First digital cranial endocast of the horned armadillo Peltephilus (Mammalia: Xenarthra): Neuroanatomy and morphology of the caudal cranium

GONZÁLEZ RUIZ, L.R.; GROHE, C.; MACPHEE, R.D.; DOZO, M.T.

París

Congreso; 5th International Paleontological Congress; 2018

The Peltephilidae or ?horned armadillos? were a group of cingulates (?armored xenarthrans?) that notably differ from typical dasypoid armadillos. Peltephilids are recorded exclusively in South America from the Eocene to the Miocene; skulls are known from the Oligocene and Miocene. We provide the first description of the cranial endocast of Peltephilus Ameghino YPM PV 15391 (early Miocene of Patagonia, Argentina), based on a three-dimensional reconstructions of the brain and ear region extracted from high- resolution X-ray computed microtomography imagery. We describe the olfactory bulbs, cerebrum (including fissures and sinuses), cerebellum, and we calculate their relative volumes. We identify the morphological origins of cranial nerves I, II, V, VII, VIII and IX. The neuromorphology of Peltephilus is similar to that of Dasypodidae as revealed by endocasts. However, the cerebral hemispheres of Peltephilus exhibit a pronounced convexity towards the parietal region and a marked widening caudally, indicating a more expanded neocortex and pyriform lobe. We also describe the inner ear (bony labyrinth, including cochlea, vestibule and semicircular canals) and the middle ear (malleus, incus and stapes). We describe the caudal cranium (basicranium and overlying cranial vault) in regard to suture placement and trackways for blood vessels and nerves. According to current phylogenetic reconstructions, peltephilids are the earliest- diverging cingulates for which cranial information exists. Our detailed description of this taxon will help toilluminate character evolution within Cingulata.