For four decades, a frequently acrimonious debate has raged in paleontological circles about the correct taxonomy for a handful of rare fossil specimens. One faction insisted the fossils were juvenile Tyrannosaurus rex; the other argued that they represented a new species dubbed Nanotyrannus lancensis. Now, paleontologists believe they have settled the debate once and for all due to a new analysis of a well-preserved fossil.
The verdict: It is indeed a new species, according to a new paper published in the journal Nature. The authors also reclassified another specimen as a second new species, distinct from N. lancensis. In short, Nanotyrannus is a valid taxon and contains two species.
“This fossil doesn’t just settle the debate,” said Lindsay Zanno, a paleontologist at North Carolina State University and head of paleontology at North Carolina Museum of Natural Sciences. “It flips decades of T. rex research on its head.” That’s because paleontologists have relied on such fossils to model the growth and behavior of T. rex. The new findings suggest that there could have been multiple tyrannosaur species and that paleontologists have been underestimating the diversity of dinosaurs from this period.
