636 TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



Comparative measurements of limh hones referred to LimnoTiyops, Manteoceras, and MesatirTiinus, in millimeters 



a Estimated. 



SECTION 4. THE POSTCRANIAL SKELETON OF UPPER 

 EOCENE TITANOTHERES 



SUBFAMILY DOLICHORHININAE 



Slender to mediportal titanotheres of the upper 

 deposits of- the Bridger Basin, Wyo., the deposits of 

 the Washakie Basin, Wyo., and the deposits of the 

 Uinta Basin, Utah. Feet mesatipodal to brachypodal. 

 Ungual phalanges truncate. Tibia slender to short. 

 Astragalus narrow. 



The general adaptations of the limbs and other 

 parts of the skeleton of the Dolichorhininae have 

 already been stated. The main features of the adap- 

 tive radiation of the skulls and feet and the geologic 

 succession are as follows: 

 Mesatirhinus: Mesaticephalic; mesatipodal; Bridger C and D, 



Washakie A. 

 Metarhinus: Mesaticephalic; mesatipodal; Washakie B, Uinta 



B 1. 

 Dolichorhinus: Dolichocephalic; brachypodal; Washakie B, 



Uinta B 2. 



In the treatment of these forms it is convenient to 

 begin with the tapir-like Mesatirhinus, on the whole 



the most primitive and central, and then to describe 

 MetarJiinus, a dwarfed, aberrant form. This will be 

 succeeded by the description of the extremely long- 

 headed Dolichorhinus, which is further distinguished 

 from the above animals by the possession of short feet. 



Mesatirhinus 



GENERAL FEATIJKES 



The parts of the skeleton of Mesatirhinus are 

 readily distinguished by the collector and student as 

 belonging to the most slender-limbed of the Imown 

 middle Eocene titanotheres. 



It is a striking proof of the generally heavy-bodied 

 proportions of the Eocene titanotheres that even 

 these most light-limbed members of the family are 

 somewhat heavier in their proportions than the 

 modern tapirs, animals which we are accustomed to 

 think of as rather heavy-bodied, forest-living, and 

 certainly not cursorial. In brief, Mesatirhinus in 

 limb structure is proportioned much as Tapirus in- 

 dicus, but the fore and hind feet were somewhat 

 broader and flatter, the back was more arched, the 



