A Much Earlier Start for Animals

Where did all the animals come from? The fossil record is virtually animal-free up until the Cambrian Explosion 540 million years ago, and then--boom--thousands of critters of all shapes and sizes show up. The mystery has plagued scientists for more than a century and a half, beginning with Charles Darwin. Now, with a brilliant bit of detective work, researchers have located our missing ancestors.

The problem with the earliest animals, from a paleontologist's perspective, is that they lacked hard parts. Without bones, beaks, claws, and shells to fossilize, these squishy creatures never became part of the geological record. That's made life difficult for evolutionary biologists. They know that natural selection had to be operating for at least tens of millions of years to give rise to all of the Cambrian critters. Yet where was the evidence that animals had actually been around that long?

The answer lies in the unique molecules they left behind. A team led by organic geochemist Gordon Love of the University of California, Riverside, hit pay dirt with one such molecule. Called 24-IPC, it is only produced by Demospongiae, a class of animals that includes most modern sponges and is thought to constitute the roots of the animal family tree. The researchers acquired 30 pristine drill cores removed from underneath the southern Arabian Peninsula by the oil company Petroleum Development Oman. The cores ran through sedimentary layers and extended back beyond the Cambrian Explosion into the Cryogenian Period, about 635 million years ago near the end of a long, global ice age.

After treating the core samples with chemicals that react with and reveal the presence of 24-IPC, the researchers found "anomalously high amounts of 24-IPC" in even the oldest parts of the core, they report in tomorrow's issue of Nature. That pegs the origins of animals at least 100 million years before the Cambrian explosion. As a result, animals appeared on Earth slowly, as Darwin suspected, and not suddenly and spectacularly, as the fossil record seems to show.

The findings seem to solve one mystery, but they intensify another. Pushing back animal origins by 100 million years places their beginnings during a time called Snowball Earth, when our planet was almost completely encased in ice. If true, it means Demospongiae arose in an extremely harsh environment, not the relatively warm seas of today. It's possible, Love says, that sponges could have emerged before Snowball Earth and inhabited a haven just large enough to allow them to survive.

It's an exciting find, says paleobiologist Kevin Peterson of Dartmouth College. And it confirms, he says, that we animals can all trace our origins back to sponges.

Elsiejay....Found this:

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Trilobites for Everyone!
By Jack Kallmeyer

Tracking Trilobites: Adventures in Paleontology by Judy Lundquist. Lexington, Kentucky: Kentucky Geological Survey, 2005. $9.43 soft cover; 70 pp; 3 pages of references; 3 pages covering Organizations, Scientific Web Sites and other Web Sites. The book is well illustrated throughout with photographs, drawings and other original art. This is Kentucky Geological Survey Special Publication 4, Series XII, available through the Survey - telephone toll free at (877) 778-7827 for ordering information.

Tracking Trilobites is a book that fills a big void for amateur fossil enthusiasts. Few publications exist that are aimed at a general audience and that communicate solid scientific information in a format and style that is accessible. It also focuses on what has to be the most popular invertebrate fossil of all.

For those of you who don't recognize the author of Tracking Trilobites, Judy Lundquist, she is an amateur paleontologist and member of the Lexington, Kentucky based Kentucky Paleontological Society. The Kentucky Geological Survey provided the review copy of this book and included some additional background information on the author. From the transmittal letter: "Ms. Lundquist has 20 years experience communicating science to the public through programs in museums and national parks, as well as a passion for paleontology. She has written paleontology articles for Blue Ridge Country and Rock & Gem magazines as well as pieces for Fossil Butte National Monument, the Florida Museum of Natural History and the Kentucky Paleontological Society."

Lundquist begins with the much needed pronunciation guide for "tri-lo-bite" and then reminds us why people like trilobites in the first place. She even cites Native American beliefs among the Ute tribe who used the Cambrian Elrathia as a talisman to protect from illness. The translation of the Ute word for trilobite shows native American recognition of extinction and the aquatic nature of the once living form.

What exactly are trilobites? Lundquist covers the basics of the three lobes but incorporates additional information in her narrative. As is typical throughout the book, she includes much more so that the reader is exposed in this case to Linnaean organization and the naming of organisms, how scientists determine relatedness and where trilobites fit into the grand scheme of the arthropod Phylum.

"Trilobite Times" is the section covering the age and time line for trilobites. Not contented with simply stating the age range in years and naming a few Eras, Lundquist provides a complete mini education in geology. Tracking Trilobites covers relative and absolute dating methods in such a way that anyone can understand the principals behind the methods and the ultimate truth of the results. Extinction, diversification and the driving forces for those processes are covered here in the same fashion.

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