The generic nameNuciruptor rubricae is derived from theLatinnuci ("nut") andruptor meaning "to break".[2] The specificrubricae refers to the red beds where the fossils have been found.[3]
A lower mandible fossil ofNuciruptor was discovered in the El Cardón redbeds of the Cerro Colorado Member of theVillavieja Formation, Honda Group, just below the San Francisco Sandstone, which has been dated to theLaventan, about 12.8 ± 0.2 million years old.[2] From the same locality, fossils ofSaimiri annectens were recovered.[4]
Nuciruptor resembles living pitheciins in having elongated, procumbent, and styliform lowerincisors with very weak lingual heels. Moreover, as in living pitheciins, the incisors are set in a procumbently oriented mandibular symphysis, and its mandibular corpus deepens appreciably under the molars. At the same time,Nuciruptor does not possess several of the distinctive synapomorphies of extant pitheciins.Nuciruptor remains more primitive than living pitheciins in that no diastemata separate its lower incisors from thecanines. Its lower canines retain the primitive structure in not having a sharply defined protocristid. P2 is not a robust or high-crowned tooth and does not have a metaconid. Neither are the otherpremolars molarised by the addition of large talonids.[5] The estimated weight ofNuciruptor was 2,000 grams (4.4 lb).[6] The genus shows similarity with another fossil primate from La Venta,Cebupithecia.[7]
AsCebupithecia,Nuciruptor is thought to be an ancestral saki (Pitheciidae).[8][9]
The Honda Group, and more precisely the "Monkey Beds", are the richest site forfossil primates in South America.[10] The monkeys of the Honda Group arguably were living in habitat that was in contact with theAmazon andOrinoco Basins, and that La Venta itself was probably seasonally dry forest.[11]
