Costa Rica Unearths Giant Sloth and Mastodon Fossils, Rewrites Memory

In Costa Rica’s Cartago province, a confidential dig has pulled giant sloth and mastodon remains from layered sediment after a citizen report on private land. Now the National Museum faces a policy choice: keep rescuing fossils, or build a permanent home.

A Tusk in the Dirt, a Country in the Layers

At the edge of the excavation, the ground tells its story in thin bands. One layer yields easily. Another holds like damp cement. Tools scrape, then stop. A brush takes over. The air has that raw, mineral smell you only notice when earth has been opened and kept open, when a place that was sealed for millennia becomes a worksite again.

Somewhere in Cartago, at a site the authorities are keeping confidential, a team has been doing this 13 times now: excavation and rescue work that has already produced 49 fossil pieces. The list reads like a skeleton assembling itself: vertebrae, a femur, phalanges, ribs, and other bone elements still being identified and studied. And one object that changes the scale of the whole scene, a complete tusk measuring one point sixty meters, plus an additional tusk fragment.

It is easy to say megafauna and move on. The trouble is that megafauna forces you to picture weight and breath, the slow confidence of animals that once inhabited ecosystems at a size most people now encounter only in museum halls or children’s books. These are not abstract remnants. They are pieces of bodies.

Preliminary studies, based on geological analysis of the terrain and different sedimentation layers, estimate that the remains of Cuvieronius, described in the notes as a giant mastodon. Eremotherium, described as a giant sloth, could be between ten thousand and forty thousand years old. The numbers are wide, but the timeframe lands in the Pleistocene, a period when Costa Rica’s fossil record often includes gomphotheres, giant sloths, glyptodonts, and toxodonts.

And it lands in a country whose deep past is often misunderstood in a very specific way.

Costa Rica did not exist as a landmass during the age of dinosaurs. At that time, the region sat at the bottom of the ocean. The Costa Rica that matters for these fossils is the Costa Rica that formed later as part of the Isthmus of Panama, a corridor for the Great American Biotic Interchange, when animals from North and South America migrated and met.

So when a tusk emerges in Cartago, it is not only a discovery. It is an argument about what kind of past this country actually has.

From a Citizen Tip to a Museum Rescue Operation

The chain of events begins with something ordinary, even modest: a citizen reports the possible presence of fossil remains on private property. A technical inspection follows, then analysis. The National Museum team determines the pieces belong to megafauna, and an excavation and rescue process begins.

This matters because it puts Costa Rica’s fossil heritage in a familiar Latin American tension between the public good and private space. The discovery is on private land, but the significance is national. The location remains confidential, protecting the site while the work proceeds, but also turning the fossil record into something that exists at a distance from public view. People hear the headlines. They cannot see the place.

The technical team leading the effort includes 12 professionals in geology, archaeology, and biology, with support from students from the University of Costa Rica engaged in academic practice. The recovery is led by geologist Joanna Méndez Herrera of the Department of Natural History, with the backing of specialists in conservation and cultural heritage protection from the National Museum. The work also includes advice from Lucas Spencer, a paleontologist at the New Mexico Museum of Natural History, and accompaniment from Costa Rican geologist and academic Guillermo Alvarado.

Even without turning the site into a spectacle, you can sense the pace and pressure: bone elements still under identification, a rescue process that has to move carefully but cannot drift, and the weight of knowing that one mistake can damage what time has preserved.

The everyday observation, implied by the structure of the work itself, is that a find like this is not a single cinematic moment. It is repeated labor. It is returning to the ground again and again, logging pieces, stabilizing them, transporting them, and keeping track of which pieces belong to which layer. It is science done in the rhythm of patience.

It is also, inevitably, a public story.

The Ministry of Culture framed the discovery as a significant contribution to scientific knowledge and to Costa Rica’s paleontological collection, and as a sign that the country is again positioned at the forefront of regional megafauna research. That framing is not just pride. It is a prompt that pushes the conversation from the dig to the broader question of what happens after the rescue.

Because fossils do not only need discovery. They need custody.

A Permanent Exhibit and the Politics of Deep Time

Here is where the policy dispute enters, quietly but decisively. The Minister of Culture and Youth, Jorge Rodríguez, instructed the National Museum to begin designing and enabling a permanent exhibition room for its paleontological collection, so that discoveries and the country’s fossil holdings can serve educational and scientific purposes.

On its face, the instruction sounds straightforward: build a home for the deep past. But the wager here is larger. A permanent hall is not merely a room with display cases. It is a commitment to continuity, staffing, conservation standards, interpretive choices, and the long-term public work of explaining what these bones mean.

It is also a way of deciding which stories become central.

Costa Rica’s natural heritage is often narrated through forests, biodiversity, and living ecosystems. A permanent paleontology space would insist that the country’s identity also includes deep time, the geology that formed a land bridge, the migrations that remade continents, and the Pleistocene animals that walked through what is now national territory.

That insistence carries power. It changes how students imagine their country. It changes what visitors think of Costa Rica. It anchors science within culture, not as a separate domain reserved for specialists.

And it arrives at a moment when the discovery itself depends on coordination, on public institutions responding to a citizen tip, and on experts operating in a confidential site that must be protected from curiosity as much as from harm.

In other words, the fossils are already doing political work. They have pulled private land into a national conversation. They have pulled museum capacity into focus. They have pulled the Ministry of Culture into the role of setting direction, not only celebrating a find.

Back at the dig, the bones remain stubbornly physical. Sediment on gloves. The slow reveal of a curve that is unmistakably a tusk. A piece lifted, wrapped, and carried as if it could still be hurt.

In Costa Rica, the past is not only behind. Sometimes it is underfoot, waiting for someone to notice the ground is speaking.

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