The genus Onchosaurus is a sclerorhynchid (extinct family of sawfish-like batoids) reported on the basis of isolated rostral spines.

Published record

An historical review of the published record includes:
  • Gervais (1852) erected Onchosaurus radicalis for a specimen (Turonian, Paris Basin, France) thought to be a reptile tooth (mosasaur) at the time. A redrawn example of this 'tooth' was provided by Cappetta (1987:154, fig. 131)
  • Leidy (1856a: 221) described Onchosaurus mirus from the Campanian "Green Sand" of New Jersey (teleost related to Sphyraena) and (1856b: 256) Ischyrhiza antiqua from North Carolina. He later (1860:120) synonymized the two as Ischyrhiza mira. Cope 1875: 280 includes Ischyrhiza as a Haplomi (pike).
  • Dames (1887b) erected Titanichthys pharao; H. Woodward (1888: 157) noted the genus was preoccupied and Dames (1887c) renamed it Gigantichthys pharao (Santonian of Egypt, see Fig. ).

  • A. S. Woodward (1889) erected Sclerorhynchus atavus based on complete skeletons (to 1 meter in length) from the Late Santonian of Syria - as a or .
  • Jaekel (1890) argued that S. atavus should actually be included as Pristiophorus.
  • Eastman (1904:298) included in Onchosaurus, both Ischyrhiza and Gigantichthys as pike.
  • Haug (1905) erected Gigantichthys numidus and Platyspondylus foureaui (Upper Albian, Algeria).
  • Garman (1913: 244-48) included no fossil taxa in ; he did include within : Propristis DAMES 1883 (Lower Tertiary, Egypt), Sclerorhynchus (Upper Cretaceous, Syria) and Amblypristis DAMES 1888 (Eocene, Egypt).
  • Priem (1914) reported Onchosaurus numidus from the Cretaceous of Egypt (as a teleost).
  • Stromer (1917) erected Onchopristis and moved Gigantichthys numidus to it (having found a relatively complete rostrum; Cenomanian, Egypt). He included as "sawfishes" ( or ) Gigantichthys, Onchopristis and Sclerorhynchus.
  • Arambourg (1935) referred to the 'ganopristines', the rostral spines that include and . In addition, he described Ganopristis leptodon and Onchosaurus maroccanus (Maas., Morocco)
  • Arambourg (1940) erected additional "sawfish" taxa, synonymized Dalpiazia with Ischyrhiza, included Ischyrhiza as a subgenus of Onchosaurus, and separated the members of Ganopristinae into two groups (the first limited to Onchosaurus and its subgenera).
  • Schaeffer (1963) erected Pucapristis branisi (Maas., Bolivia). The author noted that Onchosaurus and Ischyrhiza spines differed in histology: the former, osteodentine [Onchosaurus group] and the latter, orthodentine [Onchopristis group].
  • Cappetta (1972) included all sawfishes in with two subfamilies: Pristinae (Tertiary, spines set in sockets) and Ganopristinae (Late Cretaceous, spines fixed to rostrum by ligaments). The latter was divided into two groups: osteodentine (including Onchosaurus & Pucapristis) and orthodentine (including Dalpiazia, Ischyrhiza & Sclerorhynchus). He went on to note that Onchosaurus maroccanus had orthodentine and synonymized it with Dalpiazia stromeri.
  • Cappetta (1987) included observations and conclusions from his 1974 and 1980b papers as well. All Late Cretaceous sawfishes were included in the suborder Sclerorhynchoides CAPPETTA 1980b and the family CAPPETTA 1974 (=Ganopristinae); genera were sub-grouped as noted in Cappetta (1972). Onchosaurus (=Titanichthys DAMES 1887b = Gigantichthys DAMES 1887c; p 154) included two species, O. radicalis (fig. 131) and O. pharao - the genus ranging from the Turonian-Santonian of France, Africa and South America.
  • Lehman (1989) reported as Onchosaurus pharao, a group of peduncles (all missing caps) from the San Carlos Fm. (E-L Camp., ammonites suggested M. Camp.) of Presidio Co., TX. Based on anteroposterior width (up to 3.6 cm), the author estimated the rostral spine length as 9 cm. Specific determination aside, this would be the youngest (and ?largest) reported example of the genus.
  • Williamson et al. (1989: 241) reported as cf Onchosaurus sp. four rostral spine fragments from the Hosta Tongue, Pt. Lookout Ss. (E. Sant.) of Bernalillo Co., New Mexico.
  • Welton & Farish (1993) included this genus by reference to Lehman 1989 only, suggesting an underlying rarity in Texas.
  • Nelson (1994) raised the extant sawfishes, (), to the ordinal level -- Pristiformes.
  • Compagno (1999) included Recent sawfishes as Pristiformes.
  • Kriwet (2004) wrote that using cladistic principles and phylogenic analysis, appeared to represent a sister group to the Pristiformes and proposed the order Sclerorhynchiformes. Certain taxa (Ptychotrygon, Celtipristis, Texatrygon & Kiestus) deemed Rajiformes incertae sedis by Cappetta (1987), Cappetta & Case (1999) and Kriwet (1999b), were included in Sclerorhynchiformes. Kriwet et al. (2009) would move that latter group to a newly erected .
  • Bourdon et al (2011) speculated on the presence of Onchosaurus oral teeth in the Pt. Lookout Sandstone (E-M Santonian) of New Mexico. The basis for this hypothesis was the presence of Onchosaurus rostral spines and 3 undescribed oral teeth. Cappetta (pers. com 2009) acknowledged seeing a similar tooth-design in Morocco from sediments that yielded Onchosaurus rostral spines.

    The published record appears to have coalesced upon an Onchosaurus rostral spine-design, although it took over 125-years. Systematically, it's certainly to be expected that more than one family will finally emerge, and there continue to be more than one opinion on ordinal position. Kriwet (2004) provided a good overview of the diverse opinions, particularly of ichthyologists, on this matter. Only Bourdon et al 2011 speculated upon the Onchosaurus oral tooth-design.

    Description

    Likely similar to extant sawfishes: a flattened shark-like body with a spine-edged rostrum; unlike Tertiary taxa, the rostral spines are surface-mounted. They have been reported from the Late Cretaceous of France, Africa and South & North America.

    Rostral spines. Histology: osteodentine, no pulp cavity. The cap is much shorter than the peduncle, the enameloid is smooth and limited to the cap. Viewed laterally, the cap is strongly inclined anteriorly and somewhat erect posteriorly; there is a complete anteroposterior carina. Laterally, the cap extends beyond the peduncle and each margin may (O. pharao type) or may not (O. radicalis type) be barbed (basally). The peduncle is high, anteroposteriorly elongated basally and dorsoventrally compressed, particularly apically. The ventral and dorsal faces are tightly folded in the lower half, more so basally. The anterior edge is generally rounded and the posterior flatter with a depression extending towards the cap. Basally, the root has a distinct anteroposterior depression; the anterior and posterior portions slightly flare relative to the medial.

    ? Onchosaurus Oral teeth. Teeth, as found, are small (3-4 mm class) but robust with inflated lobes. The crown is strongly cuspidate and mesodistally compressed; enameloid smooth; shoulders low and thick, not particularly long; transverse carina complete; apron long and thick, rounded basally; and uvula short and thick. The root is high, wider laterally than the crown. The nutritive groove is narrow, parallel and complete, with a lingually positioned pore.

    Selected References

    Arambourg, C. 1935. Note préliminaire sur les vertébrés fossiles des phosphates du Maroc. Bulletin de la Société Géologique de France, Vol. 5: 413-439.
    Arambourg, C. 1940. Le Groupe des Ganopristines. Bulletin de la Société Géologique de France, Sér. 5, 10:127-147
    Bourdon, J., Wright, K., Lucas, S.G., Spielmann, J.A. and Pence, R., 2011. Selachians from the Upper Cretaceous (Santonian) Hosta Tongue of the Point Lookout Sandstone, central New Mexico. New Mex. Mus. Nat. His. and Sc., Bulletin 52; 54pp.
    Cappetta, H., 1972. Les poissons crétacés et tertiaires du Bassin des Iullemmeden (République du Niger). Palaeovertebrata, 5(5), pp 179-251.
    Cappetta, H., 1974. Sclerorhynchidae nov. fam., Pristidae et Pristiophoridae: un exemple de parallélisme chez les Sélaciens. Comptes Rendus de l'Académie des Sciences, Vol. 278, p. 225-228.
    Cappetta, H., 1980b. Les sélaciens du Crétacé supérieur du Liban II: Batoides. Palaeontographica, Abteilung A, 168, 149-229.
    Cappetta, H., 1987. Chondrichthyes II. Mesozoic and Cenozoic Elasmobranchii. In: Handbook of Paleoichthyologie, vol. 3b, Gustav Fischer Verleg, Stuttgart, 193 pp.
    Cappetta, H. and Case, G., 1999. Additions aux faunes de sélaciens du Crétacé du Texas (Albien supérieur-Campanien). Palaeoichthyologica, 9, 5-111.
    Compagno, L. J., 1999. Checklist of living elasmobranchs. In Sharks, skates, and Rays - The Biology of Elasmobranch Fishes. Hamlett, W. C. ed. John Hopkins University Press, Baltimore MD, USA. pp 471-498.
    Cope, E.D., 1875. The vertebrata of the Cretaceous formations of the west: Report. US Geological Survey Territories, 2, 1-303.
    Dames, W. B., 1883. Über eine tertiäre Wirbelthierfauna von der westlichen Insel des Birket-el-Qurun im Fajum (Ägypten), Sitzungsberichte der Königlich Preussischen Akademie der Wissenschafter zu Berlin: 129-153.
    Dames, W. B., 1887b. Über Titanichthys pharao nov. gen., nov. sp., aus der Kreideformation Ägyptens, Gesellshaft Naturforschender. Freunde zu Berlin, Vol. 5: 69-72.
    Dames, W. B., 1887c. Über Gigantichthys Pharao n.g. n. sp. aus der Kreideformation Ägyptens und über die Gattung Saurodon Hays. Gesellshaft Naturforschender. Freunde zu Berlin, pp 69-78.
    Eastman, C.R., 1904. On the Dentition of Rhynchodus and other fossil fishes. The American Naturalist, vol. 38: 295-299.
    Garman, S. 1913. The Plagiostomia (Sharks, Skates and Rays). Memoirs of the Museum of Comparative Zoology at Harvard College, 36:528 pages. Reprinted by Benthic Press (1997), Summers A. P. ed.
    Gervais, P., 1852. Zoologie et paléontologie française (animaux vertébrés): Paris v. 1, iv + 271 (text), v. 2, explanation of plates, v. 3, Plates.
    Haug, E., 1905. Documents scientifiques de la mission saharienne Paleontologique (Mission Foreau Lamy). Paris, fasc. 3, 1905, 751-832.
    Jaekel, O., 1890. Über die systematische Stellung und über fossile Reste der Gattung Pristiophorus. Zeitschr. deutsch. geol. Ges., pp. 86-120, pls. ii-v]
    Kriwet J. 1999b. Ptychotrygon geyeri n. sp. (Chondrichthyes, Rajiformes) from the Utrillas Formation (Upper Albian) of the central Iberian Ranges (East-Spain). Profil 16: 337-346.
    Kriwet, J., 2004. The systematic position of the Cretaceous sclerorhynchid sawfishes (Elasmobranchii, Pristorajea) In: Mezozoic Fishes 3 - Systematics , Palaeoenvironments and Biodiversity. Arratia & Tintori (eds.); Pfeil, Germany. pp 57-73.
    Kriwet, J., Nunn, E. and Klug, S., 2009. Neoselachians (Chondrichthyes, Elasmobranchii) from the Lower and lower Upper Cretaceous of north-eastern Spain. Zoological Journal of the Linnean Society, 2009, 155, 316-347, 12 figures
    Lehman, T., 1989. Giant Cretaceous sawfish (Onchosaurus) from Texas. Journal of Paleontology 63(4), pp 533-535.
    Leidy, K., 1856a. Notices of remains of extinct vertebrated animals discovered by Professor E. Emmons. Proceedings of the Acadamy of Natural Sciences. Philadelphia, 8:255-256.
    Leidy, K. 1856b. Notice of remains of extinct vertebrated animals of New Jersey, collected by Prof. Cook of the State Geological Survey under the direction of Dr. W. Kitchell. Proceedings of the Acadamy of Natural Sciences. Philadelphia, Vol. 8: 220-221.
    Leidy, J., 1860. Description of vertebrate fossils. In: Holmes, F., Post-Pleiocene Fossils of South Carolina. Charleston:Russell and Jones, pp 99-122.
    Nelson, J. S. 1994. Fishes of the world. John Wiley and Sons, Inc. New York. 3rd edition. 600 pp.
    Priem, F., 1914. Sur des Vertebres du Cretace et de l'Eocene d'Egypte. Bulletin de la Societe Geologique de France, 14: 366-382.
    Schaeffer, B., 1963. Cretaceous Fishes from Bolivia, with comments on Pristid evolution. Ameerican Museum of Natural History Novitates no. 2159: 1-20.
    Stromer, E., 1917. Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wiisten Agyptens. II. Wirbeltier-Reste der Baharije-Stufe (unterstes Cenoman). 4. Die Sage des Pristiden Onchopristis numidus Haug sp. und iiber die Sage der Sagehaie. Abhandl. K. Bayerischen Akad. Wiss., Math.-Phys. Ki, vol. 28, sect. 8, pp. 4-28, 1 table.
    Stromer, E., 1922. Der Bau, die Funktion und die Entstehung der Sa Gender Sagehaie. Fortschr. Naturwiss. Forsch., vol. 2: 113-124, 13 figs.
    Welton, B. and Farish, R., 1993. The Collector's Guide to Fossil Sharks and Rays from the Cretaceous of Texas. Before Time, Texas. 204 pp.
    Williamson, T., Lucas, S. and Pence, R., 1989. Selachians from the Hosta Tongue of the Point Lookout Sandstone (Upper Cretaceous, Santonian), Central New Mexico. NMGS Guidebook 40: 239-245.
    Woodward, A. S., 1889. Catalogue of the fossil Fishes in the British Museum. Part I. - XLVII. Brit Mus. Nat. Hist. 474 pp.
    Woodward, H., 1888. Notice of Memoirs 1 - Titanichthys pharo, nov. gen. et nov. sp , Aus der Kreideformation Aegyptens. The Geological Magazine New Series. Decade III. Vol V. No. IV: 157-58.

     

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