Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

University of California, Riverside study dates our ancestors

27.09.2002


Photo Caption: A type of branching burrow system that first appear at the base of the Cambrian (circa 545 million years before the present). The trace consists of a series of curved open tunnels that extended into the muddy sea floor. The tunnels were later filled with sand and the mud weathered away resulting in a cast of burrow system. The producer of this trace fossil is not known but these trace fossil nevertheless are important in that they mark the beginning of the sea floor being churned by sediment processing animals. Compared to the much simpler trace fossils in older rocks they also bear witness to the appearance of more complex animal behavior. The figured specimen is from the Lower Cambrian of Sweden. The length of each curved element is about 7 mm.


Photo Caption: A trace fossil made on the top of the sediment surface. The trace is about 1-2 mm in width. This is a common form found in Late Proterozoic sedimentary rocks. The figured specimen is from Flinders Range, South Australia.


Study suggests macroscopic bilaterian animals did not appear until 555 million years ago

The traces left behind by ancient animals may hold the key to determining when macroscopic bilaterians -- animals that are symmetric about a central axis, with a body divided into equivalent right and left halves, and with an anterior-posterior polarity (e.g., this includes worms, ants, and ranging up to humans) -- first appeared. A team led by Dr. Mary Droser, professor of geology at the University of California, Riverside, studied "trace" fossils, e.g., burrows, trails and tracks left behind by the earliest bilaterian animals. Results from their study suggest that bilaterian animals did not appear until approximately 555 million years ago.

The authors publish their findings in a paper entitled "Trace fossils and substrates of the terminal Proterozoic-Cambrian transition: Implications for the record of early bilaterians and sediment mixing" in the Proceedings of the National Academy of Sciences (PNAS). They report that these trace fossils, found in many different locations around the world, were preserved very well in sediment beds from the Early Cambrian (544 to 510 million years ago), both in terms of quality of detail and in preserving traces made close to this sediment-water interface. Trace fossils can shed light on an organism’s behavioral activity.



"The timing of the appearance of bilaterian animals, while clearly by 555 million years ago, is the subject of some debate," said Droser. "One of the most important pieces of evidence for early animals is the record of trace fossils. That is, animal burrows, tracks and trails preserved in the rock record. Based on evidence from functional morphology, many of the features that define bilaterians could only have originated in a relatively large animal that inhabited the seafloor and thus produced trace fossils. Early bilaterians, in particular, were soft-bodied and thus difficult to preserve."

The trace fossils examined in the study are from the transition between the Proterozoic Era (2.5 billion to 544 million years ago), where few animal body fossils are found, and the Cambrian (544 to 490 million years ago), where diverse animal body fossils such as trilobites are found. Proterozoic trace fossils, typically only a few millimeters wide, are found at the interface between water and sediment. The Cambrian trace fossils are more diverse in size, shape and depth of penetration into the sediment.

The researchers examined and did field work on thousands of meters of rock. "We collected samples from Australia, Newfoundland, the western United States, Scandinavia and Namibia," said Soren Jensen, co-author of the PNAS paper and a postdoctoral researcher in the department of earth sciences at UC Riverside. "These samples of ancient marine rocks were then carefully inspected, x-rayed, and thin-sectioned for microscopic examination to provide us with an even closer look."

The authors attribute the exceptional preservation of Early Cambrian trace fossils to the low levels of sediment mixing, which resulted in relatively firm substrates less prone to resuspension. Close inspection of these fossils could help determine exactly when bilaterian animals emerged, a topic of much controversy.

"There have been reports of trace fossils as old as 1 billion years old," said Droser. "But these records are scarce and, on critical examination, are not convincing. On examining the trace fossil record from 565 million years ago through until 535 million years ago, we found that the substrate conditions -- for example, the bottom of the ocean -- were such that if animals were burrowing or walking or crawling along the seafloor, their traces would have likely been preserved. We see a gradual increase in diversity and complexity of trace fossils from about 555 million years ago, known as the Cambrian Explosion and which likely reflects the appearance of bilaterians. We found no evidence for a long history of large animals before this time."

News Media Contact:
Name: Iqbal Pittalwala
Phone: 909.787.2645
Email: iqbal@citrus.ucr.edu

Iqbal Pittalwala | EurekAlert!
Further information:
http://www.earthscience.ucr.edu/
http://www.pnas.org/
http://www.ucr.edu/

More articles from Earth Sciences:

nachricht Tracking the amount of sea ice from the Greenland ice sheet
28.09.2016 | Ca' Foscari University of Venice

nachricht A perfect sun-storm
28.09.2016 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New welding process joins dissimilar sheets better

Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of light metals.
Scientists at the University of Stuttgart have now developed two new process variants that will considerably expand the areas of application for friction stir welding.
Technologie-Lizenz-Büro (TLB) GmbH supports the University of Stuttgart in patenting and marketing its innovations.

Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of...

Im Focus: First quantum photonic circuit with electrically driven light source

Optical quantum computers can revolutionize computer technology. A team of researchers led by scientists from Münster University and KIT now succeeded in putting a quantum optical experimental set-up onto a chip. In doing so, they have met one of the requirements for making it possible to use photonic circuits for optical quantum computers.

Optical quantum computers are what people are pinning their hopes on for tomorrow’s computer technology – whether for tap-proof data encryption, ultrafast...

Im Focus: OLED microdisplays in data glasses for improved human-machine interaction

The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.

“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...

Im Focus: Artificial Intelligence Helps in the Discovery of New Materials

With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.

Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...

Im Focus: Complex hardmetal tools out of the 3D printer

For the first time, Fraunhofer IKTS shows additively manufactured hardmetal tools at WorldPM 2016 in Hamburg. Mechanical, chemical as well as a high heat resistance and extreme hardness are required from tools that are used in mechanical and automotive engineering or in plastics and building materials industry. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden managed the production of complex hardmetal tools via 3D printing in a quality that are in no way inferior to conventionally produced high-performance tools.

Fraunhofer IKTS counts decades of proven expertise in the development of hardmetals. To date, reliable cutting, drilling, pressing and stamping tools made of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

European Health Forum Gastein 2016 kicks off today

28.09.2016 | Event News

Laser use for neurosurgery and biofabrication - LaserForum 2016 focuses on medical technology

27.09.2016 | Event News

Experts from industry and academia discuss the future mobile telecommunications standard 5G

23.09.2016 | Event News

 
Latest News

New imaging technique in Alzheimer’s disease - opens up possibilities for new drug development

28.09.2016 | Medical Engineering

Innovate coating extends the life of materials for industrial use

28.09.2016 | Materials Sciences

Blockchain Set to Transform the Financial Services Market

28.09.2016 | Business and Finance

VideoLinks
B2B-VideoLinks
More VideoLinks >>>