A new orang-utan relative from the Late Miocene of Thailand

Abstract

The fossil record of the living great apes is poor. New fossils from undocumented areas, particularly the equatorial forested habitats of extant hominoids, are therefore crucial for understanding their origins and evolution. Two main competing hypotheses have been proposed for orang-utan origins: dental similarities support an origin from Lufengpithecus, a South Chinese and Thai Middle Miocene hominoid; facial and palatal similarities support an origin from Sivapithecus, a Miocene hominoid from the Siwaliks of Indo-Pakistan. However, materials other than teeth and faces do not support these hypotheses. Here we describe the lower jaw of a new hominoid from the Late Miocene of Thailand, Khoratpithecus piriyai gen. et sp. nov., which shares unique derived characters with orang-utans and supports a hypothesis of closer relationships with orang-utans than other known Miocene hominoids. It can therefore be considered as the closest known relative of orang-utans. Ancestors of this great ape were therefore evolving in Thailand under tropical conditions similar to those of today, in contrast with Southern China and Pakistan, where temperate or more seasonal climates appeared during the Late Miocene.

A new Late Miocene great ape from Kenya and its implications for the origins of African great apes and humans

“…They are smaller than N. nakayamai, except for Ouranopithecus (24,25) and S. parvada (26). Among the Late Miocene Eurasian hominoids, Ankarapithecus, Sivapithecus, Lufengpithecus, and Khoratpithecus are broadly considered to belong to the Pongo clade (9,10). Although the specimens of Lufengpithecus are heavily deformed, Ankarapithecus, Sivapithecus, and Khoratpithecus have more robust mandibular bodies, which become very thick posteriorly and form a very wide extramolar sulcus between the M 3 and ascending ramus.…”

“…However, its dental morphology is so specialized that its phyletic position is unclear. Although there is a variety of Late Miocene hominoids in Eurasia, the majority of them are likely to belong to the Pongo clade (9,10). Ouranopithecus macedoniensis has often been considered to resemble African great apes (11,12), but it is known only from the Late Miocene of Greece, and its phyletic relationships are not yet agreed on (13).…”

Juvenile hominoid cranium from the late Miocene of southern China and hominoid diversity in Asia

“…Although the absence of Pongo apomorphies in YV0999 does not absolutely preclude Lufengpithecus being a member of the Pongo clade, these absences take on added significance in light of the fact that most of the key derived facial skeletal features of Pongo are expressed in the nearly contemporaneous Sivapithecus sivalensis from the late Miocene Siwaliks of South Asia (13,22), whereas at least one is expressed in Khoratpithecus piriyai from the late Miocene site of Khorat in Thailand (24,25) and K. ayeyarwadyensis from the Irrawaddy Formation in Myanmar (26). Sivapithecus shares all of the derived features of Pongo listed in Table 1.…”

The first Neogene record ofZygolophodon(Mammalia, Proboscidea) in Thailand: implications for the mammutid evolution and dispersal in Southeast Asia

“…However, the late late Miocene new rhino species, Aceratherium porpani, from the same sand pit as the Zygolophodon materials, is consistent in its chronological implications with the faunal sample from Tha Chang sand pit no. 8, which includes such taxa as Khoratpithecus piriyai and Merycopotamus thachangensis (Chaimanee et al, 2004(Chaimanee et al, , 2006Hanta et al, 2005Hanta et al, , 2008Deng et al, 2013). The occipital surface of the Tha Chang rhino is slightly inclined posteriorly or nearly vertical and the cheek teeth are subhypsodont (Deng et al, 2013).…”

“…In particular, zygodonts have never been reported from Southeast Asia, althoughSinomastodon aff. yangziensis, and Elephas (von Koenigwald, 1959;Buffetaut et al, 1988;Tassy, 1990;Tassy et al, 1992;Saegusa et al, 1999;Nakaya et al, 2002Nakaya et al, , 2003Chaimanee et al, 2004;Kunimatsu et al, 2004;Pickford et al, 2004;Suganuma et al, 2006;Thasod, 2007;Duangkrayom et al, 2010;Thasod et al, 2012).…”