In 1943, sawmill operator Daniel Edward Jones and his wife Vivian went prospecting for uranium west of their home in Delta, Colorado. In a gully near Potter Creek, they came upon a nearly seven foot-long dinosaur bone eroding out of the ground. It’s unclear exactly how and when they managed to excavate and remove the gigantic fossil, but sometime before 1955, the Joneses collected the bone and donated it to the Smithsonian Institution. That bone—identified as the humerus of a Brachiosaurus altithorax—has been on display at the National Museum of Natural History ever since.

The Potter Creek humerus (USNM V 21903) never made much of a splash scientifically. It wasn’t mentioned in any research paper until 1987, when Jim Jensen figured it alongside several other Brachiosaurus bones he collected at the same locality. The referral to Brachiosaurus has been questioned (e.g. Taylor 2009), but without any closely related dinosaurs known from Late Jurassic North America, researchers have generally been happy to use the available name.

Arguably, the Potter Creek humerus has a greater legacy as an object on display, and more specifically as an object to be touched. Since 1955, the fossil has been in easy reach of visitors, and has often been accompanied by signage inviting visitors to touch it. Extrapolating slightly from available visitation statistics and multiplying by the number of years on display, this fossil could easily have been touched by over 200 million people—possibly as many as 400 million. I’m unaware of any other dinosaur specimen that has been handled by that many individuals.

Let’s take a look at how the most-touched dinosaur bone of all time (if you know of other contenders for that title, please let me know!) has been interpreted over the years.

Photo courtesy of the Smithsonian Institution Archives.

Photo courtesy of the Smithsonian Institution Archives.

One of the largest known dinosaur limb bones

This humerus (upper arm bone) of the sauropod dinosaur Brachiosaurus alithorax was found by Mr. D.E. Jones of Delta, Colorado. It is from the Morrison formation, of late Jurassic age (about 130,000,000 years ago), in Montrose County, Colorado. Brachiosaurus was a giant among dinosaurs, much larger than the familiar Brontosaurus; it may have weighed as much as 55 tons. It is distinguished from other dinosaurs by the fact that its front legs were somewhat longer than its hind legs. This feature, the great length of the neck, and the projecting nostrils on top of the head seem to have been adaptations to its presumed life habits. Brachiosaurus was a plant eater that walked along the bottoms of lakes, lifting its head to breathe above the surface of the water. Brachiosaurus is known from North America, Africa, and Europe. This humerus is 6 feet 10 inches long, its position in the body of Brachiosaurus is shown in the sketch, where the humerus is drawn in red. Note the much smaller humerus in the nearby skeleton of the dinosaur Diplodocus.

As mentioned, the Potter Creek humerus was first put on display at NMNH in 1955. It was mounted on a wooden pedestal in front of the Diplodocus skeleton, near the front of the museum’s spacious fossil hall. As seen in the photo above, the bone’s damaged shaft was not restored, although some sort of consolidant must have been applied to keep it from crumbling all over the floor.

The 181-word text panel accompanying the fossil was likely written by curator Charles Gazin, who had led the Vertebrate Paleontology division since 1946. The text is quite long and meanders through several distinct topics—addressing what the specimen is, who found it, how old it is, where it was found, how big the animal was, what the animal looked like, how the animal behaved, where else the animal lived, the exact size of the bone, and finally how it would fit into a complete skeleton. The text does not address any qualities of the fossil that visitors can actually observe until the very end.

Consideration of how visitors use museum exhibits—and how exhibits can best meet visitors’ needs—was in its infancy at this time. At NMNH and most of its peer institutions, labels were written by curators—experts in their fields but not necessarily in best practices for communicating with broad audiences. Exhibit text was by experts, for experts, and any visitors not up to parsing dense paragraphs like this one were left to make their own meaning of the exhibits.

It is notable, however, that this label compares the Potter Creek humerus to the nearby Diplodocus. As was typical of natural history exhibits at the time, the NMNH fossil hall wasn’t arranged in any particular order. Specimens were placed on platforms or in free-standing cases. This modular design allowed the hall to be rearranged with relative ease when new specimens were acquired, but it did not lend itself to any sort of overarching narrative for the displays. This passing reference to another specimen was as close to narrative cohesion as exhibits of this era could get.

Photo courtesy of the Smithsonian Institution Archives.

Photo courtesy of the Smithsonian Institution Archives.

Would you like to touch a dinosaur bone?

This is a humerus (arm bone) of the sauropod Brachiosaurus alithorax. The position of the bone and the appearance of the animal are shown in the accompanying drawing. A close relative of Diplodocus and Camarasaurus, Brachiosaurus was the bulkiest land animal that ever lived, weighing about 55 tons. Like other sauropods, he spent most of his time in ponds, lakes, or rivers. If you want to be able to tell your friends that you touched a dinosaur bone, here is your chance.

The NMNH fossil halls were updated in 1963 as part of a decade-long, Smithsonian-wide modernization project. For the first time, an exhibit design specialist worked with the curators to compose the paleontology exhibits. Designer Ann Karras considered how visitors would move through the space, and attempted to create a coherent story of the evolution of life over time. Text panels were part of the aesthetics and organization of the exhibition, and were written with consistent style and terminology.

The text accompanying the Potter Creek humerus may have been written by Barbara Craig, and by modern standards, it’s pretty good (ignoring the now-debunked idea that sauropods spent their time in the water, and the choice to use a masculine pronoun for a dinosaur of unknown sex). The header is a call to action, inviting visitors to touch the fossil. The remaining 82 words are snappy and useful—the object is clearly identified, and the accompanying illustration is referenced right away. Visitors can find the information they want (what am I looking at? What should I do here?) right away, without having to fight through excessively long or wordy prose. It’s remarkable how well this label adheres to the standards for exhibit text that Beverly Serrell would first put forward over twenty years later.

Photo by Michael Brett-Surman.

Photo by Flickr user grafxmangrafxman.

Size in dinosaurs—how big is enormous?

Early dinosaurs were relatively small—about the size of the smaller Camptosaurus displayed to your left. However, these “small” dinosaurs were already larger than most land animals of their time. Although some lines of dinosaurs never got much larger, most produced huge forms. The average live weight of a dinosaur was about 5 tons. No other land-dwelling reptiles have ever approached this size and only about 2 percent of land-dwelling mammals have done so. The smallest dinosaur known, though no larger than a chicken, was still larger than 80 percent of all land mammals living today.

Brachiosaurus leg bone

The bone displayed below and in green in the drawing is from the upper part of the front leg of Brachiosaurus, one of the largest of all dinosaurs. Although Diplodocus had a longer neck and tail, Brachiosaurus was much taller and more massive and outweighed Diplodocus by several tons. Bones of a still larger animal similar to Brachiosaurus have been found in Colorado.

The dinosaur exhibits at NMNH were next updated in 1982. This time, the Potter Creek humerus was relocated to the right side of Diplodocus. With all of the mounted skeletons in a central corral and behind a plexiglass barrier, the role of the humerus as a designated touchable fossil was exceptionally clear. During the renovation, a fiberglass cowl was affixed to the damaged part of the humerus. This restoration makes the bone appear thicker than it actually is.

The accompanying text was written by postdoctoral research associates Jessica Harrison and George Stanley, under advisement from curator Nicolas Hotton. Their task was to balance the needs of visitors with demands for precise language from scientists. The resulting label is twice as long as the previous version and, I would argue, not nearly as useful. The primary text isn’t about the humerus at all—instead it discusses the range of dinosaur sizes and compares them to modern animals. The humerus is finally mentioned toward the bottom of the graphic, where it is once again compared to Diplodocus. For some reason, the donor is listed as Tony Jones.

Photo by the author.

Photo by the author.

How much heavier?

Sauropod dinosaur (arm bone)

Brachiosaurus altithorax

Lived 152 million years ago

Morrison Formation, Montrose Co., Colorado

USNM 21903

Donated by Eddie and Vivian Jones

You can see by it’s arm bone that Brachiosaurus (right) was bigger than Diplodocus (in front of you). The Brachiosaurus humerus is two times as thick as that of Diplodocus. That means it came from an animal that weighed nearly five times as much, about 140,000 lbs (64,000 kg)!

The most recent renovation of the NMNH fossil halls was completed in 2019. For the first time, the Potter Creek humerus is mounted vertically, in the orientation it would have held in a living Brachiosaurus. While requiring a sturdier and more sophisticated mounting structure, this display gives visitors a clearer understanding of the fossil before them.

Angela Roberts Reeder was the lead writer of the current exhibit text, assisted by several co-writers. At 51 words, this is the shortest label for the Potter Creek humerus yet. Some of the basic information—the animal’s name, how old the fossil is, and where it was found—is collapsed into a standardized and compact “tombstone” ID block. The remaining text covers a single subject: the mathematical relationship between the bone’s width and the living weight of the animal it belonged to.

This is considered good practice. According to Serrell, visitors are primarily concerned with the objects on display, not the exhibit text. They will look for text if they expect it to answer their immediate questions and improve their understanding. Visitors will quickly scan the available text, and if it doesn’t seem to be helping them, they will move on. Therefore, exhibit text needs to get to the point, and fast. Short labels aren’t about dumbing things down—they’re about finding the right words to communicate important ideas to the largest possible number of people.

Reeder’s label for the Potter Creek humerus is a great example. It immediately answers the most likely questions: “what is this thing?” and “how big was the dinosaur it came from?” Then, taking advantage of that momentary attention, it enhances visitors’ understanding by explaining how scientists can know the size of an animal from a single bone. The standardized ID block resolves most further questions without making visitors hunt though a long paragraph. Rather than trying to tackle too many concepts at once, this label omits any information on the life appearance or habits of Brachiosaurus.

Looking at the four generations of interpretation of the Potter Creek humerus, there are some recurring themes. The size of the bone and the animal it belonged to has always been referenced. And there is always an accompanying illustration showing where the bone fits into a complete Brachiosaurus. However, the earlier labels addressed the life habits of living sauropods with greater specificity (and as it turns out, inaccuracy—Brachiosaurus did not spend all its time wallowing in lakes in rivers). The newer labels are somewhat more technical, in that they focus on comparative measurements among fossils. This is surprising—I would have expected that earlier generations of paleontologists would have been more concerned with comparing figures and less interested in the total biology and ecology of extinct animals.

I was also surprised that there was not a clear trend toward shorter text. Instead, the length of the label has oscillated with each generation. And it’s worth noting that the earliest label is not burdened with excessive scientific jargon. The language has always been clear—what varies is how it is organized and how long it is overall.

References

D’Emic, M.D. and Carrano, M.T. 2019. Redescription of brachiosaurid sauropod dinosaur material from the Upper Jurassic Morrison Formation, Colorado, USA. The Anatomical Record 303:4:732–758.

Jensen, J.A. 1987. New brachiosaur material from the Late Jurassic of Utah and Colorado. Great Basin Naturalist 47:592–608.

Marsh, D.E. 2014. From Extinct Monsters to Deep Time: An ethnography of fossil exhibits production at the Smithsonian’s National Museum of Natural History. http://circle.ubc.ca/handle/2429/50177

Serrell, B. 2015. Exhibit Labels: An Interpretive Approach (2nd Edition). Rowman and Littlefield.

Taylor, M.P. 2009. A re-evaluation of Brachiosaurus altithorax Riggs 1903 (Dinosauria, Sauropoda) and its genetic separation from Giraffatitan brancai (Janesch 1914). Journal of Vertebrate Paleontology 29:3:787–803.