Fossil Hunting in the Lance Formation

Written by Mackenzie Malyszko for Tony Perez

There’s something surreal about standing in a place where dinosaurs once roamed freely — and not just any dinosaurs, but some of the last to ever walk the Earth. That’s exactly what it felt like on my recent trip to the Lance Formation in Wyoming, one of North America’s most fossil-rich windows into the final chapter of the dinosaur era.

What Is the Lance Formation?

The Lance Formation is a geologic unit dating to the very end of the Late Cretaceous period, approximately 66 to 69 million years ago, during the Maastrichtian stage—the final interval before the Cretaceous–Paleogene (K–Pg) extinction event. Predominantly exposed in eastern Wyoming, with additional outcrops extending into Montana, North Dakota, and South Dakota, the formation was named for Lance Creek, Wyoming, where some of the earliest North American fossil discoveries were made in the late 1800s during the golden age of American paleontology.

What makes the Lance Formation particularly significant is its temporal position: it preserves a detailed record of terrestrial ecosystems that existed just before the end-Cretaceous mass extinction. The fossil assemblages reflect a flourishing biosphere on the brink of collapse — one that included iconic taxa such as Triceratops, Tyrannosaurus rex, Ankylosaurus, and a variety of smaller theropods, ornithopods, crocodyliforms, turtles, mammals, and flora.

The Cretaceous period itself (spanning ~145 to 66 million years ago) was a time of dynamic evolutionary change and global restructuring. By the Maastrichtian, North America had undergone significant geographic and climatic shifts due to the retreat of the Western Interior Seaway. What remained in areas like the Lance Formation was a complex, low-lying floodplain ecosystem — river-dominated, with lush vegetation and a diversity of life adapted to semi-tropical, seasonally wet conditions. These fine-grained alluvial sediments created the ideal environment for fossil preservation, making the Lance one of the most productive Upper Cretaceous terrestrial formations in the world.

In short, the Lance Formation provides a critical snapshot of the last ecosystems to include non-avian dinosaurs, just before the asteroid impact that reshaped Earth’s biosphere. To study its layers is to examine the closing chapter of the Mesozoic Era — a chapter written in bone, mudstone, and deep time.

The Lance Formation ranges in thickness from roughly 300 feet (90 meters) in North Dakota to nearly 2,000 feet (600 meters) in certain areas of Wyoming. Its composition includes grayish sandy shale, pale sandstone layers, and occasional thin bands of lignite.

What Fossils Are Found in the Lance Formation?

If you're fascinated by the ancient world, the Lance Formation offers one of the most rewarding fossil records of the Late Cretaceous. It's a site where science and discovery converge — a place where nearly every layer of sediment holds the potential to reveal part of a vanished ecosystem. From towering herbivores to apex predators and the smallest traces of early mammals, the Lance preserves an astonishing diversity of life that once thrived just before the end-Cretaceous mass extinction.

Triceratops is by far the most common dinosaur found here. In fact, some of the most complete skulls ever unearthed have come from this formation.
Tyrannosaurus rex teeth and partial bones occasionally surface — yes, the king himself once ruled this land.
Smaller theropods, like Dromaeosaurs (raptor cousins), and Ornithomimids (ostrich-like dinos), also pop up.
You’ll also find fossilized turtle shells, crocodilian bones, fish scales, mammal teeth, and fossilized plants — helping paint a full picture of the ancient ecosystem.

During the Maastrichtian; the uppermost stage of the Late Cretaceous, this region was a low-lying coastal plain, shaped by braided river systems, floodplains, and overbank deposits — the result of sediment flowing eastward from the rising Rocky Mountains. The climate was subtropical and seasonally wet, supporting a diverse array of flora, including ferns, conifers, and flowering plants, which in turn sustained a thriving herbivore population. These river systems created fine-grained silts, clays, and sandstones— ideal conditions for the rapid burial and preservation of vertebrate remains. It’s within these ancient channels and overbank deposits that we now find exquisitely preserved fossils of dinosaurs, crocodyliforms, turtles, and early mammals. The Lance wasn't just home to dinosaurs — it was a fully functioning ecosystem teeming with life, shaped by water, vegetation, and sediment.

My Recent Trip to the Lance Formation

The Lance Formation has long been recognized as one of the most significant Late Cretaceous units in North America, so the opportunity to explore it firsthand was both exciting and professionally meaningful. The exposed strata offered clear access to well-preserved fossil-bearing layers, and I spent extended periods methodically surveying the site, focusing on fine-grained sediment deposits ideal for microfossil recovery. Slowly working through the matrix, I examined weathered surfaces and erosional pockets for fragmentary remains

The effort was well worth it.

Why the Lance Formation Still Matters

While the thrill of uncovering a fossil is undeniable, the true value of the Lance Formation lies in what it continues to reveal about the closing chapter of the Mesozoic. As one of the most well-preserved records of terrestrial life immediately preceding the K–Pg mass extinction, the Lance provides critical data on species diversity, ecosystem structure, and evolutionary trajectories during a period of global transition. Its fossil assemblages allow paleontologists to reconstruct not only which organisms lived and died there, but how they interacted, what they ate, and how they responded to environmental stressors leading up to the end-Cretaceous event.

For scientists, it remains an essential reference point in studying extinction dynamics. For collectors, students, and fossil enthusiasts, it offers something just as profound: the opportunity to connect directly with one of the most significant moments in Earth’s biological history — to hold, quite literally, a piece of that ancient world in your hands.

Thinking About Visiting or Collecting?

The Lance Formation is an incredibly rewarding site for fossil discovery, but it’s important to understand that the land it occupies is highly regulated and must be treated with care and respect. Much of the formation lies on a patchwork of private ranchlands and federally managed public lands under the jurisdiction of the Bureau of Land Management (BLM).

Collecting fossils on BLM land requires a permit, and even then, only certain types of fossils (like invertebrates and plant material) can be collected legally for personal, non-commercial use. Vertebrate fossils — including dinosaur bones, teeth, and other remains — are protected by federal law and may not be collected on public land without explicit scientific authorization. On private land, collecting is legal only with landowner permission, and responsible collectors ensure that all provenance is properly documented to maintain scientific and ethical standards.

If you’re just starting out, it’s critical to learn the rules of fossil collecting — not just for legal reasons, but to preserve the scientific value of these ancient sites for future generations.

That said, if you’re not yet ready to head into the field yourself, you can still connect with this remarkable formation. At FossilsOnline.com, we offer a carefully curated selection of authentic, legally sourced Lance Formation fossils, all recovered with landowner permission and properly prepared for study or display. Each specimen is a genuine piece of Earth's deep history, collected with care and respect for the land it came from.

The Formation Has Been Studied for Over a Century

The Lance Formation has drawn scientific attention since the late 19th century, when early fossil expeditions uncovered remarkably well-preserved dinosaur remains near Lance Creek, Wyoming. These discoveries played a key role in shaping our understanding of Late Cretaceous North American ecosystems, and the formation quickly became a focal point for paleontological research.

What makes the Lance so enduringly important is its unique combination of abundant vertebrate fossils, well-preserved microfossils, and its stratigraphic position just below the Cretaceous–Paleogene boundary. It provides a rare, continuous record of the last few million years of dinosaur evolution and the surrounding ecosystems before the mass extinction event. Because of this, researchers continue to revisit the Lance to study everything from extinction dynamics, faunal turnover, and climate change, to the diversity of small vertebrates often overlooked in more dramatic fossil discoveries.

Its extensive fossil record, accessibility, and scientific legacy ensure that the Lance Formation will remain a cornerstone of paleontological research for years to come. When customers acquire fossils from the Lance, they’re not just purchasing a specimen — they’re holding a piece of a site that has contributed to over a century of scientific exploration, and one that continues to shape our understanding of Earth’s deep past.

What I Personally Found Digging

Here is an area I spent 2 days digging. The first day, after 7 hours of digging, hardly anything was found. Just some traces of fossils letting me know I was in the right layer. Most of the material moved was overburden and the actual fossil bearing layer is only 10" thick.

Sources:

https://www.britannica.com/science/Cretaceous-Period/Correlation

Weeks, Summer. (2016). Depositional Model of a Late Cretaceous Dinosaur Fossil Concentration, Lance Formation. 10.13140/RG.2.2.23650.40646.