Onchopristis

Onchopristis
Temporal range: Barremian–Cenomanian
Rostral denticle of O. numida
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Chondrichthyes
Superorder:
Batoidea
Order:
Rajiformes
Suborder:
†Sclerorhynchoidei
Family:
†Onchopristidae

Villalobos-Segura, Kriwet, Vullo, Stumpf, Ward, & Underwood, 2021[1]
Genus:
†Onchopristis

Type species
†Onchopristis numida
(Haug, 1905)[3]
Other species
  • †Onchopristis dunklei
    McNulty & Slaughter, 1962[4]
Synonyms
Genus synonymy
    • Platyspondylus
      Haug, 1905
    • Onychopristis
      Jordan, 1923 (lapsus calami)[5]
    • Peyeria
      Weiler, 1935[6]
    • Sechmetia
      Werner, 1989[7]
    • Onchopristes
      Kirkland, 1996 (lapsus calami)[8]
    • Ochopristis
      Hunt, Santucci, & Kenworthy, 2006 (lapsus calami)[9]
Species synonymy
  • O. numida
      • Gigantichthys numidus
        Haug, 1905
      • Platyspondylus foureaui
        Haug, 1905
      • Squatina aegyptiaca
        Stromer, 1927[10]
      • Sechmetia aegyptiaca
        (Stromer, 1927)
      • Peyeria libyca
        Weiler, 1935
    O. dunklei
      • Onchopristis dunklei praecursor
        Thurmond, 1971[11]
      • Sechmetia cruciformis
        Werner, 1989

Onchopristis is an extinct genus of sclerorhynchoid from the Cretaceous of North Africa, Europe, North America, and potentially South America. It contains two valid species, O. numida and O. dunklei, though some researchers argue that both may be considered a single taxon with variation in morphology caused by a wide geographical range.[12] Specimens of Onchopristis have been discovered in coastal and fluvial deposits dated from the Barremian to the Cenomanian ages (~125-94 mya),[1] making this genus one of the oldest known sclerorhynchoid.

Discovery and naming

Restoration of O. numida

In 1905, the French paleontologist Émile Haug named Gigantichthys numidus based fragmentary rostral denticles from the Continental intercalaire of Algeria, and named Platyspondylus foureaui based on vertebrae from the same formation.[3] Articulated specimens have confirmed that the rostral denticles and vertebrae belong to the same species.[1][13] In 1917, Ernst Stromer assigned "G". numidus to a new genus Onchopristis, derived from the Ancient Greek ónkos (ὄγκος, 'barb') and prístis (πρίστις, 'saw' or 'sawfish').[2] Although the spelling "Onchopristis numidus" is commonly used for the type species, Greenfield (2021) suggested that this is grammatically incorrect and emended it to O. numida.[14]

Oral teeth from the Bahariya Formation of Egypt were named Squatina aegyptiaca by Stromer in 1927, and were later renamed as the separate genus Sechmetia by Christa Werner in 1989.[10][7] Again, articulated specimens confirmed that these teeth belong to O. numida.[1][13] In 1935, Wilhelm Weiler named Peyeria libyca for what he thought were sawfish rostral denticles from the Bahariya Formation.[6] An associated specimen of Ischyrhiza mira, a close relative of Onchopristis, indicates that "Peyeria" were actually dermal denticles from O. numida.[15] In 2003, two incomplete rostral denticles, measuring 8.15 mm (0.321 in) and 12.65 mm (0.498 in) respectively, were referred to as Onchopristis cf. O. numida from the Alcântara Formation of Brazil, but no photograph of the specimens were provided for definitive proof.[16]

A second valid species from the Woodbine Formation of Texas, Onchopristis dunklei, was named by Charles McNulty, Jr. and Bob Slaughter in 1962.[4] O. dunklei is also known from the Cenomanian of Spain and France, and from the Albian of Tunisia based on incomplete material.[1] In 1971, John Thurmond named the subspecies O. dunklei praecursor, but it is probably not distinct from O. dunklei.[11][17]

Formerly assigned material

Fourteen rostral denticles formerly identified as Onchopristis sp. from the Alcântara Formation of Brazil have been redescribed as their own genus and species, Atlanticopristis equatorialis.[18] Rostral denticles from New Zealand formerly referred to "O. d. praecursor" have also been reassigned to their own genus and species, Australopristis wiffeni.[19][12] An uncritical summary of 70 vertebrate taxa found in the Aguja Formation reports the presence of O. dunklei based on two fragmentary specimens, though the authors acknowledge the skepticism regarding the Campanian-Maastrichtian occurrence of this genus.[20] Subsequent studies have identified these specimens as Columbusia deblieuxi.[21][22]

In 2019, the isolated rostral denticles found in the possible late Maastrichtian-Paleocene strata from Mali were attributed to O. numida,[23] but these specimens more likely represent cutlassfish fangs.[24] In 2024, four fragmentary rostral denticles and an exceptionally large, 1.46 metres (4.8 ft) long rostrum of sclerorhynchoids from the Maastrichtian-aged Dakhla Formation of Egypt were referred to as Onchopristis sp.[25] However, Greenfield (2025) argued that neither of the referred material from the Dakhla Formation can be assigned to Onchopristis, and he reidentified the rostrum as an indeterminate sclerorhynchoid and the unassociated rostral denticles as Sclerorhynchus cf. leptodon.[24]

Description

Specimens of O. numida, IPUW 353500 and IGR 2818, suggest a length estimate of 2.94–4.25 m (9.6–13.9 ft) and 2.21–3.15 m (7.3–10.3 ft), respectively; such individuals would have weighed 70–150 kg (150–330 lb).[1] Like other sclerorhynchoids, it had a long rostrum with large denticles similar to sawfishes and sawsharks. This feature was convergently evolved, recently proposed as 'pristification',[26] and its closest living relatives are actually skates.[1] Isolated rostral denticles are the most common fossils of Onchopristis, but rostra, chondrocrania, jaws, oral teeth, vertebrae, and dermal denticles have also been found.[1][13]

Paleobiology

Predation

Specimens of Onchopristis have been associated with the jaws of Spinosaurus in North Africa, indicating that Spinosaurus would have preyed upon Onchopristis based on direct evidence of piscivory. An isolated fish vertebra, tentatively referred to Onchopristis, has been associated with the tooth alveolus of a possible specimen of Spinosaurus (MSNM V 4047).[27] Similarly, the dentary fragment of Spinosaurus aegyptiacus (MPDM 31) is associated with the rostral denticle of Onchopristis.[28] Additionally, the teeth of Spinosaurus and rostral denticles of Onchopristis form a bone bed at one locality in the Kem Kem beds of Morocco (Errachidia Province).[29]

References

  1. ^ a b c d e f g h 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.
  2. ^ a b Stromer, E. (1917). "Ergebnisse der Forschungreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltier-Reste der Baharîje-Stufe (unterstes Cenoman). 4. Die Säge des Pristiden Onchopristis numidus Haug sp. und über die Sägen der Sägehaie" (PDF). Abhandlungen der Königlich Bayerischen Akademie der Wissenschaften, Mathematisch-physikalische Klasse. 18 (8): 1–28.
  3. ^ a b Haug, E. (1905). "Paléontologie". In Foureau, F. (ed.). Documents scientifiques de la mission saharienne, mission Foureau-Lamy d'Alger au Congo par le Tchad. Fascicule 3. Paris: Masson. pp. 751–832.
  4. ^ a b McNulty, C.L. Jr.; Slaughter, B.H. (1962). "A new sawfish from the Woodbine Formation (Cretaceous) of Texas". Copeia. 1962 (4): 775–777. doi:10.2307/1440678. JSTOR 1440678.
  5. ^ Jordan, D.S. (1923). "A classification of fishes, including families and genera as far known". Stanford University Publications, University Series, Biological Sciences. 3 (2): 77–243. doi:10.5962/bhl.title.161386.
  6. ^ a b Weiler, W. (1935). "Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltierreste der Baharîje-Stufe (unterstes Cenoman). 16. Neue Untersuchungen an den Fischresten" (PDF). Abhandlungen der Bayerischen Akademie der Wissenschaften, Mathematisch-naturwissenschaftliche Abteilung. 32: 1–57.
  7. ^ a b Werner, C. (1989). "Die Elasmobranchier-Fauna des Gebel Dist Member der Bahariya Formation (Obercenoman) der Oase Bahariya, Ägypten". Palaeo Ichthyologica. 5: 1–112.
  8. ^ Kirkland, J.I. (1996). "Paleontology of the Greenhorn cyclothem (Cretaceous: late Cenomanian to middle Turonian) at Black Mesa, northeastern Arizona". New Mexico Museum of Natural History and Science Bulletin. 9: 1–131.
  9. ^ Hunt, R.K.; Santucci, V.L.; Kenworthy, J. (2006). "A preliminary inventory of fossil fish from National Park Service units". New Mexico Museum of Natural History and Science Bulletin. 34: 63–69.
  10. ^ a b Stromer, E. (1927). "Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltierreste der Baharîje-Stufe (unterstes Cenoman). 9. Die Plagiostomen mit einem Anhang über käno- und mesozoische Rückenflossenstacheln von Elasmobranchiern" (PDF). Abhandlungen der Bayerischen Akademie der Wissenschaften, Mathematisch-naturwissenschaftliche Abteilung. 31 (5): 1–64.
  11. ^ a b Thurmond, J.T. (1971). "Cartilaginous fishes of the Trinity Group and related rocks (Lower Cretaceous) of north central Texas" (PDF). Southeastern Geology. 13 (4): 207–227.
  12. ^ a b 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. Bibcode:2012JAfES..64...71M. doi:10.1016/j.jafrearsci.2011.11.009.
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  21. ^ Kirkland, J.I.; Eaton, J.G.; Brinkman, D.B. (2013). "Elasmobranchs from Upper Cretaceous freshwater facies in southern Utah". In Titus, A.L.; Loewen, M.A. (eds.). At the Top of the Grand Staircase, the Late Cretaceous of Southern Utah. Bloomington: Indiana University Press. pp. 153–194. ISBN 978-0253008831.
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  25. ^ Capasso, L.; Abdel Aziz, S.; Tantawy, A. A.; Mousa, M. K.; Wahba, D. G. A.; Abu El-Kheir, G. A. (2024). "The first described Onchopristis Stromer, 1917, (Elasmobranchii: †Onchopristidae) from the Marine Maastrichtian of Dakhla Formation, Western Desert, Egypt". Journal of African Earth Sciences. 220. 105415. doi:10.1016/j.jafrearsci.2024.105415.
  26. ^ Greenfield, T. (2024). "Pristification: Defining the convergent evolution of saws in sharks and rays (Chondrichthyes, Neoselachii)". Mesozoic. 1 (2): 121–124. doi:10.11646/MESOZOIC.1.2.3.
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