The prestigious journal Nature published  an interesting comment in the 1920s, which I quote in full below. It deals with a skull of alleged tertiary age which turned out to be a lusus naturae, a freak of nature, a stone shaped like a skull:
"In our issue of March 10, 1923, p. 336, we referred to a number of telegrams which had appeared in the daily Press reporting the discovery of a so-called fossilised human skull of Tertiary age in Patagonia.
At the time, we urged the need of caution in accepting such reports. Dr. Imbelloni has contributed to the Revista de la Universidad de Buenos Aires, t. li., under the title "Nota sobre los supuestos descubrimientos del Doctor J. G. Wolff en Patagonia" what may be regarded as teh final chaper in the history of hte alleged discovery. His object is to place the facts on record and at the same time to clear Argentine men of science of any suspicion of having lent support to the view that the find was genuine and of a high antiquity.
Dr. Imbelloni's account, which is written with an acid humor, makes it clear that the report was received from the first with scepticism. As soon as Dr. Eric Boman and others had an opportunity of cross-examining Dr. Wolff, they arrived at the opinion that the specimen was not a skull at all. It was not, however, available for examination. When it reached Buenos Aiers in May, it was immediately examined by a commission consisting of Dr. Boman, Dr. S. R. Dabbene, Dr. R. Lehmann-Nitsche, Prof. F. F. Outes, Dr. V. Vidakovitch, and the author, and it was at once pronounced to be a block of sandstone". 
This Dr. Wolff (others write it Wolfe) and the skull were mentioned by Riggs during his 1923 paleontological expedition to Patagonia. Riggs he had the misfortune of meeting Wolff and believing him: 
...a certain J. G. Wolfe introduced himself and offered his services to the expedition. Wolfe claimed to have been a museum curator in Rio Gallegos and to have held a commission in the Argentine army. But what aroused Riggs' interest, more than his credentials, was Wolfe's description of a "Tertiary human skull [...] They set out for El Paso de Santa Cruz, [currently this place is the town of Luis Piedrabuena, close to the mouth of the Santa Cruz River] the settlement where the skull had apparently been found. The proprietor of a local hostelry recalled that the skull had first attracted notice about 1916 and had been discovered in a roadbed near town. The first person to suspect that it might be of scientific value was said to have been an English nurse, a Mrs. Vendrino, who had worked in the area for some years. She obtained custody of the skull and it was in her possession when Wolfe had examined it earlier.
In El Paso de Santa Cruz, Riggs— who was becoming increasingly suspicious of the alleged skull— was told that Mrs. Vendrino had recently "gone mad" and had been taken to Buenos Aires for treatment. She had taken her treasured, 22-pound skull along as a trophy. Eventually, Riggs was able to track down the "skull," and his suspicions were confirmed: it was just a very curious stone, with a remarkable humanoid shape." 
Riggs later described Wolff or Wolfe as follows:
"He betrays no evidence of scientific training, [and]
is particularly lacking in ability to recognize and interpret natural objects and to derive data from them. His method ... has been to get theories from reading and then to cast about for some object to fit into the theory. ... Dr. Wolfe
has impressed us as an enthusiast with a wanderlust and no purpose beyond gratifying it. He studied law ... but found that profession too tame and colorless to suit his fancy. He ... apparently wrote extravagant stories in order to sell them. He is already, so he says, under fire of criticism of a leading scientist in Buenos Aires." 
Bear this in mind, because Wolff also discovered an ancient city in the heart of Patagonia, but I will deal with that in another post.
Unfortunately I have not been able to read Imbelloni's paper on the sandstone skull or seen any photographs of it. Why would everybody think that it was a fossil skull? was it disregarded because of Wolff's extravagant nature? or because prejudice veiled the reason of the scientists that inspected the "skull".
 Nature 113. 58-60 (12 Jan. 1924) News. Current Topics and Events.
 Larry G. Marshal, 1978. Adventures in Patagonia. Field Museum of Natural History Bulletin. March 1978 Vol 49 No. 3. pp 4+
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia2011 International Year of Forests Copyright 2009-2011 by Austin Whittall ©