[CHAPTER XIX.]
THE AISTOPODOUS MICROSAURIAN FAMILY PTYONIIDÆ, FROM THE COAL MEASURES OF OHIO.
Family PTYONIIDÆ Cope, 1875.
Cope, Geol. Surv. Ohio, II, pt. II, p. 357, 1875.
Elongate, slender, weak-limbed, aquatic microsaurians. Neural and hæmal spines of vertebræ elongated, expanded and sculptured. Ventral armature weakly developed or absent. Skull lanceolate, with long, slender teeth.
Three genera are assigned to this family: Ptyonius, Œstocephalus, and Thyrsidium. The forms are very closely related, and when additional material is secured the three genera may be found to be identical. The species included in this family are: Ptyonius pectinatus Cope, P. vinchellianus Cope, P. marshii Cope, P. nummifer Cope, P. serrula Cope, Œstocephalus remex Cope, O. rectidens Cope, Thyrsidium fasciculare Cope. The species are all exclusively from the Linton, Ohio, Coal Measures, and most of them are known from abundant material.
Cope, Geol. Surv. Ohio, II, pt. II, p. 373, 1875.
Cope designated no species as the type, but we may regard Ptyonius pectinatus as typical.
Form elongate, with long tail and lanceolate cranium. Limbs weak, a posterior pair only discovered. Three clavicular elements; abdomen protected by packed osseous rods, which are arranged en chevron, the angle directed forward. Neural and hæmal spines of caudal vertebræ expanded and fan-like. Ribs well developed. The various species vary in length from 3 to 10 inches. They are the most abundant amphibian in the Linton beds. The present genus resembles Lepterpeton Huxley ([334]), of the Kilkenny, Ireland, Coal Measures. But that genus possesses divided abdominal rods, or "oat-shaped scales," and the form of the cranium and proportions of the body are different.