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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

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, 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. 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)"

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.

v t e Archosauromorpha
Kingdom: Animalia Phylum: Chordata Class: Sauropsida Clade: Diapsida Clade: Sauria Clade: Archelosauria Sauropsida see Sauropsida Archosauromorpha see below↓
Archosauromorpha Archosauromorpha †Aenigmastropheus †Czatkowiella †Elachistosuchus? †Elessaurus †Malutinisuchus †Mecistotrachelos †Prolacertoides †Protorosaurus †Rhombopholis †Vritramimosaurus †Tanysauria Jesairosaurus? Trachelosauridae Austronaga Dinocephalosaurus Fuyuansaurus? Gracilicollum? Protanystropheus Pectodens Sclerostropheus? Trachelosaurus Sharovipterygidae? Ozimek Sharovipteryx Tanystropheidae Amotosaurus Augustaburiania Cosesaurus Fuyuansaurus? Gracilicollum? Gwyneddosaurus Langobardisaurus Luxisaurus Macrocnemus Raibliania Sclerostropheus? Tanystropheus Tanytrachelos Sharovipterygidae? Crocopoda †Boreopricea †Cryptovaranoides? †Tasmaniosaurus †Teyujagua †Allokotosauria see Allokotosauria †Rhynchosauria see Rhynchosauria †Prolacertidae? Kadimakara Prolacerta Archosauriformes see below↓
Archosauriformes Archosauriformes †Antarctanax †Cuyosuchus †Eorasaurus? †Kalisuchus †Koilamasuchus †Sarmatosuchus †Syntomiprosopus †Proterosuchidae Archosaurus Chasmatosuchus? Gamosaurus Jaikosuchus Proterosuchus Samsarasuchus Tsylmosuchus? Vonhuenia? †Protopyknosia Kranosaura Triopticus †Erythrosuchidae Bharitalasuchus Chalishevia Erythrosuchus Fugusuchus? Garjainia Guchengosuchus Shansisuchus Uralosaurus Eucrocopoda †Asperoris †Dorosuchus †Heteropelta †Litorosuchus †Marcianosuchus †Polymorphodon †Vancleavea †Euparkeriidae Euparkeria Halazhaisuchus Osmolskina †Proterochampsia see Proterochampsia Crurotarsi †Phytosauria see Phytosauria Archosauria Incertae sedis †Sikannisuchus? †Smok Avemetatarsalia see Avemetatarsalia includes birds Pseudosuchia see Pseudosuchia includes crocodilians
Related topics Tooth taxa †Crosbysaurus †Lucianosaurus †Tecovasaurus †Palaeosaurus †Protecovasaurus †Uatchitodon †Zanclodon Nomina dubia †Albisaurus †Ankistrodon †Avipes †Blomosuchus †Collilongus †Exilisuchus †Fenhosuchus †Megacnemus †Microcnemus †Vjushkovisaurus †Wangisuchus Paraphyletic groups Proterosuchia Protorosauria Thecodontia Possible members Choristodera Drepanosauromorpha Kuehneosauridae Ichthyosauromorpha Sauropterygia Thalattosauria
Category

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• Archosauriforms
• Late Triassic extinctions
• Taxa named by Sankar Chatterjee
• Taxa named by Jack Horner
• Taxa named by Sterling Nesbitt
• Taxa named by Michelle R. Stocker
• Triassic reptile stubs