Cocytinus gyrinoides Cope. Linton, Ohio, Coal Measures. Based on the ventral impression of the skull, with the well-developed branchial apparatus.
Erierpeton branchialis Moodie. Mazon Creek, Illinois, shales. Based on impression of mandibles and branchial apparatus.
Hyphasma lævis Cope. Linton, Ohio, Coal Measures. Based on incomplete and obscure amphibian body, lacking limbs.
Cope, Proc. Am. Phil. Soc., 1871, 177.
Cope, Geol. Surv. Ohio, II, pt. II, 360, 1875.
Type: Cocytinus gyrinoides Cope.
Vertebræ and ribs osseous; teeth on the premaxillary bone, none on the maxillary; hyoid elements largely developed, an axialhyal with basihyal on each side, closely united with the corresponding ceratohyal, at the end of which is an element in the position of a stylohyal; hæmal or basibranchials 3, the anterior 2, each supporting i pleural branchihyal, and the third supporting one also, the first hæmal branchihyal on the inner side of the ceratohyal, approaching the median line, and with elongate pleural element.
The reference by Cope of this genus to the Caudata is one of the most interesting facts connected with the Paleozoic Amphibia. He says: "The present genus is, then, to be referred to the neighborhood of Amphiuma and Protonopsis, but forming the type of another family" ([123]). He regards the branchial apparatus as being more fish-like than that of any of the modern genera. It is possible that Cocytinus gyrinoides was a larval branchiate and consequently aquatic form. It should be more fully compared with Erierpeton branchialis from the Mazon Creek shales when better known, as well as with Hyphasma lævis from the Linton locality.