New Species of Tyrannosaur Hints at Ancestor of T. rex

Lower jaw of a dinosaur fossilized in rock
The spectacular lower jaw of the holotype
skull had most of the teeth preserved in
their sockets

News release from Dickinson Museum Center 
All images are provided by Badlands Dinosaur Museum

A new species of dinosaur collected from BLM land in the Judith River Formation of northeastern Montana may be the “missing link” between older and younger tyrannosaur species. 

In a recently published study, researchers Elias Warshaw and Denver W. Fowler report the discovery of a new species that displays a mix of features found in more primitive tyrannosaurs (such as a prominent set of horns around the eye) as well as features otherwise known from later members of this group, including T. rex (e.g., tall eye socket and expanded air pockets in the skull). 

Four people work in the rocky ground in search of fossils. One is using a jackhammer.
Elías Warshaw uses a jackhammer to remove
overburden at the Daspletosaurus wilsoni quarry.

These findings suggest that previous research was correct in identifying several species of Daspletosaurus as a single evolving lineage and supports the descent of T. rex from this group. 

The newly discovered specimen has a unique arrangement of spiked hornlets surrounding its eye. It was named Daspletosaurus wilsoni, or "Wilson's frightful reptile," after John "Jack" P. Wilson (San Diego, California) who discovered the holotype specimen. The seemingly endless task of removing more than 25 feet (8 m) of rock that lay on top of the bones gave rise to the nickname “Sisyphus” after the figure in Greek mythology.  

Sisyphus is one of four tyrannosaur skeletons collected under permit by the Badlands Dinosaur Museum between 2017 and 2022 from lands managed by the BLM’s Glasgow Field Office in Valley County, Montana.  

Warshaw continues to research the link between T. rex and Daspletosaurus. 


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Painted image of 2 large T-Rex dinosaurs fighting over the body of another dinosaur with 2 smaller dinosaurs watching from the side and back.
The new specimen, "Sisyphus," is one of four tyrannosaur skeletons recently collected by
Badlands Dinosaur Museum. Here the four tyrannosaurs dispute ownership of the fresh
carcass of a Centrosaurus. Image © Rudolf Hima & Badlands Dinosaur Museum.

Dickinson Museum Center