EN DPAPER 



Grumpy, fuzzy, scholarly 

 type was beside himself. 

 Halfway up the ten-foot- 

 high rock wall he'd run out of toe- 

 holds, and he clung desperately to 

 the tiny fingerholds above him. 

 The wall was made of layers of 

 shale, inch-thick ledges protruding 

 irregularly from the mesa, and he 

 couldn't find a higher one to stand 

 on. The distinguished professor of 

 physiology and evolution was stuck. 



I pushed on his bottom. Someone 

 pulled him from above. Finally he 

 scrabbled onto the top of the mesa 

 and fell, prostrate, on the flat, hard, 

 dusty surface. After a minute he rolled 

 over, tears of exertion still in his eyes. 



About ten people toiled atop the 

 mesa, all paleontologists. We were 

 prospecting for fossils at one of those 

 small, scarcely known paleontologica 

 sites that abound in the western 

 United States. This one — Bear 

 Gulch — is situated on a cattle ranch 

 in central Montana. The leader of 

 our team had written profusely about 

 shark fossils of the Mississip- 

 pian period, 300 million 

 years ago. Back then, Bear 

 Gulch was an inlet of what 

 was to become the Pacific 

 Ocean. Warm and shallow, it 

 was a perfect pupping ground 

 for sharks. Occasionally a ju- 

 venile shark would die there 

 and sink to the seafloor, soon to be 

 buried in the soft, oxygen-poor bot- 

 tom mud. 



Those rich, shallow waters teemed 

 with plankton. They, too, sank to the 

 bottom when they died, forming a 

 layer on top of the mud. Bacteria 

 dined on them, oxidizing the proto- 

 plasm of the dead plankton layer. Re- 

 producing every twenty minutes, the 

 bacterial masses used up virtually 

 every molecule of available oxygen. In 

 this oxygen-starved burial place, the 

 shark carcasses remained intact until 

 the mud, gradually and under im- 

 mense pressure, became stone — shale. 

 Along with their encasement of mud, 

 the tiny sharks turned to stone. Three 

 hundred million years later, a team of 



Hard Labor 

 at Bear Gulch 



By Eugene H. Kaplan 



Layers of petrified sediment 

 in Bear Gulch, Montana 

 (above), hold some of the 

 best-preserved marine fossils 

 in the world, including this 

 300-million-year-old horse- 

 shoe crab (left). 



toiling paleontologists broke into their 

 tombs and let the sunshine in. 



The graduate students punctuated 

 their jolly conversations with 

 grunts of exertion as they pried up 

 layers of the petrified mud. The tech- 

 nique was to slip the sharp end of a 

 five-foot steel spike into the junction 

 between two layers and pound at the 

 seam until the layers loosened. Then 

 they would wedge the spike into the 

 shale and lever it upward, breaking off 

 a slab a yard or so wide. When the 

 slab was turned over, it would usually 

 reveal . . . nothing. But occasionally a 

 more professional-sounding grunt 

 drew everyone's attention to a digger 



who had found, in all its perfec- 

 tion, the imprint of a tiny shark, 

 its scales defined and its eyes 

 turned upward in a stony stare. 



My fuzzy, distinguished colleague 

 and I also grunted frequently while 

 we worked — not to prove we were 

 just as professional as the grad stu- 

 dents, but because our aging bodies 

 made it hard to lift the heavy layers 

 of rock. Sweating under a glaring sun, 

 we finally learned how to use mechan- 

 ical advantage, wedging up pieces of 

 shale with the best of them. Neverthe- 

 less, the flat undersides of slab after la- 

 borious slab had nothing to show us. 



Finally the two of us came upon a 

 curled object — shaped like a sinuous 

 peanut — embedded in the shale. Ex- 

 cited, we dragged the two-foot-wide 

 chunk of rock to the head honcho, 

 who stared at it intently and informed 

 us it was a coprolite. We looked at him 

 quizzically "It's petrified fish feces," he 

 explained. All that labor and exhaus- 

 tion only to find ancient fish poop! 



The team worked until dark, our 

 labors illuminated by a magnificent, lu- 

 minous sunset. After dinner that 

 evening the buttes and mesas rang with 

 laughter as we were presented with our 

 hard-won trophy — the coprolite — 

 which, to this day, lies in state in the 

 glass-fronted case that doubles as my 

 class museum. Thoroughly tired, and 

 mildly amused by our moment of tri- 

 umph, I crawled into my tent, pushing 

 at its nylon floor to carve out a flat 

 space amid the ubiquitous cow flops. A 

 pat of "prairie pancake" was my pillow. 



The next day, another grunt 

 brought us running. Although the 

 fossil turned out to be of little interest 

 to this group of ancient-shark special- 

 ists, to me it was a real treasure. I let 

 loose a holler. There on the under- 

 side of the rock was a small, perfect, 

 300-million-year-old replica of a 

 modern-day horseshoe crab. 



Eugene H. Kapl.4n is Axinn Distinguished 

 Professor of Conservation and Ecology at Hqfstra 

 University, in Hempstead, Sen- York. This story 

 is adapted from his book Sensuous Seas: Tiles 

 of a Marine Biologist, which will be pub- 

 lished in August by Princeton L J uivcrsity Press. 



NATURAL HISTORY July/August 2006 



