Pezosiren
Pezosiren
Pezosiren is an extinct Seekuhgattung that, in the early Eocene, lived about 50 million years ago. Two discovered in anatomical composite partial skeletons and numerous individual bones of the genus have been found in the parish of St. James, 15 km south of Montego Bay in the west of Jamaica. Holotype is a partially preserved, 19 cm long lower jaw. The only described species of the genus is Pezosiren portelli. The generic name Pezosiren ( composition of ancient Greek. Πεζός Pezos, walking, running ' and Latin. Siren, Manatee ' ) means " current manatee " and was awarded because of the still fully trained Quadrupedie the animals. The Style epithet portelli honors the discoverer of the fossil deposit Roger W. Portell.
Features
Pezosiren had a barrel-shaped torso, a relatively short neck, a seekuhartigen head and four short legs. The animal was slightly larger than a very large house pig, reaching a length of 2.1 meters. The skull is about 26.5 cm long and 14.5 cm wide. A low sagittal crest differs Pezosiren of Prorastomus, the second Seekuhgattung from the family Prorastomidae. In Prorastomus but it could have been destroyed by erosion or during preparation. The lower jaw is long ( 19 cm ) and narrow. Incisors and canines were parallel. The dental formula is uncertain, but is probably 3 1 5 3, as in all Eocene sea cows. The first upper incisor was enlarged and formed a small tusk.
The spine consists of 7 cervical vertebrae, 20 thoracic vertebrae, lumbar vertebrae 4, 4 sacral vertebrae and probably about a dozen caudal vertebrae. From the tail close to the fuselage only the vertebrae are preserved. Axis and other cervical vertebrae were not shortened as in later and today's dugongs and more reminiscent of the cervical vertebrae paläozäner Stammhuftiere ( condylarths ). The dorsal vertebrae had high spinous processes, the likely positioning on a range neckband, which could carry the weight of the head and neck on land. The caudal vertebrae lacked the enlarged transverse processes later manatees. The ribs were thick ( Pachyostose ), composed of very dense bone tissue and served the aquatic live animals as ballast. The long, narrow pelvis and legs are reminiscent of the primitive ungulates. Just a few foot bones are obtained, it is uncertain whether from the front or hind foot. They are short and flat as the country live ungulate animals, and show no signs of a conversion of feet to fins.
Way of life
Made up of silt and sandstone deposits of the Chapelton Formation, from which the fossils were recovered from Pezosiren portelli come from a lagoon, a river delta or another river mouth shape. Pezosiren was with his four well-developed legs, its made up of several vertebrae sacrum (just a vertebrae in recent manatees ) and the strong sacroiliac joint ( sacral iliac joint) good to be able to move around on land, spent most of the time but probably in the water. In this respect resembled the genus today hippos or early amphibian living whales like Ambulocetus. To move forward in the water, the animal could not use a strong, provided with a tail fin tail, as do today's manatees exclusively, because the caudal vertebrae lacked the clearly formed transverse processes, which are necessary for a strong tail muscles. Pezosiren floated rather otter -like by combined movements of body, tail and hind legs.