Amusing, but notice how stylized the people and other animals in the painting are. Also apparently sauropods were unable to hold their necks upright as they are often portrayed in drawing and fictional movies. Whether this painting is a fraud (could a 5000 year-old painting survive in such excellent condition outside like that, even if it’s overhung by rocks?) or a creatively interpreted authentic painting, I think I detect some influences of Jurassic Park.
Furthermore, the narrator makes a logical jump from the people in the picture apparently hunting the animal to the people who made the picture, or others of their culture, having seen and hunted the animal. If this is really a 5000 year-old Amazonian culture, then we would know very little about them. Maybe the picture represents a mythological event involving a mythological creature, whether related or not related to the mythological creature asserted by the narrator as having been described by natives in the 1940s. As for that, we conveniently aren’t given any quote of the actual description of the mythological creature, nor the name of the explorer, nor even the name of the river- just an assertion that the description “fits” a sauropod. Heck, if both the legend and the painting are authentic (big “ifs”), the legend may be based on people of this later culture seeing the painting, or may be entirely unrelated, or again may be due to actual retained cultural knowledge, but of a mythological creature.
I’m not saying it’s absolutely impossible for non-avian dinosaurs to have survived into recent times. But I would think critically about the evidence provided for these kinds of claims, as well as the credibility of the source. If real evidence for dinosaur coexistence with humans ever surfaces, I think we’re sure to hear about it from mainstream sources.