The skull of the present species is fully described by Jaekel. The type specimen does not offer any evidence in support of Jaekel's "perisquamosal," but rather tends to the idea that he is incorrect in his assumption of the fusion of these elements of the skull. The direction taken by the ridges and grooves on the elements preserved indicate a separation between the supratemporal and the squamosal. I do not find that the grooves have the tendency to arise from a common center of ossification in the squamosal, as suggested in the figures of Jaekel. The horn which projects backward from the squamosal is rather large and heavy for the size of the skull, and after curving slightly inward ends in a blunt point and not sharply, as Jaekel figures in his specimens. The vertebral column is indistinctly preserved and I have nothing to add to Jaekel's account given above.
In the structure of the pectoral girdle my results are greatly at variance with those of Jaekel. I do not find the remarkable elements which Jaekel has figured ([347]) in his specimens. On the other hand, I find a normal microsaurian pectoral arch ([464]), such as has been described for numerous other forms. There are present, distinctly preserved in the type specimen, the scapulæ, the clavicles, and the interclavicle, with the possibility of the coracoid. The peculiar element referred to by Cope as resembling a "lacertilian pubis" is without doubt the left scapula of the animal ([plate 16, fig. 1]). Its form compares very favorably with that of Ceraterpeton as figured by Woodward ([630]). The coracoid may be represented by the fragment which lies close to the scapula. The sculptured element lying next to the supratemporal horn of the skull is the right clavicle preserved bottom side up. Of the other two sculptured elements, one is the interclavicle, only a portion of which is preserved. The left clavicle lies beside it. The clavicles in this species have a tendency to assume the triangular shape so common in other species of Microsauria, and the interclavicle, so far as can be determined, was shield-shaped. The upper surfaces of the pectoral elements are marked by grooves for the attachment of the pectoral muscles.
Fig. 24.
A. Skull of Diceratosaurus lævis Moodie, from the Linton Coal Measures. × 1. f, frontal; j, jugal; mx, maxilla; n, nasal; or, orbit; par, parietal; pof, postfrontal; po, postorbital; pf, prefrontal; pp, postparietal; sq, squamosal; spt, supratemporal; qj, quadratojugal; pmx, premaxilla; tab, tabulare.
B. Reconstruction of skull outlines of Diceratosaurus robustus Moodie, from the Coal Measures of Ohio. × 0.75. fr, frontal; f, jugal; or, orbit; par, parietal; pof, postfrontal; po, postorbital; pp, postparietal; qj, quadratojugal; spt, supratemporal; tab, tabulare.
The ventral scutellation is present in a small patch ([plate 16, fig. 1]) near the horn of the skull. The scutæ are oat-shaped and take the usual form. The ribs are not long, are rather stout, and beyond the proximal curve are nearly straight to the obtuse tips. The heads of the ribs are so obscure that it is impossible to determine whether they were two-headed or not. They are expanded proximally and there is a slight tendency to a division of the head.
Portions of both fore limbs are preserved. The right limb possesses the humerus, separate radius and ulna, and 2 metacarpals. The other possesses only the radius, 3 metacarpals, and a portion of a phalanx. The humerus is a very stout bone and at once recalls that of Amblyrhynchus. The ends are expanded and there are roughnesses on the bone for the attachment of muscles. The radius and ulna are subequal in size. They are both expanded more proximally than distally. The carpus was cartilaginous. An additional specimen of this species is figured on [plate 16, fig. 5]. This adds to our knowledge of the pelvis especially.
| Measurements of the Type. | |
| mm. | |
| Length of entire specimen | 80 |
| Length of tabulate horn of skull | 20 |
| Width at base | 4 |
| Width at tip | 2.5 |
| Length of right humerus | 16 |
| Width at middle of shaft | 3 |
| Width at proximal end | 5 |
| Width at distal end | 5.5 |
| Length of radius | 9 |
| Length of ulna | 9 |
| Width of radius at proximal end | 2.5 |
| Width at middle | 1.5 |
| Width at distal end | 2 |
| Width of various portions of ulna same as radius. | |
| Length of the only phalanx preserved | 5 |
| Length of vertebra | 5 |
| Width of vertebra | 4 |
| Length of longest rib | 17 |
| Width of rib at widest part | 1.5 |
| Width of clavicle | 18 |
| Length of clavicle | 20 |
| Length of interclavicle | 25 |
| Width of interclavicle | 16 |
| Length of single side of chevron scute | 7 |
| Width of same | .25 |
The specimen (No. 2566, Am. Mus. Nat. Hist.) on which Cope based his Tuditanus mordax is composed of two plates of the above-described species.
Diceratosaurus lævis Moodie.