Trimerorhachis
Trimerorhachis | |
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A large skull of Trimerorhachis insignis (AMNH 7116) in the American Museum of Natural History | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Order: | †Temnospondyli |
Suborder: | †Dvinosauria |
Family: | †Trimerorhachidae |
Genus: | †Trimerorhachis Cope, 1878 |
Species | |
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Trimerorhachis is an extinct
Description
The length of the largest specimens of Trimerorhachis is estimated to have been almost a metre (3.3 feet) in length. Trimerorhachis has a large triangular head with upward-facing eyes positioned near the front of the skull. The trunk is long and the limbs are relatively short. The presence of a branchial apparatus indicates that Trimerorhachis had external gills in life, much like the modern axolotl.[1] The body of Trimerorhachis is also completely covered by small and very thin osteoderms, which overlap and can be up to 20 layers thick. These osteoderms act as an armor-like covering, especially around the tail. Their weight may have helped Trimerorhachis sink to the bottom of lakes and rivers where it would feed.[2]
History
Trimerorhachis was first described by Edward Drinker Cope in 1878. Specimens are often preserved as masses of bones that are mixed together and densely packed in slabs of rock.[3] Fossils are rarely found in articulation, although a slab of rock has been found with sixteen skulls and their associated vertebrae in an intact position.[1] Most of these fossils preserve skulls and dorsal vertebrae, but rarely any other bones. Paleontologist S.W. Williston of the University of Chicago commented in 1915 that "it will only be by the fortunate discovery of a connected skeleton that the tail, ribs, and feet will be made known."[3] A nearly complete specimen was discovered the following year near Seymour, Texas, and Williston was able to describe the entire postcranial skeleton of Trimerorhachis.[4]
In 1955, paleontologist
A second species called T. sandovalensis was named from New Mexico in 1980. A nearly complete skeleton from the Abo Formation near Jemez Springs has been designated the holotype, but other fossils of the species are found throughout the state, giving it a wide distribution.[6]
Paleobiology
Environment
Trimerorhachis was probably a fully aquatic temnospondyl. Like most dvinosaurs, it had external gills. The
During the Early Permian, the area of New Mexico and Texas was a broad coastal plain that stretched from an ocean in the south to highlands in the north. Other common animals that lived alongside Trimerorhachis included
Brooding
Small bones that likely belong to immature Trimerorhachis individuals have been found in the
Another possible explanation for the small bones is that they were originally located in the throat and were pushed into the pharyngeal pouch during fossilization. If this was the case, Trimerorhachis may have eaten its young instead of brooding them. This type of cannibalism is widespread in living amphibians, and most likely occurred among some prehistoric amphibians as well.[2]
See also
- List of prehistoric amphibians
References
- ^ hdl:2027.42/48206.
- ^ JSTOR 1304028.
- ^ JSTOR 30066442.
- S2CID 128401645.
- ^ Colbert, E.H. (1955). "Scales in the Permian amphibian Trimerorhachis" (PDF). American Museum Novitates (1740): 1–17.
- ^ a b Berman, D.S.; Reisz, R.R. (1980). "A new species of Trimerorhachis (Amphibia, Temnospondyli) from the Lower Permian Abo Formation of New Mexico, with discussion of Permian faunal distributions in that state". Annals of the Carnegie Museum. 49: 455–485.
- S2CID 59045725.
- .