Topic summary
Notoungulates
Extracted from the Wikipedia article Notoungulata.
Description and ecology
Notoungulates are united by a number of morphological characters of the skull, including a large epitympanic sinus (part of the inner ear) within the squamosal bone, as well as a "crochet" on the metaloph (a raised crest present on mammal teeth) of the upper molars. Notoungulates varied widely in body size, with early diverging notoungulates like Simpsonotus, and some hegetotheriid and interatheriid typotherians having a body mass of approximately 1–2 kilograms (2.2–4.4 lb), while the toxodontid Toxodon is suggested to have had a body mass exceeding 1,000 kilograms (2,200 lb). Typotheres generally occupied small-medium body size niches, while toxodontians were generally medium-large sized animals.