Onchopristis is a large genus of sawskate from the Early to Late Cretaceous (Barremian-Cenomanian). The species fossils found in various places that concluded its habitat, like North America, North Africa, Brazil, and New Zealand. [1]
This genus includes two species, O. numida and O. dunklei. Speculated to be euryhaline (saltwater and freshwater tolerance), it swam up the rivers of the Bahariya Formation and the other locales it is found in. Both species are around 3.25 to 4.5 metres in length.
Taxonomy[]
Despite formerly being classified within Pristidae, or the sawfishes, more recent phylogenetic analyses suggest it belonged to a family known as Sclerorhynchidae in the order Rajiformes, closer to skates (Rajidae) than pristids. A more recent phylogenetic analysis suggests that Sclerorhynchidae split up into several families, all under the clade Sclerorhynchoidea.
Onchopristis belonged to Onchopristidae as a result of the new phylogenetic analysis.
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.
Paleobiology[]
As with modern sawfish, Onchopristis's eyes were on top of its head, potentially to spot possible predators; and its mouth and gills were under its body. It used its long rostrum to detect prey under the sand. Unlike sawfish, sawskates had barbed teeth on their rostrum; potentially as a defence mechanism as at least two genera (Onchopristis and Atlanticopristis) lived alongside spinosaurids, which possibly hunted them. They are probably oviparous, depositing egg cases upstream, away from predators.
Most of the time, it was possible that it lived out in the ocean.
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:
| Sclerorhynchodei |
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Appearance in other media[]
Jurassic Park[]
- Onchopristis appeared in the video game Jurassic World: The Game.
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Read more Onchopristis on Jurassic Park Wiki |
Reference[]
- 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/