Spathicephalus mirus (Watson 1926; Late Carboniferous, 320 mya) was described, "unlike that of any other early tetrapod, with a flattened, square-shaped skull and jaws lined with hundreds of very small chisel-like teeth." The extended orbit shape traditionally allied Spathicephalus with Baphetes, but here it nests with two other flat-headed temnospondyls, Greererpeton and Koilops, apart from Baphetes.
The fossil does not show tooth replacement as every tooth is present without gaps. Distinct from derived temnospondyls, but like basal forms, the palate is closed on this bottom-feeder. Long before the publication of Koilops Milner et al. 2009 nested Spathicephalus close to Eucritta and Baphetes, but that relationship was not recovered in the LRT, despite sharing a closed palate. The elongate orbit without intrusions is convergent with that of Baphetes.