Necrosuchus
| Necrosuchus | |
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| Artist's restoration | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Archosauromorpha |
| Clade: | Archosauriformes |
| Order: | Crocodilia |
| Family: | Alligatoridae |
| Subfamily: | Caimaninae |
| Clade: | Jacarea |
| Genus: | †Necrosuchus Simpson, 1937[2] |
| Type species | |
| †Necrosuchus ionensis Simpson, 1937
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Necrosuchus is an
History and naming
The fossil remains of Necrosuchus were unearthed on April 3, 1931 during the First Scarritt Expedition in the Argentinian
Simpson explains the meaning of the generic name as being a compound word of "nekros" meaning "dead," and "suchus" meaning crocodile. Simpson described how "a well-meaning lady asked us if it were dead", which inspired his choice of name. The specific name refers to the Las Violetas site: ion is "violet" in Latin.[2]
Description
The dentary teeth of Necrosuchus are more or less evenly spaced throughout the holotype, only the 12th and 13th teeth lying closer together than the others (however even then without being in direct contact). The upper margin of the jaw is notably concave between the 1st and 4th tooth and between the 4th and 13th, after which it remains straight. The teeth show very little differentiation from one another in morphology, however the difference in tooth size is striking and almost equal in its degree to that of extant genus Caiman. Although the degree of enlargement is similar, the distribution is not the same and more similar to that seen in Leidyosuchus (many of the species used for comparison being now considered Borealosuchus) according to Simpson. The first two teeth are of the same size, followed by a decrease in size for tooth three. The 4th dentary tooth is the largest of the lower jaw and followed by a series of noticeably smaller teeth (a similar condition is seen in extant caimans). Unlike in extant taxa however, the 13th tooth is enlarged to the point that it almost rivals the 4th dentary tooth in size, and the transition in size before and after it is much less abrupt.[2] The 13th tooth's status of second largerst tooth in the dentary differentiates Necrosuchus from all other caimans other than Purussaurus brasiliensis and some species of Paleosuchus. Necrosuchus differs from Purussaurus through its slender mandibular ramus as well as the size of the first four dentary and from Paleosuchus through the anatomy of the atlantal ribs and the lack of mediolaterall compression on the posterior dentary teeth.[5]
The postcranial remains include 4 dorsal vertebrae that were preserved in articulation. They are procoelous with rectangular neural spines and lacking their transverse processes due to preservation. At some point in the past, the vertebrae had been identified as dorsals 5 to 8, but the basis for this assignment is not known. However, the study by Brochu confirms that this assumption was correct based on the anatomy of the hypapophyseal keel. The last two dorsals are also preserved in articulation with the sacral vertebrae. The sutures of the dorsal and sacral neurocentrals are unfused and still open, suggesting that the animal was not yet fully grown by the time of its death. The
Phylogeny
Early analysis of Necrosuchus believed it to be a close relative of
Caimaninae
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The following
Caimaninae
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References
- ^ PMID 34567843.
- ^ a b c d Simpson, George Gaylord (1937). "An ancient eusuchian crocodile from Patagonia" (PDF). American Museum Novitates (965): 1–20.
- ^ "†Necrosuchus Simpson 1937". Paleobiology Database. Fossilworks. Retrieved 17 December 2021.
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