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Fossil embryos

 
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Mighty_EmperorOffline
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PostPosted: 25-01-2004 19:23    Post subject: Fossil embryos Reply with quote

Just ran across this:

Quote:
Fossil embryos delight scientists

Paul Rincon
BBC News Online science staff

UK and Chinese researchers have linked a fossil embryo to a particular animal species for the very first time.

Palaeontologists sifted 6,000 kilograms (13,200 lbs) of rock excavated from southern China, yielding 100 fossil embryos dated to 500 million years ago.

The fossils belong to an extinct species of worm and scientists now know more about its development than that of its closest living relatives.

Details of the research are published in the scientific journal Nature.

Quote:
Clearly [embryonic] mechanisms had evolved 500 million years ago
Dr Philip Donoghue, Bristol University


Prior to this research, there were only about 15 true fossil embryos known to science.

"People have found dinosaur embryos before, but they're not real embryos, they've got bits of bone and shell.

"But these are real embryos composed entirely of layers of cells," said co-author Dr Philip Donoghue, a palaeontologist at Bristol University.

"Clearly [embryonic] mechanisms had evolved 500 million years ago."

Grain by grain

The embryos, which belong to the species Markuelia hunanensis , come from rock excavated from the Bitiao Formation in Wangcun, Hunan, southern China, and date to Middle and Lower Cambrian times.

These Cambrian worms would have lived in a deep offshore marine setting, rich in organic matter and poor in oxygen.

Markuelia is a scalidophoran, a group which still has living representatives today. These include the priapulids and the loriciferans.

To get at the fossils, the scientists dipped the rocks in acetic acid to dissolve the calcium carbonate surrounding them. The embryos themselves are composed of calcium phosphate, which is not dissolved by the acid.

The researchers then had to sift grain-by-grain through the residue left behind to identify the embryos, a process Dr Donoghue admits was laborious and time-consuming.

The fossils each measure less than half a millimetre in length.

Dr Donoghue said he now wanted to study the development of Markuelia 's closest living relatives in order to determine the alterations in gene expression responsible for differences in appearance between the extinct and living worm species.

"We want to unravel their development more fully so we can determine the mechanisms behind the evolution of particular anatomical features," Dr Donoghue explained.

Important work

"Embryos from rocks of this age have been known for a few years now. But it's still very important work. It's good stuff," said Professor John Peel, director of the Museum of Evolution at the University of Uppsala, Sweden.

He added that this kind of research was key to understanding relationships between groups of organisms, because differences between phylogenetic groups are often strongly reflected in the way their embryos develop.

Dr Donoghue claims the fossils have settled a decades-old debate about the common ancestor of two animal groups: arthropods and nematodes.

Some researchers believe this ancestral creature had a smooth, or unsegmented, body.

But the embryos, which are close in time to the arthropod-nematode ancestor, are segmented.

Donoghue thinks this suggests that nematodes lost their ancestral segmentation and evolved a smooth body plan, not vice versa.

Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/1/hi/sci/tech/3393543.stm

Published: 2004/01/15 10:40:52 GMT

© BBC MMIV
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ramonmercadoOffline
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PostPosted: 10-04-2014 22:26    Post subject: Reply with quote

More fossilized embryos. This time it might represent rhe discovery of a new organism: The fossilized embryos the researchers found were significantly smaller than other fossil embryos from the same time period, suggesting they represent a yet undescribed organism. Additional research will focus on identifying the parents of these embryos, and their evolutionary position.

Quote:
Researchers find rare fossilized embryos more than 500 million years old
April 10th, 2014 in Other Sciences / Archaeology & Fossils

These are deep-water Ediacaran fossils from the Mackenzie Mountains, NW Canada (Narbonne et al.). 1, Hiemalora (left) and Aspidella (right); 2, Namalia Germs, 1968; 3, Primocandelabrum Hofmann, O'Brien and King, 2008 with Aspidella-like holdfasts, several of which exhibit stems or fronds (arrows); 4, close-up of Primocandelabrum showing an Aspidella-like disc at its base and candelabra-like branches at the distal end of the preserved frond (arrows). Scale bars represent 1 cm or 1 cm increments. Credit: Narbonne, et al.

These are deep-water Ediacaran fossils from the Mackenzie Mountains, NW Canada (Narbonne et al.). 1, Hiemalora (left) and Aspidella (right); 2, Namalia Germs, 1968; 3, Primocandelabrum Hofmann, O'Brien and King, 2008 with Aspidella-like holdfasts, several of which exhibit stems or fronds (arrows); 4, close-up of Primocandelabrum showing an Aspidella-like disc at its base and candelabra-like branches at the distal end of the preserved frond (arrows). Scale bars represent 1 cm or 1 cm increments. Credit: Narbonne, et al.

The Cambrian Period is a time when most phyla of marine invertebrates first appeared in the fossil record. Also dubbed the "Cambrian explosion," fossilized records from this time provide glimpses into evolutionary biology when the world's ecosystems rapidly changed and diversified. Most fossils show the organisms' skeletal structure, which may or may not give researchers accurate pictures of these prehistoric organisms. Now, researchers at the University of Missouri have found rare, fossilized embryos they believe were undiscovered previously. Their methods of study may help with future interpretation of evolutionary history.

"Before the Ediacaran and Cambrian Periods, organisms were unicellular and simple," said James Schiffbauer, assistant professor of geological sciences in the MU College of Arts and Science. "The Cambrian Period, which occurred between 540 million and 485 million years ago, ushered in the advent of shells. Over time, shells and exoskeletons can be fossilized, giving scientists clues into how organisms existed millions of years ago. This adaptation provided protection and structural integrity for organisms. My work focuses on those harder-to-find, soft-tissue organisms that weren't preserved quite as easily and aren't quite as plentiful."

Schiffbauer and his team, including Jesse Broce, a Huggins Scholar doctoral student in the Department of Geological Sciences at MU, now are studying fossilized embryos in rocks that provide rare opportunities to study the origins and developmental biology of early animals during the Cambrian explosion.

MU researchers find rare fossilized embryos more than 500 million years old
This is a Cambrian embryo fossil exposed by acid etching on rock surface. Polygonal structure on surface indicative of blastula-stage of development. Credit: Broce, et al.

Broce collected fossils from the lower Cambrian Shuijingtuo Formation in the Hubei Province of South China and analyzed samples to determine the chemical makeup of the rocks. Soft tissue fossils have different chemical patterns than harder, skeletal remains, helping researchers identify the processes that contributed to their preservation. It is important to understand how the fossils were preserved, because their chemical makeups can also offer clues about the nature of the organisms' original tissues, Schiffbauer said.

"Something obviously went wrong in these fossils," Schiffbauer said. "Our Earth has a pretty good way of cleaning up after things die. Here, the cells' self-destructive mechanisms didn't happen, and these soft tissues could be preserved. While studying the fossils we collected, we found over 140 spherically shaped fossils, some of which include features that are reminiscent of division stage embryos, essentially frozen in time."

The fossilized embryos the researchers found were significantly smaller than other fossil embryos from the same time period, suggesting they represent a yet undescribed organism. Additional research will focus on identifying the parents of these embryos, and their evolutionary position.

Schiffbauer and his colleagues published this and related research in a volume of the Journal of Paleontology which he co-edited. The special issue, published by the Paleontological Society, includes several papers that analyze fossil evidence collected worldwide and includes integrated research focusing on this time frame, the Ediacaran–Cambrian transition. Schiffbauer and Broce's research, "Possible animal embryos form the lower Cambrian Shuijingtuo Formation, Hubei Province, South China," was funded by the National Science Foundation.

Provided by University of Missouri-Columbia

"Researchers find rare fossilized embryos more than 500 million years old." April 10th, 2014. http://phys.org/news/2014-04-rare-fossilized-embryos-million-years.html
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