THE CONTROVERSY CONTINUES: AN OVERVIEW OF EVIDENCE FOR HYRACOIDEA-TETHYTHERIA AFFINITY

ABSTRACT Mammalian taxonomists recognize 20 orders of living mammals which are classified in Monotremata (1 order), Marsupialia (1 order), and Eutheria (18 orders). The latter two groups are more closely related to each other than either of them is to the former. Until about twenty years ago there was little agreement among mammalogists as to the major groupings within Eutheria; the now-famous “bush-like radiation” prevailed. Recent morphological and molecular evidence enable us to divide the clade Eutheria into subclades. Of particular interest to this study is the grouping of ungulate-related mammals because it contains three subsets whose phylogenetic positions are controversial. They are: (1) Tubulidentata, (2) Artiodactyla, Cetacea, and Perissodactyla; and (3) Hyracoidea, Proboscidea, and Sirenia. I will focus on the latter—Hyracoidea-Tethytheria (Proboscidea and Sirenia). Controversies on the relationships of Hyracoidea to other eutherian mammals have raged for over 200 years. They have been classif...