Bosco's RockPile

Shell, Wyoming (DinoSafaris quarry)

Sarah / Sophie — The Stegosaurus

  • Location
    Shell, Wyoming (DinoSafaris quarry)
  • Formation
    Morrison Formation (Jurassic)
  • Season
    2003–2004

The Sarah / Sophie Stegosaurus is one of the most complete Stegosaurus specimens known to science — and the story of how it came out of the ground at Shell, Wyoming begins a season before the main dig.

Discovery began in 2003. The first tail vertebrae were found at the end of that season, but the animal’s identity was still open. It was in July 2004, after the excavation resumed, that the diagnostic tail spikes — the thagomizer — were exposed and photographed, confirming the genus in the field.

The dig was at a DinoSafaris quarry near Shell, run by Bob Simon. It landed there partly by circumstance: Kirby Siber’s team had been locked out of their usual Wyoming site, the Howe Quarry, which redirected the season to Shell. The primary excavation of the Stegosaurus was carried out by Bob Simon, Don Pfister, and me — before Kirby Siber’s team arrived. Throughout the dig I also ran the DinoSafaris website as its webmaster, documenting the work as it happened.

Identification in the field came the way it usually does — not from obvious bone at first, but from iron-staining and a change in matrix texture, then the first dermal plates, and finally the unmistakable tail spikes. The two-week dig covered excavation, stabilization, mapping, and jacketing in hard Morrison matrix, in mountainous terrain, hot and dry, with the crew housed in a log cabin.

Among the visitors at the quarry was Dr. Paul Sereno, who worked hands-on at the site, brushing bone at the bone–matrix interface. A Torvosaurus tooth was recovered nearby as an associated find — not part of Sarah’s skeleton, but from the same ground.

The animal was named “Sarah” in the field, after Sarah, the daughter of rancher John “Ed” Anderson, whose Red Canyon Ranch hosted the Shell digs. After the fossil was sold and prepared, it was renamed “Sophie” in London by the museum’s largest donor, for his own daughter. Today it is on display at the Natural History Museum, London — one of the most complete Stegosaurus specimens ever found, and the first used to scientifically estimate the body mass of a Stegosaurus.

One animal, two names, one dig. (“Sundance” in some older captions refers to the Sundance Formation — a marine unit of belemnites and oysters — not a second animal and not a second dig.)

Field photographs

Bob Boscarelli on the ridge above the Sarah Stegosaurus quarry, Shell Wyoming, July 2004
Bob Boscarelli on the ridge above the Sarah Stegosaurus quarry, Shell Wyoming, July 2004
The Shell Wyoming landscape and Red Canyon Ranch area, Bighorn Basin, site of the Sarah Stegosaurus discovery
The Shell Wyoming landscape and Red Canyon Ranch area, Bighorn Basin, site of the Sarah Stegosaurus discovery
Shell Canyon cliff face showing the Jurassic Morrison Formation geological context, Bighorn Basin Wyoming
Shell Canyon cliff face showing the Jurassic Morrison Formation geological context, Bighorn Basin Wyoming
Bob Simon, organizer of the Red Canyon Ranch excavations, at the Sarah Stegosaurus quarry in Shell Wyoming
Bob Simon, organizer of the Red Canyon Ranch excavations, at the Sarah Stegosaurus quarry in Shell Wyoming
First Stegosaurus dorsal plate fragments exposed at the Shell Wyoming quarry, July 2004
First Stegosaurus dorsal plate fragments exposed at the Shell Wyoming quarry, July 2004
Stegosaurus thagomizer tail spines in situ with quarter for scale, Shell Wyoming, July 2004
Stegosaurus thagomizer tail spines in situ with quarter for scale, Shell Wyoming, July 2004
Stegosaurus bone elements with deep blue-purple mineralization emerging from Morrison Formation matrix, Shell Wyoming 2004
Stegosaurus bone elements with deep blue-purple mineralization emerging from Morrison Formation matrix, Shell Wyoming 2004
Bob Boscarelli examining exposed Stegosaurus skeletal elements at the Shell Wyoming quarry, July 2004
Bob Boscarelli examining exposed Stegosaurus skeletal elements at the Shell Wyoming quarry, July 2004
Bosco with Dr. Paul Barrett of the Natural History Museum, London, beside the mounted "Sophie" — the Shell, Wyoming Stegosaurus he helped excavate, now one of the most complete specimens on public display.
Bosco with Dr. Paul Barrett of the Natural History Museum, London, beside the mounted "Sophie" — the Shell, Wyoming Stegosaurus he helped excavate, now one of the most complete specimens on public display.
In-situ skeletal map (field drawing) of the "Sarah" Stegosaurus at Red Canyon Ranch, Shell Wyoming — each element plotted where it lay in the Morrison Formation quarry, 2004.
In-situ skeletal map (field drawing) of the "Sarah" Stegosaurus at Red Canyon Ranch, Shell Wyoming — each element plotted where it lay in the Morrison Formation quarry, 2004.
Bob Boscarelli with paleontologist Paul Sereno at the Sarah Stegosaurus dig, Shell Wyoming, July 2004
Bob Boscarelli with paleontologist Paul Sereno at the Sarah Stegosaurus dig, Shell Wyoming, July 2004
The plaster field jacket from the 2004 dig — labeled "SARAH '04" with a field sketch of the animal — how the bones rode out of the Shell Wyoming quarry.
The plaster field jacket from the 2004 dig — labeled "SARAH '04" with a field sketch of the animal — how the bones rode out of the Shell Wyoming quarry.
School children studying the mounted "Sophie" at the Natural History Museum, London — the specimen's second life, an ocean away from the Wyoming quarry.
School children studying the mounted "Sophie" at the Natural History Museum, London — the specimen's second life, an ocean away from the Wyoming quarry.

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