Metaxytherium

Metaxytherium is an extinct genus of dugong that lived from the Miocene until the end of the Pliocene. Fossil remains have been found in Africa, Asia, Europe, North America (Güines and Lagunitas Formations, Cuba), and South America (Paraná Formation, Argentina, Pirabas Formation, Brazil and Montera Formation, Peru).
Taxonomy.
There are eight species of "Metaxytherium" recognized as valid: "M. albifontanum", "M. arctodites", "M. crataegense", "M. floridanum", "M. krahuletzi", "M. medium", "M. serresii", and "M. subapenninum".
The genus "Thalattosiren" Sickenberg 1928 was once thought to be distinct from "Metaxytherium", but is now considered a junior synonym of "M. medium".
Evolution.
The relict species "M. subapenninum" represents the last stage of evolution of "Metaxytherium", showing an increase in body size and in tusk size and a rostral reinforcement responding to a long-term climatic cooling. These aquatic herbivores lived in warm coastal waters and inland waterways, feeding on seagrass. "Metaxytherium subapenninum" lived in the early and late Pliocene of Italy and Spain (age range: 3.6 to 2.588 million years ago). It is the only species of sirenians that lived in the northwestern coasts of the Mediterranean Sea in the Pliocene. It disappeared from the Mediterranean around 3 million years ago because of the progressive climate cooling. Fossils of these dugongs have been found, from the second half of the nineteenth century, in Piedmont, Emilia-Romagna, Liguria and Tuscany.
Paleobiology.
"Metaxytherium" lived in coastal waters and inland waterways, and there is evidence that they were preyed on by sharks. According to the University of Florida, "Metaxytherium floridanum" was one of the most common mammals found in Florida during the Neogene.