Thalassocnus

Thalassocnus Temporal range: Late Miocene–Late Pliocene PreЄ Є O S D C P T J K Pg N
Thalassocnus skeleton in its hypothetical swimming pose, Muséum national d'histoire naturelle, Paris
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Subclass:	Theria
Infraclass:	Eutheria
Superorder:	Xenarthra
Order:	Pilosa
Family:	†Nothrotheriidae
Subfamily:	†Thalassocninae
Genus:	†Thalassocnus de Muizon & McDonald, 1995
Species
†Thalassocnus antiquus †Thalassocnus natans †Thalassocnus littoralis †Thalassocnus carolomartini †Thalassocnus yaucensis

File:Thalassocnus skeleton.jpg

Closeup of Thalassocnus skull, Muséum national d'histoire naturelle, Paris

Thalassocnus is an extinct genus of apparently semiaquatic (for the geologically oldest species) or fully aquatic (for the geologically most recent species) marine sloth from the Miocene and Pliocene of South America. Fossils found to date have been from the coast of Peru and Chile. They were apparently grazers of sea grass and seaweed. The various species of this genus provides the best-documented case of gradual adaptation to a secondarily aquatic lifestyle. This is documented both at the morphological level, such as a progressive flattening of the radius and at the microanatomical level, which shows a progressive increase in compactness of the long limb bones and ribs. They may have used their powerful claws to anchor themselves to the sea floor to facilitate feeding, similar to the behavior of the marine iguana.

The older species, T. antiquus, T. natans and T. littoralis, show indications of partial adaptation to grazing, with little evidence of transverse mandibular movement while eating, and abundant dental striae indicating ingestion of sand from feeding on vegetation stranded on beaches or in shallow (less than 1 m deep) water. The later species, T. carolomartini and T. yaucensis were apparently specialized grazers that fed in deeper water; they display distinct evidence of transverse mandibular movement and lack dental striae.

	Megatheriidae Hapalops Nothrotheriidae Nothrotheriinae Nothrotherium Nothrotheriops Thalassocninae T. antiquus T. natans T. littoralis T. carolomartini T. yaucensis

Presumed phylogeny of Thalassocnus, with relationship to several nothrotheriines and a megatheriid.

References

• William F. Perrin, Bernd Wursig, and J. G.M. Thewissen. Encyclopedia of Marine Mammals, Pg.72.
• World Encyclopedia of Dinosaurs & Prehistoric Creatures: The Ultimate Visual Reference To 1000 Dinosaurs And Prehistoric Creatures Of Land, Air And Sea ... And Cretaceous Eras (World Encyclopedia) by Dougal Dixon