land. Benanav, a true twenty-first-cen- 

 tury adventurer, first read about the 

 place on the Internet, then developed 

 an itch to see it for himself. 



Now, a quick glance at the Web 

 shows that you can travel to 

 Taoudenni in relative comfort: there 

 are outfitters willing to whisk tourists 

 out and back in vehicles with four- 

 wheel drive. Benanav wanted none of 

 that. He wanted to ride with the camels, 



nature.net 



First Animals 



By Robert Anderson 



The geologic timescale was one of 

 the great achievements of nine- 

 teenth-century science. Yet the oldest 

 named division of geologic time was 

 the Cambrian, beginning 540 million 

 years ago. All time before the Cam- 

 brian was a great unknown, simply 

 designated Precambrian, even though 

 life on Earth began more than 3.5 bil- 

 lion years ago. The earliest multicelled 

 animals, for instance — enigmatic, 

 mostly soft-bodied creatures that lived 

 in the latest phase of the Precam- 

 brian — only rarely left fossils. 



But recently the International 

 Commission on Stratigraphy (ICS) 

 came up with an official name for the 

 80 or so million years immediately 

 preceding the Cambrian: the Ediaca- 

 ran period. Interest in Ediacaran times 

 has grown, because the fossils show 

 that the period marks an unprece- 

 dented flowering in the diversity of 

 life-forms following the end of a 

 global freeze-over. 



At the ICS Web site (stratigraphy, 

 org/down.htm), click on one of the in- 

 ternational charts to get the latest offi- 

 cial update. Nail icons on the multi- 

 color timechart indicate a specific layer 

 of rock somewhere in the world that 

 serves as the base of its period. The 

 baseline for the Ediacaran, for instance, 



burn camel dung to boil his tea, and 

 dine on the same sandy rice and dried 

 goat meat that real caravan drivers eat. 



Fortunately, he located a former 

 camel driver named Walid who was 

 willing to take a crazy American to a 

 place most Tuaregs viewed with fear and 

 disgust. Even more fortunately, Benanav 

 knew enough Arabic to converse a bit 

 with his guide, and he and Walid hit it 

 off right from the start. By the end of 

 chapter one, the two men, astride two 



is a postglacial carbonate layer in the 

 Enorama Creek section of the Flinders 

 Ranges, some 250 miles due north of 

 Adelaide, Australia. The name for the 

 new period comes from the Ediacara 

 Hills, a 570-million-year-old site in the 

 Flinders Ranges where some of the 

 first animals big enough to be seen with 

 the unaided eye are preserved in good 

 detail. The Palaeos site (palaeos.com/ 

 Ecology/Biota/Ediacara.html) has more 

 information on those animals, along 

 with a list of links. 



In "The Measure of Deep Time," 

 at the Web site of NASA's Astrobiol- 

 ogy Institute, writer David Morrison 

 gives a summary of the new slice of 

 time, with an illustration of the key 

 events that define it (nai.arc.nasa.gov/ 

 news_stories/news_detail.cfm?ID=291 ). 

 At www.paleoportal.org/time_space/ 

 period. php?period_id=1 7 you can find 

 out whether there are Precambrian 

 rocks in your area. Click on the arrow 

 beside "Any state." At talkorigins.org/ 

 origins/faqs-youngearth.html you'll find 

 several pages related to the construc- 

 tion of the geologic timescale. 



Go to www.palaeos.com/Proterozoic/ 

 Neoproterozoic/Neoproterozoic.html to 

 get a quick rundown on what it must 

 have been like to live on our planet 

 during the Ediacaran. At the Miller 

 Museum of Geology in Kingston, On- 

 tario, an online exhibit of "The Dawn 

 of Animal Life" (geoi.queensu.ca/museum/ 

 exhibits/dawnex.html) has many images 

 of the latest Precambrian fossil discov- 

 eries. On display in the physical mu- 

 seum are the oldest animal fossils in 



camels, have set out from Timbuktu to 

 join the salt merchants on their journey. 

 What follows is indeed a rousing ad- 

 venture, with enough rancid meat, dust 

 storms, thirsty days, and star-spangled 

 nights to keep the pages turning. 



Laurence A. Marschall, author of The 

 Supernova Story, is the W.K.T. Sahm profes- 

 sor of physics at Gettysburg College in Pennsyl- 

 vania. He is the 2005 winner of the Education 

 prize of the American Astronomical Society. 



the world, spongelike rings dating back 

 600 million years. At the Smithsonian's 

 early life exhibit you'll find a wonderful 

 diorama (www.mnh.si.edu/museum/Virtual 

 Tour/Tour/First/Early/i ndex.html) that 

 brings the Ediacaran back to life. 



The University of California Mu- 

 seum of Paleontology in Berkeley has 

 another online exhibit of the earliest 

 animals, along with a map (click on 

 "Localities") of where some of the fos- 

 sils were discovered (www.ucmp.berkeley. 

 edu/vendian/vendian.html). To confuse 

 matters, this site, like many others, has 

 not yet adopted the name Ediacaran. 

 Instead the sites use the alternate, Rus- 

 sian name — Vendian — a name derived 

 from Siberian strata of the same age. 



The most remarkable Ediacaran- 

 age discovery comes from the Dou- 

 shantuo Formation in southern 

 China. Here, ancient tissue was re- 

 placed by calcium phosphate, pre- 

 serving the cellular structure of small 

 sponges and jellyfish in exquisite de- 

 tail. Even microscopic eggs and em- 

 bryos are visible. But most exciting of 

 all is the 2004 discovery of the oldest 

 known "bilateran," an animal with bi- 

 lateral symmetry, whose descendants 

 include everything from worms to us. 

 Investigators have so far identified ten 

 bilaterans — each about the size of the 

 period at the end of this sentence. Go 

 to pharyngula.org/index/weblog/com 

 ments/pre_cambrian_coelomate to read 

 more about those remarkable fossils. 



Robert Anderson is a freelance science 

 writer living in Los Angeles. 



64 



NATURAL HISTORY March 2006 



