Fossil find puts ‘Lucy’ story on firm footing

By Jonathan Amos
Science correspondent, BBC News

New fossil evidence seems to confirm that a key ancestor of ours could walk upright consistently – one of the major advances in human evolution.

The evidence comes in the form of a 3.2 million-year-old bone that was found at Hadar, Ethiopia.

Its shape indicates the diminutive, human-like species Australopithecus afarensis had arches in its feet.

Arched feet, the discovery team tells the journal Science, are critical for walking the way modern humans do.

“[The bone] gives a glimpse of foot anatomy and function,” explained William Kimbel, director of the Institute of Human Origins at Arizona State University, US.

“It is the fourth metatarsal bone, which resides on the outside of the middle part of your foot, and which helps support the well-developed arches of the foot that we see in the soles of modern human feet.

“The bone that was recovered from the Hadar site has all the hallmarks of the form and function of the modern human foot,” he told the BBC.

Arch types
Palaeo-scientists knew A. afarensis spent some of its time standing tall; that much has been clear since 1974 when they first examined a skeleton of the species, famously dubbed “Lucy”, also found near the village of Hadar in the Ethiopian rift valley.

But the absence of important foot bones in all of the specimens uncovered to date has made it difficult for researchers to understand precisely how much time Lucy and her kin spent on their feet, as opposed to moving through the branches of trees.

Human feet are very different from those of other primates. They have two arches, longitudinal and transverse.

These arches comprise the mid-foot bones, and are supported by muscles in the soles of the feet.

This construction enables the feet to perform two critical functions in walking. One is to act as a rigid lever that can propel the body forwards; the other is to act as a shock absorber as the feet touch the ground at the end of a stride.

In our modern ape cousins, the feet are more flexible, and sport highly mobile large toes that are important for gripping branches as the animals traverse the tree tops.

Professor Kimbel and colleagues tell Science journal that the feet of A. afarensis’ say a lot about the way it lived.

It would have been able to move across the landscape much more easily and much more quickly, potentially opening up broader and more abundant supplies of food, they say.

“Lucy’s spine has the double curve that our own spine does,” Professor Kimbel said.

“Her hips functioned much as human hips do in providing balance to the body with each step, which in a biped of course means that you’re actually standing on only one leg at a time during striding.

“The knees likewise in Lucy’s species are drawn underneath the body such that the thighbone, or femur, angles inwards to the knees from the hip-joints – as in humans.

“And now we can say that the foot, too, joins these other anatomical regions in pointing towards a fundamentally human-like form of locomotion in this ancient human ancestor.”

A. afarensis is thought to have existed between about 2.9 million and 3.7 million years ago, and the Hadar area has yielded hundreds of fossil specimens from the species.

Long road
Commenting on the latest research, Professor Chris Stringer, a palaeoanthropologist at London’s Natural History Museum, said scientists were gradually filling in the detail of this creature’s position in the human origins story.

“Bipedalism in Lucy is established, but there has been an issue about how much like our own that bipedalism was,” he told BBC News.

“Was it a more waddling gait or something more developed?

“And certainly there’s evidence in the upper body that the Australopithecines still seemed to have climbing adaptations – so, the hand bones are still quite strongly curved and their arms suggest they’re still spending time in the trees.

“If you are on the ground all the time, you need to find shelter at night and you are in a position to move out into open countryside, which has implications for new resources – scavenging and meat-eating, for example.

“If the Australopithecines were on that road, they were only at the very, very beginning of it.”

Fossil female pterosaur found with preserved egg

By Jonathan Amos
Science correspondent, BBC News
It was the males which carried a crest, the latest research published in Science magazine suggests

For fossil hunters, it represents one of those breakthrough moments.

A pterosaur has been found in China beautifully preserved with an egg.

The egg indicates this ancient flying reptile was a female, and that realisation has allowed researchers to sex these creatures for the first time.

Writing in Science magazine, the palaeontologists make some broad statements about gender differences in pterosaurs, including the observation that only males sported a head-crest.

David Unwin, a palaeobiologist in the Department of Museum Studies at the University of Leicester, was part of the research team.

He told the BBC the discovery was astonishing: “If somebody had said to me a few years back that we would find this kind of association, I would just have laughed and said, ‘yeah, maybe in a million years’, because these sorts of things are incredibly rare.”

Pterosaurs, also sometimes referred to as pterodactyls, dominated the skies in the Mesozoic Era, 220-65 million years ago. Although reptiles like the dinosaurs were plodding on the ground below them, they were not actually dinosaurs themselves – a common misconception.

This particular specimen has been dated to about 160 million years ago.

It was found by Junchang Lü and colleagues and excavated from sedimentary rocks in the famous fossil-hunting grounds of Liaoning Province in China. Liaoning has yielded many of the great finds in recent years, including a series of feathered dinos that have transformed thinking on bird evolution.

The new creature is from the Darwinopterus genus, or grouping, but has been dubbed simply as “Mrs T” (a contraction of “Mrs Pterodactyl”) by the research team.

The state of the egg’s shell suggests it was well developed and that Mrs T must have been very close to laying it when she died.

She appears to have had some sort of accident as her left forearm is broken. The researchers speculate she may have fallen from the sky during a storm or perhaps a volcanic eruption, sunk to the bottom of a lake and then been preserved in the sediments.

“The most important thing about this particular individual is that she has a relatively large pelvis compared to other individuals of the same pterosaur, Darwinopterus,” explained Dr Unwin.

“This seems quite reasonable – females lay eggs, they probably need a slightly wider pelvis. And then the really exciting thing is that she has a skull which lacks any kind of adornment or decoration whatsoever. When we look at other individuals of Darwinopterus, we find quite a few individuals with a large crest on the skull.

“We’re very confident now that we’re dealing with two genders here – males with big crests and small hips, and females with no crest on the skull and large hips.”

The female fossil partially prepared (A). After being fully prepared (B), the egg is clear to see (red circle)

Jonathan.Amos-INTERNET@bbc.co.uk

Audio included on original page: http://www.bbc.co.uk/news/science-environment-12242596

Early T. Rex ancestor found in South America


By RANDOLPH E. SCHMID, AP Science Writer Randolph E. Schmid, Ap Science Writer
Thu Jan 13, 6:23 pm ET

WASHINGTON – Back at the dawn of the dinosaur era, a quick-moving predator set the stage for the famous and fearsome giants that followed in its footsteps, according to new research. “It was a little dinosaur, but it carried a big evolutionary stick,” said Paul C. Sereno of the University of Chicago, a leader of the team that discovered Eodromaeus.

The 4-foot-long hunter lived 230 million years ago in what is now South America and appears to be the ancestor of such creatures as Tyrannosaurus rex.

“It is stunning,” Sereno said of the find, reported in Friday’s edition of the journal Science.

Its features, such as a balancing tail and air pockets in the skull, show it was closely related to T. rex, he said.

But while it stood on two feet like T. rex, Eodromaeus (pronounced eyo-DRO-may-us) was a lightweight at just 10- to 15-pounds.

“This is a very exciting find indeed,” said Oliver W. M. Rauhut, a curator at the Bavarian State Collection for Palaeontology and Geology in Munich, Germany.

“The origin and early diversification of dinosaurs is still poorly understood,” said Rauhut, who was not on the research team.

Nick Longrich of the department of geology and geophysics at Yale University agreed: “It’s very significant, because it helps give us a better idea of what the ancestor of carnivorous dinosaurs — including Tyrannosaurus, Allosaurus and the birds — would have looked like.”

“A new species of early dinosaur is always an exciting find, especially when the specimens are so complete, like Eodromaeus,” added Randall B. Irmis, a professor of geology and geophysics at the University of Utah.

It shares many features with an early carnivorous dinosaur named Tawa from New Mexico and reported last year by Irmis and colleagues.

The similarity supports the idea that these early carnivorous dinosaurs moved between North and South America during the Late Triassic period, said Irmis, who was not part of Sereno’s research team.

In addition to the discovery of Eodromaeus — which means dawn runner — the researchers proposed reclassifying a previously known dinosaur called Eoraptor.

It was similar in size to Eodromaeus, but differences in the teeth indicate Eoraptor more likely was an ancestor of the giant plant-eating sauropod dinosaurs than the hunting theropods like T. rex with which it had been associated, according to Sereno, Paul N. Martinez of the National University of San Juan in Argentina, and their co-authors.

“The reclassification of Eoraptor actually makes perfect sense … the teeth have always made me wonder,” said Longrich, who was not on the research team.

Added Longrich, “this paper helps sort out the origin of several major groups — the big carnivores like T. rex, the birds, and the giant plant eaters like Apatosaurus,” formerly known as Brontosaurus.

The new find brings scientists to within a few million years of the original “Eve” dinosaur, Sereno commented. But now the search gets elusive because of the lack of bones below the level where Eodromaeus was found.

Lower, there are footprints but not bones, Sereno said.

The Eodromaeus’ fossils were discovered in the late 1990s in the Ischigualasto formation in northeastern Argentina.

___

Online: http://www.sciencemag.org

Vast Amber Deposit from India

New Trove of Fossils Suggests Global Distribution of Tropical Forest Ecosystems in the Eocene

ScienceDaily (Oct. 26, 2010) — A vast new amber deposit in India has yielded 100 fossil spiders, bees, and flies that date to the Early Eocene, or 52-50 million years ago. These arthropods are not unique — as would be expected on an island (which India was at that time) — but have close evolutionary relationships with fossils from the Americas, Europe, and Asia. The amber is also the oldest evidence of a tropical broadleaf rainforest in Asia.

Bees, termites, spiders, and flies entombed in a newly-excavated amber deposit are challenging the assumption that India was an isolated island-continent in the Early Eocene, or 52-50 million years ago. Arthropods found in the Cambay deposit from western India are not unique — as would be expected on an island — but rather have close evolutionary relationships with fossils from other continents. The amber is also the oldest evidence of a tropical broadleaf rainforest in Asia.

The discovery is published this week in Proceedings of the National Academy of Sciences.

“We know India was isolated, but when and for precisely how long is unclear,” says David Grimaldi, curator in the Division of Invertebrate Zoology at the American Museum of Natural History. “The biological evidence in the amber deposit shows that there was some biotic connection.”

“The amber shows, similar to an old photo, what life looked like in India just before the collision with the Asian continent,” says Jes Rust, professor of Invertebrate Paleontology at the Universität Bonn in Germany. “The insects trapped in the fossil resin cast a new light on the history of the sub-continent.”

Amber from broadleaf trees is rare in the fossil record until the Tertiary, or after the dinosaurs went extinct. It was during this era that flowering plants rather than conifers began to dominate forests and developed the ecosystem that still straddles the equator today. The new amber, and amber from Colombia that is 10 million years older, indicates that tropical forests are older than previously thought.

In the research paper, Grimaldi, Rust, and colleagues describe the Cambay amber as the oldest evidence of tropical forests in Asia. The amber has been chemically linked to Dipterocarpaceae, a family of hardwood trees that currently makes up 80 percent of the forest canopy in Southeast Asia. Fossilized wood from this family was found as well, making this deposit the earliest record of these plants in India and showing that this family is nearly twice as old as was commonly believed. It most likely originated when portions of the southern supercontinent Gondwana were still connected.

Also reported in the paper are 100 arthropod species that represent 55 families and 14 orders. Some of these species are early relatives of highly social, or eusocial, insects like honey bees and stingless bees, rhinotermitid termites, and ants, suggesting that these groups radiated during or just prior to the early Eocene. And many of the Cambay fossils have relatives on other continents — although not where it would be expected. Rather than finding evolutionary ties to Africa and Madagascar, landmasses that India had most recently been linked to as part of Gondwana, the researchers found relatives in Northern Europe, Asia, Australia, and the Americas.

“What we found indicates that India was not completely isolated, even though the Cambay deposit dates from a time that precedes the slamming of India into Asia,” says Michael Engel, a professor in the Department of Ecology and Evolutionary Biology and curator of entomology at the University of Kansas. “There might have been some linkages.”

Climate might have also played a role in the fauna found in the Cambay amber. The Early Eocene was a time of great climatic warmth: the tropics reached the poles. The researchers predict that the climate would have had an effect on the distribution of arthropods.

“The Cambay Formation spans a period of great warmth which led to a profusion of tropical groups spread around the world,” says Grimaldi. “The diversity and evolutionary relationships in the Cambay deposit show how profound an effect climate has on groups.”

In addition to Grimaldi, Rust, and Engel, authors include Tom McCann, Frauke Gerdes, and Monica Solórzano-Kraemer of the Universität Bonn in Germany; Hukam Singh of Birbal Sahni Institute of Palaeobotany in India; Rajendra S. Rana and Lacham Singh of H.N.B. Garhwal University in India; Ken Anderson of Southern Illinois University in Carbondale; Nivedita Sarkar and Ashok Sahni of the University of Lucknow in India; Paul C. Nascimbene of the American Museum of Natural History; Jennifer C. Thomas of the University of Kansas; and Christopher J. Williams of Franklin and Marshall College in Pennsylvania. The research was funded in part by several organizations: American Museum of Natural History, U.S. National Science Foundation, National Geographic Society, and DFG (German Research Foundation).