A diminutive tyrannosaur lived alongside <i>Tyrannosaurus rex</i>
Whether <i>Nanotyrannus lancensis</i> represents a distinct taxon or an immature <i>Tyrannosaurus rex</i> is a decades-long controversy. The <i>N. lancensis</i> holotype (CMNH 7541) is an isolated skull and ceratobranchials, but limb osteohistology of <i>Nanotyrannus</i>-like individuals implies that these individuals were immature <i>Tyrannosaurus</i>, suggesting that the <i>N. lancensis</i> holotype is also immature. We demonstrate that ceratobranchial ("hyoid") histology is useful for ontogenetic assessment in extant and extinct archosaurs. The ceratobranchial histology of the <i>N. lancensis</i> holotype indicates that it was nearing or had reached skeletal maturity, suggesting that it is taxonomically distinct from the coeval <i>Tyrannosaurus rex</i> and that Hell Creek (and equivalent) ecosystems supported a diverse assemblage of predatory dinosaurs approaching the Cretaceous-Paleogene extinction.
Authors
- Patrick M. O’Connor (ORCID: https://orcid.org/0000-0002-6762-3806)
- Michael D. D’Emic (ORCID: https://orcid.org/0000-0002-6162-7005)
- Christopher T. Griffin (ORCID: https://orcid.org/0000-0003-3201-1866)
- Holger Petermann (ORCID: https://orcid.org/0000-0002-3847-2244)
- Ashley W. Poust (ORCID: https://orcid.org/0000-0001-7955-613X)
- Riley S. Sombathy (ORCID: https://orcid.org/0000-0003-3450-6889)
- Caitlin Colleary (ORCID: https://orcid.org/0000-0003-2634-7355)
- Zachary S. Morris (ORCID: https://orcid.org/0000-0002-6836-0569)
- Matteo Fabbri (ORCID: https://orcid.org/0000-0002-1257-1594)
- Jeb Bugos (ORCID: https://orcid.org/0000-0003-2336-1442)
Institutions
- University of Nebraska–Lincoln (US)
- Planetary Science Institute (US)
- American Museum of Natural History (US)
- Johns Hopkins University (US)
- Princeton University (US)
- Cleveland Museum of Natural History (US)
- Natural History Museum of Los Angeles County (US)
- Denver Museum of Nature and Science (US)
- Yale University (US)
- Ohio University (US)
- Robert S. Peabody Museum of Archaeology (US)
- Adelphi University (US)
Publication Details
- Journal
- Science
- Published
- 2025-12-04
- DOI
- https://doi.org/10.1126/science.adx8706
- Citations
- 2
- Primary Topic
- Paleontology and Evolutionary Biology
- Type
- article
- Field-Weighted Citation Impact
- 8.66