The origin of chalicotheres (Perissodactyla, Mammalia)

Abstract

ABSTRACT. Description of a new genus of perissodactyl, Protomoropus, for the species 'Hyracotherium' gabuniai Dashzeveg and its inclusion with a diversity of other primitive perissodactyls in a cladistic analysis results in the following higher order changes to our knowledge of perissodactyl phylogeny. Protomoropus is sister taxon to the Chalicotheriidae plus Lophiodontidae, which themselves are confirmed as sister groups. The previously monofamilial superfamily Chalicotherioidea is extended to include all three taxa. Paleomoropus and Lophiaspis are shown to be primitive lophiodontids. Various genera of the Isectolophidae are shown to be stem members of a clade that includes chalicotheres and lophiodonts. The infraorder Ancylopoda is extended to include them. Inclusion of isectolophids in the Ancylopoda rather than as stem tapiromorphs results in the break up of the clade Tapiromorpha. Instead, the modern perissodactyl groups, comprising the horse superfamily Equoidea and that of the rhinos and tapirs, the Ceratomorpha (here reduced in rank to parvorder), form a new clade which is here named infraorder Euperissodactyla nov. The Brontotheriidae form the sister group to Ancylopoda plus Euperissodactyla. The clade comprising Ancylopoda plus Euperissodactyla is named suborder Lophodontomorpha nov. The Chalicotherioidea and Chalicotheriidae evolved in Asia. The Lophiodontidae arose following dispersal from Asia to North America. Dispersal continued to Europe, where the family radiated.

Stratigraphic and micropaleontological constraints on the middle Eocene age of the mammal-bearing Kuldana Formation of Pakistan

“…Overall, the tapiromorph assemblage from the upper part of the upper Ghazij Formation is most similar to that from the Wutu fauna in the Homogalax interval, suggesting a potentially similar age for both faunas. The faunas from the Orientolophus interval contain very primitive taxa such as the isectolophid Orientolophus and the basal chalicotherioid Protomoropus (Ting 1993;Hooker and Dashzeveg 2004). These forms are clearly more primitive than any of the Ghazij taxa and possibly ancestral to them, suggesting that the fauna from the upper part of the upper Ghazij Formation is decidedly younger than the early Bum− banian Orientolophus interval.…”

“…The poorly known Orientolophus was described from the earliest Eocene Lingcha Formation in South China (Ting 1993). Orientolophus is generally consid− ered to be the most primitive isectolophid known (Froehlich 1999;Hooker and Dashzeveg 2004), and is more primitive than Gandheralophus in terms of a weaker parastyle and a weaker metaloph and hypolophid, as well as stronger upper molar conules and m1-2 hypoconulids. Karagalax was de− scribed by Maas et al (2001) from the Barbora Banda locality in Pakistan, and is probably early middle Eocene in age (Gingerich 2003).…”

Early Eocene fossils suggest that the mammalian order Perissodactyla originated in India

“…Because molecular studies indicate that perissodactyls and afrotheres share a distant common ancestry among placentals, we included a Cretaceous eutherian and a marsupial as outgroups. Characters were compiled from published sources 4,5,11,44,45 . In many cases, these characters were modified and new characters and character states were developed.…”

New Craniodental Materials of Litolophus gobiensis (Perissodactyla, “Eomoropidae”) from Inner Mongolia, China, and Phylogenetic Analyses of Eocene Chalicotheres

“…The Bumbanian Protomoropus gabuniai from Naran Bulak Formation, Naran Bulak area, Mongolia, is based on the holotype and a paratype originally identified as ''Hyracotherium'' gabuniai, specimens originally referred to Homogalax namadicus, and new material of a maxilla with P4-M3 (Hooker and Dashzeveg, 2004). However, the same new material was also assigned to Homogalax namadicus by other authors (Lucas and Kondrashov, 2004).…”

“…However, the same new material was also assigned to Homogalax namadicus by other authors (Lucas and Kondrashov, 2004). We follow Hooker and Dashzeveg (2004) regarding the identification of those specimens. As observed by Hooker and Dashzeveg (2004), Litolophus differs from Protomoropus in having ''a more mesial position of the ectoloph attachment of the metaloph, posteriorly extended protocone on the molars, more closely approximated paracone and metacone on P4, and autapomorphic elongation of the molars and reduction in size of the premolars.''…”