Protopyknosia

Protopyknosia is an extinct clade of archosauriform reptiles from the Late Triassic of India and the United States. First identified by Sterling Nesbitt et al. in 2021,^[1] the clade contains two genera: Kranosaura and Triopticus. Members of Protopyknosia characteristically have an unusually domed head reminiscent of the later pachycephalosaurian dinosaurs in an example of convergent evolution.^[2] The clade was defined by Nesbitt et al. 2021 as the "most inclusive clade containing Triopticus primus, but not Passer domesticus (the house sparrow), Triceratops horridus, Alligator mississippiensis (the American alligator), Sphenodon punctatus (the tuatara), Heloderma suspectum (the Gila monster), or Chrysemys picta (the painted turtle)"

Protopyknosia Temporal range: Late Triassic, ~229–211 Ma PreꞒ Ꞓ O S D C P T J K Pg N Carnian-Norian
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauromorpha
Clade:	Archosauriformes
Clade:	†Protopyknosia Nesbitt et al., 2021
Genera
†Kranosaura †Triopticus

References

1. Nesbitt, S. J.; Stocker, M. R.; Chatterjee, S.; Horner, J. R.; Goodwin, M. B. (2021). "A remarkable group of thick-headed Triassic Period archosauromorphs with a wide, possibly Pangean distribution". Journal of Anatomy. 239 (1): 184–206. doi:10.1111/joa.13414. PMC 8197959. PMID 33660262.
2. Stocker, M.R.; Nesbitt, S.J.; Criswell, K.E.; Parker, W.G.; Witmer, L.M.; Rowe, T.B.; Ridgely, R.; Brown, M.A. (2016). "A Dome-Headed Stem Archosaur Exemplifies Convergence among Dinosaurs and Their Distant Relatives". Current Biology. 26 (19): 2674–2680. doi:10.1016/j.cub.2016.07.066. PMID 27666971.