Ancient reptile walked on two legs

Walking on two legs million of years before dinosaurs

November 2, 2000 - BBC

A newly discovered fossil of a reptile that walked on two legs shows that bipedal locomotion evolved long before the dinosaurs.

This discovery has shown interesting and exciting things happening in the evolutionary history of reptiles well before the advent of dinosaurs.

The exquisitely preserved, 290-million-year-old skeleton of Eudibamus cursoris was dug up in a German quarry by an international team of scientists.

It is the oldest known member of the Parareptilia, a major group of primitive reptiles. Eudibamus does not appear to be a direct ancestor to later reptiles, including some dinosaurs, that adopted a bipedal posture and gait.

This may indicate that the ability to walk upright on two legs arose several times independently during reptile evolution.

Built for speed

Although only 26.1 cm (10.3 inches) long, the Eudibamus fossil contains a wealth of clues about how the reptile moved.

The skeleton shows all the signs of bipedalism

Scientists say the creature's upper limbs were relatively short for its overall size, while its lower limbs were relatively long. The reptile also had an unusually long foot and tail, proportions usually indicative of bipedal locomotion.

They think the long tail could have served as a sort of rudder, compensating for changes in the animal's centre of gravity as it moved along in an upright position.

Other evidence of bipedalism comes from the arrangement of the hip, knee, and ankle joints in the reptile's lower limb. The surfaces of these joints are arranged so that the bones in the legs formed a straight line when the hind limbs were fully extended.

Dinosaurs and mammals

This means that the creature's ankles and knees were able to flex and extend in only one plane in a similar way to how human knees and ankles move mostly back and forth, but not side to side.

Eudibamus cursoris appears to be the earliest known tetrapod, or four-legged vertebrate, to adopt this distinctive posture and gait.

"This find is fascinating because it confirms that bipedalism is an innovation that has happened several times," said Professor Robert Reisz, of the University of Toronto at Mississauga.

"It happened in some dinosaurs, and their bird descendants, and it happened in mammals, so it must be a good idea in terms of evolution."

Evolved several times

"There are only a couple of times in evolutionary history when animals have gone from a sprawled posture like that of a four-legged lizard to an upright posture when they tuck their limbs under the body.

The fossil was uncovered in a German quarry

"It happened once in dinosaurs and again with mammals. So to find an example of an animal that did this before dinosaurs or mammals is particularly exciting."

According to the researchers, who report their work in the journal Science, even on four legs, the creature's distinct posture would have distinguished its movement from the sprawling gait used by the other tetrapods of the time.

Eudibamus belongs to an extinct family of early reptiles with an unusually large geographic range, compared to its contemporaries in the early Permian (about 290 to 268 million years ago).

Unique locality

"It was thought that the ability to run on two legs and stand upright first emerged in dinosaurs and their relatives. But this discovery has shown interesting and exciting things happening in the evolutionary history of reptiles well before the advent of dinosaurs," said professor Reisz.

The teeth of Eudibamus indicate that it was a plant eater, so it was not using its speed to chase food. Instead, it probably used its sprinting speed to escape predators.

Professor Reisz and colleagues plan to continue excavations at the German quarry, which has already yielded a number of other well-preserved fossils. "It's a super site, a unique locality," said the palaeontologist,

"And it gives us a chance to show that some neat things were happening with reptiles in the Palaeozoic, long before the appearance of dinosaurs."

Discovery Of Fossil Mollusks In Alaska Links Histories Of Arctic Ocean And Isthmus Of Panama

June 12, 2000 - AP

Finding two fossil mollusks in a California collection led a researcher funded by the National Science Foundation (NSF) to undertake field work in Alaska that he says links the formation of the Isthmus of Panama approximately 3.6 million years ago to a reversal of water flow through the Bering Strait.

Louie Marincovich, of the California Academy of Sciences, is the first to produce fossil evidence that the flow of water through the strait, which separates Russia and Alaska, was reversed from southward to northward by the uplifting of the Isthmus. He also is the first to date the flow shift.

Marincovich's findings also validate computer models of Northern Hemisphere oceanography for that time period, at least as they affected the Arctic Ocean.

"This discovery was only possible because someone picked up two fossils in Alaska in the 1970's, not knowing what they were and donated them to the California Academy of Sciences, where I recognized them 25 years later," Marincovich said. "I was going through the collections with another topic in mind when I saw them and had my 'Eureka moment,' when I knew they were the first datable evidence of the Bering Strait's being open."

Astarte, the fossil mollusk, lived only in the Arctic and North Atlantic oceans until prior to the opening of the strait.

The discovery of an Astarte in southern Alaska in rocks almost 5.5 million years old led Marincovich to conclude that the Bering Strait must have first opened at that time. In order to be found in southern Alaska, Astarte must have migrated southward through Bering Strait.

What was puzzling about his find is that nearly two million years passed before mollusks from the Pacific began migrating northward through the open Bering Strait to the Arctic and North Atlantic oceans. Pacific mollusks first appear in the fossil record there only 3.6 million years ago.

Marincovich's research on fossil mollusks in the North Pacific, Arctic and North Atlantic oceans led him to conclude that the direction of seawater flow through the Bering Strait gateway must have changed from a southerly flow to a northerly one around 3.6 million years ago. This reversal in flow direction had been theorized by computer models of past ocean flow, and was thought to have been caused by formation of the Isthmus of Panama as a land barrier where a broad tropical seaway between North and South America had existed for millions of years.

The formation of this tropical isthmus caused drastic shifts in Northern Hemisphere ocean currents, and initiated the flow of the Gulf Stream. However, just when these changes took place and affected the Arctic Ocean was a mystery not predicted by the computer models.

Marincovich's work was funded by the Arctic natural sciences section of NSF's Office of Polar Programs. An article about his findings may be found in the June issue of Geology, a publication of the Geological Society of America.

Life On Earth Said 600 Million Years Older Than Thought

Penn State Eberly College Of Science--January 1999

The ancestors of major groups of animal species began populating Earth more than 600 million years earlier than indicated by their fossil remains, according to the largest study on the subject using gene sequences, recently completed at Penn State. The research suggests that animals have been evolving steadily into different species for at least 1200 million years, which challenges a popular theory known as the Cambrian Explosion that proposes the sudden appearance of most major animal groups, known as phyla, 530 million years ago. A paper describing the research will be published in the January 22, 1999, issue of the Proceedings of the Royal Society of London (Series B) by Penn State Undergraduate Student Daniel Y.-C. Wang, Postdoctoral Fellow Sudhir Kumar, and Associate Professor of Biology S. Blair Hedges.

To gauge the pace of evolution, the research team tested hundreds of gene sequences to find those that developed mutations at a constant rate over time. "Because mutations start occurring at regular intervals in these genes as soon as a new species evolves--like the ticking of a clock--we can use them to trace the evolutionary history of a species back to its actual time of origin," Hedges explains.

By comparing individual genes in pairs of species, the researchers identified 75 nuclear genes that had accumulated mutations at a fairly constant rate relative to one another during their evolution. The genes were from species representing three major taxonomic groups, or phyla, of animals (arthropods, chordates, and nematodes), plus plants and fungi.

The scientists then calibrated these molecular clocks to an evolutionary event well established by fossil studies--the divergence of birds and mammals about 310 million years ago. "A clock isn't any good unless it is calibrated to a time that everyone else agrees on," Hedges explains, "and just about everyone agrees on the date when reptilian ancestors of birds and mammals appeared because it is based on well-accepted studies of fossils." Using this date as a secure calibration point--and the mutation rate for each of the constant-rate genes as a timing device--the researchers were able to determine how long ago each of the species originated.

"Not only are all these genes telling us that a wealth of animal species in at least three phyla were already on Earth millions of years before their fossils start appearing," Hedges says, "but they also are telling us when three of the major kingdoms of living things--animals, plants, and fungi-- first diverged from a common ancestor and began evolving down separate evolutionary paths." That date--about 1.6 billion years ago--is the earliest yet obtained by gene studies for this evolutionary event, according to Hedges.

The Penn State team used more than twice as many genes to date the origin of the three major animal phyla as had been used in any other study since gene sequences first became available in the Genbank public databases maintained by the National Institutes of Health (NIH) during the 1970s. "We wanted to have so much data that the conclusions from our study of this controversial issue could be very robust," Hedges comments. Earlier studies using many fewer genes were disturbing to some researchers because they yielded a wide range of dates for the origin of animal species, although all the gene studies agreed that the event occurred well before the Cambrian period. "Our methodology and our larger data set should have had a stabilizing effect; and in fact, our study resulted in a date intermediate between the earlier estimates," Hedges says.

If the results of his team's genetic study are correct, Hedges says the scientific question must change from "How did all these species evolve so suddenly early in the Cambrian period?" to "Why don't we see any fossils of these species long before the Cambrian period?" Among the suggested answers are that changes in the Earth's atmosphere led to the development of hard external skeletons in animals that had only soft external skeletons before the Cambrian period. "Hard body parts like external skeletons are most likely to become fossils," Hedges explains. Species not likely to fossilize, like earthworms, typically live and die without leaving a trace of their existence--except in the genes of their descendants.

Another hypothesis is that many species of animals with skeletons were living on Earth before the Cambrian period, but they were so small that their fossils have not yet been found. "The further back in time you want to look in the fossil record, the fewer places there are on Earth to look," Hedges explains. Fossils have to be safely encased in sedimentary rock, which, over time, melts or becomes deformed by the movement of the Earth's crust. Sedimentary rocks over 3 billion years old are very rare. "If we can find very-old and very-fine-grained phosphate sediments, which can preserve even soft bodies, we might have the potential of finding fossils of these early animals, even if they were only microscopic in size," Hedges says. "We seem to be missing the fossils of a lot of species."

Hedges says his research might be useful for finding life on other planets. "If we can learn when different stages of life evolved on Earth, we can compare those dates to events in the chemical evolution of Earth's atmosphere and ocean, such as when oxygen and other important gases increased," Hedges explains. Research with this goal is an important focus in Penn State's Astrobiology Research Center. "Our goal is to see if the early history of life on Earth can give us clues for how to predict life on other planets and in other solar systems," Hedges says. "We hope to be able to predict the kinds of lifeforms that are likely to exist on other planets, based on those that existed during Earth's history, just by measuring the chemical content of the planet's atmosphere."

80-million-year-old fossil may be oldest marsupial

New York -December 2, 1998

Scientists in Mongolia have uncovered a pair of fossils that may contain evidence of some of the earliest characteristics of marsupials, or mammals that develop their young in a pouch. The newly discovered specimens of Deltatheridium, an opossum-like animal, are 80 million years old, which would mean they lived among the dinosaurs.

The discovery more closely defines the time period when marsupials emerged, said Guillermo W. Rougier, a paleontologist at the University of Louisville and the American Museum of Natural History in New York.

Rougier was among three researchers who found the specimens at Ukhaa Tolgod in the deserts of Mongolia. Their research will be published Thursday in the journal Nature. Marsupials represent one of three branches of mammals. The two other branches are monotremes, such as the egg-laying duckbilled platypus, and placentals such as humans that develop their young inside the body. Besides opossums, modern marsupials include kangaroos and wallabies. Most live in South America and Australia, but the Mongolian fossils suggest they originated in Asia. Deltatheridium had large molars and sharp canine teeth, and probably hunted lizards and smaller mammals. Researchers said the Deltatheridium specimens share many traits with modernmarsupials, such as a bony feature in the back of the jaw where chewing muscles attached.

Oldest reptile nests discovered in Arizona's Petrified Forest

October 28, 1998

The world's oldest known reptile nests have been identified in Arizona, presenting the problem that protective parenting habits developed much earlier in the history of life than previously believed. The 62 bowl-like depressions in a sandstone layer in Petrified Forest National Park were dated at 220 million years old, twice as old as any previously known reptile nests.

The nests -- holes in the sand that over time turned into stone -- were probably made by crocodile-like creatures called phytosaurs or by aetosaurs, which were armored reptiles, said Stephen Hasiotis, a consulting geologist for Exxon who discovered the sites. Other scientists said the discovery suggests that at least 220 million years ago, during the Triassic Period, some vertebrates stopped laying their eggs directly on the ground and started protecting them in nests.

The nests do little to resolve one of the hottest debates in paleontology: How helpless were baby dinosaurs? Many researchers believe that dinosaur babies hatched soft-boned, blind and helpless, like baby birds. They argue that dinosaur adults were tender, caring parents and that the young remained in the nest for feeding and protection.

But recent analyses of some dinosaur embryos suggest they were born with strong bones and muscles in order to immediately avoid predators, much like modern alligators and ostriches. Hasiotis discovered the nests in 1996 when he was a research associate at the University of Colorado. He said he frequently walked past dozens of depressions without realizing their significance. Only in the twilight did he recognize their nest-like features -- smooth sides, a rim and partial footprints trampling what once was the sandy shoreline of an ancient river.

No eggs or shell fragments were found in the Arizona nests. The walls of the nests appear to have been compacted, a feature shared with the nesting sites of modern-day crocodiles, which stay near their nests and guard their eggs from predators. Like modern animals, the ancient creatures might have dug several test holes before deciding on the right location.

The oldest reptile fossils are dated to about 300 million years old. Prior to the Arizona discovery, the oldest fossil nest of any kind was a 110 million-year-old sea turtle nest. It was located on the dry plains of eastern Colorado on what was the coast of a shallow, ancient sea. Paleontologist Gale Bishop of Georgia Southern University, one of the turtle nest experts, described the Arizona discovery as "quite convincing."

Evidence of billion-year-old worm-like animals found in rock

September 30, 1998 - AP

Researchers say they have found tiny tunnels preserved in rock in India that were dug by burrowing, worm-like creatures more than a billion years ago. The finding indicates complex animals may have evolved far earlier in Earth's history than previously believed. The tunnels, about the size of a soda straw, are thought to be the oldest trace fossil ever found and probably were carved by worms that lived under the muck at the bottom of a shallow sea, Adolph Seilacher of Yale University said Wednesday.

Multicellular animals made a dramatic appearance in the fossil record about 540 million years ago at the beginning of what is called the Cambrian period. Animals then developed skeletons, shells and mineralized bodies that were preserved in the fossils.

Before that, it has been believed, life consisted of primitive, soft-bodied organisms that left no trace in the fossil record. Scientists generally believed that life started some 4 billion years ago with simple, single-celled creatures that crept slowly up the evolutionary ladder until there was an explosion of new, complex life forms during the Cambrian.

But Seilacher, a professor emeritus at the University of Tubingen in Germany, said that discovery of the worm tunnels in India shows that there were multicellular animals, with complicated and intricate lifestyles, more than a half-billion years before the Cambrian. "This means that the birth of multicellular animals was at least twice as long ago as we thought," he said. The announcement, made at a German news conference, met with immediate skepticism among some paleontologists.

Seilacher and his colleagues found the tunnels, now eroded to mere meandering grooves, in sandstone in northern India. The rock was formed from sand that once was the floor of a shallow sea. Seilacher said he believes the worm-like creatures lived in the sand and fed on a mat of decaying organic matter that coated the sea floor. The organic matter, he said, probably was the bodies of microorganisms and algae that lived in the water, died and sank to the bottom.

Seilacher said the path of the tunnels seems to purposely follow the contours of the sea floor, as if the animals were feeding from below on the organic debris. Some of the tunnels have branches, he said, suggesting that the animals sometimes dug forward and then backed out to take a new burrowing path. This suggests a complex life form that had nerves, instincts and senses. The shape of the tunnels, said Seilacher, suggests the animals moved by a wavelike action and could have been coated with a mucous that eased the passage through the sand.

Seilacher said the sand containing the tunnels hardened over time to become rock and this preserved the impressions of the tunnels. In recent geologic times, the rock has been lifted up and layers eroded away, revealing the tunnels as grooves in the soft stone. Runnegar said a troubling element of Seilacher's conclusion is that there is a 400 million-year gap in the fossil record between the worm tunnels and the hard-bodied fossils of animals from the Cambrian period.

Fossils Found in China date back 570 million years

New York -February 4, 1998 - AP

Scientists have found fossil embryos that might be the oldest known remains of creatures with definite left and right sides -- a group that includes people and the vast majority of modern-day animals.

The embryos are part of spectacular trove of small but highly detailed fossils found in China. The fossils are some 570 million years old, give or take 20 million years, and come from an early and poorly understood stage in animal evolution.

The discoveries don't reveal any major surprises about evolution, but experts say they're important because they show that exquisitely preserved fossils of soft-bodied animals can still be recovered from that crucial era.

The embryos are about the size of sand grains. They might be the earliest known remains of "bilaterians," which are animals that, unlike sponges or jellyfish, have definite left and right sides. That's everything from worms to us.

The fossils come from a time before animals developed skeletons, shells or even limbs. Basic body differences were just appearing. Creatures of this era lived in water and included sponges and animals resembling jellyfish and sea anemones.

By some 565 million to 560 million year ago, animals had gotten complex enough to crawl through mud, leaving worm-like tracks. But it wasn't until about 535 million years ago that animals started diversifying rapidly into the basic body plans seen today, like those of mollusks, starfish, snails, and animals with a spinal cord.

Just what set off this "Cambrian explosion" is a major mystery that the new findings might help illuminate.

The embryos described in Knoll's paper were balls of cells, like early embryos of animals today, and scientists don't know what kind of animal they would have become.

The Science paper describes some embryos and the oldest known fossils of sponges. The sponge finding is significant because it confirms evidence from genetic studies and analysis of their simple anatomy that sponges would be that old.

The fossils were found in Guizhou Province of southern China. The animals probably lived in water a few yards deep, and soon after they died their tissues were rapidly replaced with calcium phosphate, which has preserved their structure in such exquisite detail.