The phylogeny of the Rhinocerotoidea (Mammalia, Perissodactyla)

Abstract

A new phylogeny of the Superfamily Rhinocerotoidea is proposed, based upon an analysis of shared derivrd characters of the skull, teeth and skeleton. Hyrachyus is considered the primitive sister-taxon of the three rhinocerotoid families (Amynodontidae, Hyracodontidae, Rhinocerotidae) , and the amynodonts appear to be the sister-group of hyracodonts and rhinocerotids. The relationships of primitive hyracodonts and rhinocerotids are clarified. Menoceras and Pleuroceras (new Subfamily Menoceratinae) are removed from the Diceratheriinae, since they appear to be more closely related to higher rhinoceroses than they are to Dicel-atherium. Of the three major monophyletic groups of higher rhinocerotids (aceratherines, teleoceratines and rhinocerotines), the last two groups are more closely related to each other than either is to areratherines. Toxothertum and Schirotherozdes are tentatively removed from the Rhinocerotoidea and placed in the Lophiodontidae.

Evolutionary Transitions in the Fossil Record of Terrestrial Hoofed Mammals

“…These creatures were widespread around the Holarctic region of Eurasia and North America in the Paleocene and early Eocene and do indeed share many characters in common with perissodactyls. Phenacodonts, in turn, provide a link between perissodactyls and the most primitive clades of ungulates (Prothero et al 1988). Moving even closer to true perissodactyls, we have the late Paleocene Chinese fossil known as Radinskya, which is a close sister group to almost all the earliest perissodactyls (McKenna et al 1989).…”

“…However, when it comes to a third major hoofed mammal clade, the tethytheres (elephants, sirenians, and their kin), there is a conflict between molecular evidence which places them in the Afrotheria (Springer et al 2004;Murphy et al 2001) and the morphological and paleontological evidence that unites them with ungulates (Novacek 1986(Novacek , 1992Novacek and Wyss 1986;Novacek et al 1988;Prothero et al 1988;Prothero 1993;Gheerbrant et al 2005). We will not discuss this issue further here, because numerous laboratories and paleontologists are working to Fig.…”

“…The sister taxon of artiodactyls is still controversial (Prothero et al 1988;Theodor et al 2005;Rose 2006;Prothero and Foss 2007). Various candidates have been proposed, ranging from archaic ungulates like the huge predatory mesonychids to the coatimundi-like arctocyonid ungulates such as Chriacus.…”

“…My particular favorite is the evolution of the rhinoceroses, which I have studied for over 30 years (Prothero et al 1986Prothero , 2005. The earliest rhino relatives like Hyrachyus are barely distinguishable from contemporary tapiroids (Fig.…”

“…These include not only familiar groups such as the odd-toed perissodactyls (horses, rhinos, and tapirs) and even-toed artiodactyls (pigs, peccaries, hippos, camels, deer, giraffes, pronghorns, cattle, sheep, and antelopes) but also their extinct relatives. Depending upon which phylogeny is accepted, many paleontologists also consider elephants, sirenians, and hyraxes to be ungulates as well (see Novacek 1986Novacek , 1992Novacek and Wyss 1986;Novacek et al 1988;Prothero et al 1988;Prothero 1993;Prothero and Schoch 2002;Gheerbrant et al 2005). Nearly all of these groups have an excellent fossil record since the early Eocene because they are relatively large-bodied with robust bones so they fossilize easily, and they were widespread among the Holarctic continents.…”