Modern Lissamphibians (Frogs, Salamanders, and Caecillans) are considered to be descended from a group of small, lightly-built, terrestrial Temnospondyls called the Amphibamiforms, known from Carboniferous, Permian, and Triassic deposits. The assumed relationship between Amphibamiforms and Lissamphibians is based upon the presence of bicuspid, pedicellate teeth in some adult Amphibamiforms, one of few traits which is common to all modern Lisamphibian groups. The general skull shape of Amphibamiforms also tends to resemble that of Lissamphibians, though these, as with the skeletons in general, are more simplified in Lissamphibians than in Amphibamiforms, presumably as a result of changes in timing and rate of developmental processes in Lisamphibians.
In a paper published in the Zoological Journal of the Linnean Society on 21 March 2024, Calvin So of the Department of Biological Sciences at George Washington University, Jason Pardo of the Negaunee Integrative Research Center at the Field Museum of Natural History, and Arjan Mann, also of the Integrative Research Center at the Field Museum of Natural History, and of the Department of Paleobiology at the Smithsonian National Museum of Natural History, describe a new species of Amphibamiform Temnospondyl from the Early Permian Lower Clear Fork Formation of Texas.
The new species is described from a single partial skull comptising a near complete roof and occiput with a partial braincase, and mandibles. It is given the name Kermitops gratus, where 'Kermitops' is a combination of the name 'Kermit', in reference to the famous Lissamphibian and beloved Muppets’ character created and originally performed by Jim Henson, and '-ops', the Greek for 'face', while 'gratus' means 'gratitude' in Latin, in thanks to the Smithsonian National Museum of Natural History vertebrate palaeontology curator Nicholas Hoton III, and other members of the Smithsonian National Museum of Natural History field party that were involved in the collection efort.
The skull is approximately 3 cm long along the midline and 2 cm wide at the level of the occiput. There is some taphonomic distortion on both sides, making the orbits appear slightly more ovoid than they would have in life, and the left orbit is partially disarticulated. The anterior palate and braincase are lost but the remainder of the skull is well-preserved, even showing a full arrangement of palpebral ossicles in place and showcasing fine dermal ornamentation on the dorsal skull. The margins of the orbit are slightly raised, resulting in a differentiation of the orbital margin from the rest of the skull roof surface. The snout is long and parabolic in shape, consistent with the morphology seen in Micropholids.
Attempts to include Kermitops gratus in phylogenetic trees using different methods produced quite different results, suggesting that insufficient sampling of the group has been done to achieve a consensus hypothesis. Notably, So et al. failed to find a clear relationship between Lissamphibians and Amphibamiform taxa with pedicellate bicuspid teeth, which would seem to indicate either that the trait evolved separately numerous times within the Amphibamiformes, or that it was present in the earliest members of the group, and lost multiple times.
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