Pseudoprepotherium is an extinct genus of sloths of the family Mylodontidae. It was widespread across northern South America during the Early to Late Miocene epoch around 21 to 5.3 million years ago. Fossils of the animal have been found in Brazil, Venezuela, and Peru. Pseudoprepotherium lived in a tropical climate with a water-rich environment. Their known remains are limited to limb bones, except for a few skulls and teeth. Based on these remains, they were most likely medium to large-sized mylodontid. The genus was described in 1961 and currently contains three species, which were originally assigned to the genus Prepotherium.
Description Pseudoprepotherium is a medium to a large-sized member of the family Mylodontidae. The material documented so far consists mainly of limb bones but includes individual skulls and remains of jaws. Body weight of around 550 kg is reconstructed for the smaller relatives using a thigh bone around 42 cm long. Large molds with femur lengths of 56 to 59 cm are estimated to have weighed between 1.52 and 1.86 tons A surviving skull has a length of 43 cm, but is partly deformed laterally, which means that only a few features are recognizable. A bent profile line was characteristic. Because of this, the rostrum and the cranium were at an angle of 130° from each other. At the occipital bone, the articular processes for the cervical spine protruded with little prominence. The alveoli of the five teeth per row of teeth typical of mylodon can be seen on the upper jaw, but the two front teeth are poorly preserved. From the alveoli, it can be seen that the rearmost tooth was the smallest and possibly had two lobes (bilobate). The fourth and third teeth were each elongated. As is usual in the Mylodontidae, the femur stood out due to its flat, board-like shape in front and behind. The shaft was slightly curved at the side. There was only a shallow indentation between the spherical condyle and the greater trochanter. The great calculus was massive but not very elevated. Its apex was at or slightly below the level of the condyle and thus lower as compared to Magdalenabradys. The lesser trochanter was only weakly developed. The third trochanter appeared as a slight bulge around the middle of the shaft and continued as an edge to the lower end of the joint. The position roughly matched that of Magdalenabradys, but was lower than that of Eionaletherium. The lower end of the joint was partially rotated out of the shaft axis. The inner articulated roller became larger than the outer. The lower one was somewhat narrower than the upper end of the joint. A tibia associated with a femur about 56 cm long measured 29 cm in length. This corresponds to the ratio known in other mylodons of extremely short lower sections of the hindlimbs compared to the upper ones. As a result, the tibia was only half the length of the femur. The proportions are broadly similar to Lestodon, while Glossotherium possessed even shorter lower leg sections. The shaft of the tibia narrowed sharply in the middle while the ends of the joints protruded far.
Paleobiology Due to its far northern distribution in South America, Pseudoprepotherium was probably more adapted to tropical climate conditions. The find locations in the deposit units of the Urumaco sequence also speak in favor of this. A possibly related Pseudoprepotherium tibia from the Middle Miocene Pebas Formation near Iquitos in the western Amazon Basin, about 23 cm long, shows more than 60 bite marks, the size and arrangement of which suggest that they were probably caused by a juvenile Purussaurus. The size of the bite marks, from three to 15 mm in diameter, allows the length of the attacker to be reconstructed to be around 4m. It caught its prey with its front teeth. Attacks on the hind legs are also known by modern crocodiles.
Classification
… excerpt ends here. Continue reading the full article.
