A giant saw-snouted ray of the Kem Kem rivers
Onchopristis was a large ray with a long, flattened snout, the rostrum, lined on both sides with enlarged, barbed spikes. It belongs to the Sclerorhynchoidei, an extinct group that looks like modern sawfishes but is more closely related to skates; the “saw” evolved independently. Calling it a sawfish is a common and convenient shorthand, but it is not a member of the living sawfish family.
The fossils sold as Onchopristis teeth are these rostral denticles, not jaw teeth. Each is a hard, enameloid-capped spike with a backward-pointing barb near the tip, which gives the genus its name, from the Greek for “barb”. Martill and Ibrahim described aberrant rostral teeth from the Kem Kem beds, showing that the shape is more variable than the classic single-barb hook [2].
What recent research shows
In 2021, Villalobos-Segura and colleagues described skeletal remains of Onchopristis from the mid-Cretaceous, including a mouth with oral denticles, and interpreted the animal as euryhaline, able to live in both fresh and salt water [1]. That fits its setting: the Kem Kem Group is a Cenomanian river and delta system, made up of the Gara Sbaa and Douira formations, whose fossils are mostly isolated remains of fishes, turtles, crocodyliforms, pterosaurs and dinosaurs [3]. Onchopristis shared these rivers with Spinosaurus, which may have preyed on large fish, though how much it hunted in water is still debated.
The type species was first named Gigantichthys numidus by Haug in 1905. The spelling O. numidus is still widely used, while some recent authors prefer O. numida; both refer to the same species.
Key facts
| Scientific name | Onchopristis numida (also O. numidus) |
|---|---|
| Group | Sclerorhynchoidei (Batoidea), extinct saw-snouted rays |
| Geological age | Cenomanian, early Late Cretaceous (about 100–94 million years) |
| Formation | Kem Kem Group (Gara Sbaa and Douira formations) |
| Locality in Morocco | Kem Kem escarpment, Taouz and Begaa area, Errachidia Province |
| Typical size | about 2–7 cm (0.8–2.8 in) per rostral denticle |
How to judge an Onchopristis tooth
- Barb: a complete, sharp barb is the key feature of a good Onchopristis tooth. Worn barbs are common because many denticles were rolled in river gravels; the Kem Kem Group even contains abraded denticles in pebble lags [3].
- Cap and base: a glossy enameloid cap on a fibrous, often lighter-colored base is normal.
- Repairs: long denticles frequently break across the shaft and are glued. Hairline repairs are acceptable when disclosed; restored barbs or tips are a different matter. Our listings state natural, repaired or restored.
- Size claims: treat dramatic body-size figures in sales copy with caution. The skeleton is rarely preserved, and estimates depend on the method used.
How the rostrum worked
Living sawfishes and sawsharks, which evolved their toothed snouts independently, use the rostrum to stun or impale small fish with sideways swipes and to probe soft sediment for buried prey. Onchopristis probably used its rostrum in a broadly similar way, but the hooked barbs are unusual and their exact function is not known.
Each Onchopristis tooth was anchored in the rostral cartilage by its base. After death the cartilage decayed, and the denticles were scattered through the river sands, which is why complete rostra are rare and isolated denticles are common.
Onchopristis teeth for shops and collectors
An Onchopristis tooth pairs naturally with Kem Kem dinosaur material: same rivers, same age, and an animal most customers have never heard of. A small Onchopristis tooth works well in lots; large, complete specimens with sharp barbs are display pieces. Approved trade buyers see lot prices after they apply for a wholesale account; to combine them with Spinosaurus teeth, request a quote. See all Moroccan fish fossils.
References
- Villalobos-Segura, E., Kriwet, J., Vullo, R., Stumpf, S., Ward, D. J. & Underwood, C. J. (2021). The skeletal remains of the euryhaline sclerorhynchoid †Onchopristis (Elasmobranchii) from the ‘Mid’-Cretaceous and their palaeontological implications. Zoological Journal of the Linnean Society 193(2): 746–771. doi:10.1093/zoolinnean/zlaa166
- Martill, D. M. & Ibrahim, N. (2012). Aberrant rostral teeth of the sawfish Onchopristis numidus from the Kem Kem beds (?early Late Cretaceous) of Morocco and a reappraisal of Onchopristis in New Zealand. Journal of African Earth Sciences 64: 71–76. doi:10.1016/j.jafrearsci.2011.11.009
- Ibrahim, N., Sereno, P. C., Varricchio, D. J., Martill, D. M., Dutheil, D. B., Unwin, D. M., Baidder, L., Larsson, H. C. E., Zouhri, S. & Kaoukaya, A. (2020). Geology and paleontology of the Upper Cretaceous Kem Kem Group of eastern Morocco. ZooKeys 928: 1–216. doi:10.3897/zookeys.928.47517
Frequently asked questions
Is Onchopristis a sawfish?
Not in the strict sense. Onchopristis belongs to the Sclerorhynchoidei, an extinct group of rays that evolved a toothed rostrum independently of modern sawfishes and is more closely related to skates. Sawfish is still a convenient everyday name, and we use it so buyers can find these fossils.
Are Onchopristis teeth actually teeth?
They are rostral denticles: enlarged, tooth-like spikes set along the sides of the snout, not teeth from the jaws. Onchopristis also had small oral teeth, but the large barbed spikes sold in the trade come from the rostrum. They are hard, enameloid-capped structures, which is why they fossilize well.
Did Onchopristis live in fresh water?
Its fossils are found in the Kem Kem river and delta deposits, and a 2021 study of its skeleton describes it as euryhaline, meaning it could tolerate both fresh and salt water. It probably moved between coastal and river environments, as some living rays and sawfishes do.
How old are Onchopristis teeth from Morocco?
They come from the Kem Kem Group, which is Cenomanian in age, roughly 100 to 94 million years old. That is the same rock unit that yields Spinosaurus and Carcharodontosaurus teeth, so Onchopristis denticles are often found and sold together with Kem Kem dinosaur material.