Purgatorius: earliest ancestor after dinosaur extinction

February 11, 2026General

Source: Who was our ancestor when the dinosaurs died? by Stefan Milo

Site mentioned

📍 Hell Creek

Meet Purgatorius: our earliest known ancestor, discovered in the Hell Creek Formation of Montana. This tiny 15cm, 100g tree-dweller lived just 100,000 years after the asteroid that ended the dinosaurs. 🌳🐾

Key facts claimed:

- Plesiadapiforms are stem primates - early primates ancestral to modern primates

- Plesiadapiforms lack large brains and true orbital bars, some had claws

- Purgatorius was found in the Hell Creek Formation, Montana in deposits dating to ~100,000 years after the asteroid impact

- Purgatorius had primate-like back teeth and ankle bones for grasping

- It was a tree-dwelling (arboreal) animal about 15 cm long weighing no more than 100g

Key facts

Plesiadapiforms are our closest cousins - nearly primates but not true primates
Plesiadapiforms lack large brains and true orbital bars, some had claws
Purgatorius was found in Hell Creek, Montana in layers dating to 100,000 years after the asteroid impact
Purgatorius had primate-like back teeth and ankle bones for grasping
It was a tree-dwelling (arboreal) animal about 15 cm long weighing no more than 100g
Purgatorius is considered our earliest known ancestor that survived the asteroid impact
The angiosperm co-evolution hypothesis suggests primate evolution was driven by flowering plants
Primates may have survived the nuclear winter by being generalists - eating insects, fruits, and flowers

Sources

[PDF] "Purgatorius" in - ResearchGateresearchgate.net

Purgatorius is a genus of primitive primates known from the early Paleocene of Montana. (United States) and Saskatchewan (Canada). It.

Fossils flesh out the tale of the first primates - Cosmic Logcosmiclog.com

The evidence comes from an analysis of tooth fossils that were unearthed in the Hell Creek area of northeastern Montana. Get the full story ...

UF Researcher Helps Confirm Ancient Primates Once Walked with ...news.clas.ufl.edu

Published in Royal Society Open Science, the study analyzed 65.9 million-year-old fossils of the early primate Purgatorius, the oldest genus in ...

Earliest-known fossil primate discovered in Montanaleakeyfoundation.org

A new Leakey Foundation-supported study published Feb. 24 in the journal Royal Society Open Science documents the earliest-known fossil evidence of primates.

Our earliest primate ancestors rapidly spread after dinosaur extinctionvcresearch.berkeley.edu

Purgatorius, named after the Purgatory Hills in Montana, is known only from North American fossils. ... Purgatorius fossils in the Hell Creek area ...

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