was conducted under a stereomicroscope, light microscope and scanning electron microscope.

The age of the plant at 125 million to 130 million years is based upon comparisons to other fossils in the same area, notably the freshwater algae charophytes, which places Montsechia in the Barremian age of the early Cretaceous period, making this flowering plant a contemporary of dinosaurs such as the brachiosaurus and iguanodon.

The precise, painstaking analysis of fossilized structures remains crucial to paleobotany, in contrast to other biological fields, due to the current inability to know the molecular characters of ancient plants from millions of years ago, Dilcher said.

This careful examination was particularly important to Montsechia since most modern observers might not even recognize the fossil as a flowering plant.

"Montsechia possesses no obvious 'flower parts,' such as petals or nectar-producing structures for attracting insects, and lives out its entire life cycle under water," he said. "The fruit contains a single seed" -- the defining characteristic of an angiosperm -- "which is borne upside down."

In terms of appearance, Dilcher said, Montsechia resembles its most modern descendent, identified in the study as Ceratophyllum. Also known as coontails or hornworts, Ceratophyllum is a dark green aquatic plant whose coarse, tufty leaves make it a popular decoration in modern aquariums and koi ponds.

Next up, Dilcher and colleagues want to understand more about the species connecting Montsechia and Ceratophyllum, as well as delve deeper into when precisely other species of angiosperms branched off from their ancient forefathers.

"There's still much to be discovered about how a few early species of seed-bearing plants eventually gave rise to the enormous, and beautiful, variety of flowers that now populate nearly every environment on Earth," he said.

Source: Indiana University [August 17, 2015]

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Remains of ancient primate found in Oregon

Scientists have unearthed fossil teeth and a jaw fragment in Oregon. And these have helped flesh out the features of an ancient animal that once lived in North America. A new species of primate, it had features similar to a modern lemur’s.

Artist’s conception of what North America’s last nonhuman primates might have
 looked like. The animals are shown on a hackberry tree. It’s the most common 
plant known from the sediment layer in which the fossils were found 
[Credit: Christopher Herndon]

Primates are a group of mammals that includes monkeys, lemurs, gorillas and humans. The Sioux are a tribe of Native Americans. The newfound primate’s genus name comes from a Sioux term for monkey: Ekgmowechashala. These last nonhuman primates to live in North America vanished around 26 million years ago. No other primates lived in North America until humans arrived well over 25 million years later. This timeline comes from the new study. It was published June 29 in the American Journal of Physical Anthropology.

Joshua Samuels works for the National Park Service in Kimberly, Ore. As a paleontologist, he studies ancient fossils. He and his colleagues dug up the ancient primate bones between 2011 and early 2015. They found two complete teeth, two partial teeth and a jaw fragment.

All came from rocky sediment at Oregon’s John Day Formation. This rock layer, or stratum, contains fossils from between 30 million and 18 million years ago. A tooth and jaw fragment from the same species had been found there previously. All the fossils belong to a new species of Ekgmowechashala, the researchers say. Partial jaws and teeth of a related species had turned up at sites in South Dakota and Nebraska.

The scientists figured out the age of the fossils based on their position between layers of volcanic ash. The ages of those layers was already known. That let the scientists determine that the new fossils must be between 28.7 million and 27.9 million years old.

Where did the primates come from?

Millions of years ago, land connected what is now Alaska and Russia. The ancient primates probably crossed that “land bridge” around 29 million years ago, the researchers now say. That journey would have taken place some 6 million years after other North American primates had died out.

Samuels says the new fossils appear to resemble those from a 34-million-year-old primate from Thailand, in Southeast Asia. The new fossils also are similar to a 32-million-year-old primate from Pakistan, which lies between the Middle East and India.

Erik Seiffert is a paleontologist at Stony Brook University in New York. He suggested an Asian–North American primate connection back in 2007. But Samuels and his team “have laid out the evidence in more detail,” Seiffert now says.

Some researchers suspect Ekgmowechashala’s closest present-day relatives would have been tarsiers. These small primates live on islands in Southeast Asia. Other scientists think the now extinct North American primates were more closely related to lemurs. They exist only in Madagascar. It’s an island off of the East Coast of southern Africa.

K. Christopher Beard agrees with Samuels’ team that Ekgmowechashala is likely more related to the lemurs. A paleontologist, Beard works at the University of Kansas in Lawrence. But he argues that to confirm this, scientists need to find ankle bones. They should point out whether the ancient primate species had a greater kinship to lemurs or to tarsiers.

Author: Bruce Bower | Source: Student Science [August 13, 2015]

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