Onchopristis

O. numida. Credit: Gasmasque on the Wikimedia Commons.

*Onchopristis* is a genus of Sclerorhynchoidei "sawskate" that lived in the Americas, Europe, Africa and Asia from the Early-Middle Cretaceous.

## Description

*Onchopristis* resembles a massive sawfish, with a barbed rostrum, six fins, one fluke, and a flat body. *Onchopristis* had both its gills, and mouth on the underside of its body, presumably eating its prey off of the river bed. *Onchopristis* may have been very much like modern sawfish. Each individuals snout was covered in denticles. Denticles for *O. numidus* were curved and serrated, with a single barb sticking out of the side. While denticles from O. dunklei were less curved, with two barbs on one side, and a shifted serrated edge on the other. The rostrum was roughly 1-2 meters (3.3-3.6 feet) long. *Onchopristis* may have differed from modern sawfish by being more flat, with smaller fins. A small formation of denticles at the tip of the rostrum is distinctly mustache-shaped. These denticles are very thin with no serrations or barbs on them. This feature is only documented in two specimens, and is unique to the genus.

The first cranial remains of *O. numidus* are known from 2 well-preserved specimens from the Kem Kem; IPUW 353500 and IGR 2818. These preserve most of the skull and rostrum, which helps determine the development and arrangement of the rostral denticles. With these specimens, a size of 2-4 meters long is found. The cranium resembles other sclerorhynchoids. The robust hypertrophied rostrum with wood-like mineralization covers an inner layer of tessellate cartilage located at its center. Thick lateral layers of densely porous cartilage on the sides of the rostral cartilages is similar to that in *Ischyrhiza*, *Schizorhiza* and differentiates *Onchopristis* on the genus level. These remains should help in phylogenetic analyses.

## Paleoecology

*Onchopristis* was one of the many larger fish species within the Kem Kem Formation, North Africa. It is often presumed or speculated as a potential food source for *Spinosaurus* and the other spinosaurids of the Kem Kem such as *Sigilmassasaurus*. Oral teeth of *O. dunklei* from the Aguja Formation prove it coexisted with *Deinosuchus* in some regions. *Onchopristis* is named after the elongated barbed snout lined with teeth for slicing its food. *Onchopristis* would have eaten fish, like its smaller relative *Schizorhiza*, and the shark *Cretalamna*.

## Classification

In 2021, a publication by Tyler Greenfield aimed at correcting technical mistakes in Sclerorhynchoidei finds several nomenclatural issues within the entire suborder. Of these, he finds *O. numidus* to be a grammatical error. "*Pristis*" is feminine and "*numidus*" is masculine. This creates a gender disagreement. To amend this, he proposes *O. numida* to take priority as valid nomenclature over *"O. numidus"*. Greenfield (2021a) finds:

## Synonyms

* O. numidus *(amended)*
* *Gigantichthys numidus (preoccupied)* (=*O. numida*)
* *Onychopristis* (lapsus)
* *Ochopristis* (lapsus)
* *Platyspondylus* (=*O. numida*)
* *Squatina aegyptiaca* (=*O. numida*)
* *Sechmetia*
* *Peyeria* (=*O. numida*)
* *O. d. dunklei* (=*O. dunklei*)
* *O. pharao*

## Gallery

Denticles from *O. numidus* (top) and *Ischyrhiza* (bottom).IPUW 353500 and IGR 2818.
## References

* https://en.wikipedia.org/wiki/Onchopristis
* Dutheil, Didier B. “Les Cladista Du Cenomanien Continental Du Sud-Est Marocain Et Les Ichthyofaunes Associees.” 2000.
* https://www.tandfonline.com/doi/abs/10.1080/02724634.1992.10011475
* https://www.mapress.com/bn/article/view/bionomina.22.1.3
* https://paleobiodb.org/classic/basicTaxonInfo?taxon\_no=96159
* https://academic.oup.com/zoolinnean/article/193/2/746/6125166
* https://incertaesedisblog.wordpress.com/2022/01/12/updates-on-sawskates/