# Fossil discoveries in Hell Creek Formation

> Live situation record from CLSTR: https://clstr.news/situations/discovery-of-fossilized-feathers-in-dinosaur-coprolite
> Updated: 2026-09-22T20:15:00.000Z. Sources: 19. Developments: 4.

Paleontologists have identified exceptionally well-preserved feathers within a 66-million-year-old coprolite, or fossilized dung, located in the Hell Creek Formation of Montana, USA. The specimen contains remnants of Hesperornithiformes—an extinct group of aquatic, largely flightless birds—alongside fish scales and small bone fragments.

Researchers believe the coprolite was produced by a large carnivorous dinosaur, such as a Tyrannosaurus rex or Nanotyrannus. Using micro-CT scanning and microtomography, scientists analyzed the three-dimensional structure of the feathers without destroying the fossil. Some experts suggest the quality of preservation may exceed that of specimens found in amber.

In a study published in the journal Current Biology, the discovery is being used to investigate the mass extinction event caused by an asteroid impact at the end of the Cretaceous period. By analyzing the morphological differences in these ancient feathers, such as variations in thermal insulation or aerodynamic capabilities, researchers aim to understand the evolutionary divide between the lineages that perished, like the Hesperornithiformes, and the Neornithes group, from which all modern birds descend. Recent research suggests that insulating plumage played a critical role in the survival of certain prehistoric birds, helping avian ancestors endure the extreme cold and darkness caused by the impact winter following the Chicxulub asteroid impact.

In a related discovery within the same formation, paleontologists unearthed a trackway consisting of four massive three-toed footprints. Identified as belonging to an adult Tyrannosaurus rex, this find provides rare evidence regarding the predator’s movement and behavior through its ancient landscape.

## Timeline

### 2026-09-22: Paleontological discoveries reveal dinosaur evolution and avian survival secrets

New paleontological studies reveal how the small dinosaur Foskeia pelendonum fills evolutionary gaps and how insulating feathers helped avian ancestors survive the mass extinction 66 million years ago.

2 sources. https://clstr.news/cluster/paleontological-discoveries-reveal-dinosaur-evolution-and-avian-survival-secrets

### 2026-09-15: Montana fossilized feather found in dinosaur dung aids extinction research

A 66-million-year-old fossilized bird feather found inside dinosaur excrement in Montana offers new clues about avian survival during the Cretaceous mass extinction.

2 sources. https://clstr.news/cluster/montana-fossilized-feather-found-in-dinosaur-dung-aids-extinction-research

### 2026-09-13: Hell Creek Formation fossils reveal dinosaur diet and movement

Paleontologists in Montana have discovered 66-million-year-old fossilized feces containing well-preserved bird feathers and bones, alongside a rare trackway of an adult Tyrannosaurus rex.

4 sources. https://clstr.news/cluster/fossilized-dinosaur-feces-reveals-66-million-year-old-feathers

### 2026-09-10: Fossil feather in dinosaur dung may explain bird survival

A 66-million-year-old fossil feather found inside dinosaur dung may explain why modern bird ancestors survived the mass extinction event caused by an asteroid.

11 sources. https://clstr.news/cluster/fossilized-dinosaur-dung-reveals-ancient-bird-feathers

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Cite as: Fossil discoveries in Hell Creek Formation. CLSTR, https://clstr.news/situations/discovery-of-fossilized-feathers-in-dinosaur-coprolite