Pliobates cataloniae lived 11.6 million years ago.
Researchers have identified a new species of small ape that existed before the evolutionary split of humans/great apes (hominids) and gibbons (the 'lesser apes' or hylobatids).
The discovery -- a partial skeleton found during the construction of a landfill in Barcelona, Abocador de Can Mata, in 2011 -- fills a gap in the fossil record, giving researchers another piece of information about the evolution of great and small apes.
Named Pliobates cataloniae, the new species has important implications for reconstructing the last common ancestor of the two groups (the living hominoids). Pliobates cataloniae lived 11.6 million years ago.
"This fossil discovery is providing a missing chapter to the beginning of ape and human history," said Sergio Almecija from the George Washington University (GW).
Anthropologists previously thought that great apes were present before small apes, mainly due to the lack of small apes and ancient gibbons in the fossil record.
"We used to think that small apes evolved from larger-bodied apes, but this new species tells us that small and large apes may have co-existed since hominoids originated," Mr Almecija explained.
"Alternatively, Pliobates might indicate that great apes evolved from gibbon-size ape ancestors," the researcher added.
Scientists concluded the fossil remains belong to an adult female that weighed between nine and 11 pounds, consumed soft fruits and moved through the forest canopy by climbing and suspending below branches.
"These remains clearly belong to an ape, but they are so small. Then we realised, maybe we are looking at this the wrong way. Maybe some early ape ancestors were smaller than we thought," Mr Almecija said.
The findings were published in the journal Science.