Younginiformes

Younginiformes is a group of diapsid reptiles known from the Permian-Triassic of Africa and Madagascar. It has been used as a replacement for "Eosuchia".^[1] Younginiformes (including Acerosodontosaurus, Hovasaurus, Kenyasaurus, Tangasaurus, Thadeosaurus and Youngina) were historically suggested to be lepidosauromorphs, but are currently thought to be basal non-saurian neodiapsids.^[2][3] The group is sometimes divided into two families, Tangasauridae and Younginidae. The monophyly of the group is disputed. A 2009 study found them to be an unresolved polytomy at the base of Neodiapsida,^[4] while a 2011 study recovered the group as paraphyletic.^[5] A 2022 study recovered the Younginiformes as a monophyletic group of basal neodiapsid reptiles, also including Claudiosaurus and Saurosternon as part of the group.^[6] Some younginiforms like Hovasaurus and Acerosodontosaurus are thought to have had an amphibious lifestyle, while others like Kenyasaurus, Thadeosaurus and Youngina were probably terrestrial.^[4]

Younginiformes Temporal range: Middle Permian–Early Triassic PreꞒ Ꞓ O S D C P T J K Pg N
Skull of Youngina
Life restoration of Youngina
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Neodiapsida
Order:	†Younginiformes Romer, 1945
Families
†Tangasauridae Haughton, 1924 †Younginidae Broom, 1914

Classification

Included genera:

• Tangasauridae
  • Acerosodontosaurus Currie, 1980
  • Hovasaurus Piveteau, 1926
  • Kenyasaurus Harris & Carroll, 1977
  • Saurosternon? Huxley, 1868
  • Tangasaurus Haughton, 1924
• Younginidae
  • Claudiosaurus? Carroll, 1981
  • Heleosuchus? Owen, 1876
  • Thadeosaurus Carroll, 1981
  • Youngina Broom, 1914

2011 phylogeny showing a paraphyletic Younginiformes:^[5]

Neodiapsida	Orovenator Lanthanolania Tangasauridae Tangasaurus Acerosodontosaurus Hovasaurus Younginidae Thadeosaurus Youngina Claudiosaurus Sauria

Phylogeny of Younginiformes from Simões et al. 2022:^[6]

Sauropsida	"Parareptilia" (paraphyletic) Neodiapsida Younginiformes Claudiosaurus germaini Youngina capensis Hovasaurus boulei Acerosodontosaurus piveteaui Saurosternon bainii Eunotosaurus Weigeltisauridae Sauria Archelosauria Lepidosauromorpha

References

1. Gauthier, J.; Estes, R.; de Queiroz, K. (1988). "A phylogenetic analysis of Lepidosauromorpha" (PDF). In R. Estes; G. Pregill (eds.). Phylogenetic relationships of the lizard families. Stanford: Stanford University Press. pp. 15–98. Archived (PDF) from the original on 2023-12-09.
2. Laurin, Michel (January 1991). "The osteology of a Lower Permian eosuchian from Texas and a review of diapsid phylogeny". Zoological Journal of the Linnean Society. 101 (1): 59–95. doi:10.1111/j.1096-3642.1991.tb00886.x.
3. Ezcurra, Martín D.; Scheyer, Torsten M.; Butler, Richard J. (2014-02-27). Ketmaier, Valerio (ed.). "The Origin and Early Evolution of Sauria: Reassessing the Permian Saurian Fossil Record and the Timing of the Crocodile-Lizard Divergence". PLOS ONE. 9 (2): e89165. Bibcode:2014PLoSO...989165E. doi:10.1371/journal.pone.0089165. ISSN 1932-6203. PMC 3937355. PMID 24586565.
4. Bickelmann; Müller; Reisz (2009). "The enigmatic diapsid Acerosodontosaurus piveteaui (Reptilia: Neodiapsida) from the Upper Permian of Madagascar and the paraphyly of "younginiform" reptiles". Canadian Journal of Earth Sciences. 46 (9): 651–661. Bibcode:2009CaJES..46..651S. doi:10.1139/E09-038.
5. Robert R. Reisz; Sean P. Modesto; Diane M. Scott (2011). "A new Early Permian reptile and its significance in early diapsid evolution". Proceedings of the Royal Society B. 278 (1725): 3731–3737. doi:10.1098/rspb.2011.0439. PMC 3203498. PMID 21525061.
6. Simões, Tiago R.; Kammerer, Christian F.; Caldwell, Michael W.; Pierce, Stephanie E. (2022-08-19). "Successive climate crises in the deep past drove the early evolution and radiation of reptiles". Science Advances. 8 (33): eabq1898. Bibcode:2022SciA....8.1898S. doi:10.1126/sciadv.abq1898. ISSN 2375-2548. PMC 9390993. PMID 35984885.

Sources

• Lambert, D.; Naish, D.; Wyse, E. (2001). Encyclopedia of Dinosaurs and prehistoric life. London: Dorling Kindersley. p. 77. ISBN 0-7513-0955-9.