| Prorastomus | |
|---|---|
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Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Sirenia |
| Family: | †Prorastomidae |
| Genus: | †Prorastomus Owen, 1855 |
| Species: | †P. sirenoides |
| Binomial name | |
| †Prorastomus sirenoides Owen, 1855 | |
Prorastomus sirenoides is an extinct species of primitivesirenian that lived during theEocene Epoch 40 million years ago inJamaica.
The generic nameProrastomus, a combination ofGreekπρῷρα (prōra), prow, andστόμα (stoma), mouth, refers to the lower jaw of the animal "resembling the prow of awherry".
Thegenus nameProrastomus comes fromGreekprora meaning "prow" andLatinstomus meaning "mouth." In 1892,naturalistRichard Lydekker respelled it asProrastoma with afeminine ending, however this was unjustified asstomus is masculine in Latin.[1]
Prorastomus is one of twogenera of the familyProrastomidae, the otherPezosiren. These two species are the oldestsirenians, dating to theEocene.[1]
The first specimen wasdescribed bypaleontologistSir Richard Owen in 1855, and, being found in Jamaica in theYellow Limestone Group, pointed to the origin of Sirenia as being in the New World rather than the Old World as was previously thought. However, the modern understanding ofAfrotheria as a clade that originally diversified in Africa overturns this idea. Theholotype specimen, BMNH 44897, comprises a skull, jaw, andatlas of theneck vertebrae. When Owen first acquired the skull, it was broken in two between the eyes and thebraincase. Another specimen was found in 1989 in the same formation, USNM 437769, comprising thefrontal bone, a tusk, vertebrae fragments, andribs.[1]
While modern sirenians are fully aquatic, the 1.5-metre (5 ft)Prorastomus was predominantly terrestrial, judging from the structure of its skull. Judging from its crown-shapedmolars and the shape of its snout, it fed on soft plants.[2] The snout is long, narrow, and, at the tip, bulbous. Thenasal bones are larger than other sirenians. Thenasal ridge is well developed, indicating it had a good sense of smell. Thefrontal bones are smaller than usual for sirenians, though, as in other sirenians, it had a pronouncedbrow ridge.[1] SincePezosiren has asagittal crest, it is possible theProrastomus specimen had one too before being eroded away.[3]
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