Former US President Teddy Roosevelt was approached by the American gold prospector Martin Sheffield in 1903, who suggested that he organize an expedition to hunt a mysterious huge lizard-like monster with a curved neck-.
This information surfaced in a New York Times article published on March 31, 1922:
ROOSEVELT WANTED TO HUNT MONSTER; Ex-President Thought of Patagonia Expedition When He Went to South America. KEEN OVER TALE ... John Barrett Gave Him in 1903 an Explorer's Account of Strange Amphibian.
The newspaper heard about it from Mr. John Barrett, late Director of the Pan American Union and Minister to Argentina during President Roosevelt’s administrations during the famous 1922 plesiosaur expedition (sent to hunt a plesiosaur close to Lake Epuyen).
According to Barret, Sheffield "had reported that he had seen what appeared to be a plesiosaurian monster, or huge amphibian, swimming in the waters of a Southern Andean jungle lake, I recalled that nearly twenty years ago, in November, 1903, ". 
Apparently Sheffield had fought in Cuba during the 1898 Spanish-American war, and has somehow met Roosevelt there.
Interesting and verifiable
This is indeed interesting. Because it could be verifiable:
- We could check when Sheffield arrived in Argentina (before or after 1898).
- We know that in 1903 he had met Clemente Onelli then working with the Argentine Border Committee marking out the frontier with Chile. Onelli later (1922) organized the Plesiosaur expedition. Could he have been in Buenos Aires at the same time?
- Why did he wait for 19 years (from 1903 to 1922) before reporting the "lizard" again? Did he tell Onelli in 1903? And was ignored by him?
- Can the details mentioned by Barrett be tracked and proven? Did any of those mentioned in the article record the event?
- What about the handwritten letter by Roosevelt himself? Did Roosevelt write memoirs?
 Roosevelt wanted to hunt monster New York Times, NY. 31.03.1923.
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia
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