616 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



511, 513, 514, 520-522, 685). Measurements of the 

 limb bones are given above. 



Adaptive distinctions from Palaeosyops. — This mate- 

 rial enables us to further distinguish LimnoTiyops from 

 Palaeosyops. Manus and pes mesatipodal rather 

 than brachypodal; all limb bones more slender; 

 humerus relatively shorter; ulna more curved, with 

 distinctive olecranon process; manus narrow; lunar 



Figure 526. — Left manus, radius, and ulna of 

 Mesatirhinus pelenioni (doubtfully referred) 



Princeton Mus. 10013, upper Bridger, placed here for com- 

 parison with the manus of Limnohyops (fig. 527). Aj, 

 Front view of manus; As. top view of carpus; A3, inner 

 side view of carpus; Bi, distal view of radius and ulna; Ba, 

 proximal view of radius. One-third natural size. 



more acutely wedge-shaped distally. Magnum not 

 so wide; metacarpals more slender, femur with more 

 slender, curved shaft. Astragalus more slender, 

 with narrow sustentacular and cuboidal facets; cal- 

 caneum with narrow sustentaculum; metatarsals 

 narrow, Mts V more curved, metatarsals not expand- 

 ing distally; ungual phalanges truncate and square 

 distally. 



Palaeosyopine syngenetic characters. — Among the 

 more obscurely but syngenetically important char- 

 acters tending to ally this animal to Palaeosyops are 

 an astragalus having in common the following 

 peculiarities: A pit for a ligament on the internal or 

 tibial face just below the trochlear keel, a rather 

 sharp extension of the superior edge of the navicular 

 facet, a prominent protuberance near the distal end 

 of the tibial face, an inward projection of a sinus or 



fossa tending to separate the sustentacular facet 

 from the well-developed facet for the tibial sesamoid. 

 Other resemblances with the Palaeosyopinae are seen 

 in the subglobose shape of the distal facets of the 

 metapodials, in the marked anteroposterior depth of 

 the scaphoradial and other carpal facets, in the 

 depth of the proximal metapodial facets, and in the 

 femur with patellar facet facing anteriorly. 



Distinctions from the Manteoceras-Dolichorhinus 

 group. — Limnohyops is separated from Mesatirhinus 

 by the following characters: Limb bones of more 

 graviportal type; humerus longer, radius stouter, 

 more curved; ulna more curved and with larger 

 olecranon; manus somewhat broader and shorter 

 throughout; femur flatter, femur and tibia a little 

 stouter but of about the same relative length; astra- 

 galus broader, sustentacular facet farther in toward 

 the middle of the bone; sustentacular facet broader, 

 not so straight sided, forming a much more open angle 

 with the navicular facet, inferior astragalocalcaneal 

 facet smaller; a pit on the internal or tibial face of the 

 astragalus just below the trochlear keel; metatarsals 

 a little shorter and broader. Notwithstanding these 

 differences there are many general adaptive resem- 

 blances to Mesatirhinus, especially in the femur, 

 tibia, and metatarsals. The differences, however, 

 appear to indicate generic separation. 



Limnohyops is analogous to Manteoceras, especially 

 in the general characters and proportions of the 



Figure 527. — Manus, radius, and ulna of Limnohyops mono- 

 conus (doubtfully referred) 



Am. Mus. 11699, Bridger B 2. Ai, Right manus, front view; A2, right carpus, out- 

 side view; As, phalanges of median digit; At, distal view of radius and ulna. One- 

 third natural size. (Compare fig. 525.) 



humerus, tibia, astragalus, and pes — so much so, in 

 fact, that it was formerly referred provisionally to 

 that genus, from which, however, it is distinguished, 

 so far as known, by the following characters: Scaph- 

 oid deeper anteroposteriorly, trapezoid facet more 



