June 23, 2008

Hanksville Harboring Jurassic ‘Bone Jackpot’

By Brian Maffly, The Salt Lake Tribune

Jun. 23--HANKSVILLE -- An ancient river, which probably dried up one season, only to swirl and surge with monsoonal violence the next, once braided through this area just southeast of what is now Utah's San Rafael Swell.

The river must have slowed here, shedding its load of sand, silt, gravel, trees, clams and dinosaur carcasses, dismembered chunks of big lizards that lived 145 to 150 million years ago.

Locals had known this area as a boneyard for years. Four decades ago, before a 1972 law made such scavenging illegal on federal land, the late Ernie Shirley dug up some 5-foot femurs and displayed them in his Hanksville rock shop.

But what is now proving to be a landmark trove of late-Jurassic treasures remained unknown to professional scientists until last summer, when Bureau of Land Management geologist Francis "Buzz" Rakow directed a group of Illinois paleontologists here. The ground is littered with fossilized bone fragments, detritus that is a tantalizing clue to what lies beneath.

The group, representing the Burpee Museum of Natural History, were two days into a five-week dig when they struck "the bone jackpot," uncovering at least 30 bones with no end in sight of well-preserved and partially articulated specimens.

"We fanned out and if you see bone, brush away the overburden. Everywhere someone sat we ran into something. It's like throw a stone and that's where you start working," said the museum's Scott Williams on Thursday while escorting reporters to the site.

A diplodocus specimen was found by someone pushing a broom.

Because team members were looking for sauropods, the massive long-necked dinosaur species, they chose to look in Utah's famed Morrison formation, the sandstone layer that gave us the Cleveland-Lloyd and Dinosaur National Monument quarries. The 300-meter layer of affluvial debris was deposited 145 to 155 million years ago, and the Burpee team zeroed in on the Brush Basin deposit near the top.

"They started exposing bone and it went on and on, until it got to the end and it was connected to another bone," said BLM paleontologist Scott Foss, who administers fossil excavations on Utah's federal land. "It makes it difficult to get a bone out of the ground."

The dig thus far has been confined to a small mesa above a wash that flows into Muddy Creek, although scientists suspect bones will eventually be found over a much larger area.

A short distance away, petrified trunks of huge coniferous trees are eroding out of the ground. Fossils of freshwater clams were also found, indicating the environment probably supported fish.

Learning new things about the environment these creatures inhabited is a goal of the project, said scientists as they toiled to liberate five specimens, all within a pace or two of each other. The bones were all aligned, suggesting the direction of the flow of the ancient river.

Katie Tremaine, an undergraduate at Northern Illinois University (NIU), scoured the crumbling gray sandstone, or matrix, around connected allosaurus bones with a hand-held pneumatic jack hammer.

"Here we have articulation and that is a very new experience," said Tremaine, a part-time Burpee employee who has volunteered past summers on the museum's digs in Montana's Hell Creek formation.

"There's a fairly complete specimen here, 13 articulated vertebrates and another six here. We have bones from every part of the body," explained Williams, a former police officer who now manages collections at the museum where he had volunteered since boyhood and has helped establish its successful dinosaur program.

A few feet away, Michael Henderson, a museum curator, was encasing part of a camarasaurus in a plaster "field jacket." After the tops of the bone are exposed, they are painted with a vinyl-acetone mixture, covered with aluminum foil, then draped in plaster-soaked burlap strips. The team then digs underneath the specimen, rolls it over and repeats the jacketing process. These white cocoons will be shipped to the Burpee Museum where the matrix will be removed.

"There will be a couple of people getting their Ph.D.'s from this site," said Henderson, himself an NIU doctoral student. "We want to learn the taphonomy, how the bones came to be preserved. There is an interesting story here. We'll be able to paint a very detailed picture of the environment here 147 million years ago."

The scientists' field identifications remain tentative, but they are fairly certain of the suspected camarasaurus, a sauropod known for its stout bone structure. This species' distinctive humerus, an upper arm bone that has a fat knuckle at the shoulder and tapers toward the elbow, matches that of the Burpee specimen. The scientists are less certain of their brachiosaurus specimen, whose bones seem small for this species of sauropod.

The diplodocus specimen was identified from its cervical vertebrae. This specimen's 5-foot femur is the biggest bone they have recovered. One 18-inch femur is believed to belong to a baby apatosaurus, which would be a rare and scientifically invaluable find if the identification proves correct.

Williams expects to truck 3,500 pounds of material to the museum in Rockford, Ill., by the time he calls it a season next week. The Burpee team will be back next spring, or possibly as soon as September with plans to recover the rest of the six specimens they have started, and eventually broaden the search for more specimens and develop educational programs and interpretive facilities in partnership with the BLM. The agency will close the spot to casual rock gathering while it formulates plans.

"The locals were keeping places like this a secret. They didn't want the wrong people coming in and trashing it," said Hanksville resident Carolyn Kiteley. "Now that the right people are digging it, people are very supportive."

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--Yale's Peabody Museum of Natural History, New Haven, Conn.

--The Museum of Northern Arizona, Flagstaff

--Raymond M. Alf Museum of Paleontology, associated with the private Webb Schools in Claremont, Calif., brings students to the Grand Staircase-Escalante National Monument. In 2002, an Alf group found a skull of a previously unknown species of duck-billed dinosaur.

--Field Museum of Natural History in Chicago. This institution, which was active in early Utah paleontology, is expected to return.

Museums working in Morrison formation (late Jurassic) include:

--Burpee Museum near Hanksville

--Natural History Museum of Los Angeles County is exploring outside Blanding.

--Museum of Western Colorado in Grand Junction is exploring around Moab.

Working in Uinta Basin (Eocene-era mammals):

--San Diego Natural History Museum

- Compiled by Brian Maffly


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