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How did Tyrannosaurus mcraeensis differ from Tyrannosaurus rex?
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tyrannosaur
The fossilized remains of Sue, the most complete Tyrannosaurus rex skeleton in the world, on display at the Field Museum of Natural History, Chicago.
Tyrannosaurus mcraeensis is a distinct species of tyrannosaur identified following a 2024 reexamination of fossils originally classified as Tyrannosaurus rex.12
The primary differences between the two species include:
- Temporal Range: The fossils of T. mcraeensis predate those of T. rex by approximately 6 to 7 million years.1
- Morphology: Paleontologists determined that the shape of the T. mcraeensis fossils—specifically the partial skull and lower jaw—differed sufficiently from those of T. rex to warrant its classification as a separate species.12
These fossils were originally discovered in 1983 in the Hall Lake Formation of New Mexico and were initially attributed to T. rex before the 2024 analysis established them as a new, earlier species.1