Probainognathus
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Probainognathus Temporal range: Triassic, 235–221.5 Ma |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Order: | Therapsida |
| Suborder: | Cynodontia |
| Family: | †Probainognathidae |
| Genus: |
†Probainognathus Romer, 1970 |
| Species: | †P. jenseni |
| Binomial name | |
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Probainognathus jenseni Romer, 1970 |
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Probainognathus meaning “progressive jaw” is a genus of extinct cynodont therapsid that lived around 235 to 221.5 million years ago, during the Middle Triassic in what is now South America. Probainognathus is a member of the family Probainognathidae, and is a close relative of the family Chiniquodontidae. The various similarities to Chiniquodontidae led Alfred Romer to initially suggest Probainognathus be placed within that family, but it was subsequently decided that the differences were enough to warrant its placement within Probainognathidae.Probainognathus jenseni was a species of small, carnivorous cynodonts which possessed features that provide a connection between cynodonts and mammals. The major feature being jaw joint articulation that not only included the quadrate and articular bones, but also the squamosal and dentary bones. This development in the jaw joint is an important step in the evolution of mammals as this squamosal-dentary articulation is the joint all extant mammals possess. These findings provide evidence that Probainognathus should be placed on the line ascending towards Mammalia.
Probainognathus was first described and named by Harvard paleontologist, Alfred Sherwood Romer in 1970.Probainognathus jenseni is the focus of this description, and was named generically for its advanced jaw articulation, literally meaning “progressive jaw” in Greek, and specifically for James A. Jenson, a Harvard collector on the trips to recover the specimen.
Probainognathus was a small cynodont, the apparent body size of which is inconsistent across sources, ranging from being about the size of a rat, to the size of a small dog.
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