A recent study, in collaboration with a team of paleontologists of Sapienza University, identified new elements in the biology and feeding behavior of a late Pleistocene giant sloth (Catonyx tarijensis) from the Bolivian Altiplano. This mammal was of much larger size than current species living in Central and South American tropical forests, quadrupedal and unable to climb trees, but not really much different.

Thanks to computerized tomography, the researchers analyzed the inner and outer anatomy of a complete skull of a specimen living in the Bolivian highlands. They examined the hyoid bone, but also the digital 3D models of the brain cavity, cranial nerves and paranasal sinuses.
They observed how this sloth species, now completely extinct, had reduced paranasal sinuses compared to other fossils, showing, instead, similarities with those found in the modern Hoffman's two-toed sloth (Choloepus hoffmanni), a small (6-7 kilograms) extant arboreal form.

Moreover, the results of the 3D analyses of the Catonyx's nervous system show reduced growth in the hypoglossal nerve, the motor control of the extrinsic muscles of the tongue which, together with a very robust hyoid bone, indicates limited tongue protrusion probably compensated by the prehensile capabilities of its lips. From this and other morphological elements, the researchers have been able to confirm that Catonyx tarijensis was a browsing species, typical of environments with variegated vegetation.

The tomographic analyses were carried out by Dr Dawid A. Iurino at the PaleoFactory laboratory of the Department of Earth Sciences of Sapienza University, coordinated by Prof Raffaele Sardella. The project was initially launched by Dr Alberto Boscaini of CONICET (Argentina) in collaboration with the National Natural History Museum of La Paz (Bolivia), and the University of Tennessee and Chattanooga (USA).

"The application of tomography – explains Raffaele Sardella – keeps disclosing precious anatomical details with the potential to provide palaeontologists with information helpful to recreate, with even more precision, the paleoecology of these fascinating mammals. They are just the tip of the iceberg hiding a longer and articulate evolutionary history, which roots go back to the Eocene."
 

References: 

Cranial Anatomy and Paleoneurology of the Extinct Sloth Catonyx tarijensis (Xenarthra, Mylodontidae) From the Late Pleistocene of Oruro, Southwestern Bolivia - Alberto Boscaini, Dawid A. Iurino, Bernardino Mamani Quispe, Rubén Andrade Flores, Raffaele Sardella, François Pujos and Timothy J. Gaudin - Frontiers in Ecology and Evolution, 07 April 2020 | https://doi.org/10.3389/fevo.2020.00069

Further Information 

Raffaele Sardella
Department of Earth Sciences
raffaele.sardella@uniroma1.it