The earliest hylobatid (gibbon) from the Late Miocene of China

Ji et al. 2022 report,
“Yuanmoupithecus xiaoyuan, a small catarrhine from the Late Miocene of Yunnan in southern China, was initially suggested to be related to Miocene proconsuloids or dendropithecoids from East Africa, but subsequent reports indicated that it might be more closely related to hylobatids. Here, detailed comparisons of the material, including seven newly discovered teeth and a partial lower face of a juvenile individual, provide crucial evidence to help establish its phylogenetic relationships. Yuanmoupithecus exhibits a suite of synapomorphies that support a close phylogenetic relationship with extant hylobatids. Furthermore, based on the retention of several primitive features of the dentition, Yuanmoupithecus can be shown to be the sister taxon of crown hylobatids.

Yuanmoupithecus maxilla and cheek teeth.

Ji et al. 2022 continue:
“Currently then, Yuanmoupithecus represents the earliest known definitively identified hylobatid and the only member of the clade predating the Pleistocene. It extends the fossil record of hylobatids back to 7–8 Ma and fills a critical gap in the evolutionary history of hominoids that has up until now remained elusive. Even so, molecular estimates of a divergence date of hylobatids from other hominoids at about 17–22 Ma signifies that there is still a substantial gap in the fossil record of more than 10 million years that needs to be filled in order to document the biogeographic origins and early evolution of hylobatids.”

Figure 1. Earlier the LRT nested gibbons, rather than more chimp-like australopitheciens in the lineage of humans.

Based on molar sizes,
the authors estimate their Miocene gibbon weighed about six kilograms,the same as gibbons today. Molar structure indicates a gibbon-like fruit diet. Sahelanthropus (Fig 1) is from Chad (Africa) 7mya. Proconsul (Fig 1), from Kenya, is 2x-3x older.

References
Ji X et al (10 co-authors) 2022. The earliest hylobatid from the Late Miocene of China. Journal of Human Evolution 171:103251

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