16,000 fossil footprints in central Bolivia reveal dinosaur behavior

TORO TORO, Bolivia (AP) — Legend once had it that the huge, three-toed footprints scattered across the central highlands of Bolivia came from supernaturally strong monsters — capable of sinking their claws even into solid stone.

Then scientists came here in the 1960s and dispelled children's fears, determining that the strange footprints in fact belonged to gigantic, two-legged dinosaurs that stomped and splashed over 60 million years ago, in the ancient waterways of what is now Toro Toro, a village and popular national park in the Bolivian Andes.

Now, a team of paleontologists, mostly from California’s Loma Linda University, have discovered and meticulously documented 16,600 such footprints left by theropods, the dinosaur group that includes the Tyrannosaurus rex. Their study, based on six years of regular field visits and published last Wednesday in the peer-reviewed journal PLOS One, reports that this finding represents the highest number of theropod footprints recorded anywhere in the world.

“There’s no place in the world where you have such a big abundance of (theropod) footprints,” said Roberto Biaggi, a co-author of the study led by Spanish paleontologist Raúl Esperante. “We have all these world records at this particular site.”

The dinosaurs that ruled the earth and roamed this region also made awkward attempts to swim here, according to the study, scratching at what was squishy lake-bottom sediment to leave another 1,378 traces.

They pressed their claws into the mud just before water levels rose and sealed their tracks, protecting them from centuries of erosion, scientists said.

“The preservation of many of the tracks is excellent,” said Richard Butler, a paleontologist at the University of Birmingham who was not involved in the research. He said that, to his knowledge, the number of footprints and trackways found in Toro Toro had no precedent.

“This is a remarkable window into the lives and behaviors of dinosaurs at the end of the Cretaceous,” Butler added, referring to the period around 66 million years ago at the end of which an asteroid impact abruptly extinguished all dinosaurs and 75% of living species along with them, according to scientists.

Although they've survived for millions of years, human life has threatened these traces. For decades, farmers threshed corn and wheat on the footprint-covered plateaus. Nearby quarry workers didn’t think much of the formations as they blasted rock layers for limestone. And just two years ago, researchers said, highway crews tunneling through hillsides nearly wiped out a major site of dinosaur tracks before the national park intervened.

Such disturbances may have something to do with the area's striking absence of dinosaur bones, teeth and eggs, experts say. For all of the footprints and swim traces found across Bolivia’s Toro Toro, there are virtually no skeletal remains of the sort that litter the peaks and valleys of Argentine Patagonia and Campanha in Brazil.

But the lack of bones could have natural causes, too. The team said the quantity and pattern of tracks — and the fact they were all found in the same sediment layer — suggest that dinosaurs didn’t settle in what is now Bolivia as much as trudge along an ancient coastal superhighway stretching from southern Peru into northwest Argentina.

The range in footprint sizes indicated that giant creatures roughly 10 meters (33 feet) tall moved in a herd with tiny theropods the size of a chicken, 32 centimeters (1 foot) tall at the hip.

In presenting a snapshot of everyday behavior footprints “reveal what skeletons cannot,” said Anthony Romilio, a paleontologist at the University of Queensland in Australia who also did not participate in the study. Just from footprints, researchers can tell when dinosaurs strolled or sped up, stopped or turned around.

But the reason they flocked in droves to this wind-swept plateau remains a mystery.

“It may have been that they were all regular visitors to a large, ancient, freshwater lake, frequenting its expansive muddy shoreline,” offered Romilio.

Biaggi suggested that they were “running away from something or searching for somewhere to settle.”

What's certain is that research into this treasure trove of a dinosaur tracksite will continue.

“I suspect that this will keep going over the years and many more footprints will be found right there at the edges of what’s already uncovered," Biaggi said.

DeBre reported from Buenos Aires, Argentina.

Park ranger José Vallejos stands next to petrified dinosaurs footprints in Carreras Pampa in Toro Toro National Park, north of Potosi, Bolivia, Saturday, Dec. 6, 2025. (AP Photo/Juan Karita)

Tourists look at the petrified footprints of dinosaurs at Carreras Pampa in Toro Toro National Park, north of Potosi, Bolivia, Saturday, Dec. 6, 2025. (AP Photo/Juan Karita)

A view of the Toro Toro National Park, where petrified dinosaur footprints are visible, north of Potosi, Bolivia, Saturday, Dec. 6, 2025. (AP Photo/Juan Karita)

Petrified footprints by dinosaurs are visible in Carreras Pampa in Toro Toro National Park, north of Potosi, Bolivia, Saturday, Dec. 6, 2025. (AP Photo/Juan Karita)

A petrified footprint by a dinosaur is visible in Carreras Pampa in Toro Toro National Park, north of Potosi, Bolivia, Saturday, Dec. 6, 2025. (AP Photo/Juan Karita)

INDIANAPOLIS (AP) — The Indianapolis Colts confirmed their worst fear Monday.

Starting quarterback Daniel Jones suffered a torn right Achilles tendon during another devastating loss at Jacksonville. Then came more bad news. Backup Riley Leonard arrived at the team complex with an injured right knee.

It's a two-punch combination the Colts (8-5) simply cannot afford as their once-promising season teeters, their playoff hopes fade and coach Shane Steichen and general manager Chris Ballard are likely to start hearing more questions about their future prospects.

Amid all that, their hunt for a new quarterback has them linked to a surprise name — 44-year-old Philip Rivers — who may need a crash course in the Colts' playbook, especially if Leonard can't play Sunday at Seattle (10-3).

“Chris and his staff are working through that right now, so you guys will probably have an update Wednesday when I talk to you guys,” Steichen said. “But we're working through that.”

Leonard, a rookie, did what he could in his first extensive action Sunday, though he didn't exactly look like he could navigate a couple wins out of Indy's final four games. Veteran Brett Rypien joined the practice squad Oct. 15 and still isn't on the active roster, though Steichen said Rypien probably would start if Leonard can't go next weekend.

And the best in-house hope — Anthony Richardson — also may be out. The No. 4 overall draft pick in 2023 still has not practiced since fracturing an orbital bone in mid-October. While Steichen hopes he can return this season, it doesn't appear Richardson will be cleared to practice this week.

Where does that leave Indy now?

“We really can't dwell on it," defensive end Kwity Paye said. “We have second and third stringers and backups for a reason and those guys are going to have to be ready to step up when their number is called. Just fill the position as they can and try to make some plays.”

Perhaps most discouraging is that last month, Indy appeared poised to end its four-year playoff drought. The Colts held a seemingly comfortable lead in the AFC South as they fought for the conference's No. 1 seed. Since then, everything has unraveled.

The Colts have lost three straight and four of five, dropping into a tie for second in the division race, one game behind Jacksonville. They are trying to fight their way out of the No. 8 seed without their starting quarterback and maybe their backup quarterback as they head to Seattle before playing back-to-back home games against San Francisco (9-4) and Jacksonville (9-4) and a regular season-ending trip to Houston (8-5).

How desperate are they? Well, they're bringing in Rivers who hasn't taken a snap since leading the Colts to the playoffs in 2020 and has been a high school coach in Fairhope, Alabama, since retiring in January 2021.

Losing a player who spent the first half of this season in the MVP discussion was emotionally jarring Sunday. The lingering ripple effects could be much more damaging, though, especially if Leonard can't play — and they all know it.

“The offense has to be tailored around the quarterback, for sure, on what he does well, and then you go,” Steichen said.

Blake Grupe. Hey, it's a small victory. Indy's third kicker of the season had a solid start. The New Orleans Saints castoff made both of his field goals attempts and his only extra point attempt.

What doesn't? Jones’ interception on the first pass of the game led to one Jags TD, Jonathan Taylor’s fumble led to another, and without Jones the offense seemed to be stuck in the mud on a rainy day. Defensively, Indy allowed a season-high 36 points.

Leonard. Sure, he made some of the expected mistakes given his lack of experience and, yes, he's hurt. But the plays he made illustrated why Indy made him a sixth-round draft pick in April. No, he's not ready to lead a playoff push, but he appears capable of becoming a reliable backup.

Jones. In addition to missing the final four games, Jones could also miss out on a hefty pay raise. In March, he signed a one-year deal worth $14.5 million including bonuses — a bargain for an NFL starting quarterback — and seemed destined to hit the jackpot this spring. Some thought he could command a multiyear deal worth between $45 million and $50 million per year. But a recovery process that's likely to stretch into September or beyond could lower his price tag.

In addition to Jones and Leonard, RT Braden Smith and backup DE JT Tuimoloau left Sunday's game with concussions, and Smith also hurt his neck. WR Alec Pierce also was evaluated for a concussion at game's end, but Steichen provided no update Monday. Indy's Pro Bowl secondary also took another hit. Sauce Gardner sat out Sunday with a strained calf and Charvarius Ward entered the concussion protocol Monday for the second time since October. The good news: Two-time Pro Bowl DT DeForest Buckner (neck) can be activated from injured reserve this week.

6, 12 — Indy opened the season on a historic scoring and efficiency binge. But during this three-game skid — and against three good defenses — they've scored only six TDs in 12 red-zone trips.

First, Indy must sort out its options at quarterback. Then it can start focusing on what to do next at Seattle.

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Indianapolis Colts head coach Shane Steichen celebrates a touchdown with quarterback Daniel Jones (17) during the first half of an NFL football game against the Jacksonville Jaguars, Sunday, Dec. 7, 2025, in Jacksonville, Fla. (AP Photo/Phelan M. Ebenhack)

Indianapolis Colts quarterback Riley Leonard (15) looks to throw over Jacksonville Jaguars defensive end Josh Hines-Allen (41) during the first half of an NFL football game, Sunday, Dec. 7, 2025, in Jacksonville, Fla. (AP Photo/John Raoux)

Indianapolis Colts quarterback Daniel Jones (17) walks off the field after an injury during the first half of an NFL football game against the Jacksonville Jaguars, Sunday, Dec. 7, 2025, in Jacksonville, Fla. (AP Photo/Phelan M. Ebenhack)

Indianapolis Colts quarterback Daniel Jones (17) grabs his leg after an injury during the first half of an NFL football game against the Jacksonville Jaguars, Sunday, Dec. 7, 2025, in Jacksonville, Fla. (AP Photo/Phelan M. Ebenhack)