(News) Nanotyrannus holotype CMNH 7541 was an adult (Griffin et al., 2025)!

Nanotyrannus fans are eating good this year! My friend "Luke" notified me that Dr. Christopher Griffin's paper describing the Nanotyrannus holotype's age has officially been published. I contacted Griffin earlier this year, and he said that the paper was submitted for peer-review. Now, it's out! We officially have two specimens of Nanotyrannus that are adults!

In his 2024 abstract, Griffin et al. said that the Nanotyrannus lancensis holotype, CMNH 7541, had an EFS (External Fundamental System) in its hyoid bone. This determined that the individual was mature when it died, and not a juvenile. Now, we have a picture of said EFS in the specimen. Griffin et al., (2025) provided a figure (Figure 3):

Description:

The EFS is shown in the middle (B), and posterior/caudal (C), portions of the ceratobranchial/hyoid bone. It's possible that the EFS is located at the anterior/cranial area of the bone (A), but it's not entirely certain. The bone is damaged at the front. However, the EFS is present throughout the rest of the hyoid (pp. 2-3, Results: The ontogenetic status of Nanotyrannus lancensis type specimen). Other reptiles, but extant and extinct, contained EFS in their ceratobranchial bones as well. This includes a mature specimen of Coelophysis that has an EFS in its ceratobranchial, and femur. This indicates that the hyoid can be used to determine maturity (pp. 1-2, Results: Ceratobranchial histology in extant reptiles; Ceratobranchial histology in extinct dinosaurs; Figures 1-2).

Extant archosaurs with EFS in their ceratobranchial/hyoid bones (Figure 1):

Description:

Extinct archosaurs/dinosaurs (Figure 2):

Description:

Aside from the maturity of the specimen, the authors hypothesize that CMNH might be different from BMRP 2002.4.1 ("Jane"), and a SWAU specimen. Heck, it might be another eutyrannosaur. Speaking of, the scholars concluded that Nanotyrannus was an eutyrannosaurian. They laid out two hypotheses: that CMNH could've been a dwarf specimen of Tyrannosaurus, possibly a male; or, the specimen was an eutyrannosaurian. The scholars went with the latter hypothesis (p. 3, Results: The ontogenetic status of Nanotyrannus lancensis type specimen):

The SWAU specimen is the Nanotyrannus specimen SWAU HRS 08438 ("Zuri"). This specimen is immature (Supplementary Materials, p. 19 Figure S9).

We now have two specimens of Nanotyrannus that were skeletally mature, or were borderline mature. The first is CMNH 7541 (Griffin et al., 2025), and the second is NCSM 40000 ("Bloody Mary") (Zanno and Napoli, 2025). Nanotyrannus has officially struck back, and it won twice. This makes me wonder if Stygimoloch, and Dracorex, were separate taxa from Pachycephalosaurus? Other dinosaur taxa previously studied more-than-likely suffered the same fate, so they should probably be re-examined too. Either way, lumping a taxon into a previously established one just because it's not fully grown may not always be the best method. I'm guilty of this myself, which is why I thought Nanotyrannus could've been Dryptosaurus aquilunguis back in 2022. Nowadays, I use the generic names Nanotyrannus or Dryptosaurus interchangeably, but I stick to the species names lancensis or lethaeus, for the animal.

Links:
Griffin et al., (2025):
https://www.science.org/doi/10.1126/science.adx8706?fbclid=PAVERFWAOgC4FleHRuA2FlbQIxMABzcnRjBmFwcF9pZA8xMjQwMjQ1NzQyODc0MTQAAaeDc5JF0qycTqEA749YCOkRehMLbusYoDsHTA2XL-zYcYq3ANzssLHjTatoNg_aem_bnEV9_2W5YRextcMPVcdTA
Griffin et al., (2024) (Abstract):
https://psdinosaurs.blogspot.com/2024/10/news-nanotyrannusdryptosaurus-lancensis.html
Zanno and Napoli (2025) (Abstract):
https://www.nature.com/articles/s41586-025-09801-6