A case of beginner's luck for an amateur geologist He discovers dinosaur leg bone in Arbutus

December 05, 1998|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

An amateur geologist poking around on a desolate, rubble-strewn lot in Arbutus has stumbled across what appears to be part of a leg bone of Maryland's official state dinosaur, Astrodon johnstoni.

Rick Smith, 44, found the bone last Sunday after just four trips to the property. He could hardly believe his beginner's luck.

"The idea of finding a dinosaur bone less than two miles from my house is pretty mind-boggling," he said.

The find was identified on Tuesday by Washington geologist Peter Kranz. "I believe it is the upper end of the femur of a juvenile," he said. The original bone was perhaps 4 feet long, but only 21 inches of it remain.

With the landowner's permission, the 250-pound boulder that holds the bone was trucked yesterday to the Maryland Science Center in Baltimore, where the staff was trying to figure out how to display it as part of the "Dinosaurs of Jurassic Park" exhibit.

Stephanie Ratcliffe, the center's exhibit director, said it's an odd-looking specimen. There is some obvious fossilized bone, but most of it is a femur-shaped cavity in the rock where the rest of the fossil bone has weathered away. It looks as if some of the bone had been plucked from a big lump of clay.

Astrodon, which means "star-tooth," was a long-necked plant-eater that grew to 30 feet and perhaps 10 tons. It lived about 110 million years ago in what geologists call the early Cretaceous period.

It was first described in 1859 based on a single tooth found in Prince George's County. The same geological formation, which runs from Washington through Baltimore to Cecil County, has yielded an assortment of bone fragments, teeth and dinosaur tracks ever since.

Smith, an analytical chemist at Aberdeen Proving Ground, belongs to the Maryland Geological Society. But he never had considered looking for dinosaur fossils until he heard Kranz speak recently at Arbutus Elementary School.

"I was really dumbfounded to learn they [dinosaurs] were around," Smith said.

With guidance from Kranz and reference books, he began prospecting with his son Jeremy, 8. Kranz believes the Arbutus lot is the same property where another amateur paleontologist, Robert Eberle of Parkville, found a hunk of Astrodon femur in 1990. Kranz said that fossil is now at the Smithsonian Institution.

The original deposits there have been heavily disturbed. The lot is littered with construction rubble, and terraced by bulldozers that shoved aside the large boulders of iron-rich siderite. One boulder held the Astrodon bone.

Kranz surmised that a flood swept through an ancient swamp and buried both the Astrodon bone and a great deal of wood in fine clay sediment. Clear impressions of wood can still be seen on the surface of the boulder.

Over time, the waterlogged bone was replaced by minerals that preserved its original sponge-like internal structure. The clay turned to siderite.

Kranz said the fossil is probably Astrodon "because it's too big to be anything else."

But he added it is "not in good enough shape to learn anything new. It's not a valuable scientific specimen." It's real value may be in demonstrating that "ordinary people armed with a limited amount of knowledge can go out and look for dinosaur bones and have a reasonable amount of success."

Pub Date: 12/05/98

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