PRONOMOTHER1UM 161 



dating Merycochoerus, a form that was undoubtedly either in the stem stock or a branch therefrom 

 in thz Promerycochcerus-Merycochcerus line, of which Pronomotherium is the terminal and most 

 specialized genus. 



Etymology: Pronomotherium (juts forward + beast, in allusion to the supposed proboscis of 

 this animal). 



Species: 



P. altiramus (Douglass) 1901. 



P. elrodi (Douglass) 1901. 



P. laticeps (Douglass) 1900. Genotype. 



P.madisonium (Douglass) 1901. 



P. siouense Sinclair 1915. 



P. species Gazin 1932. 



Pronomotherium altiramus (Douglass) 1901 

 Figs. 4, 114-116 



Original Reference: New species of Merycochcems in Montana. Pt. II. Amer. Jour. Sci. (4), XI, 

 pp. 73-75, fig. 1 {Merycochoerus altiramus). 



Synonyms: Merycochoerus altiramis Trouessart 1905; P. altiramum Douglass 1907; P. altiramis Matthew 

 1909. 



Type Locality: On the east side of the lower Madison Valley, about ten miles from Three Forks, 

 Gallatin County, Montana. 



Geologic Horizon: Upper Miocene (Madison Valley). The type lay in a layer or pocket of sand in the 

 bluffs. 



Types: Holotype, Cat. No. 759 CM., major part of right ramus, with well-preserved molars and pre- 

 molars. Collected by E. Douglass in 1895. Plesiotype, greater portion of skull, found in 1902 at the same 

 locality but imbedded five feet above the place where the holotype lay on the surface. In Douglass' description 

 (1907A) the skull bore Cat. No. 9740 A.M.N.H. by error, the correct number at that time being 9746 

 A.M.N.H. Subsequently the specimen was presented to the Carnegie Museum. Douglass had no doubt that this 

 skull and the holotype lower jaw were from one and the same individual. 



Specific Characters: The plesiotype skull, although of a young animal, represents the 

 largest known species. In comparison with the skull of P. laticeps, it is larger and longer, but not 

 much broader posteriorly. The zygomata are relatively light, with the posterior portions neither 

 high nor heavy, although the malar bones are moderately deep below the orbit. The skull does not 

 expand so abruptly near the orbits as it does in P. laticeps. The widening is more gradual back of 

 the premolars, so that the origin of the zygomatic arch above M 2 is not nearly so marked. The 

 nasals are missing, as is much of the superior contour of the face. The lacrimal fossa is very marked 

 and is nearly horizontal, as in P. laticeps. The frontals are flat. The round orbits are elevated. 

 The face is elongate in advance of the orbits, and the length of the dental series is greater than the 

 length of the skull posterior to M'\ The heavy, prominent temporal ridges join above the glenoid 

 surface to form a low, short sagittal crest. The supraoccipital crest overhangs the occipital condyles, 

 and the wings are directed almost sidewise. The brain case is anteroposteriorly short and moder- 

 ately wide. The palatonarial border lies behind M'\ The palate is long but not so wide as that of 

 P. laticeps. 



Douglass described the posterior part of the palate, which he considered to be of peculiar form, 

 as follows: 



It is concave between the last molars and a little posterior to them, and the borders are thick and rounded. 

 In the middle of this concavity is a low median longitudinal ridge. Posterior to this concave area is an area that 

 is convex antero-posteriorly and concave transversely, being bounded laterally by two antero-posteriorly flattened 

 processes. I cannot say how much of this portion of the skull belongs to the pterygoids and how much to the 

 palatines. 



