DURHAM, N.C. -- The fossil teeth and jawbones of two new species oftiny monkey-like creatures that lived 37 million years ago have beensifted from ancient sediments in the Egyptian desert, researchers havereported.
They said their findings firmly establish that the common ancestor ofliving anthropoids -- including monkeys, apes and humans -- arose inAfrica and that the group had already begun branching into many speciesby that time. Also, they said, one of the creatures appears to havebeen nocturnal, the first example of a nocturnal early anthropoid.
The researchers published their discovery of the two new species --named Biretia fayumensis and Biretia megalopsis -- in an article in theOctober 14, 2005, issue of the journal Science. First author on thepaper was Erik Seiffert of the University of Oxford and OxfordUniversity Museum of Natural History. Other co-authors were ElwynSimons and Prithijit Chatrath of Duke University, William Clyde of theUniversity of New Hampshire, James Rossie of Stony Brook University,Yousry Attia of the Egyptian Geological Museum, Thomas Bown ofErathem-Vanir Geological in Boulder, Colo., and Mark Mathison of IowaState University. The research was supported by the National ScienceFoundation and the Leakey Foundation. Field work in Egypt wasfacilitated by the Egyptian Mineral Resources Authority and theEgyptian Geological Museum.
The researchers discovered the fossils over the course of the last fewyears at a site called Birket Qarun Locality 2 (BQ-2) about 60 milessouthwest of Cairo in the Fayum desert. BQ-2 has only beensystematically excavated for about four years, said Seiffert, incontrast to a much younger Fayum site, called L-41, which has beenexplored for the last 22 years by Simons and his colleagues.
"BQ-2 and surrounding localities have tremendous potential,which is exciting because they are so much older than other Fayumsites," said Seiffert. "There will certainly be much more informationabout early anthropoid evolution coming out of BQ-2 over the next fewyears." The sediments at BQ-2 lie nearly 750 feet below those of L-41and were dated at around 37 million years old by measuring telltalevariations in magnetic fields in the sediments due to ancientfluctuations in the earth's magnetic fields. According to Simons, otheranthropoids exist at BQ-2 and will soon be described,
The latest fossils of the new species consist of tiny teeth andjaws, whose shapes yield critical clues about the species whose mouthsthey once occupied. For example, a tooth root from the species Biretiamegalopsis is truncated, indicating that it had to make room for thelarger eyesocket of a nocturnal animal.
"These finds seem to indicate that Biretia megalopsis must have hadvery large eyes, and so was likely nocturnal," said Seiffert. "This hasnever been documented in an early anthropoid. The simplest explanationis that Biretia's nocturnality represents an evolutionary reversal froma diurnal ancestor, but that conclusion is based solely on the probablepattern of relationships. If down the road we find out that ourphylogeny was wrong, Biretia could end up being very significant forour understanding of the origin of anthropoid activity patterns."
According to Simons, analyses of the teeth of the two species clearlyplace them as members of a group called parapithecoids, known as "stem"anthropoids because they constitute the species of early creatures fromwhich the subsequent "crown" anthropoid line arose."The finding of these parapithecoids from such an ancient time confirmsthat crown anthropoids -- a group including all modern anthropoids --have their earliest known beginnings in Africa," said Simons. "Theyshow that findings by other researchers of isolated examples ofpossible higher primate fossils in Asia do not constitute evidence ofan ancestral crown anthropoid lineage there."
According to Seiffert, the latest findings help fill in the gap betweenlater anthropoids and the oldest undisputed anthropoid, calledAlgeripithecus, found in Algeria, which lived around 45 million yearsago. That species had been characterized by only a few teeth, whichprecluded significant insight into the species, said Seiffert.
Seiffert also noted that previously, the only evidence for anthropoidsat 37 million years ago in Africa was a single tooth, attributed to aspecies called Biretia piveteaui. What's more, the latest discoveriesof the two species suggest that a 57-million-year-old African primatecalled Altiatlasius from Morocco might even be the earliest anthropoidancestor.
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