Breakthrough Discovery of Purgatorius Fossils in Colorado's Denver Basin

Researchers have unearthed the southernmost fossils of Purgatorius, the earliest known relative of all primates including humans, in Colorado's Denver Basin at the renowned Corral Bluffs site. These tiny teeth, smaller than a fingertip, date to approximately 65.9 million years ago, mere hundreds of thousands of years after the asteroid impact that wiped out non-avian dinosaurs. This find pushes the known geographic range of archaic primates southward by over 500 miles from previous sites in Montana and Saskatchewan, painting a picture of swift post-extinction dispersal and diversification.

The Corral Bluffs project, led by the Denver Museum of Nature & Science (DMNS), has been a hotspot for Paleocene mammal fossils since its discovery in 2016. Traditional surface collecting overlooked these minuscule specimens, but intensive screen-washing techniques—processing thousands of pounds of sediment—revealed the elusive teeth among remains of fish, turtles, and crocodilians. This methodical approach, supported by volunteers, students, and interns from partnering universities, underscores the value of collaborative field training in paleontology.

Understanding Purgatorius: The Shrew-Sized Primate Pioneer

Purgatorius represents the basal-most plesiadapiform, a group debated as stem-primates or close relatives to the primate lineage. Measuring shrew-sized, it boasted specialized ankle bones for arboreal life, grasping hands, and forward-facing eyes suited for tree navigation—hallmarks of early primate adaptations. Its diet likely included fruits and insects, aligning with the rapid rebound of angiosperms post-extinction.

Previous fossils, primarily from northern sites, suggested a delayed southern expansion due to lingering environmental devastation. However, paleobotanical data indicates vegetation recovery within decades, challenging that view. The Colorado specimens, with unique dental traits like distinct cusp patterns, hint at an earlier or undescribed species, awaiting confirmatory material.

This discovery reframes Purgatorius not as a northern holdout but a resilient opportunist colonizing recovering ecosystems swiftly.

The Corral Bluffs Project: A Hub for University-Led Paleontology Research

Initiated by DMNS Curator of Vertebrate Paleontology Dr. Tyler Lyson, the Corral Bluffs project has yielded dozens of new mammal species, documenting the first million years of post-K-Pg recovery. A nearly $3 million NSF grant awarded in 2023 funds advanced equipment and multidisciplinary teams, including botanists and geochemists from universities like University of Colorado Boulder and University of Oregon.

University collaborations are central: Lead author Dr. Stephen Chester from Brooklyn College (CUNY) integrates the find into his plesiadapiform research, training graduate students in microvertebrate analysis. Postdoc Dr. Jordan Crowell at DMNS exemplifies career paths blending academia and museums. Such projects offer hands-on opportunities for aspiring paleontologists, fostering skills in fieldwork, microfossil preparation, and phylogenetic analysis essential for research jobs in evolutionary biology.

The site's partnership with the City of Colorado Springs ensures long-term access, enabling sustained datasets that illuminate mammal radiation—a boon for university curricula in vertebrate paleontology.

Unveiling the Fossils: Methods and Challenges in Microfossil Recovery

Discovering these fossils required processing over 8,000 pounds of matrix using screen-washing: sediments are sieved through fine mesh, dried, and meticulously sorted under microscopes. This labor-intensive process, involving students and volunteers, contrasts with surface prospecting that favors larger bones. The three upper molars exhibit Purgatorius traits—high crowns, shearing crests—but novel morphologies suggesting lineage diversity.

• Size: ~2mm x 2mm, fitting on a fingertip.
• Age: Puercan 1 (Pu1) landsurface, ~550,000-650,000 years post K-Pg.
• Preservation: Amid diverse fauna, indicating thriving ecosystems.

Such techniques highlight sampling bias: 150 years of collecting missed small taxa. Universities like CUNY emphasize these methods in labs, preparing students for higher ed career advice in fieldwork-intensive disciplines.

Evolutionary Implications: Rapid Dispersal and Primate Origins Debate

The Colorado find implies northern origins for archaic primates, with southward migration tracking floral recovery. This rapid biogeography challenges models of prolonged recovery, aligning with evidence of opportunistic radiation filling dinosaur niches.

Plesiadapiforms like Purgatorius bridge to Euprimates (~56 Ma), but debate persists: Do they share key primate traits (e.g., postorbital bar)? Proponents cite arboreality; critics note rodent-like features. This discovery bolsters plesiadapiform primacy, urging refined phylogenies.

For US universities, it enriches evolutionary biology courses, linking fossils to genomics in primate research programs.

Key Researchers and University Contributions to the Study

Dr. Stephen Chester (Brooklyn College, CUNY) leads, leveraging expertise in plesiadapiform evolution. His lab trains students in dental morphology and CT scanning.Full study here. Dr. Jordan Crowell (DMNS postdoc, formerly university researcher) identified unique traits. Dr. Tyler Lyson (DMNS) directs the broader NSF-funded effort, collaborating with academics nationwide. Dr. David Krause (DMNS) provides curatorial insight.

These museum-university ties exemplify interdisciplinary training, vital for faculty positions in anthropology and paleontology.

Overcoming Sampling Bias: Lessons for Future Paleontological Expeditions

Traditional methods biased toward megafauna; microfossil techniques reveal hidden diversity. Corral Bluffs exemplifies this, yielding Purgatorius amid Pu1 fauna. Experts predict more finds with scaled efforts.

Universities incorporate these in programs: Field schools at CU Boulder train in screen-washing, preparing for grants like NSF's. This enhances employability in research assistant jobs.

Post-K-Pg Recovery: Corral Bluffs as a Window to Mammalian Radiation

Corral Bluffs documents ecosystem rebound: Multituberculates, early ungulates alongside Purgatorius. Flowering plants' resurgence fueled insect/fruit booms, enabling primate ascent. Lyson's project maps this timeline, with university partners analyzing isotopes for diet/climate.

Such data informs climate resilience studies, relevant to modern biodiversity loss.

Careers in Paleontology: From Fieldwork to Academia

This study highlights paths: Postdocs like Crowell transition to faculty; undergrads gain via DMNS internships. US universities offer postdoc opportunities in paleo, with NSF grants funding digs. Rate professors in evolutionary anthro via Rate My Professor for program insights.

Demand grows for primate paleo experts amid evolution debates.

Photo by Bhanu Khan on Unsplash

Future Directions: More Fossils and Primate Phylogeny Refinements

Ongoing Corral Bluffs work promises skulls/jaws for species confirmation. Integrating genomics (ancient DNA?) could test plesiadapiform-primate links. Universities gear up with AI-aided microfossil ID.

Explore higher ed career advice, higher ed jobs, university jobs, and rate my professor for paleo paths.