Prehistoric Utah Rock Art Does Not Depict a Pterosaur, Study Confirms

Dealing what they say is a “mortal blow” to the interpretation of some creationists, a team of archaeologists has concluded that a panel of rock art in Utah portrays all manner of fantastic figures, but it does not, in fact, depict a pterosaur.

The findings are the result of the first scientific study of a well-known set of pictographs in Black Dragon Canyon, in the sandstone canyons of southeastern Utah’s San Rafael Swell.

The images, first documented in the 1920s, form a rich tableau of eerie, human-like and animal figures, painted in the familiar red-ochre technique known as the Barrier Canyon style.

But due to a combination of poor preservation and decades of defacement, the scene has appeared to some observers to depict a pterosaur — a winged reptile that lived during the age of the dinosaurs — leading some creationists to cite it as evidence that humans and dinosaurs co-existed.

The age of the panel itself is unknown, as rock art is nearly impossible to date, but the Barrier Canyon style is known to have been used by archaic hunter-gatherers in the Four Corners region from about 500 years ago to at least 2,500 years ago.

A photo shows the putative “pterosaur” of Black Dragon Canyon, with the white chalk outline visible.

Although numerous studies by anthropologists and other scientists have found that the Black Dragon art depicts no winged monsters, their findings have been dismissed by creationists as being tainted by anti-religious bias.

So the team of researchers, led by French archaeologist Jean-Loıc Le Quellec, used photographic technology and chemical analysis to verify where pigment actually appears on the rock, to eliminate any subjective interpretation of what the images might look like.

“By removing interpretational bias, the new technology finally lays to rest the Black Dragon Canyon pterosaur,” writes Le Quellec and his colleagues in the journal Antiquity.

“In order to close this debate and finish off a monster that has already been wounded by the attacks of our predecessors, we present here two new analyses of this panel, each of which avoids any idiosyncrasy but which deal a mortal blow to readings that evoke a pterodactyl.”

The first technique used by the team was a relatively new image-enhancing technology known as decorrelation stretch, or D-Stretch.

A close-up photograph shows the figures taken to be a head and right wing of a pterosaur or winged dragon. (Jean-Loïc Le Quellec et al., Antiquity)

The technique, originally used by space scientists to enhance aerial photos, separates colors that appear to overlap — like red ochre on red sandstone — and enhances their differences to make them distinct.

This was necessary, the team notes, in part because, in 1947, a rock-art enthusiast named John Simonson drew a heavy chalk outline around the figures on the panel, to point out the flying reptile that he saw in it.

The outline, along with other defacements done to the images over the years, made it more difficult to see the panel’s true component parts, the team notes.

“The illusion of continuity comes in part from the chalked outline, and partly from the fact that the painting has become slightly diffuse on the wall, perhaps as a result of it being wetted by indelicate photographers,” they write.

The same figures as seen by D-Stretch. The blue lines reveal where chalk was used to “artificially join” the figures into a single image, researchers say. (Jean-Loïc Le Quellec et al., Antiquity)

But the images revealed by the D-Stretch image enhancement are arguably even stranger than a Cretaceous flying reptile.

What had been mistaken for the pterosaur’s mouth and neck was really an anthropomorph, or human-like shape. Its putative left wing was another, larger anthropomorph with haunting, hollow eyes. And where some people saw a right wing, artists had actually painted an enormous serpent, with its giant mouth agape.

While all unique in some ways, these animal and human-like forms are all consistent with Barrier Canyon art throughout the region, including in the panel that defines the style: the Great Gallery in Canyonlands National Park. [Discover new findings about the famous art: “Famous Utah Rock Art May Be Thousands of Years Younger Than Was Thought“]

In addition, the study authors point out, the D-Stretch method offers the benefits of being objective and repeatable.

“The advantage of the method adopted here is that it meets the scientific criterion of replicability—anyone with D-Stretch at their disposal and detailed photographs will obtain the same results,” they write.

The team then sought to test their findings using an additional method.

Portable X-ray fluorescence, or PXRF, is another new technology that’s transforming rock art research. Using hand-held x-ray scanners, researchers can test materials in the field, without touching them, and receive readings about their chemical composition.

In rock art, this technique has already produced many surprises about the kinds of pigments ancient artists have used around the West. [See what it revealed in Texas: “Ancient Rock Art in Texas Yields ‘Surprising’ New Finds“]

In Black Dragon Canyon, the team used it to detect the presence of iron in the red ochre. This would determine where ochre was actually applied to the sandstone, providing the outlines of the true images.

Researchers conducted 67 one-minute x-ray scans on various parts of the panel, and then mapped out their readings to reveal where red ochre had been painted on the rock.

The most striking results came in the center of the panel, where the head meets the wings of the would-be pterosaur.

There, x-ray fluorescence detected no traces of iron, and therefore no red ochre, in the same places where D-Stretch showed an absence of pigment.

Where some saw the heart of a pterosaur, in other words, there was simply empty space.

“One cannot therefore interpret the panel as if it were a single image,” the authors say, “unless, of course, one behaves akin to those authors who ‘conduct their investigations in reverse: they have a pet theory and they look for evidence to support it.’”

Taken together, the evidence appears to put to rest the theories of those who would believe that humans once shared the earth with pterosaurs or dragons.

Beyond that, the new research also provides valuable new data about the varied and mysterious Barrier Canyon style.

The giant-eyed figure at Black Dragon Canyon, for example, turns out to have tiny arms and legs, a pelt of fox fur on its back, and an object in its hands, perhaps a snake, as is found in many other Barrier Canyon motifs.

Black-dragon-canyon rock art
A composite of the images revealed by D-Stretch shows the original panel before it was defaced, consisting of a small human-like “supplicant” figure in the center, a large spirit figure to its left, male and female sheep on the left and a giant serpent-like form on the right. (Image Jean-Loïc Le Quellec et al., Antiquity)

Similarly, the smaller human figure near the center of the panel appears to be bent over in a posture sometimes described as “supplication,” the team notes.

Both figures are flanked by animals, with familiar male and female sheep on the left, and the ghastly serpent on the right.

Just what this scene means remains unclear. But if other “pet theories” persist, the researchers note that the rock art at Black Dragon Canyon has now been studied with scientific and reproducible methods that others can try for themselves.

“In contrast to previous approaches, we have analysed this panel using two different methods that exclude the intervention of any personal bias and in accordance with a methodology that is fully replicable,” the researchers conclude.

“The results obtained definitively refute the readings that are based on a single image, and objectively confirm the presence of several distinct subjects.”
Le Quellec, J., Bahn, P., & Rowe, M. (2015). The death of a pterodactyl Antiquity, 89 (346), 872-884 DOI: 10.15184/aqy.2015.54

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  1. pip jones

    I think they look more like Goats than sheep. They seem far better drawn than the humanoid form. The smaller form on the right when I first looked at it, before reading the article seemed like a Stag leaping and landing from right to left. I thought the open mouthed monster was a depiction of a waterfall and river.

  2. ankyloman

    The “snake” once thought to be a pterosaur’s wing is very strange. especially the “head” and “mouth.” The rendering is not at all similar to what seems to be a snake being held by the large figure at the left. Are there other images known that unambiguously represent a snake in this way? To me the big “snake” looks more like a crude depiction of a river with a rapids or falls at the left end.

  3. TomConoley

    Some top-level scientists put a lot of time, effort, and skills into this. Let’s leave it at that.

    1. Elma

      May I post images to tell why rock art was done. Most rock
      art are done in 3D. The truth is down there and its time….. Blessings

  4. Pigtails

    I personally think it is a person casting a net into a river. There seems to be two fish on the bank besides him. The tall figure is sowing seeds and the goats are the animals they like to hunt. This is a magic spell for prosperity. Painted by the shaman to ensure a good harvest and good hunting. Just my two centimes.