However, while these are now recognized as coming from the Ediacaran period, they were thought at the time to have been formed in the Cambrian.[75] From 1872 onwards small shelly fossils, none more than a few millimeters in size, were found in very Early Cambrian rocks, and later also found in rocks dating to the end of the preceding Ediacaran period, but scientists only started in the 1960s to recognize that these were left by a wide range of animals, some of which are now recognized as molluscs.[4]