Temporal range: Middle Pleistocene-Early Holocene
(possible Early Pleistocene record)
(Ameghino, 1888 [originally Mastodon])
Proboscideans in South America were first described by Georges Cuvier in 1806 but failed to given them specific names beyond "Mastodon". It was Fischer in 1814 who gave the “mastodonte des cordillères” specimen the first specific name "Mastotherium hyodon".:340In 1824, Cuvier gave the specific names of "Mastodon andium" to the “mastodonte des cordillères” specimen, and "Mastodon humboldtii" to the “mastodonte humboldien”. Due to the Principle of Priority, this means that "Mastodon andium" was invalid, as "Mastotherium hyodon" was named first from the same specimen. Today, neither tooth is considered diagnostic to any specific taxon. Notiomastodon,[nb 1] "southern mastodon" was named by Cabrera (1929). It was assigned to Gomphotheriidae by Carroll (1988).
For centuries, the taxonomy of gompotheres, including Notiomastodon had been subject to debate, with many genus and species names for similar South American Gompotheres. The species genus is currently under dispute, whether it should belong to Notiomasodon or Stegomastodon as regardless of genus, the species is considered synonymous with Haplomastodon by most authors, as the specimens were not considered morphologically distinct from this species. This article treats Notiomastodon separately because in phylogenetic analyses, Notiomastodon/Stegomastodon platensis specimens are not sister taxa, which would make the genus Polyphyletic. However some authors think that this is inconclusive, as they think the North American Stegomastodon material is too scarce and fragmentary to make a definitive statement 
Notiomastodon belongs to the family Gomphotheriidae, a group of animals distantly related to modern elephants and mammoths. Notiomastodon seems to have had a 4 million year long ghost lineage, diverging from the clade that contains Rhynchotherium and Cuvieronius around the Late Miocene. This would imply that Notiomastodon had been evolving in southern Central America where the fossils are poorly sampled, prior to its migration into South America during the Pliocene or Pleistocene.
Phylogenetic position among trilophodont Gomphotheres according to Mothé et al., 2016:
Notiomastodon platensis is known from MECN 82, a 35-year-old male that would be approximately 2.52 metres (8.3 ft) tall, with an estimated weight of 4.4 tonnes (4.3 long tons; 4.9 short tons). It had two tusks on either side of its trunk, like other members of Gomphotheriidae. Unlike close relative Cuvieronius its tusks were not twisted, however their length and shape are observed as greatly variable depending on the individual.
Notiomastodon has been described as the 'lowland gomphothere'. The genus tended to inhabit seasonally dry, open forests, with a range lining most of the South American coastline and lowland interior, bar the Guiana Shield, with particularly large concentrations along the coast of Peru and in northeastern Brazil.
Whereas the other representative of South American gomphotheres, Cuvieronius, inhabited the mountainous Andes region from Ecuador to southern Peru and Bolivia, as well as lowland areas in north-east Peru 
The diet composition of Notiomastodon varied widely depending on location, but probably primarily consisted of a mix of C3 shrubs and C4 grasses, whilst also serving as a primary disperser of the seeds for a variety of different plant species.
Notiomastodon probably had a similar population structure and behaviour to extant elephants.
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- Cuvier, Georges (1806). "Sur différentes dents du genre des mastodontes, mais d'espèces moindres que celle de l'Ohio, trouvées en plusieurs lieux des deux continents". Annales du Muséum d'Histoire Naturelle. 7: 401–420.
- Fischer, Gotthelf (1813). Zoognosia tabulis synopticis illustrata in Usum Praelectionem Academiae Imperialis Medico-Chirurgicae Mosquensis Edita: Vol 3. Classium, ordinum, generum illustratione perpetua aucta [Illustrated Zoognosia in Synoptic Tables, Produced from Lectures in the Imperial Medico-Surgical Academy of Moscow by the Author, Gotthelf Fischer: Vol. 3, Classes, Orders, Genera, Enlarged Throughout with Illustration] (in Latin). 3 (1 ed.). Moscow: Nikolai Sergeyevich Vsevolozhsky.
- Cuvier, Georges (1824). "Recherches sur les ossemens fossiles, ou l'on rétablit les caractères de plusieurs animaux dont les révolutions du globe ont détruit les espèces".
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- νότιος. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project
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- Mothé, Dimila; Ferretti, Marco P.; Avilla, Leonardo S. (12 January 2016). "The Dance of Tusks: Rediscovery of Lower Incisors in the Pan-American Proboscidean Cuvieronius hyodon Revises Incisor Evolution in Elephantimorpha". PLOS ONE. doi:10.1371/journal.pone.0147009.
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