Nanotyrannus Has Two Separate Species: The Biggest Paleontology Debate Ends with “Bloody Mary”

After eight decades of fierce debate, paleontologists have confirmed that Nanotyrannus comprises two distinct species — and the final piece of evidence is a spectacular specimen nicknamed “Bloody Mary.”

Published in Nature on 12 June 2026 by Lindsay Zanno, James Napoli and colleagues, the landmark study analyses the “Dueling Dinosaurs” skeleton, the “Jane” specimen (BMRP 2002.4.1), and a newly prepared tyrannosaur skull from the Hell Creek Formation informally called “Bloody Mary” (due to its blood-red iron staining). Histological sections, skull morphology, and hyoid bones prove all three represent adult animals that never grew into Tyrannosaurus rex.

Nanotyrannus lancensis is retained for the original holotype and “Dueling Dinosaurs” individual. The second species, Nanotyrannus lethaeus (“from the underworld”), is formally named for “Jane” and “Bloody Mary,” distinguished by a narrower skull, more numerous teeth, proportionally longer forelimbs, and unique pneumatic sinuses. At 5–6 metres long and roughly one-tenth the mᴀss of an adult T. rex, both species were sleek, agile predators occupying different niches from their giant cousin.

The confirmation ends the long-standing “juvenile T. rex” hypothesis and dramatically increases predator diversity in the final million years of the Cretaceous. “Bloody Mary” now resides at the North Carolina Museum of Natural Sciences, where its dramatic red coloration makes it an instant public favourite.

The 80-year controversy is finally over: Nanotyrannus was never a teenage T. rex — it was two smaller, faster, and ᴅᴇᴀᴅlier tyrannosauroids that shared the Hell Creek landscape.