Sphenacodontia (original) (raw)

From Wikipedia, the free encyclopedia

(Redirected from Sphenacodontoidea)

Clade of synapsids

SphenacodontiaTemporal range: Late Pennsylvanian-Recent, 304–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N
3D restoration of Dimetrodon grandis, a sphenacodontid
Restoration of a pair of Alopecognathus angusticeps, a therocephalian therapsid
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Sphenacomorpha
Clade: SphenacodontiaRomer & Price, 1940
Subgroups
†_Haptodus[1] †Hypselohaptodus[1] †Ianthodon[2] Pantherapsida Spindler, 2016[3] †Kenomagnathus_ †_Tetraceratops_ †Palaeohatteriidae Sphenacodontoidea †_Shashajaia_ †Sphenacodontidae Therapsida

Sphenacodontia is a stem-based clade of derived synapsids. It was defined by Amson and Laurin (2011) as "the largest clade that includes Haptodus baylei, Haptodus garnettensis and Sphenacodon ferox, but not Edaphosaurus pogonias".[4] They first appear during the Late Pennsylvanian (Upper Carboniferous) epoch. The earliest sphenacodontians were small carnivores, though the group also includes large carnivores, such as the famous Dimetrodon (Sphenacodontidae). The group includes Therapsida, the only living subclade of Synapsida (including living mammals), which is most closely related to Sphenacodontidae within Sphenacodontia as part of the subclade Sphenacodontoidea.

The defining characteristics of Sphenacodontia include a thickening of the maxilla visible on its internal surface, above the large front (caniniform) teeth; and the premaxillary teeth being set in deep sockets. All other (sister group and more primitive) synapsid clades have teeth that are set in shallow sockets.[5][6] The subclade Sphenacodontoidea is defined by the presence of a frontal orbital process that extends far laterally (outwards to the sides), a deep prefrontal pocket (a cavity present near the upper front/anterodorsal edge of the orbit/eye socket), and teeth on the vomer bone of the roof of the mouth (part of the palatal dentition) are absent.[6]

Members of Sphenacodontia first appeared during the Late Carboniferous (Kasimovian) at latest by ~304 million years ago. The earliest members of the group were small-bodied 1–10 kilograms (2.2–22.0 lb) carnivores like Haptodus though Sphenacodontidae would come to include large terrestrial carnivores like Dimetrodon.[7] Therapsida is suggested to have split away from other lineages of Sphenacondontia before the end of the Carboniferous prior to ~299 million years ago.[7] The early evolutionary history of Therapsida is obscure, with no confirmed fossils prior to beginning of the Middle Permian around 274 million years ago, leaving an over 20 million year ghost lineage. Therapsids would come to dominance in the Middle Permian, along with the extinction of all non-therapsid sphenacontians.[8]

Pantelosaurus, from the Early Permian

Secodontosaurus, Early Permian

The following taxonomy follows Fröbisch et al. (2011), Benson (2012) and Spinder (2016) unless otherwise noted.[3][4][9]

Class Synapsida

Sphenacodontia in a cladogram after Fröbisch et al., 2011:[9]

Cladogram modified from Huttenlocker et al. (2021):[11]

  1. ^ a b Spindler, Frederik (15 August 2019). "Re-evaluation of an early sphenacodontian synapsid from the Lower Permian of England" (PDF). Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 111: 27–37. doi:10.1017/S175569101900015X. S2CID 202192911. Retrieved 8 October 2019.
  2. ^ a b Spindler, F.; Scott, Diane; Reisz, Robert (October 2014). "New information on the cranial and postcranial anatomy of the early synapsid Ianthodon schultzei (Sphenacomorpha: Sphenacodontia), and its evolutionary significance". Fossil Record. 18 (1): 17–30. Bibcode:2014FossR..18...17S. doi:10.5194/fr-18-17-2015.
  3. ^ a b Spindler, F. 2016. Morphological description and taxonomic status of Palaeohatteria and Pantelosaurus (Synapsida: Sphenacodontia). Freiberger Forschungshefte C550(23): 1–57. https://www.researchgate.net/publication/321129043_Morphological_description_and_taxonomic_status_of_Palaeohatteria_and_Pantelosaurus_Synapsida_Sphenacodontia
  4. ^ a b Benson, R.J. (2012). "Interrelationships of basal synapsids: cranial and postcranial morphological partitions suggest different topologies". Journal of Systematic Palaeontology. 10 (4): 601–624. Bibcode:2012JSPal..10..601B. doi:10.1080/14772019.2011.631042. S2CID 84706899.
  5. ^ R. R. Reisz, David S Berman, Diane Scott (1992). "The cranial anatomy and relationships of Secodontosaurus, an unusual mammal-like reptile (Synapsida: Sphenacodontidae) from the Early Permian of Texas". Zoological Journal of the Linnean Society. 104 (2): 127-184. doi:10.1111/j.1096-3642.1992.tb00920.x.{{[cite journal](/wiki/Template:Cite%5Fjournal "Template:Cite journal")}}: CS1 maint: multiple names: authors list (link)
  6. ^ a b Laurin, Michel; Reisz, Robert R. (1997). "Autapomorphies of the main clades of synapsids". Tree of Life Web Project. Archived from the original on October 27, 2023.
  7. ^ a b Huttenlocker, Adam K.; Singh, Suresh A.; Henrici, Amy C.; Sumida, Stuart S. (December 2021). "A Carboniferous synapsid with caniniform teeth and a reappraisal of mandibular size-shape heterodonty in the origin of mammals". Royal Society Open Science. 8 (12) 211237. Bibcode:2021RSOS....811237H. doi:10.1098/rsos.211237. ISSN 2054-5703. PMC 8672069. PMID 34925870.
  8. ^ Duhamel, Alienor; Wynd, Brenen; Wright, April Marie; Moopen, Atashni; Benoit, Julien; Rubidge, Bruce (2026-03-11). "Rethinking therapsid phylogeny through Bayesian and cladistic approaches". Scientific Reports. 16 (1) 13171. Bibcode:2026NatSR..1613171D. doi:10.1038/s41598-026-38195-2. ISSN 2045-2322. PMC 13103076. PMID 41813723.
  9. ^ a b Jörg Fröbisch; Rainer R. Schoch; Johannes Müller; Thomas Schindler; Dieter Schweiss (2011). "A new basal sphenacodontid synapsid from the Late Carboniferous of the Saar-Nahe Basin, Germany" (PDF). Acta Palaeontologica Polonica. 56 (1): 113–120. Bibcode:2011AcPaP..56..113F. doi:10.4202/app.2010.0039.
  10. ^ Spindler, Frederik (2020). "The skull of Tetraceratops insignis (Synapsida, Sphenacodontia)". Palaeovertebrata. 43 (1): e1. doi:10.18563/pv.43.1.e1. S2CID 214247325.
  11. ^ Huttenlocker, A. K.; Singh, S. A.; Henrici, A. C.; Sumida, S. S. (2021). "A Carboniferous synapsid with caniniform teeth and a reappraisal of mandibular size-shape heterodonty in the origin of mammals". Royal Society Open Science. 8 (12) 211237. Bibcode:2021RSOS....811237H. doi:10.1098/rsos.211237. PMC 8672069. PMID 34925870.

Categories: