Mesotheriidae - Characteristics

Characteristics

Mesotheriids were small to medium sized notoungulates; larger forms were approximately the size of a sheep (Shockey et al., 2007). Additionally, the family is characterized by specializations of the teeth and skeleton. In the dentition, all mesotheriids have ever-growing incisors with enamel restricted to the anterior surface, a condition termed gliriform, as it also occurs in Glires (rodents and lagomorphs). The cheek teeth (premolars and molars) of mesotheriids are high-crowned (hypsodont) and in advanced members of the family, the cheek teeth are also ever-growing (Shockey et al., 2007). Mesotheriid skeletons are heavily built and show features associated with digging in living mammals. In particular, fossorial characteristics of mesotheriids include deeply fissured claws, presence of a sesamoid bone in the elbow and reinforcement of the pelvic girdle by addition of vertebrae to the sacrum and fusion of the sacrum and innominate (Shockey et al., 2007).