A single extant species represents this genus and at least one author suggests that it should be treated as a Ginglymostoma subgenus. Compagno (1984) pointed out several details, including the dentitions, which differed sufficiently, to justify a separate genus. The sole representative, Nebrius ferrugineus (LESSON, 1830), is a tropical in-/near shore shark of the Pacific and Indian Oceans. It is a large (to 3.2 m) nocturnal bottom dweller of continental and insular shelves (1 to 70 meters) which feeds on corals, crustaceans, sea urchins, cephalopods and fish.

Compagno notes that the teeth of N. ferrugineus are compressed into the sides of the jaw, creating imbricated rows (not the case with Ginglymostoma), two or three of which are functional. He goes to point out that as an individual grows, the teeth become proportionately thicker & broader relative to height, the central cusp longer compared to the cusplets and the labial flange becomes shorter and broader. These ontogenetic characteristics should be kept in mind when examining fossil teeth.

Cappetta (1987:80) included three species in this genus:

  • N. bequaerti (LERICHE, 1920) [Paleocene of Africa],
  • N. blanckenhorni (STROMER 1905) [Eocene Africa] and
  • N. thielensis (WINKLER 1873) [Eocene of Europe and North America].
    Cappetta also included as Ginglymostoma angolense DARTEVELLE & CASIER, 1943 teeth from the Eocene of Africa which are very similar to N. thielensis, blanckenhorni and the below mentioned N. obliquus.

    Kent (1994) cites Ward & Weist (1990) as including N. blanckenhorni and N. thielensis in the Chesapeake region (Nanjemoy for the former and Nanjemoy & Piney Point for the later), and notes that N. blanckenhorni has been reported from Alabama and N. thielensis from Georgia. Case & Cappetta (1997: 137 pl 6.3) reported Nebrius sp for a single damaged tooth from the Kemp Clay (Maastrichtian) of Texas. Purdy (1998) reported this genus from the Williamsburg Formation (Thanetian - Late Palaeocene) of South Carolina. Nebrius thielensis has been included by Müller (1999:34) in the Piney Pt and by Kent (1999:16) in the Nanjemoy Formations of Virginia.

    Ward (pers com, 1999) notes that Leidy (1877) described N. obliquus from the New Jersey marls and suggests that the teeth currently ascribed to N. thielensis & N. blanckenhorni should be referred to as N. obliquus.

    Other than certain Ginglymostoma teeth, those from Nebrius are quite distinctive. The root has a typical orectolobid design - margino-lingual foramina and, when viewed basally, the lobes form a "V" and include a central pore. The crown is broad and wide with a prominent apron and numerous cusplets. Unlike Ginglymostoma, the central cusp is only slightly larger than the lateral cusplets, the later being much more numerous in Nebrius. When viewed labially, the crown is asymmetrical. The mesial cutting edge is convex and longer than the distal.


     


    Selected References

    Cappetta, H., 1987. Chondrichthyes II: Mesozoic and Cenozoic Elasmobranchii. Handbook of Paleoichthyology, 3B. Gustav Fischer Verlag, Stuttgart and New York, 193 pp.
    Case, G. and Cappetta, H.. 1997. A new selachian fauna from the late Maastrichtian of Texas. Münchener Geowissenschaften Abhandungen 34:131-189.
    Kent, B. 1994. Fossil Sharks of the Chesapeake Region. Egan Rees & Boyer, Maryland, 146 pp.
    Kent, B. 1999. Sharks from the Fisher/Sullivan Site. In: Weems, R. E. et al., 1999. Early Eocene Vertebrates and Plants from the Fisher/Sullivan Site (Nanjemoy Formation) Stafford County, Virginia. Virginia Division of Mineral Resources, Pub 152. 159pp.
    Leidy, J., 1877. Description of Vertebrate Remains, chiefly from the Phosphate Beds of South California. Journal of the Academy of Natural Sciences of Philadelphia, 2nd Ser. 8:209-261, 30-34. Philadelphia.
    Müller, A. 1999. Ichthyofaunen aus dem atlantischen Tertiär der USA. Leipziger Geowissenschafteb, Leipzig, 9/10: 1-360.
    Purdy, R. 1998. Chondrichthyan Fishes from the Paleocene of South Carolina. In: Paleobiology of the Williamsburg Formation (Black Mingo Group; Paleocene) of South Carolina, U.S.A., Albert Sanders ed. Transactions of Amer. Philo. Scty., vol 8 (4), pp 122-146.
    Ward, D. J. and Wiest, R.L., 1990. A checklist of Paleocene and Eocene sharks and rays (Chondrichthyes) from the Pamunkey Group, Maryland and Virginia, USA. Tertiary Res., 12(2) p 81-88.

     

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