Where the facts come from
Every factual claim on this site links to its source. This is the full list.
How we checked
Each fact was written in our own words alongside its source. Our build script stores the text of every source and, for each fact, checks that the key words and figures really appear in it. 192 of 192 checks passed when this site was last built (10 November 2026). Where we couldn’t find a named source saying something, we left it out. Where good sources disagree, we say so and give both.
Where sources differ
- Closest relatives. Thought closer to squid, octopuses and cuttlefish (Natural History Museum; Imperial College, 2021), or described as relatives of the nautilus (BGS, Britannica), with the nautilus as nearest living relative (NHM folklore article).
- How old. Ammonoidea from about 450 million years ago (NHM), ammonoid fossils from the Devonian, 419 million years ago (Britannica), or ammonites over about 140 million years of the Jurassic and Cretaceous (BGS).
- Depth. Perhaps down to about 400 m (NHM), or probably no deeper than 100 m (BGS).
- The largest specimen. 1.8 m, perhaps 2.5 to 3.5 m complete (NHM); 1.95 m, about 2.55 m complete (BGS); or 205 cm (Britannica).
- Food. Crustaceans, bivalves, fish and plankton (NHM); plankton, plants of the sea floor and slow seabed animals (BGS); zooplankton, crustaceans and other ammonoids, as predators (Britannica).
- The name. From the Greek Cornu Ammonis, after Jupiter Ammon (NHM), or from the Egyptian god Amun, Zeus Ammon to the Greeks (BGS).
- Mary Anning’s family. Nine children (NHM), at least nine (Geological Society), or ten (BBC News), with only two surviving.
- The first ichthyosaur. Skull found by Joseph in 1811 and skeleton by Mary in 1812 (NHM), or found by Mary in 1811 (BBC News).
- Her age when her father died. Ten, in her own account (Geological Society), or 11 (BBC News).
All sources (19)
- Natural History Museum: What is an ammonite? (32 facts)
- British Geological Survey: Ammonites (29 facts)
- Natural History Museum: Snakestones, ammonites in myth, magic and science (27 facts)
- Natural History Museum: Mary Anning, the unsung hero of fossil discovery (22 facts)
- West Dorset Fossil Collecting Code of Conduct (PDF, Charmouth Heritage Coast Centre) (13 facts)
- BBC News: Ammonite, who was the real Mary Anning? (17 October 2020) (10 facts)
- Encyclopaedia Britannica: Ammonoid (10 facts)
- Natural History Museum: How to find fossils on the beach (8 facts)
- British Geological Survey: Fossils (7 facts)
- Imperial College London: Rare Jurassic fossil reveals never-before-seen ammonite anatomy (5 facts)
- Natural History Museum: Mary Anning’s fossils (5 facts)
- UNESCO World Heritage: Dorset and East Devon Coast (5 facts)
- Natural History Museum: Fantastic fossils in the UK and where to find them (4 facts)
- Undercliffs Fossil Collecting Code, version 2 (PDF, Charmouth Heritage Coast Centre) (4 facts)
- Natural History Museum: What is a fossil? (3 facts)
- Visit Dorset: Monmouth Beach, Lyme Regis discovery trail (3 facts)
- Geological Society: Mary Anning, first discoveries (2 facts)
- IUGS Geoheritage: Jurassic Coast, Lyme Regis (2 facts)
- Geological Society: Mary Anning and the Geological Society (online exhibition) (1 fact)