Species: Tremacebus harringtoni
Tremacebus harringtoni is a species dating to the early Miocene or possibly the late Oligocene. It was found in Argentina.
T. harringtoni has a dental formula of 188.8.131.52 (upper), a short, broad snout, vertical nuchal plane, broad interorbital distance, and intermediate sized, laterally directed, orbitals (larger than known diurnal species, but smaller than known nocturnal species). It also has a more posteriorly directed foramen magnum. One point of controversy concerning T. harringtoni relates to the amount of postorbital closure. It was originally thought that T. harringtoni had incomplete postorbital closure. Later research indicated that postmortem breaking was the cause of the incomplete closure. Some researchers have suggested that T. harringtoni is directly ancestral to either Aotus (the Owl Monkey) or Callicebus (the Titi Monkey). At any rate, here is another picture of the skull:
Both of these pictures came from DigiMorph – run by the University of Texas at Austin. DigiMorph also has an extensive bibliography on T. harringtoni (just click on the “Literature and Links” tab…