Endocranial Morphology and Paleoneurology in Notoungulates: Braincast, Auditory Region and Adjacent Intracranial Spaces

MARTÍNEZ, GASTÓN; MACRINI, THOMAS; DOZO, MARÍA TERESA; VERA, BÁRBARA; GELFO, JAVIER

Paleoneurology of Amniotes

Springer Nature

Año: 2023; p. 761 - 809

Notoungulates are the most diverse group of South American native ungulates(SANUs). A review of the endocranial morphology of notoungulates ishere provided, concerning the braincast, the auditory region and otherintracranial spaces associated to the caudal vasculature (e.g. internal carotidartery and dural sinuses), whose study have been notably stimulated by theCT scanning techniques. A bulged temporal lobe, the presence of an obliquesulcus (suprasylvian sulcus), and the position of the rhinal fissure roughlydifferentiate the notoungulate braincast from that of other SANUs. Within theorder, braincasts range from almost lissencephalic and comparatively reducedin height (e.g. Notostylops murinus), to convoluted, anteriorly wide anddorsoventrally more developed (e.g. later diverging toxodonts). Concerningthe relative brain size, and pending a precise assessment of the brain size/bodysize allometry for notoungulates, no evidence of marked increase during thelate Eocene-Pleistocene lapse emerges from the data. Additionally, inferenceson sensory capabilities are discussed based on the size of the olfactory bulbs,piriform and temporal lobes, and dimensions of the osseous labyrinth. Despiteimprovements in knowledge during the last two decades on most of the abovementioned topics, there is still much work to be done on such an iconic groupof SANUs.