Koskinonodon
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Koskinonodon Temporal range: Late Triassic, 227–208 Ma |
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| K. perfecta skeleton at the AMNH | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Order: | †Temnospondyli |
| Suborder: | †Stereospondyli |
| Family: | †Metoposauridae |
| Genus: |
†Koskinonodon Branson and Mehl, 1929 |
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Koskinonodon is an extinct genus of large temnospondyl amphibians. These animals were part of the family called Metoposauridae, which filled the crocodile-like predatory niches in the late Triassic. It may have reached up to 3 m (10 ft) in length, with a 65-cm-long skull. It was an ambush hunter, snapping up anything small enough to fit in its huge jaws. It was very common during the Late Triassic (Norian age) in what is now the American Southwest.
The skull of Koskinonodon differs from the skulls of other closely related organisms in a few key ways. It is wider overall and features eye sockets that are very anterior and forward oriented, more so than its contemporaries. Also, the skull has prominent slime canals, which are used for transporting mucus, as well as large external nares. In addition, the upper jaw is relatively weak and thin, used only for holding teeth. Their large jaws could have held many teeth at once, maybe even over 100 on each side of the upper and lower jaws, but the actual number varies constantly over the animal’s lifetime due to natural causes such as fighting, eating, disease, etc. The sheer size of the skull is one of the most defining traits for the genus Koskinonodon and its species.
Other more minor skull traits characterize Koskinonodon as well: elongation of the lachrymal, shortening of the prefrontal, reduction of the interclavicle, and the most characteristic is the center lachrymal entering margin of the orbit. While the shortened prefrontal is a characteristic of the Metapsauridae family, it is shorted even more in Koskinonodon. The interclavicle is reduced in the way that it has many hexagonal pits as well as grooves and ridges. The skull of Koskinonodon is also covered in this reticulate ornamentation. Some researchers believe that Koskinonodon has a shorter posterior process of the interclavicle, which may discriminate it from other closely related species, while others believe that there is not enough information to make that distinction.Koskinonodon also has ossified opisthotics, the more posterior of the bones surrounding the inner ear.
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