Posted by: Loren Coleman on August 8th, 2009
What if some South American “sea monster” stories were actually based on sea-going sloths? It is a wild idea, right?
From Peru, the discovery of these animals was first announced in May 1995, but have they swam under the sonar of most “sea cryptid” discussions?
The species, as suggested by this image, is certainly unique-looking. The animal is one that most people don’t even realize once existed.
“Ground sloths (Gravigrada, Xenarthra) are known from middle or late Oligocene to late Pleistocene in South America and from late Miocene to late Pleistocene in North America. They are medium to gigantic in size and have terrestrial habits. Discovery of abundant and well preserved remains of a new sloth (Thalassocnus natans), in marine Pliocene deposits from Peru drastically expands our knowledge of the range of adaptation of the order. The abundance of individuals, the absence of other land mammals in the rich marine vertebrate fauna of the site, and the fact that the Peruvian coast was a desert during the Pliocene suggest that it was living on the shore and entered the water probably to feed upon sea-grasses or seaweeds. The morphology of premaxillae, femur, caudal vertebrae (similar to those of otters and beavers) and limb proportions are in agreement with this interpretation.” [Nature 375, 224 - 227 (18 May 1995)] The research was reported by C. de Muizon and H. Greg McDonald in Nature.
In 2004, de Muizon, McDonald, Salas and Urbina reported on the evolution of the feeding strategy of the sloths: “The aquatic sloth Thalassocnus is represented by five species that lived along the coast of Peru from the late Miocene through the late Pliocene. A detailed comparison of the cranial and mandibular anatomy of these species indicates different feeding adaptations. The three older species of Thalassocnus (T. antiquus, T. natans, and T. littoralis) were probably partial grazers (intermediate or mixed feeders) and the transverse component of mandibular movement was very minor, if any. They were probably feeding partially on stranded sea weeds or sea grasses, or in very shallow waters (less than 1 m) as indicated by the abundant dental striae of their molariform teeth created by ingestion of sand. The two younger species (T. carolomartini and T. yaucensis) were more specialized grazers than the three older species and had a distinct transverse component in their mandibular movement. Their teeth almost totally lack dental striae. These two species were probably feeding exclusively in the water at a greater depth than the older species.” Journal of Vertebrate Paleontology: Vol. 24, No. 2, pp. 398–410.