New Analysis Settles Debate on Small Tyrannosaur Fossils

Strategic Insights -

Paleontologists have long debated the origins of small tyrannosaur fossils found in the Western United States, with some arguing that they belonged to a teenage version of Tyrannosaurus rex, while others claimed they belonged to a distinct species within the tyrannosaur family. A new study appears to have settled the dispute, with a fossil specimen in a North Carolina museum identified as belonging to Nanotyrannus lancensis, a distinct group of tyrannosaurs.

Key Takeaways:

  • The new study suggests that the small tyrannosaur fossils found in the Western United States belong to Nanotyrannus lancensis, a distinct species within the tyrannosaur family, rather than a teenage version of Tyrannosaurus rex.
  • The fossil specimen in the North Carolina museum, which was 20 years old when it died, showed anatomical differences from T. rex, including significantly larger forelimbs and hands, a vestigial third finger, and a distinct pattern of skull nerves.
  • The team's analysis of over 200 tyrannosaur fossils for comparison helped identify these anatomical differences, which are set early in an animal's development and cannot be changed in adulthood.
  • The new study also suggests that Nanotyrannus may be more closely related to the East Coast branch of the tyrannosaur family, and that the animals underwent significant changes in their growth and biology during their evolution.
  • The study's findings have significant implications for our understanding of the growth and biology of Tyrannosaurus rex, and suggest that the assumption that T. rex was the lone large predator of its environment may need to be reevaluated.

Statistics:

  • 40 years: the amount of time that dinosaur experts have been debating the origins of small tyrannosaur fossils.
  • 100 million years: the estimated time when an inland sea may have broken North America into separate islands, leading to the separation of different tyrannosaur lineages.
  • 200: the number of tyrannosaur fossils that were studied by the research team for comparison.
  • 20 years: the age of the Nanotyrannus specimen when it died.
  • 1999: the year when a group of researchers argued that the small tyrannosaur skull and similar specimens belonged to T. rex.

Sources:

  • "Paleontologists said in on Thursday"

+ Source: North Carolina Museum of Natural History

  • "In the 1980s, fossil hunters found a small tyrannosaur skull from the same rock formation that had produced T. rex"

+ Source: University of Maryland

  • "The team's analyses show that Nanotyrannus most likely belongs to an early offshoot of the tyrannosaur lineage that split 100 million years ago"

+ Source: Study authors

  • "The team also found evidence that Jane — long considered an immature T. rex — was in fact yet another species in the Nanotyrannus genus"

+ Source: Study authors