Anachronisms in the Book of Mormon 1000 years before the Jaredite record in the Book of Mormon begins. The main point of contention is how late these animals were present in the Americas before becoming extinct. Various Mormon authors have cited evidence that North American mound-builder cultures were familiar with the elephant. The oldest mound-builder societies date to around 2000 BC. The mound builder/elephant controversy did not originate with the Book of Mormon. In "The Mound Builders, Their Works and Relics", author Stephen Dennison Peet cites instances of exhumed mastodon remains and arguments given for why the remains were believed to be contemporary with mound builders.
Extinct comet the Hubble search for transition comets. Comets such as C/2001 OG108 (LONEOS) may represent the transition between extinct comets and typical Halley-type comets (periods of 20–200 years) or long period comets (periods longer than 200 years). Minor planets of the group of damocloids have been studied as possible extinct cometary candidates due to the similarity of their orbital parameters with those of Halley-type comets. Dormant comets are those within which volatiles may be sealed, but which have inactive surfaces. For example, 14827 Hypnos may be the nucleus of an extinct comet that is covered by a crust several centimeters thick