The skull is oval, elongate, truncate behind, and the quadrate angles project into sharp horns. The orbits are elongate ovals and their center lies in the median line which divides the skull transversely. The nostrils are elongate and have an oblique position. The pineal foramen lies in the posterior third of the skull.
Teeth are preserved on both maxillæ and premaxillæ. They are simply sharp pleurodont denticles, and seem to have been fairly abundant. The bones have been completely carbonized and nothing of the original texture is preserved, although the details of the structure are beautifully preserved. ([PLATE 25, fig. 3.])
The skull is somewhat triangular in its general form. The premaxilla lies on the anterior border of the cranium, and forms the median border of the nostril. The suture which separates the maxilla and the premaxilla is not evident, and it may not be correctly defined in the figure ([fig. 23]). The nasal is a very large element and is elongate. It unites with the premaxilla, the lacrimal, the prefrontal, and the parietal. It is acuminate behind and the point is inclosed by the pref rental and the parietal. The frontal is quite narrow and elongate, and does not border the orbit; its posterior boundary is not accurately represented. The radiations on the surface indicate the extent of the element. The parietals are remarkable in being smaller than the frontal and nasal. The pineal foramen is inclosed in the median suture in the anterior third of the parietals. The parietal has the usual relations of that element. The postparietal lies posterior to the parietal, but a portion of its bounding sutures are destroyed. The prefrontal forms the antero-interior border of the orbit and borders the postfrontal posteriorly, in an unusual manner. The lacrimal is a large element and is clearly separable from the other cranial elements. It, with the prefrontal, forms the anterior border of the orbit. The maxilla is very elongate and forms the larger part of the lateral border of the skull. Sharp-pointed teeth are present on it and they may have been pleurodont. The lateral border of the orbit probably received a portion of the maxilla. The postfrontal and the postorbital form the greater part of the posterior boundary of the orbit. The postorbital seems to be divided by a median suture which would indicate an intertemporal bone, but this is not certain. The appearance may be due to a fracture. The supratemporal is a large element bordering the parietal and lies in front of the tabulare. The squamosal is elongate to form the posterior horn-like extension of the skull. The tabulare is transversely elongate and has the usual relations. The jugal widens to a fan-shape backwards, and helps to form the lateral border of the orbit. Its lateral and anterior boundaries are not assured. The quadratojugal seems to lie as indicated, although the anterior part of the suture is not distinct. It is apparently an elongate element and with the maxilla forms the lateral border of the skull. The base of the skull as restored ([fig. 23]) is irregular and may have had a slightly different form.
The genus Stegops is exceptional in the elongate character of the cranial elements of the single species known. In this respect it recalls the species Diceratosaurus lævis described below. The large size of the nasals, frontals, and lacrimals and the small size of the parietals are, so far as I am aware, unparalleled among the other Coal Measures Amphibia of North America.
| Measurements of the Type. | |
| mm. | |
| Median length of the skull | 56 |
| Width across tips of horns | 46 |
| Width at base of horns | 40 |
| Width across orbits | 44 |
| Diameter of the orbit | 8 |
| Length of the orbit | 15 |
| Interorbital space | 16 |
| Length of the nostril | 2 |
| Diameter of the pineal foramen | 1 |
| Length of the teeth | 1.5 |
| Length of the horn from base | 7.5 |
| Width of horn at base | 4 |
MOODIE
1. Dorsum of skull of Diceratosaurus punctolineatus (Cope), from the Coal Measures of Linton. Ohio. Original in the Museum at Berlin University. × 2. After Jaekel. po=postorbital: fr= frontal; pof=postfrontal; j=jugal; la=lacrimal; mx = maxilla; ps="perisquamosal;" pp=post-parietal; pmx= premaxilla.
2. Ventral surface of the skull of Diceratosaurus punctolineatus (Cope ), from the Coal Measures of Linton, Ohio. × 2. After Jaekel. a=anterior palatine vacuity; ex=exoccipital; j=jugal; mx=maxilla; tr=transverse; pal=palatine; pt=pterygoid; pr=prevomer; ps="perisquamosal;" pv=posterior or suborbital palatine vacuity; ph=parasphenoid.