Abstract
The Saguinus oedipus group often has the sagittal crest in cranium, whereas the Amazonian tamarins possess no crest. This suggests that the former may be more developed than the latter in cranial dimensions related to the temporalis muscle. I choosed bizygomatic breadth (left zygion-right zygion), braincase breadth (left euryon-right euryon) and postorbital breadth (left frontosteion-right frontosteion) for the cranial dimensions, and S. geoffroyi and S. mystax for representatives of the S. oedipus group and Amazonian tamarins, respectively. I also measured maximum cranial length (prosthion - opisthocranion) for an indicator of the cranial size. S. geoffroyi has wider bizygomatic breadth relative to maximum cranial length than S. mystax, whereas the differences between the tamarins are insignificant in the postorbital breadth and braincase breadth. Thus, expansion of the zygomatic arch provides a space for enlargement of the temporalis muscles in S. geoffroyi, although males of Cebus apella, which have convergent temporal lines, obtain the larger space by deepening anterior part of the temporal fossa.
