Ianthodon
| Ianthodon Temporal range: Pennsylvanian,
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| I. schultzei cranial and skeletal reconstruction | |
Scientific classification 
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| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Synapsida |
| Clade: | Eupelycosauria |
| Clade: | Metopophora |
| Clade: | Haptodontiformes |
| Genus: | †Ianthodon Kissel & Reisz, 2004 |
| Type species | |
| †Ianthodon schultzei Kissel & Reisz, 2004
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Ianthodon is an extinct genus of basal haptodontiform synapsids from the Late Carboniferous about 304 million years ago. The taxon was discovered and named by Kissel & Reisz in 2004.[1] The only species in the taxon, Ianthodon schultzei, was found by separating it from a block that also contained the remains of Petrolacosaurus and was initially thought to contain elements of Haptodus. The evolutionary significance of the taxon was not realized until a publication in 2015.[2] The fossil of this organism was discovered in Garnett, Kansas.[2]
Description
[edit | edit source]Ianthodon was first named by Kissel & Reisz in 2004;[1] elements on the holotype slab reidentified as Ianthodon provided more details in 2014.[2] This single juvenile skeleton with delicate bones has an estimated skull length of around 10 cm, which is similar to other taxa, such as Haptodus,[3] during the same development stage.[1][4] The specimen was easily distinguished from the skeletal element of Petrolacosaurus[5] by the position and the proportion of foramen and supinator process in the humeri.
Skull
[edit | edit source]It can be distinguished from Haptodus[3][6] by its narrower skull and dentition. The higher number of precanine maxillary teeth and the more rectangular shape of the humerus distinguish the holotype of H. garnettensis[5] from that of Ianthodon. The teeth of Ianthodon have wide bases but slender crowns, unusual among contemporary amniotes and indicating that Ianthodon occupied a different trophic niche from the bulbous-crowned Haptodus to which it was closely related.[6] Like other sphenacodonts, Ianthodon has a tall lacrimal bone, and so would have had a proportionally taller snout than more basal synapsids such as varanopids and eothyridids.[2][7]
Classification
[edit | edit source]Ianthodon belongs to the clade Sphenacodontia within the clade Sphenacomorpha. Ianthodon has been considered the basalmost-known sphenacodont.[2] The cladogram below follows a cladistic analysis by Spindler and colleagues, 2014.[2]
See also
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References
[edit | edit source]- ^ a b c Kissel, R. A. & Reisz, R. R. Synapsid fauna of the Upper Pennsylvanian Rock Lake Shale near Garnett, Kansas and the diversity pattern of early amniotes. In G. Arratia, M. V. H. Wilson & R. Cloutier (eds.). Recent Advances in the Origin and Early Radiation of Vertebrates. Verlag Dr. Friedrich Pfeil, 2004.
- ^ a b c d e f Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b Currie, P. J.: A new haptodontine sphenacodont (Reptilia: Pelycosauria) from the Upper Pennsylvanian of North America, J. Paleontol., 51, 927–942, 1977
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- ^ a b Roger B. J. Benson (2012) Interrelationships of basal synapsids: cranial and postcranial morphological partitions suggest different topologies, Journal of Systematic Palaeontology, 10:4, 601-624, DOI: 10.1080/14772019.2011.631042
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