CHAPTER XIX. 



THE AISTOPODOUS MICROSAURIAN FAMILY PTYONIID^, FROM THE COAL 



MEASURES OF OHIO. 



Family PTYONHD^ffi Cope, 1873. 

 Cope, Geol. Surv. Ohio, 11, pt. 11, p. 357, 1875. 



Elongate, slender, weak-limbed, aquatic microsaurians. Neural and haemal 

 spines of vertebrae elongated, expanded and sculptured. Ventral armature weakly 

 developed or absent. Skull lanceolate, with long, slender teeth. 



Three genera are assigned to this family: Ptyonius, QLstocephalus, and Thyr- 

 sidiutn. 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. nutntnifer 

 Cope, P. serrula Cope, CEstocephalus remex Cope, O. rectidens Cope, Thyrsidium fas- 

 cictilare Cope. The species are all exclusively from the Linton, Ohio, Coal Measures, 

 and most of them are known from abundant material. 



Genus PTYONroS Cope, 1875. 

 Cope, Geol. Surv. Ohio, 11, pt. 11, 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 di.scovered. Three clavicular elements; abdomen protected by packed 

 osseous rods, which are arranged en chevron, the angle directed forward. Neural 

 and haemal spines of caudal vertebrae 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)1 of the Kilkenny, Ireland, Coal Measures. But that genus possesses divided 

 abdominal rods, or "oat-shaped scales," and the form of the cranium and propor- 

 tions of the body are different. 



The genus is closely related to, possibly identical with, CEstocephalus, but addi- 

 tional material will be required to settle this point. 



Cope (123) gives the following key for the separation of the 5 species: 



X. Abdominal rods coarser, not more than 10 in 5 mnr. 



Median pectoral shield discoid, radiate ridged; muzzle short P. nummifer 



Median pectoral shield oval, pitted and ridged P. marshii 



XX. Abdominal rods hair-like, 15 or more in 5 mm. 



Median pectoral shield with radii from the center, the principal forming a cross; form wider. . P. vinchellianus 



.Middle pectoral with pits at the center and few or no radii; form narrow P. pectinatus 



Middle pectoral shield narrow, closely reticulate medially, and radiate towards the circumference; size 



half that of last P. serrula 



Ptyonius pectinatus Cope. 



Cope, Proc. Acad. Nat. Sci., 1868, p. 216. 



Cope, Trans. Am. Phil. Soc., xiv, p. 20, 1869. 



Cope, Trans. Am. Phil. Soc., xv, p. 266, 1874. 



Cope, Geol. Surv. Ohio, 11, pt. 11, p. 377, pi. xxvii, tig. 7; xxviii, figs. 2, 3, 6; pi. xxix, fig. 2; pi. xxx, fig. 2; 



pi. XXXV, figs. 1-3; pi. xli, fig. I, 1875. 

 Moodie, Proc. U. S. Nat. Mus., 37, p. 24, pi. 8, fig. 3, 1909. 

 SCHWARZ, Beitrage zur Paleontologie und Geologic Osterreich-Ungams und des Orients, Bd. xxi, p. 83, 



figs. 23, 24, 26, 1908. 



139 



