TRACKING DIATRYMA: FOSSIL FOOTPRINTS IN THE CHUCKANUT FORMATION

Diatryma Restoration & Size Comparison

Long before glaciers sculpted the familiar ridges and waterways of western Washington, a vast subtropical delta sprawled across the region that would one day become Bellingham Bay. 

Arriving today, you see evidence of this in the many fossils to be found in the region. 

Beneath today’s scenic Chuckanut Drive lies a story written in stone — layer upon layer of siltstone, sandstone, mudstone, and conglomerate that make up the Chuckanut Formation, a fossil-rich archive of ancient swamps and floodplains.

Imagine stepping into that Eocene world. The air is heavy with humidity, thick with the scent of wet earth and resin. Towering dawn redwoods (Metasequoia) rise above a dense understorey of ferns, laurels, and figs. 

Glyptostrobus, the Chinese swamp cypress, forms stands along the riverbanks, its knees jutting from the warm, tea-colored water. 

Palms sway beside oxbow lakes where turtles and crocodilians bask on fallen logs. The landscape would look more at home in modern-day Louisiana or Belize than in the shadow of the North Cascades.

Diatryma Tracks, Washington State

The geology that preserves this lush world was born of fire, flood, and shifting plates. 

During the Eocene, the Pacific Northwest lay near the edge of the North American Plate, where fragments of volcanic island arcs — the terranes that make up much of western Washington — were accreting, colliding, and buckling under tectonic pressure. 

Rivers carried eroded sediments from the rising ancestral Cascades into broad, lowland deltas, where they built up thick beds of sand and mud. Over millions of years, those sediments hardened into rock, entombing the life that once flourished there.

Among the most remarkable of the Chuckanut fossils are footprints — delicate, fleeting impressions that speak to the creatures that wandered through this swampy paradise. One of these was Diatryma, Gastornis, a colossal flightless bird that could reach nearly nine feet tall. 

With massive legs and a deep, powerful beak, Diatryma was a relic of an ancient avian lineage that arose soon after the age of dinosaurs. They would have been most impressive to see, though they would likely chase you down for a wee taste! 

Gastornis giganteus

Descended from earlier ground-dwelling birds of the Paleocene, Diatryma and its kin once roamed both North America and Europe, their fossils turning up from Wyoming to France. 

Though once imagined as fearsome predators, new evidence suggests they were likely omnivores or even herbivores, using their beaks to crack seeds, fruits, or tough vegetation.

Diatryma shared the Eocene floodplains with a cast of strange and wonderful mammals. There were Pantodonts and Dinoceratans — heavy-bodied, blunt-footed herbivores with a primitive charm, precursors to later hoofed mammals. 

Small early horses trotted through the marshy margins, while shorebirds and amphibians left fleeting traces in the soft mud. Above it all, ancient dragonflies and early bats flitted through the dense canopy.

The Chuckanut Formation preserves this bygone world in exquisite detail — not as bones and teeth, but as fossil leaves, tracks, and impressions, the whispers of a time when Washington was a tropical delta at the edge of a newborn continent. 

Today, when you drive along Chuckanut’s winding road or hike its rocky bluffs, you are traveling through the ghost of an Eocene bayou — a landscape alive with the echoes of towering trees, swamp-dwelling beasts, and the thunderous stride of the mighty Diatryma.

Image Credit: Lead Image By Tim Bertelink - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=49203812 edited by Fossil Huntress

Image Credit: Diatryma Restoration and Size Comparison: Gastornis giganteus: By Vince Smith from London, United Kingdom - Diatryma, a large flightless bird from the Eocene of WyomingUploaded by FunkMonk, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=28298676