ABSTRACT
The cranial anatomy of Palaechthon is more primitive than that known for other plesiadapoids, and its dental morphology approaches that of the Early Paleocene paromomyid Purgatorius unio, which is primitive enough to be a possible common ancestor of plesiadapoids and primates of modern aspect. The cranial measurements used to compare Palaechthon with extant mammals were subjected to a principal-components analysis. The details of the geologic setting of Palaechthon nacimienti were published by Alphadon wilsoni & F. S. Szalay. As Wilson & Szalay point out, the most marked differences between Palaechthon nacimienti and P. alticuspis are in the proportions of the antemolar teeth. The skull of Palaechthon nacimienti is too poorly preserved to permit a realistic reconstruction of the masticatory musculature, but, as pointed out in a preliminary report the anterior temporalis and medial pterygoid appear to have been especially well-developed.
