By WAYLON CUNNINGHAM
Dr. Susan Hovorka and Dr. Linda McCall, scientists with the Jackson School of Geoscience at The University of Texas, said on a recent trip to the South San Gabriel tracks that there’s a good reason to doubt their authenticity. Namely, that they’re too perfect.
When asked for general insight into how dinosaur tracks are formed, mentioning almost by accident the specific South San Gabriel tracks, the scientists noted that these trackways weren’t actually in the files at the Bureau of Economic Geology, their research unit in the department. They proposed a visit.
The search for a dinosaur commenced one morning in early March. Though the tracks are only a short hike upstream from US Highway 183, and a well-known spot for locals, they’re actually quite hard to find. They lie in the shallow part of the riverbed, and therefore spend a good part of the year covered by running water.
Spotted are some reputed sauropod dinosaur tracks nearby, but they’re not the theropod tracks that were the subject of the search. These sauropod trackways are also well-known in the area, at least to academics, as possible evidence of the controversial idea that these giant, long-necked herbivores (best known by “Brontosaurus”) might have ventured out to the kind of shallow seas that once covered this area.
The sauropod trackways here are faint. As vaguely round depressions, they blend easily into the surrounding pockmarks of the riverbed. The theropod trackways were supposed to be much more clearly defined. Pictures online show them as dramatic, three-clawed outlines that just scream “dinosaur.” It’s not hard to see why they, and not the sauropod trackways, have become such a favorite with local travel bloggers.
It began drizzling after an hour or so of searching. Finally they are spotted with the help of a geotagged photo on Google Maps. The water had already risen enough to lightly cover them, but a couple of hands easily cleared out the basin of the prints. The tracks are just as awe-inspiring as photographs had led to expect. But the sense of wonder was short-lived.
Squatting to examine one, Hovorka says something seems strange.
“They should look like messy dog footprints,” she said. She runs a finger along the inside rim of the depression.“It’s rare for a track to be this beautifully preserved.”
There’s no ridge in the limestone slightly raised around the tracks. The pressure of the foot setting down usually pushes up the mud around it. Many of the tracks are flat on the inside, where the curve of the claw would otherwise dig into.
McCall takes measurements and photographs them next to rulers. She counts 12 prints, spaced out between 55 to 59 inches, all evenly aligned with one another and each measuring about 18 inches from heel to claw.
Hovorka says a missing print would be good, or maybe a missing claw. But nothing is missing. The tracks sputter out briefly from under the eastern bank, curving toward the center for a moment before drifting back under the bank. The movement they capture might have lasted only a few seconds. The limestone slab covers what came before and after.
There are, however, a few points of credibility for Hovorka. One is what appears to be raised bubbles in the second print. Another is that they could be ornithopod (“bird footed”) tracks instead of theropod (“beast footed”), and putting aside the specifics of these tracks, the existence of orinthopods here do make sense.
The mud flat that covered here, and all of Central Texas for hundreds of miles, would have been replete with worms, shrimp and fish. These are foods that modern day birds eat, and an ornithopod dinosaur probably would’ve had a similar diet. After all, the key to the past, Hovorka says, is the present.
But ultimately the only evidence that could prove the matter to Hovorka and McCall, one way or the other, lies underneath that limestone slab. Short of using extreme measures, or just waiting until erosion takes its course, the evidence is a wash.
“There were dinosaurs here, that’s for certain,” she says. “I’m just not sure about these tracks. I’m not saying for certain that they’re fake, but these could have easily been manufactured.”
The idea might not be as far-fetched as it sounds.
In her own life, Hovorka says as a child she was shown the footprints of where the archangel Saint Gabriel once walked in Indiana.
And even here, just 100 miles north of this bend on the South San Gabriel, an area to the southwest of Dallas holds the honor of being one of the world’s most prolific sites for dinosaur tracks— and some of the most infamous fakes.
Poor farmers in the region during the Great Depression learned they could sell the chiseled-out tracks for significant profit to visiting tourists and paleontologists. And when the supply got low, accounts would later testify, they learned some ways to carve more in. Throwing in a few human footprints only raised the price. These were used later in the century by some as proof of a compressed timeline, in which dinosaurs and humans walked together. Later analysis culled these fakes from the ranks of the genuine records. Some of the “human” footprints that were really that old were found to have been mis-read from the elongated feet of some dinosaurs.
To date, half a dozen “human” footprints and two “saber-tooth tiger” trackways have been identified as manufactured and removed.
But to be clear, those kind of tracks are in the minority. The area that is now Dinosaur State Park near Glen Rose truly is “extremely prolific” in the amount of genuine tracks it contains, says Austin Paleontology Society President Erich Rose. “There’s hundreds of yards and thousands of feet of these trackways there.” And even more have been exposed in recent years from flooding.
Unlike fossils, trackways are actually fairly common, Rose explains. There are probably close to 100 scattered throughout the Glen Rose formation, a limestone formation spanning most of Texas, including Dinosaur Valley State Park and the South San Gabriel. Where exposed, the formation shows Texas as it was 100 million years ago— a shallow sea full of broad lagoons and tidal flats. And dinosaurs.
One site with parallel trackways has been interpreted by some as recording an ancient chase scene. Another appears to show a stampede.
But Rose also says that footprints can be a funny thing.
“They can be really vague, or, they can be super pristine. Sometimes you’re looking at the actual mud they were formed in, and sometimes you’re looking at the layer that was below them,” he said.
It’s why he isn’t convinced that the relatively rare “perfection” of the South San Gabriel tracks should cast doubt on them.
“The tracks are real. They’ve been well known for close to 100 years now,” he said.
In fact, Rose visited the tracks himself 10 years ago. The indented ring around one of the tracks remains from the technique his colleagues used to create a plaster mold of the print. He still has a copy of it, as do many members in his group.
But because that was 10 years ago, he offers one qualification: “Could someone have carved a few new ones or even cleaned up some of the old ones? I don’t know,” Rose said.
Other area paleontologists expressed a similar sentiment.
Dr. Rena Bonem, a geoscientist at Baylor University specializing in Paleoecology, wrote in an email that having examined photos of the tracks, “they look authentic and no more perfect than other tridactyl tracks around the state.” She said she would have to look at them in person to be sure, but “it’s certainly likely that they are dinosaur tracks.”
From the Heritage Museum of the Texas Hill Country, Everett Deschner also said he could not make a firm judgement on their authenticity from photos, but that they do show “all the attributes of a theropod track.”
But perhaps the most experienced opinion comes from Dr. James Farlow, a Professor of Geosciences at Indiana University. After publishing dozens of articles and books on dinosaur footprints, he’s often considered one of the leading experts in the subject. In an email to Liberty Hill Living, he wrote that he had been to the area sometime in the late 1980s, and maybe even saw these tracks in particular.
“The appearance of the footprint itself looks pretty reasonable to me, although that ring around it gives me pause,” he wrote. “I almost wonder if somebody ineptly tried to make a cast of a print, and ended up partly filling up the print with the casting medium.”
Apart from the ring, though, he agreed that this is “probably a theropod dinosaur trackway.” But again, a firm pronouncement might require more than photos.
A skim through the literature of first-hand accounts from paleontologists sheds little light.
Where the South San Gabriel River is mentioned as a site, it is usually limited to a marking on a state map alongside dozens of other trackway sites in the Glen Rose formation. Additionally, it is often not specified whether the reference is to the round, vaguely-defined sauropod trackways, or the more dramatic, deeper theropod tracks.
But one interesting detail does reveal itself in the confusion. The earliest found reference to the site is in a 1974 article from UT Austin paleontologist Dr. Wann Langston, Jr. In this survey of Texas’ trackways from the Mesozoic era (256 to 66 million years ago), Langston mentions the South San Gabriel, and describes the sauropod trackways in detail, but makes no mention of the nearby theropod trackway.
He writes, “Several short, roughly parallel trails at the top of the Glen Rose Limestone exposed in the bed of the South San Gabriel River […] seem to show graduations between relatively featureless basin-like depressions and more conventional sauropod tracks such as those which I believe may be attributable to Pleurocoelus.”
He goes on to speculate why the tracks appear so faintly.
“The present condition of the San Gabriel tracks is the result not only of originally shallower and perhaps firmer mud, smaller (and hence lighter) individuals, but also of weathering, apparently both before burial and after exposure,” he wrote.
A plate showing the tracks is marked, “Supposed Sauropod trackway.”
Why would Langston take such lengths to describe a weakly imprinted specimen when there was a decidedly more pronounced trackway just yards away? Could it have been that the three-clawed track simply wasn’t there?
Farlow says Langston’s omission might not be that surprising.
“Theropod tracks are not at all uncommon in central Texas,” he writes. “I’ve published papers in the scientific literature about such prints since 1981, and am still working on these footprints.”
A certain amount of uncertainty and debate is baked into the scientific process. Put another way, even wrong questions generate valuable answers.
And the geological sciences have no shortage of questions. Even just within the South San Gabriel, the theropod tracks aren’t the only disputed formation. One can find what appear to be fossilized troughs intermittently throughout the river’s winding. Hovorka says a proper explanation for this phenomenon as it is found elsewhere has yet to find consensus. Some say they’re natural formations, others that they’re more recent marks left by wagon wheels of pioneers.
“Sometimes we as scientists confess, we don’t know,” she says.
Truths, she continues, are built up over time through a network of inferences, as fragmentary evidence accumulates to corroborate one another and anticipate new discoveries. There’s no eureka moment, smoking gun or “missing link.”
Take for instance the shallow sea that covered Central Texas. The proof is vast and overwhelming, but more importantly commonplace. Feet away from the theropod tracks (or chisel marks), seashells, oysters and clams are embedded in the limestone walls.
Even the inconspicuous cracks in the limestone bed of the river have a name — joints. They’re the products of colossal pressure, and following them points at a perpendicular angle to a much larger tension. In this case, that’s the Balcones Fault. It’s what gave us Mount Bonnell, Barton Springs, and Interstate 35. Highways are often planned to follow the natural geography, and so it’s no coincidence they often inadvertently follow long tectonic seams, where the shallow soil makes for easy roadways. If the present is the key to the past, the reverse is true as well.
“You don’t have to travel halfway around the world to do geology,” Hovorka. “It’s in your backyard, it’s right here.”