First in situ documentation of a fossil tooth attributed of †Otodus megalodon from the deep sea of Rio Grande Rise, South Atlantic Ocean
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Abstract
The shark †Otodus megalodon is one of the main marine predators of the Cenozoic, with fossil records ranging from 15.9 to 3.6 Ma and a distribution considered cosmopolitan. However, some regions of the planet still lack unequivocal records of the species, including the South Atlantic Ocean. Although there are records of teeth on continental South America, this work presents the first record of a †O. megalodon tooth in the South Atlantic Ocean (offshore). The tooth was collected by the Geological Survey of Brazil (SGB), in 2012, on the Rio Grande Rise (RGR) from a dredge haul between 664–667 m depth at station 4340-IV-150-HAS and is embedded in a phosphatized ferromanganese crust. The sample exhibits a porous, botryoidal surface, with internal lamination alternating dark Fe-Mn-rich layers and light calcium- and phosphate-rich layers. The morphological description indicates a triangular tooth, with TH = 57.1 mm, CH = 45.2 mm, and CW = 36.2 mm. The cutting edges are worn due to marine abrasion. The predominant color is black (N2–N3, Munsell), reflecting Fe-Mn coating. Strontium isotope analyses performed on equivalent materials indicate ages between 21.7 and 14.5 Ma (Early–Middle Miocene). This interval coincides with the period of greatest diversity and broad distribution of †O. megalodon, supporting the interpretation that the tooth corresponds to this geological interval. The presence of the tooth in deep-sea settings and associated with Fe-Mn crusts is unusual, as most findings occur in coastal environments. The results presented suggest that the RGR may have served as a migratory route or feeding area for large pelagic predators during the Miocene, possibly associated with local productivity and regional paleoceanographic conditions. The record reinforces the scientific and strategic importance of the RGR and highlights the need to expand paleontological and paleoceanographic investigations in the deep waters of the South Atlantic Ocean.
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