Paracochloceras fisheri
Late Triassic
Gabbs Formation
Mineral County, Nevada

106mm limestone block with at least five tiny 10mm heteromorph ammonites. This species is one of the earliest knpwn heteromorphs. Very rare.

Few collectors are aware that the earliest known heteromorph ammonites are not from the Middle Jurassic, but much earlier in the Late Triassic during the end of the Norian stage. A few species are known, all quite small, but possessing the classic turricone shape that we would see again in the Cretaceous. This is the first and only example we have ever had of these earliest heteromorphs.

For a review of Triassic heteromorphs (PDF) see: Shevyrev, A. A. (2005). Heteromorph ammonoids of the Triassic: a review. PALEONTOLOGICAL JOURNAL C/C OF PALEONTOLOGICHESKII ZHURNAL, 39, S614