| Ianthodon | |
|---|---|
 | |
| I. schultzei cranial and skeletal reconstruction | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Synapsida |
| Clade: | Eupelycosauria |
| Clade: | Metopophora |
| Clade: | Haptodontiformes |
| Genus: | †Ianthodon Kissel & Reisz, 2004 |
| Type species | |
| †Ianthodon schultzei Kissel & Reisz, 2004 | |
Ianthodon is an extinctgenus of basalhaptodontiformsynapsids from theLate Carboniferous about 304million 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 ofPetrolacosaurus andHaptodus. The evolutionary significance of the taxon wasn't realized until a publication in 2015.[2] The fossil of this organism was discovered inGarnett, Kansas.[2]
Ianthodon was first named by Kissel & Reisz in 2004,[1] and a more detailed specimen was reevaluated 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 asHaptodus,[3] during the same development stage.[1][4] The specimen was easily distinguished from the skeletal element ofPetrolacosaurus[5] by the position and the proportion of foreman and supinator process in thehumeri.
It can be distinguished fromHaptodus[6][3] by its narrower skull and dentition. The higher number of precaninie maxillary teeth and the more rectangular shape of the humerus distinguish the holotype ofH. garnettensis[5] from that ofIanthodon. The teeth ofIanthodon have wide bases but slender crowns, unusual among contemporaryamniotes and indicating thatIanthodon occupied a differenttrophic niche from the bulbous-crownedHaptodus 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 asvaranopids andeothyridids.[7][2]
Ianthodon belongs to the cladeSphenacodontia within the clade Sphenacomorpha.Ianthodon has been considered thebasalmost known sphenacodont.[2] Thecladogram below follows a cladistic analysis by Spindler and colleagues, 2014.[2]
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