L Sprague de Camp's "Employment" (as by Lyman R Lyon) (short story, free): Making prehistorical animals from their fossils!
This, however, is not a monster story; it's more a light fun read. We see the reification of
- "a huge wolf, about the size of a Great Dane, but twice as muscular and ten times as mean-looking."
- "a specimen of Arctotherium, the immense bear from the California Pleistocene."
- A couple of elephants.
Story summary.A machine that does a sort of biochemical equivalent of electrolysis. Put a certain solution in a tank. Add as much fossil of a single animal as you have. Also add a lot of rock from area immediately surrounding the location where fossil was found; apparently, in the process of fossilization, many of the molecules of animal's body would have drifted to surrounding rock!
Put on the power, & over the next few days, stray molecules of animal that had diffused through surrounding rock are pulled back to their correct places, & you have ... the original animal back, skin, hair & all! Only its heart needs to be revived with a separate electrical process, & you get a fully grown animal.
Fact sheet.First published: Astounding, May 1939.
Among the stories from Astounding/Analog issues edited by John Campbell.
Related: Stories of L Sprague de Camp.