Dimetrodon tooth

Dimetrodon sp.

Wellington/Ryan Fm., Waurika, OK, USA

Post-canine/posterior tooth

This tooth is likely from D. limbatus, given the locality and presence of serrations: https://www.nature.com/articles/ncomms4269

The same paper also rules out other serrated Sphenacodonts by the enamel ornamentation. Its smaller size could indicate that it's from a juvenile.

It differs from the comparatively abundant broken Orthacanth shark tooth cusps in the microfossil matrix (what most people are likely to confuse with): the enamel texture is not smooth, the crown is very broad (indicating it's likely a posterior, in addition to its size), it has fine serrations that differ in shape from the sharks', and the base doesn't flare out. Were this crown complete, you'd also notice a conical/rounded depression in the base.

A beautiful tooth from one of our surprisingly close cousins.