Fossil IdentifierFIELD GUIDE
Ammonite identification
A coiled shell is the starting clue for many ammonites. Examine how the spiral is built, whether ribs repeat across it, and whether internal chambers or suture lines are visible.
Features to compare
| Feature | What to look for | What it cannot prove |
|---|---|---|
| Flat spiral coil | Shell winds in one plane | Some ammonites have different shell shapes. |
| Ribs or knobs | Repeated surface ornament | Wear can remove detail. |
| Chambers | Partitions inside the shell | Not every specimen exposes its interior. |
| Sutures | Lines at chamber-wall contacts | Complexity is useful, but a worn photo may be inconclusive. |
Ammonite or another coiled shell?
A spiral alone is not enough. Compare the overall shape, repeated ornament, and visible chamber structure. Ammonites and nautiloids can both preserve coiled, chambered shells; gastropod shells are another possible look-alike. Avoid assigning a species from the general outline.
Take the views that answer different questions
Photograph the broad face to show the coil, the edge to show shell thickness, and any broken surface that already exposes chambers. Do not break a specimen to obtain a better photo. Include scale and note where the fossil was found.
Keep the identification at the right level
“Possible ammonite” is more useful than a confident species name without enough detail. Save the result with your images so you can compare it with a regional reference later. An expert may need geological context and finer shell detail for a more precise name.
Questions collectors ask
Is every spiral fossil an ammonite?
No. Other shells and geological patterns can look similar. Chambers, ornament, and context help distinguish them.
Can the app identify an ammonite species?
It may suggest a likely match. Treat a species name as provisional when the specimen is worn or important diagnostic features are missing.
References & further reading
Prepared with AI assistance and linked public educational references. No specialist review is claimed.