Naples Daily News
September 20, 2002
Photography by Gary Coronado

Foraging for fossils: A Lee County man guides day trips to prehistoric Florida

Where now are cow patties around which Mark Renz recommends driving and over which he even more heartily recommends stepping sharks once swam, and later mammoths and mastodons roamed. Once what is now land was sea floor. And once what is now a trickling tributary to the Peace River in DeSoto County was a great river.

Antonio Lo Pinto of Genoa, Italy, from left; Ann Alessi of Fort Myers; fossil tour guide Mark Renz of LeHigh Acres; and Laura Alessi of Garnerville, N.Y., look for a variety of fossils found on the bottom of a tributary to the Peace River near the town of Arcadia.

Renz leads daylong expeditions to this private cattle ranch near the town of Arcadia, about 100 miles north of Naples. He and those who pay $60 a head come inland from the Gulf of Mexico to hunt for fossilized sharks' teeth, extinct horse teeth, turtle and tortoise shell, armadillo armor, and the big, mostly elusive prize, mammoth and mastodon bones.

An amateur paleontologist and author of "Fossiling in Florida: A Guide for Diggers and Divers" and "Megalodon: Hunting the Hunter," Renz began leading fossil hunting trips about six years ago. The native Floridian was introduced to Florida's fossiling possibilities while on a fishing trip in the Caloosahatchee River with his brother. When the fish weren't biting, his brother said he knew where they could find some sharks' teeth in the riverbank.

"I thought, why in the world are there sharks' teeth in this freshwater river?" Renz said. His interest piqued, he began reading up on the subject and discovered they were fossilized sharks' teeth, anywhere from 5 million to 10 million years old. His studies and burgeoning interest took him exploring for other places to find fossils, and his interests led him to leave his job as a newspaper reporter to start Fossil Expeditions.

"Eleven or 12 years ago," Renz said, "I would have said you were crazy if you said I'd be digging in a creek for bones."

Today, Renz takes out an average of two to three groups a week to more than 20 sites he has discovered and gained permission from private landowners to visit. In addition to the general public, Renz also takes out teachers and student groups during the school year.

The best part for participants is that they're allowed to keep the fossils they find. And for Renz the best part is conveying his knowledge of ancient Florida history and seeing the discovery of his clients.

"I find most often people are most interested in sharks' teeth, but when they find a variety of fossils, they start getting into that as well," Renz said. "I try to encourage people when they're out not just to look for fossils but to look at the wildlife. We've had fox here; otters come and check us out."

On a Monday in early September, Renz had nine in his group. They had met up at the Burger King in Arcadia at 9 a.m., where they proceeded to follow him to a locked field through which a stream meanders toward the Peace River.

"This creek has probably been here at least 6,000 to 10,000 years," Renz said.

The creek, the banks of which are 12 feet high in places, cuts through a gentle valley that Renz says is an old riverbed. Before it was a river, it was a saltwater bay, Renz said, and varying sea levels over millions of years have been causing the area to switch from land to sea to land again.

"That's why they'll dig up a horse tooth next to a shark's tooth next to a beer bottle from last night's drunk," he said.

Upon arrival at the site, Renz unpacked the tools of the trade: shovels and wooden frames with quarter-inch mesh metal screen.

He skidded down the sand bank of the creek, waded in to about waist-deep and began probing the bottom with his shovel.

"Hear that?" he said, wiggling the planted shovel. "That's the crunch. Good and crunchy." In the sand bottom of the stream, fossil hunters look for the layer that contains larger rocks that lies just above a layer of clay.

"When you come across blue-green clay, it's the bottom of the ocean," Renz advised. "Dig as deep as you can until you hit that blue-green clay, and then skim it."

In that layer above the clay, some of the things that sound like rocks or gravel on the shovel will be fossilized remains of prehistory.

"I know the stuff's here, it's just a matter of finding it," Renz said.

That's where the screen comes in. Each shovelful of sand is dumped into the wood-framed screen, and with a bit of swishing what could be left is fossils.

Sure enough, after a couple of minutes and a shovelful or two through the screen, Renz was pulling out such common fossils as the roof plate of a puffer fish's mouth, tiger shark teeth, a piece of bone and what might be a piece of mammoth tooth.

As he let loose the fossil hunters in pairs one to shovel, the other to screen the inexperienced could see that the process was a little harder than Renz made it look, but within a half hour, the various pairs were calling on Renz for identifications of their finds.

"Fossilized alligator scute," he determined, holding the piece of body armor. "That's U.B. unidentified bone," he said of another black chunk of fossilized bone. "Here, like a giant Hershey's Kiss," he said of another piece, "is a leg spur from a giant tortoise."

"Deer molar if you look at it closely, it's got a label underneath," Renz joked with Jesse Lippert, 13, who had come down from Sarasota fossil hunting for the first time with his aunt, P.D. Kelly.

"When I was little, I used to dig in my sand box," Jesse said of his initial interest in fossil hunting.

"Most people when they walk around look up," Kelly said, but she's always been interested in what's on and in the ground. So a fossil hunting day trip was a natural for her and her nephew.

"I already found what I hoped to find," Jesse said, "a big shark's tooth and (a) gator plate."

Helene Collins and her friend, Mike Nashwinter, both of Cape Coral, have been fossil hunting for about 10 years.

"I personally didn't know there was all this history behind Florida," Collins said. "I thought all they had was beaches."

Fossil hunters with shovels and wood-framed sifters head toward the river in search of sharks' teeth, alligator scutes, horses' teeth and other artifacts.

Once she learned Florida had more than beaches, and that it has fossils, she began hunting regularly as much for the pastime as for the thrill of the hunt.

"I find it really relaxing. It's very peaceful," Collins said. "And hopefully we'll find the big one someday."

The big one has been eluding Nashwinter for 10 years. For him, the big one would be a complete mammoth or mastodon tooth.

"Just one complete tooth," he said while digging. "Is that so much to ask for, Mark?"

"Yes," Renz said jokingly. "Yes it is."

Renz sees a progression from the amateur collector who's out to find something "to put on the mantle to show Aunt Shirley." The next step is really learning about the fossils and recognizing the common ones as opposed to the rare ones. When collectors hit that stage, they can be helpful to paleontologists, who can't be out digging everywhere at once.

"Part of my responsibility," said Renz, who holds a state fossil collecting permit that covers the groups he takes out, "is that if I come across anything important to science, I give it to them."

About five years ago, Renz did just that after finding a nearly complete dugong skeleton. A close relative of the manatee, dugongs still survive in the Pacific Ocean but have been extinct locally for thousands of years. The 10 million-year-old skeleton found at a phosphate mine in Polk County now is part of the permanent collection of the Florida Museum of Natural History in Gainesville.

Despite this and other success stories, Renz recognizes scientists' concerns that people with little knowledge are digging up fossils on their own and that fossil evidence may be lost to ignorance. In western states, where such glamorous and valuable fossils as Tyrannosaurus rex skeletons have been unearthed, the debate over this has become heated.

"The relationship between amateurs and professionals is a marriage," Renz said. "We have to get along."

Renz believes his tours are important to keep the interest alive and to educate people about Florida's ancient history. He keeps an eye out for significant finds but says people typically wind up with very common fossils like sharks' teeth. And scientists, he said, "could care less about sharks' teeth."

If you go

Fossil Expeditions What: A daylong trip led by author Mark Renz to hunt for fossils of prehistoric sharks, mammoths, mastodons, sloths, camels bison, whales and turtles. Separate expeditions are available to hunt for fossilized shells. Participants may keep what they find, but unusual finds must be donated to the Florida Museum of Natural History in Gainesville. Where: Expedition locations vary depending on weather and water level, but many take place near Arcadia, about 100 miles from Naples. Exact location and directions will be supplied prior to the expedition. When: Call to arrange, but trips, which on average take place two or three times a week, typically begin at 9 a.m. and end at 3 p.m., not including drive time. Cost: $60 per person. Details: Most of the day will likely be spent in knee- to waist-deep water, so wear shoes and clothes that can get wet. Pack a lunch, water, sunscreen change of clothes and a towel. Information: (239) 368-3252, (800) 304-9432 or