Biology:Whaitsiidae
Whaitsiidae is an extinct family of therocephalian therapsids.[1] Whaitsiids were among the most diverse therocephalians of the Late Permian, though they would go extinct at the end-Permian mass extinction.
Description
Whaitsiids and their closest relatives (hofmeyriids and Ophidostoma) are grouped together in the clade Whaitsioidea. Some of their distinctive traits include a reduced number of postcanine teeth, a broad skull, and a boomerang-shaped lower jaw.[2] At the front, the lower jaws have a loose rather than solid connection at the symphysis (chin), while at their rear the jaw joint is streptostylic.[3] This would have given whaitsioids an unusually wide and flexible gape among therapsids, not dissimilar to snakes.[2]
The sides of the snout are concave, while the suborbital and postorbital bars are thick, allowing the orbits (eye sockets) to point more forwards than in other therocephalians.[1] A few whaitsiids were large by therocephalian standards,[1][4] though they were still smaller than most gorgonopsians.
Classification
Whaitsiidae is named after Whaitsia, a junior synonym (defunct later name) for Therioganthus. Theriognathus remains the best-described member of the family.[3][5] Whaitsioids are one of three major groups in the clade Eutherocephalia, alongside Akidnognathidae and Baurioidea. Historically, many therocephalians have been classified as "whaitsiids" or "whaitsioids" at some point, though in modern use Whaitsiidae is a smaller and more narrowly-defined family.[1][2][4]
A few studies have argued that cynodonts (and consequently mammals) are descended from whaitsiid therocephalians, based on cynodont-like features in the skull of Theriognathus.[6][7][8] Other studies strongly disagree, arguing that therocephalians and cynodonts are separate sister clades.[1][3] A 2024 analysis of therapsid snout structures suggests that cynodonts may still be descended from eutherocephalians, just not whaitsiids in particular.[9]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Huttenlocker, A. (2009). "An investigation into the cladistic relationships and monophyly of therocephalian therapsids (Amniota: Synapsida)". Zoological Journal of the Linnean Society 157 (4): 865–891. doi:10.1111/j.1096-3642.2009.00538.x.
- ↑ 2.0 2.1 2.2 Huttenlocker, Adam K.; Smith, Roger M. H. (2017). "New whaitsioids (Therapsida: Therocephalia) from the Teekloof Formation of South Africa and therocephalian diversity during the end-Guadalupian extinction" (in en). PeerJ 5. doi:10.7717/peerj.3868. ISSN 2167-8359. https://peerj.com/articles/3868.
- ↑ 3.0 3.1 3.2 Huttenlocker, Adam K.; Abdala, Fernando (2015). "Revision of the first therocephalian, Theriognathus Owen (Therapsida: Whaitsiidae), and implications for cranial ontogeny and allometry in nonmammaliaform eutheriodonts" (in en). Journal of Paleontology 89 (4): 645–664. doi:10.1017/jpa.2015.32. ISSN 0022-3360. Bibcode: 2015JPal...89..645H. https://www.researchgate.net/publication/290624176.
- ↑ 4.0 4.1 Liu, J.; Abdala, F. (2023). "Late Permian terrestrial faunal connections invigorated: the first whaitsioid therocephalian from China". Palaeontologia Africana 56: 16–35.
- ↑ Huttenlocker, Adam K.; Browning, Claire; Peecook, Brandon R.; Smith, Roger M. H.; Viglietti, Pia A. (2025-01-01). "The stratigraphic record of the therocephalian Theriognathus (Synapsida) and its utility as a biostratigraphic index in Karoo-Aged basins". Journal of Vertebrate Paleontology 45 (sup1). doi:10.1080/02724634.2024.2441899. ISSN 0272-4634. Bibcode: 2025JVPal..4541899H.
- ↑ Kemp, T. S. (1972-04-27). "Whaitsiid Therocephalia and the origin of cynodonts" (in en). Philosophical Transactions of the Royal Society of London. B, Biological Sciences 264 (857): 1–54. doi:10.1098/rstb.1972.0008. ISSN 0080-4622. Bibcode: 1972RSPTB.264....1K. https://royalsocietypublishing.org/rstb/article/264/857/1/54135/Whaitsiid-Therocephalia-and-the-origin-of.
- ↑ Abdala, Fernando (2007). "Redescription of Platycraniellus elegans (Therapsida, Cynodontia) from the Lower Triassic of South Africa, and the cladistic relationships of eutheriodonts" (in en). Palaeontology 50 (3): 591–618. doi:10.1111/j.1475-4983.2007.00646.x. ISSN 0031-0239. Bibcode: 2007Palgy..50..591A. https://www.researchgate.net/publication/229442670.
- ↑ Botha, J.; Abdala, F.; Smith, R. (2007). "The oldest cynodont: new clues on the origin and early diversification of the Cynodontia" (in en). Zoological Journal of the Linnean Society 149 (3): 477–492. doi:10.1111/j.1096-3642.2007.00268.x. https://www.researchgate.net/publication/314116724.
- ↑ Pusch, Luisa C.; Kammerer, Christian F.; Fröbisch, Jörg (2024-03-05). "The origin and evolution of Cynodontia (Synapsida, Therapsida): Reassessment of the phylogeny and systematics of the earliest members of this clade using 3D-imaging technologies" (in en). The Anatomical Record 307 (4): 1634–1730. doi:10.1002/ar.25394. ISSN 1932-8486. https://anatomypubs.onlinelibrary.wiley.com/doi/full/10.1002/ar.25394.
Template:Therocephalia Wikidata ☰ Q7990454 entry
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