DISCOVERY OF THE TITANOTHERES AND ORIGINAL DESCRIPTIONS 



175 



Sphenocoelus uintensis Osborn, 1895 



Cf. Sphenocoelus uintensis Osborn, this monograph, page 419 



Original reference. — Am. Mus. Nat. Hist. Bull., vol. 

 7, pp. 98-102, figs. 12-15, 1895 (Osborn, 1895.98). 



Type locality and geologic horizon. — Northeastern 

 Utah; Metarhinus zone (Uinta B 1). 



Holotype. — "Represented by the posterior portion 

 of a slvull" (Am. Mus. 1501). (See fig. 111.) 



convex sagittal ridges. The occiput is rather broad, and below 

 it are two widely set occipital condyles which are directed 

 obliquely downward and backward. On either side of these 

 the exoccipitals extend down into obtuse paroccipital processes, 

 which are closely joined to the post-tympanics. The external 

 auditory meatus is open inferiorly. In front of this the post- 

 glenoid process faces somewhat inward; the glenoid facet is 

 L-shaped, two narrow arms extending out upon the squamosal, 

 and a broad arm descending upon the postglenoid. The dis- 

 tinctive feature of the zygoma is the presence of a deep depres- 

 sion just behind the lateral arm of the glenoid facet. 



FiGUKE 111. — Type (holotype) of Sphenocoelus uintensis 

 Posterior half of cranium. Am. Mus. 1601. After Osborn, 1895. 



, Basal view; Aa, top view; As, occipital view; 

 natural size. 



fiew of left side. One-third 



Specific characters. — Osborn writes: 



This new genus is represented by the posterior portion of a 

 skull, which is distinct from any cranium known to the writer. 

 Its most distinctive feature is the presence of a pair of pits in 

 the floor of the skull upon either side of the narrow presphenoid 

 [basisphenoid]. These pits were at first mistaken for the for. 

 lac. media, but more careful investigation shows that they are 

 roofed over by bone and apparently do not communicate at 

 all with the cranial cavity. The pit on the right side is per- 

 fectly preserved and clearly exhibits these characters. The 

 pits are 42 millimeters long, 14 millimeters wide, and' 2 milli- 

 meters deep. 



The skull has a long, narrow cranium surmounted posteriorly 

 by a sagittal crest, which diverges anteriorly into two decidedly 



Skull measurements 



Millimeters 



Width across zygomatic arches 230 



Height of occiput 142 



Breadth 117 



Breadth of occipital condyles 130 



Basioccipital to top of sagittal crest 114 



The foramina of the skull are related to those of the Peris- 

 sodactyla, for there is a long alisphenoid canal, upon the outer 

 side of the anterior opening of which is the foramen. Just 

 behind the posterior opening of the canal is the foramen ovale, 

 and between these foramina are the two pits above mentioned. 

 This foramen is separated by a very wide plate of bone from the 

 for. lac. medium, which is partly filled by the periotic mass. 



