Digital cranial endocast of Pseudoplohophorus absolutus (Xenarthra, Cingulata) and its systematic and evolutionary implications

The endocast morphology of P. absolutus is similar to that of Pleistocene glyptodonts: large olfactory bulbs, a small cerebrum with a single neocortical sulcus, and a large cerebellum. However, the relative brain size is larger than in the Pleistocene forms, with values of the encephalization quotient (EQ) close to that of extant armadillos. A comparison between xenarthrans orders shows that Cingulata (glyptodonts and armadillos) have lower EQ values than Pilosa (sloths and vermilinguas).

This could possibly be related to certain restrictions and benefits imposed by the presence of the carapace in cingulates. Furthermore, because the carapace restricts the development of the cervical musculature that supports the skull, the small size of the brain in glyptodonts could be a trade-off (along with others) to reduce the weight of the skull.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP