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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

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". 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. 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, while a 2011 study recovered the group as paraphyletic. A 2022 study recovered the Younginiformes as a monophyletic group of basal neodiapsid reptiles, also including Claudiosaurus and Saurosternon as part of the group. Some younginiforms like Hovasaurus and Acerosodontosaurus are thought to have had an amphibious lifestyle, while others like Kenyasaurus, Thadeosaurus and Youngina were probably terrestrial.

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:

Phylogeny of Younginiformes from Simões et al. 2022:

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.

v t e Sauropsida (Reptilia sensu lato)
Kingdom: Animalia Phylum: Chordata Superclass: Tetrapoda Clade: Amniota Tetrapodomorpha see Tetrapodomorpha Reptiliomorpha see Reptiliomorpha Sauropsida see below↓
Sauropsida Sauropsida †Australothyris †Erpetonyx †Microleter †Acleistorhinidae Acleistorhinus Carbonodraco Colobomycter Delorhynchus Feeserpeton Karutia Klastomycter †Bolosauridae Belebey Bolosaurus Eudibamus †Mesosauria Brazilosaurus Mesosaurus Stereosternum †Millerettidae Broomia Heleophilus Milleretta Millerosaurus Milleropsis Nanomilleretta †Procolophonia see Procolophonia Diapsida see below↓
Diapsida Diapsida †Adelosaurus? †Claudiosaurus †Cryptovaranoides †Dolerosaurus †Elachistosuchus †Eunotosaurus? †Feralisaurus †Heleosuchus †Kenyasaurus †Kudnu †Lanthanolania †Maiothisavros †Microzemiotes †Orovenator †Palacrodon †Palaeagama †Saurosternon †Sphodrosaurus †Younginidae Galesphyrus Thadeosaurus Youngina †Tangasauridae Acerosodontosaurus? Hovasaurus Tangasaurus †Weigeltisauridae Coelurosauravus Glaurung Rautiania Weigeltisaurus †Drepanosauromorpha Ancistronychus Avicranium Dolabrosaurus Drepanosaurus Hypuronector Kyrgyzsaurus Longisquama? Megalancosaurus Protoavis? Skybalonyx Unguinychus Vallesaurus †Kuehneosauridae Icarosaurus Idiosaura? Kuehneosaurus Kuehneosuchus Pamelina Rhabdopelix? †Choristodera see Choristodera †Ichthyosauromorpha see Ichthyosauromorpha †Sauropterygia see Sauropterygia †Thalattosauria see Thalattosauria Sauria (Crown-Reptilia) Lepidosauromorpha see Lepidosauromorpha Includes Lepidosauria includes rhynchocephalians and squamates Archelosauria Archosauromorpha see Archosauromorpha Includes Archosauria includes birds and crocodilians Pantestudines see Pantestudines Includes Testudines turtles
See also Possible sauropsids Araeoscelidia Captorhinidae Protorothyrididae Recumbirostra Varanopidae Other taxa Anapsida Captorhinida Eureptilia Parareptilia Lanthanosuchoidea Millerosauria Procolophonomorpha Ankyramorpha Neodiapsida Eosuchia Younginiformes Avicephala Eolacertilia Euryapsida
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