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El Fosil Community Museum, Boyaca, Colombia

The Museo Comunitario El Fósil is a paleontological gem nestled in Villa de Leyva, Boyacá, Colombia. It’s built around an extraordinary in-situ fossil: the nearly complete skeleton of a Kronosaurus boyacensis, a massive marine reptile from the Early Cretaceous period, estimated to be over 115 million years old.

But that’s just the beginning. The museum also showcases the holotype of Padillasaurus leivaensis, a towering brachiosaurid dinosaur that stood over 12 meters tall and stretched 17 meters long. Visitors can explore around 400 fossil specimens, including ammonites, plant fossils, and fragments of other prehistoric creatures1.

Set in the scenic Monquirá region, the museum offers a unique blend of science and nature. It’s open daily from 8:00 a.m. to 6:00 p.m., and admission is COP 25,000 for adults and COP 15,000 for children.

El Fosil Community Museum (Museo Comunitario El Fósil)


Map of the Province of Alto Ricaurte, Boyacá, Colombia
The Alto Ricaurte region in Boyacá, Colombia, is a paleontological treasure trove, renowned for the Paja Formation, a Lower Cretaceous Lagerstätte that has captivated scientists worldwide. This formation is celebrated for its exceptional fossil preservation and diversity, making it one of the most significant fossil sites in South America.

  • Among the remarkable discoveries are new species of marine reptiles like pliosaurs and ichthyosaurs, sea turtles, dinosaurs, ammonites, and a variety of plant fossils and bivalves. The area’s fossil record offers a vivid snapshot of life from over 100 million years ago, when this part of Colombia was submerged under a shallow sea.
  • Beyond its fossil wealth, Alto Ricaurte also boasts geodiversity—from striking rock outcrops and tectonic features to karst landscapes and erosion-sculpted terrain. This combination of paleontological and geological features has led scientists to advocate for stronger geoconservation efforts in the region.

The in-situ fossil, nearly complete skeleton of a Kronosaurus boyacensis
Originally described in 1992 as Kronosaurus boyacensis, this nearly complete skeleton was discovered in 1977 near Villa de Leyva and became the centerpiece of the Museo El Fósil. However, in 2021, after a more detailed reexamination, scientists reclassified it as a new genus and species: Monquirasaurus boyacensis.

  • This marine reptile was a pliosaur, a type of short-necked plesiosaur with a powerful bite and four strong flippers. The fossil measures about 7.3 meters long as preserved, though estimates suggest the living animal may have reached 9 to 11 meters in length and weighed up to 14 metric tons. It lived during the Aptian stage of the Early Cretaceous, around 115 million years ago, when the region was submerged under a shallow sea.
  • What makes this fossil so special is that it’s preserved in situ—still embedded in the rock where it was found. The museum was literally built around it, allowing visitors to see the creature as it was discovered. It’s a rare and powerful window into Colombia’s prehistoric marine ecosystems.

Monquirasaurus family tree
Monquirasaurus boyacensis belongs to the Pliosauridae family, a group of short-necked plesiosaurs known for their powerful jaws and marine adaptations. Here's how it fits into the broader evolutionary tree:

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Reptilia
  • Superorder: †Sauropterygia
  • Order: †Plesiosauria
  • Family: †Pliosauridae
  • Genus: †Monquirasaurus
  • Species: †Monquirasaurus boyacensis

Monquirasaurus was originally misclassified as Kronosaurus boyacensis in 1992, but a more detailed study in 2021 revealed it to be a distinct genus. It shares its family tree with other massive marine predators like Kronosaurus, Liopleurodon, and Pliosaurus, all of which ruled the oceans during the Jurassic and Cretaceous periods.


Fossil formation
Fossil formation is a rare process that unfolds over millions of years. Here’s a simplified breakdown of the typical steps:

  1. Death: It all begins when an organism dies. Most soft tissues decay quickly, so fossilization usually involves hard parts like bones, shells, or wood.
  2. Burial: The remains must be rapidly buried by sediment—like mud, sand, or volcanic ash—to protect them from scavengers, decay, and weathering.
  3. Lithification: Over time, layers of sediment build up and compress, turning into rock. This pressure helps preserve the buried remains.
  4. Permineralization or Replacement: Groundwater rich in minerals seeps into the remains. These minerals crystallize in the tiny spaces within bones or shells, or even replace the original material entirely, turning it into stone.
  5. Exposure: After millions of years, erosion or excavation may bring the fossil back to the surface, where it can be discovered and studied.

There are also other fossilization pathways—like amber entrapment, freezing, or impressions—but this five-step process is the most common for hard-bodied organisms.


Earth’s evolutionary story
Earth’s evolutionary story from the Precambrian to the Holocene is a sweeping saga of transformation—spanning over 4.5 billion years. Here's a high-level journey through the major stages:

  1. Precambrian (4.6 billion – 541 million years ago)
    • Hadean, Archean, and Proterozoic eons make up this vast stretch of time.
    • Earth formed, cooled, and developed a crust and oceans.
    • Life began with simple single-celled organisms, like bacteria and archaea.
    • By the late Proterozoic, photosynthetic cyanobacteria had oxygenated the atmosphere, and multicellular life began to emerge.
  2. Paleozoic Era (541 – 252 million years ago)
    • Kicked off with the Cambrian Explosion, a burst of biodiversity in the oceans.
    • Life diversified into invertebrates, fish, and the first land plants and animals.
    • Ended with the Permian-Triassic extinction, the most severe extinction event in Earth’s history.
  3. Mesozoic Era (252 – 66 million years ago)
    • Known as the Age of Reptiles.
    • Dinosaurs, marine reptiles, and flying pterosaurs dominated.
    • Flowering plants appeared, and early mammals evolved.
    • Ended with the Cretaceous-Paleogene extinction, which wiped out the non-avian dinosaurs.
  4. Cenozoic Era (66 million years ago – present)
    • Divided into the Paleogene, Neogene, and Quaternary periods.
    • Mammals and birds diversified and flourished.
    • Grasses spread, shaping ecosystems like savannas and prairies.
    • Hominins evolved in Africa, leading to the rise of Homo sapiens.
  5. Holocene Epoch (11,700 years ago – today)
    • A relatively brief but transformative period.
    • Marked by the end of the last Ice Age.
    • Humans developed agriculture, cities, and civilizations, dramatically altering ecosystems and the planet itself.
    • This timeline is like Earth’s autobiography—written in stone, fossils, and DNA.

The skeleton of Monquirasaurus boyacensis and its reconstruction


Reconstruction of marine life at the time of Monquirasaurus boyacensis
During the Early Cretaceous, around 115 million years ago, the seas that covered what is now Colombia teemed with an astonishing array of marine life—Monquirasaurus boyacensis was just one of the apex predators in this vibrant ecosystem.

  • This region, part of the Paja Formation, was a shallow epicontinental sea nestled between the proto-Pacific Ocean and the Tethys Ocean. The waters were warm, oxygen-poor at the bottom, and rich in nutrients—ideal for preserving fossils and supporting a diverse food web.
  • Here’s a glimpse of the marine cast that shared the seas with Monquirasaurus:
    • Other pliosaurs like Stenorhynchosaurus and Sachicasaurus, which may have competed or coexisted with Monquirasaurus.
    • Plesiosaurs, with their long necks and small heads, likely feeding on fish and small cephalopods.
    • Ichthyosaurs, dolphin-like reptiles that were swift swimmers and agile hunters.
    • Marine turtles, some of which were already quite large and well-adapted to ocean life.
    • Ammonites, the coiled-shelled cephalopods that were both predators and prey.
    • Bony fish and sharks, forming the mid-level predators and prey base.
    • Terrestrial plant debris and spores, carried into the sea, hinting at lush coastal environments nearby.
  • This ecosystem was so rich that scientists believe it supported a rare seventh trophic level, meaning predators like Monquirasaurus may have preyed on other large carnivores. It was a world of giants, and Monquirasaurus was one of its most formidable rulers.

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Location

Location: Via el Fósil, Villa de Leyva, Boyacá, Colombia