Tapirusosaurus

Tapirusosaurus is an extinct species of quadrupedal dinosaur that belonged to the prosauropod/Plateosauria family. It was also among the last ever prosauropod so far in existence, living in North America in the Late Jurassic period (155-145 million years ago), and it survived competition from sauropods by becoming semi-aquatic, much like tapirs, which fill a similar niche to this dinosaur, hence the dinosaur's name. It is also named after its skull was discovered, which had a large nasal hole, so paleontologists suggested that this dinosaur had a short trunk like a tapir. It was about the same size as a modern day bull African elephant. It was also protected by small but heavy armored for protection against predators like Allosaurus and others. Despite its defense, this dinosaur became extinct for some unknown reason.

History
In the mid 1910s, people in the American midwest discovered some herbivorous dinosaur skulls with large nasal holes, so they correctly realized that these dinosaurs had short tapir-like trunks. Back then, however, only their skulls were found, so they once thought that these dinosaurs were part of the sauropod family, so they incorrectly recontructed their full body to resemble that of a common sauropod like Apatosaurus and such, and even inaccurately drew them and sculpted them as Apatosaurus-like sauropods with short trunks. That trend has been continuing for a long time, that was finally solved when in December 14th, 1974, that when the full body of the real Tapirusosaurus had been discovered, proving that these dinosaurs weren't sauropods as once thought, but among the last prosauropods in existence. Its small bony armor were later discovered in 1986, adding more confusion on the people who realized what Tapirusosaurus was, until they realized that the bony armor of these dinosaurs were used for protection against predatory dinosaurs.