What is a goniatite?
“Goniatite” is the everyday name for Palaeozoic ammonoids whose suture lines, where the internal walls meet the shell, form simple zigzags of rounded saddles and pointed lobes. The genus Goniatites itself is Carboniferous; most Moroccan goniatite fossils are older, from the Devonian, and belong to other genera. In the trade the word is also stretched to cover any polished small ammonoid, and some sellers even apply it to Cretaceous ammonites. We use it only for Palaeozoic ammonoids.
The Devonian ammonoids of the Anti-Atlas
The Tafilalt and Maïder basins around Erfoud and Alnif hold one of the world’s best records of early ammonoid evolution. The oldest known Moroccan ammonoids come from the lower Emsian of the Tafilalt, roughly 405 million years old[4]. The early evolution of their shells, from loosely to tightly coiled forms, has been traced in detail[2].
A detailed study of late Emsian and Eifelian sections in the eastern Anti-Atlas established a fine-scale ammonoid succession and revised the taxonomy of its ammonoids[1]. Younger, late Givetian beds at Hassi Nebech contain an exceptionally rich late Givetian ammonoid fauna, much of it preserved in limonite[3].
| Scientific name | Devonian ammonoids (several orders and many genera) |
|---|---|
| Geological age | Early to Late Devonian (Emsian–Famennian), about 405–360 million years |
| Formation | Devonian cephalopod limestones and shales of the Tafilalt and Maïder |
| Locality in Morocco | Erfoud and Alnif area, e.g. Hassi Nebech |
| Typical size | About 1–8 cm; polished display pieces up to about 10 cm |
Colors and preservation
The color of a Moroccan goniatite depends on its bed. Many come from gray to dark limestones, where the shell is replaced by calcite. Others, such as the late Givetian ammonoids of Hassi Nebech, were collected loose from shales and are mostly preserved in limonite, an iron oxide that gives a rusty brown color[3]. Brown Late Devonian limestones of the Tafilalt, such as the Gonioclymenia Limestone, give warmer tones. None of these colors is added; they reflect the chemistry of the rock in which the shell was buried.
Polished goniatites
Most goniatite fossils sold from Morocco are cut and polished. Grinding through the shell exposes the chambers and the suture pattern, and a final polish gives a glossy finish in shades of gray, brown and black, depending on the surrounding limestone and on iron minerals in the shell. Smaller pieces are sold loose as “buttons”; larger ones are left in a polished limestone frame.
When you hold a polished goniatite fossil up to the light, the sutures should read as a clean, repeating zigzag around the whorl. Good specimens show sharp, continuous sutures and an intact outline. Lower grades may be ground too deep, with blurred chambers or a broken center. Because polishing is part of the product, we describe goniatites as polished rather than restored, and note any filled voids or repaired edges separately.
Buying notes
- Ask for the period on the label. A “goniatite” that is Jurassic or Cretaceous is an ammonite mislabeled.
- Genus names on polished pieces are often generic. Accurate identification usually needs the sutures, coiling and cross-section.
- For wholesale, goniatites are sorted by diameter and polish quality, which keeps a reseller’s tray consistent.
Goniatites also appear in polished slabs and objects in Fossil Decor, often next to Orthoceras. For the Cretaceous side, see Goulmima ammonites or return to all Moroccan ammonites. Shops can order sorted lots through a wholesale account.
References
- Klug, C. (2002). Quantitative stratigraphy and taxonomy of late Emsian and Eifelian ammonoids of the eastern Anti-Atlas (Morocco). Courier Forschungsinstitut Senckenberg 238: 1–109. schweizerbart.de (publisher record)
- Korn, D. & Klug, C. (2003). Morphological pathways in the evolution of Early and Middle Devonian ammonoids. Paleobiology 29(3): 329–348. doi:10.1666/0094-8373(2003)029<0329:MPITEO>2.0.CO;2
- Bockwinkel, J., Becker, R.T. & Ebbighausen, V. (2013). Late Givetian ammonoids from Hassi Nebech (Tafilalt Basin, Anti-Atlas, southern Morocco). Fossil Record 16(1): 5–65. doi:10.1002/mmng.201300001
- Becker, R.T., Klug, C., Söte, T., Hartenfels, S., Aboussalam, Z.S. & El Hassani, A. (2019). The oldest ammonoids of Morocco (Tafilalt, lower Emsian). Swiss Journal of Palaeontology 138(1): 9–25. doi:10.1007/s13358-019-00189-1
Frequently asked questions
How old are Moroccan goniatites?
Most come from Devonian rocks of the Tafilalt and Maïder, between roughly 405 and 360 million years old. The oldest known Moroccan ammonoids are from the lower Emsian of the Tafilalt, about 405 million years old. Each listing gives the period and, where known, the stage.
Is a goniatite an ammonite?
Goniatites are ammonoids, the same broad group as ammonites, but older and with simpler zigzag sutures. Strictly, ammonite refers to later Mesozoic forms. The trade often uses both words loosely, so check the geological period on the label. A Devonian date means a goniatite; a Jurassic or Cretaceous date means an ammonite.
Why are Moroccan goniatites polished?
The shells are embedded in hard limestone, and polishing is the most effective way to show their internal chambers and suture pattern. A good polish follows the middle of the shell, giving sharp sutures and a clean outline. Over-grinding blurs the chambers and lowers the grade.