Formation · Devonian
El Otfal Formation
Middle Devonian unit, Alnif · Issoumour · Jbel Issoumour · Drâa-Tafilalet
The Devonian limestones of the eastern Anti-Atlas around Alnif, Issoumour and Jbel Oufatene supply the spectacular free-standing Moroccan trilobites: Drotops, Walliserops with its trident, Dicranurus with coiled horns, Koneprusia, Cyphaspis and dozens more, air-abraded from the matrix over days. This is also the world capital of trilobite fakery: cast resin fakes, real trilobites with resin-sculpted spines, and composites of several individuals are all common. Under UV, resin and paint fluoresce differently from limestone; a seller should state a restoration percentage (twenty to twenty-five per cent is normal for a spiny phacopid) and disclose any replaced spines or eyes.
| Country | Morocco |
|---|---|
| Region | Alnif, Issoumour, Jbel Issoumour, Drâa-Tafilalet |
| Age | Eifelian, Middle Devonian |
| Age range | ~393–388 Ma |
| PBDB collections | 12 collections, 41 occurrences· Paleobiology Database |
Collecting and legality
Moroccan trilobites are legal to export through dealers with paperwork; the risk is authenticity rather than law. The beds are dug by hand by village collectors around Alnif, Issoumour and Mrakib, and the finished specimens are prepared in Erfoud and Rissani workshops.
Lithology and setting
Grey-black nodular limestones and marls of a Devonian carbonate ramp on the Gondwanan margin of the Anti-Atlas.
Commonly recorded taxa (PBDB)
Genera most often recorded from this unit in the Paleobiology Database (first 200 occurrences): Gerastos (6), Austerops (5), Ceratarges (3), Heliopeltis (3), Cyphaspis (2), Montanproetus (2), Asteropyginae (1), Belenopyge (1), Boeckops (1), Cornuproetus (Cornuproetus) (1), Erbenochile (1), Hollardops (1), Icriodus (1), Leonaspis (1), Leptaena (1).
Source: Paleobiology Database
Elsewhere
Cite this article
Stratum Study. "El Otfal Formation" (Formation). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/formations/el-otfal-formation. Accessed 2026-09-20.
@misc{stratum-el-otfal-formation,
title = {El Otfal Formation},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/formations/el-otfal-formation}},
year = {2026},
note = {Formation article, Stratum Study pack 2026.09, as of 2026-09-19; sources: stratum, pbdb, commons. Accessed 2026-09-20.}
} Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.