A new species of Tyrannosaur has been identified from a fossil unearthed in New Mexico, providing intriguing clues into the origins and evolution of the infamous Tyrannosaurus rex.
Fossil’s Unique Features Point to New Species
The nearly complete skull fossil was originally discovered in 2013 in the Zuni Basin near Elephant Butte Lake in New Mexico. Now, over a decade later, a new study published this week in Scientific Reports has concluded that the fossil represents a new species of Tyrannosaur, which researchers have named Tyrannosaurus mckraeensis.
What sets this new species apart are unique features of its skull and jaw bones. T. mckraeensis had a longer snout and numerous small, blunt teeth as compared to later Tyrannosaurs like T. rex. This suggests T. mckraeensis likely had a different diet than T. rex, possibly eating more small prey rather than large animals.
Additionally, an analysis of the fossil’s bones shows T. mckraeensis grew much faster than T. rex, reaching near full size around age 14 compared to age 20 for T. rex. This rapid growth supports the hypothesis that earlier Tyrannosaurs filled a different evolutionary niche than later giant species.
Discovery Helps Map Tyrannosaur Evolution
The identification of this new Tyrannosaur adds an important data point in understanding the evolutionary lineage of these iconic predatory dinosaurs. T. mckraeensis lived approximately 72 million years ago during the late Cretaceous period, making it the earliest known relative of T. rex found in North America so far.
As this simplified family tree shows, T. mckraeensis fits between earlier Tyrannosaurs like Daspletosaurus and later giant species like T. rex. This suggests Tyrannosaurs likely originated in North America before evolving into larger apex predators.
More broadly, the fossil helps illuminate fauna dynamics during a time when parts of North America were segmented into isolated landmasses by rising seas. T. mckraeensis lived on Laramidia, essentially an island continent formed by shallow seas flooding central North America. Finding an early Tyrannosaur fossil there lends support to the conclusion that Tyrannosaurs first evolved on Laramidia before migrating north and eventually dying out.
Many Questions Still Remain
While an important discovery, the T. mckraeensis fossil raises as many questions as it answers about Tyrannosaurs. For one, it remains unclear exactly how and why Tyrannosaurs transitioned from smaller species like T. mckraeensis to massive predators like T. rex. Identifying more intermediate specimens would help reveal rate and drivers of that evolutionary change.
Additionally, some researchers question whether T. mckraeensis warrants classification as a completely new species. Its skull does display enough unique characteristics to differentiate it from Daspletosaurus, but some scientists argue subtle physical variety alone may not indicate speciation. More comparative study of existing Tyrannosaur specimens could help settle these lingering debates.
Finally, where and how T. rex itself first evolved remains mysterious. Future fossil hunting in Canada and northern U.S. is likely needed to pin down both the direct ancestors of T. rex and where the first giant Tyrannosaur took form.
So while representing an exciting development, the T. mckraeensis fossil leaves unsolved puzzles about the ascent of T. rex as undisputed ruler. As one paleontologist summarized, “It’s not often you get to name a new species of dinosaur. It’s even rarer to find one that fills in a gap in the family tree of one as iconic as the tyrant king itself…But instead of answering all our questions about the tyrant dinosaurs, this discovery has actually given us more mysteries to solve.”
The table below summarizes key details on the newly discovered Tyrannosaur:
|Near Elephant Butte Lake, New Mexico
|72 million years ago
|Approximately 30 feet long
|Smaller prey than later Tyrannosaurs
|Unique physical features
|Longer snout, small blunt teeth
Next Steps: Additional Study and Conservation
In the wake of this announcement, next steps for researchers include conducting more comparative analyses to firmly establish physical differences between T. mckraeensis and other Tyrannosaurs. Digitally reconstructing the fossil skull through 3D modeling would also enable precise size and shape evaluations.
Looking beyond just the new species itself, scientists will continue combing New Mexico and the western U.S. for additional Tyrannosaur fossils that could further illuminate evolutionary changes leading to T. rex. Finding a more complete T. mckraeensis skeleton would be particularly valuable.
More broadly, conservation efforts in the fossil-rich Zuni Basin take on heightened importance with this discovery. Protecting lands where T. mckraeensis roamed from commercial excavation and establishing responsible collecting procedures could lead to more discoveries that shed light on the ascent of T. rex.
In sum, while the identification of this new species answers some key questions about T. rex‘s lineage, it also opens up new lines of inquiry for paleontologists. And as fate would have it, the next fossil to better elucidate the Tyrannosaur family tree may still lie buried in New Mexico’s ancient badlands, waiting to be uncovered.
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