SYSTEMATIC REVISION 55 



This genus is known only from the cast of a cavity in the sandstone and so 

 only the external form can be made out. It is evidently closely related to Pareia- 

 sanrus, but has numerous prominent spines on the posterior edge of the skull, 

 resembling in this regard the Pareiasaurians from Northern Russia. 



Genus SCLEROSAURUS H. v. Meyer. 



Sclerosaurus H. v. Meyer, Paleontographica, Bd. VII, pp. 35-4°, Taf. 6. 

 Labyrlnthodon Wiedersheim, Abh. Schweiz. pal. Gesell. Bd. 5. 

 Aristoiesmus Seeley, Proc. Roy. Soc, vol. 59, pp. 167-169. 

 AristoJesmus Seeley, Quart. Journ. Geol. Soc, vol. 56, pp. 620-645. 

 Sclerosaurus v. Huene, Geol. u. pal. Ablmdlg. n. b., Bd. VI, Heft I. 



The specimen was found in the Buntersandstein near Rheinfelden. 



Skull completely roofed over and the posterior bones carrying prominent spines, 

 especially the squamosal, quadrate, and quadratojugal. Skull flatter than that of 

 Elginia. Occipital condyle hemispherical, as in Pareiasaurus and Elginia. Von 

 Huene figures large palatal vacuities in his reconstruction of the palate, but there 

 seems no warrant for this in the specimen or from analogy with other Pareiasaurians. 

 External nares, terminal and vertical. Seven blunt conical teeth preserved in the 

 maxillary and four rather sharper ones in the premaxillary, but it is not certain that 



Fig. 14. — Outline reconstruction of Sclerosaurus. After von Huene. 



this is the complete number. Surface of the skull smooth with the exception of the 

 projections at the back of the skull. Seeley and Wiedersheim report twenty-two 

 presacral vertebrae, v. Huene twenty-one. Vertebrae notochordal and shorter on 

 the lower line than the upper, leaving spaces for intercentra; a sharp keel on the 

 lower surface of the centrum gives it a triangular section. Neural spines short, 

 with the upper ends expanded and rugose where they came in contact with the 

 dorsal plates. Transverse processes strong and heavy with single articular faces 

 for the single-headed rib. Three sacral vertebrae, the ribs of the anterior and pos- 

 terior being larger than the middle one. Shoulder girdle with free scapula, cora- 

 coid and precoracoid, cleithrum probably present. Carpus with two rows of bones, 

 a proximal, consisting of radiale and ulnare, and a distal with four elements. In 

 the pelvis the pubis and ischium meet each other at an angle and resemble more 

 the same bones in Pareiasaurus than in the Diadectidce and Captorhintda?; the ilium 

 resembles that of Dicynodon. Astragalus and calcaneum united in a single large 

 element, the distal row not ossified. Dorsal armor consisting of six rows, the inner 

 two rows lying on either side of the neural spine and overlapping the postzyga- 

 pophyses; each with a dorsal keel and a pitted sculpture. Outer rows of smaller 

 irregular plates. 



