Friend sent me a photo of a Vulnerable and Endemic in Argenina freshwater turtle in Iguazu National Park, Argentina for ID. Photo credit: A. Holberg. This area is World Heritage Natural Site. 3 species of freshwater turtle are seen here.
Williams' South-American Side-necked Turtle (Phrynops williamsi) is in the Bearded Toadheads (Phrynops) genus. It is native to southeastern Brazil, Uruguay, and Argentina. It's preferred natural habitat is freshwater wetlands, at altitudes of 80–1,000 m (260–3,280 ft). https://www.inaturalist.org/taxa/39619-Phrynops-williamsi
Conservation Status: Vulnerable in Argentina (AHA Asociación Herpetológica Argentina)
Link to confirmed observations nearby: (head and shell markings appear to be the same) https://www.inaturalist.org/observations/194881637 and
https://www.inaturalist.org/observations/103661950
INaturalist Project: Tortugas de Argentina https://www.inaturalist.org/projects/tortugas-de-argentina
HerpMapper: https://www.herpmapper.org/taxon/Phrynops_williamsi
Reptile Database: https://reptile-database.reptarium.cz/species?genus=Phrynops&species=williamsi