Only adapids and omomyids have turned up at North American and European sites of comparable age; several African simians dating to about 40 million years ago have been discovered since 1988.
The proposed Chinese simian, dubbed Eosimias sinensis, displays several jaw and tooth features that distinguish it from adapids and omomyids, Beard argues.
Various investigators have promoted either omomyids or adapids living between 55 million and 36 million years ago as simian ancestors (SN: 1/12/91, p.20).
Dissenters, such as Simons, view the adapids
as more likely simian ancestors.
In particular, Ciochon's group stresses the similarities between Amphipithecus, and hence anthropoids, and a family of lower primates called adapids, which led to modern-day lemurs and lorises.
"But [even] if it is, I don't think it shows that adapids are related to anthropoids," he says.
Philip Gingerich, director of the Museum of Paleontology at the University of Michigan in Ann Arbor and a strong proponent of adapid origins, is greatly encouraged by the new paper.