May 8, 1733 two workers, Anders Halfwarder and Olof Sigräfwer, excitedly reported to superintendent Johan Gråberg, who was inspecting the quarry of Nybro near the village of Wamlingebo (Gotland, Sweden), a very strange discovery. While cutting large blocks of sandstone (of the 419Ma old Silurian Hamra-formation), Halfwarder spotted a frog sitting in the middle of a large boulder he just cut in two.
Gråberg followed the two men into the quarry, where they showed him a grayish frog, with the mouth covered by a yellow membrane. The animal barely reacted to touch, finally Gråberg lost his patience and beat the creature to death with a shovel. Later that day Gråberg regret his action "for being the Slayer of that extraordinary Animal, which might have lived for many hundreds of years within its stony Prison", so he recovered the body and contacted various scholars to solve this apparent zombie-mystery. Finally the physician and self-declared naturalist Dr. Johan Phil got interested in the case.
Phil argued that frog-spawn had entered in some way the rock and developed over the following years into a fully grown frog. His paper, presented to the Swedish Academy of Sciences, was however rejected during a meeting in November 1741 and put in the archives. Only an excerpt, containing the account by Gråberg and an engraving showing the geologic section of the quarry and a figure of the frog, was published in the Transactions of the Academy.
The frog of Nybro was treasured in the natural history collection of Count Carl Gustaf Tessin at Akerö Castle, however got lost after 1760.
Stories of animals entombed in stone seem to have a long tradition. Supposed discoveries are reported from England and France. The German collector Count Fürstenberg, so it is said, displayed in 1664 a rock in which an enclosed frog croaked.
Naturalist Carl Linnaeus (1707-1778) considered it possible that amphibians could live for centuries trapped inside rocks. In 1818 the mineralogist E.D. Clarke (1769-1822) reported the discovery of three living specimens of a salamander species believed to be extinct since the Cretaceous - supporting the idea that the animals were trapped inside the rocks even for eons.
It seems that the "toad-in-the-hole" was very popular in the Victorian era. Many books about regional geology - like "A delineation of the strata of Derbyshire" - mention not only fossils in various strata but also the discovery of living frogs or toads inside compact rocks (however the animals, so the text, died almost immediately).
Various hypothesis were formulated to explain the toad-in-the-hole phenomenon - the work of the devil, spontaneous generation, animals entrapped during the biblical flood or a juvenile animal grown too large to leave its prison.
Professor William Buckland, notorious for his interests in strange geologic phenomena, decided to test this hypothesis with an experiment. He sealed 24 toads in niches carved into a block of limestone and a block of sandstone and buried them for one year in his garden. In December 1826 the two blocks were recovered and examined. All the toads in the sandstone block were dead and decayed, in the porous limestone some toads were still alive, two of them had even gained weight. Buckland however noted that some of the seals were damaged. In a second experiment, with intact seals, no animal survived.
So the toad-in-the-hole seemed to be a biological impossibility, however still in 1862 the physician and author Frank Buckland (son of William Buckland) and paleontologist & monster-hunter Richard Owen had to protest against the public display of a frog-in-the-coal-block coming from the Welsh mine of Cwm-Tylery.
Buckland studied the living animal and concluded that, if the story was real, it was more plausible that the animal entered the mine and became entrapped in the coal during recent mining operations. The frog was not removed from public display, but the letter of protest prompted an intense debate about the veracity of such findings in various newspaper.
Fig.3. A toad-in-the-hole discovery, illustration by Philip Henry Gossefor his "Romance of Natural History" (1861), image in public domain.
The stories of entombed animals became stranger yet. A report of 1803 (Fiske O. in the Memoirs of the American Academy of Arts and Sciences) describes the discovery of a mouse inside a rock, unfortunately the animal managed to escape shortly after the discovery. The Illustrated London News published in 1856 the amazing story of a living Pterodactylus anas (apparently a goose-shaped reptile) found inside rocks dated to the Cretaceous period - the hoax should be obvious…
The last famous toad-in-the-hole specimen was reported from Texas in 1928. Here a toad supposedly survived 31 years entombed inside a cornerstone of a courthouse. Old Rip, so his nickname, became the star of a freak show (and later inspired a Bugs Bunny cartoon).
Despite the notoriety of this phenomenon (more than 210 historic reports exists) no physical evidence or real toad-in-the-hole survives.
Many descriptions of such cases came at best from second- or third-hand experience, newspaper at the time feed the interest of the public by reprinting again and again old stories or inventing new ones. Many toads were suspiciously often found by clergymen, who used them as evidence to discuss the formation of rocks by a biblical flood or by divine intervention.
The few studied examples were exposed as hoax already at the time of their presumed discovery and the only specimen that survives today, hosted in the Booth Museum of Natural History in Brighton, was donated to the museum by amateur naturalist Charles Dawson in 1901 … a name notoriously connected to the Piltdown-Man fraud.
BONDESON, J. (1999): The Feejee Mermaid and other Essays in Natural and Unnatural History. Cornell University Press: 315