DIGGING DEEPER IN THE SOUTH SAN GABRIEL DINOSAUR TRACKWAYS

Published in Liberty Hill Living magazine, Summer 2017

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The dinosaur tracks at this bend of the San Gabriel River are so fresh, it’s easy to imagine they were left just minutes ago. Every detail of the foot’s soft anatomy has been almost perfectly preserved, down to the pattern of its pads, the tendons of its claws. A slow process of sediment filling in over eons has hardened into limestone what once were simple pockets in the mud— not unlike the actually fresh dog tracks just yards away.

This is a glimpse into the life of a dinosaur in Texas, one hundred million years ago.

Or maybe not, says Dr. Susan Hovorka.

She and Dr. Linda McCall, scientists with the Jackson School of Geoscience at UT Austin, say there’s good reason to doubt the authenticity of the South San Gabriel theropod tracks. Namely, they’re too perfect.

We had spent the past hour searching for this trackway just a half a mile upstream from the collapsed bridge by Highway 183. Though it’s only a slight hike from the highway and a well-known spot for locals, its placement in the shallow part of the riverbed means it spends much of the year covered by running water.

Supposedly, there are other tracks in the area too. Left by Sauropods— the giant, long-necked herbivores like the famous Brontosaurus—they are even harder to find. Faint and described only as “vaguely round depressions” by local blog posts, it would be easy to miss them among the surrounding pockmarks of the riverbed.

The Sauropods are of interest to academics–it is rare to find such lumbering creatures in Texas, a great sea for much of the Earth’s life–but not to the tourists and locals. Hence, our interest in the clawed tracks, left by another type of dinosaur called a theropod (“beast footed”).

No record of them actually existed with the Bureau, whose job it is to record such things. Hovorka says my email was the first she had heard of them.

A drizzle had just begun when we finally spotted the tracks 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 them out.

Their dramatic outline screamed “dinosaur.”

But there was a problem.

“They should look like the messy dog footprints,” Hovorka says, squatting to examine one of the footprints. She runs a finger along its inside rim. “It’s rare for a track to be this beautifully preserved.”

Furthermore, there’s no ridge in the limestone slightly raised around the tracks. The pressure of the foot setting down usually pushes the mud around it up, she says. And many of the tracks are flat on the inside too, where the curve of the claw would have dug downwards.

McCall takes measurements. She counts twelve prints, spaced out between fifty five to fifty nine inches, all evenly aligned, each measuring about 18” heel to claw.

“A missing print would be good, or if one was missing a claw. That would be more like what we see in others,” Hovorka says.

But nothing is missing. The tracks appear briefly out of the eastern bank, curve toward the center, and drift back again to disappear under the bank. The movement they capture might have lasted only a few seconds. A limestone slab covers what came before and after.

There are, however, a few details that add to their credibility. One is that there appear to be raised bubbles in the second print. Another, that the existence of theropod tracks 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. Just as modern day birds eat these, our theropod creature likely would have as well. The key to the past is the present, Hovorka says.

Hovorka hesitates to call the tracks outright fakes. The only evidence that prove or disprove them, she says, lies beneath the limestone slabs on either side. If the tracks continue underneath the slabs (which came later in the geological timeline), they’re real. If they don’t, they’re likely 20th century hoaxes.

Until erosion takes it course, though, the truth 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.”

Such fakes are not uncommon. As a child, Hovorka was once shown the footprints of where the archangel Saint Gabriel was said to have walked in Indiana. He didn’t, she says. And one hundred miles north of this bend on the South San Gabriel, one of the world’s most prolific sites for dinosaur trackways has also seen its most infamous fakes.

Poor farmers in the area during the Great Depression learned they could sell chiseled-out tracks to visiting tourists and paleontologists. And when the supply got low, as accounts would later testify, they learned they could always make a few “extra.” Throwing in a few human footprints to the mix, alluding to their co-existence, only raised the price.

To date, half a dozen “human” footprints and two “saber-tooth tiger” trackways have been identified as manufactured and removed.

To be clear, fake tracks are in the minority. The area now called Dinosaur State Park truly is teeming with genuine tracks, 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.

Trackways, unlike fossils, are fairly common. There are probably close to a hundred scattered throughout the Glen Rose formation, a limestone formation spanning most of Texas, including Dinosaur Valley State Park and the South San Gabriel.

One site with parallel trackways has been interpreted by some as recording an ancient chase scene. Another appears to show a dinosaur “stampede.”

But footprints can be a funny thing, Rose says.

“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.”

It’s why he isn’t convinced that the relatively rare perfection of the South San Gabriel tracks are enough to cast doubt on them.

In fact, Rose visited the tracks himself ten years ago.

An indented ring remains around one of the tracks, from when created a plaster mold of the print.

“The tracks are real,” he says definitively. “They’ve been well known for close to 100 years now.”

Other local paleontologists expressed a similar sentiment.

Dr. Rena Bonhem, 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.”

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.”

Perhaps the most experienced opinion comes from Dr. James Farlow, who is considered one of the leading experts in dinosaur footprints. He wrote in an email that he had been to the area sometime in the late 1980’s, if not to these particular tracks.

“The appearance of 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, but one interesting detail stands above the rest.

The earliest found reference to the site is in a 1974 article from Dr. Wann Langston, Jr., a paleontologist at UT Austin writing a survey of trackways in Texas 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. The Sauropod tracks are faint, he writes, and it is difficult to say for sure that they are not simply roundish depressions.

It begs the question: 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 be that the three-clawed track simply weren’t there yet?

For Dr. Hovorka, a certain amount of uncertainty and debate is baked into the scientific process. Put another way, there is no such thing as a wrong question.

The geological sciences in particular have no shortage of questions. Just down the river from the supposed theropod tracks are what appear to be fossilized troughs. This type of formation is quite common in limestone beds in the area, Hovorka says, but no one can agree on what exactly they are. Some say they’re natural formations, but others say they’re more recent marks left by the wagon wheels of pioneers.

“Sometimes we as scientists confess, we don’t know,” she says.

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