"The oldest known primate skeleton and early haplorhine
evolution." Nature published online 5 June 2013.
Four scientists present evidence that the 47-million-year-old Darwinius masillae is not a haplorhine primate like humans, apes and monkeys, as the 2009 research claimed.
The scientists who last year formally described Darwinius concluded that it was an early haplorhine, and even suggested that Darwinius and other adapiform fossils "could represent a stem group from which later anthropoid primates evolved."
They further argue that Darwinius lacks most of the key anatomical features that could demonstrate a close evolutionary relationship with living haplorhines (apes, monkeys, humans, and tarsiers).
For instance, haplorhines have a middle ear with two chambers and a plate of bone that shields the eyes from the chewing muscles.
After evaluating 360 morphological features, Seiffert decided that, although the adapiforms shared certain traits with anthropoids--the loss of a third upper and lower premolar, for example--those characteristics had arisen more than once among primates and were "most parsimoniously interpreted as evolutionary convergences" Ida was not a haplorhine
anthropoid, in other words, but rather a strepsirrhine (a group including lemurs and lorises) that "left no known descendants."
Early primates soon diverged into three major lines: the strepsirhine primates noted above, and a diurnal haplorhine
line that led both to anthropoid primates (monkeys, apes, and humans) and to a tarsier line that reverted from a diurnal adaptation to become a highly specialized nocturnal predator with large eyes as a readaptation to dim light.
Divergence between strepsirrhines (lemurs and lorises) and haplorhines
(tarsiers and anthropoids) is correlated with intense volcanic activity on the Lebombo Monocline in Africa about 180 million years ago.