Carcharhinus plumbeus, the Sandbar shark, is a world-wide species inhabiting continental/insular shelves of warm temperate to tropical seas. It is bottom-associated ranging from coastal waters and river mouths to depths of 280m (usually 20-50m). A medium-sized shark reaching 2.5 - 3 meters (average about 1.5m), it feeds mainly on bony fishes but also small sharks, cephalopods, and other inverts. (Ref.: Bigelow & Schroeder 1948: 368 as C. milberti (MÜLLER & HENLI, 1841); Compagno 1984:493, Garrick 1982:132, Compagno et al 2005, and FishBase.org.)

The dentition is cutting-clutching in design; cutting provided by a single functional row of triangular uppers with a serrate cutting-edge. Teeth usually number 14 per quadrate (plus symphyseals, range 13-15/12-15) displaying gradational dignathic heterodonty. Two tooth variations are present, one sharply angular (as some of the included fossils) and the other more rounded (as the Recent example).

Using the Recent tooth-set (Fig. ) as a descriptive basis, the upper teeth have a triangular cusp, upright in the first two positions followed by distally inclined files; the final 3-4 teeth are abruptly reduced. The cutting edge is complete and fully serrate; serrations are uniformly small, but are often coarser on the oblique shoulders. The crown itself is remarkably thin and serves as a useful diagnostic key. In lower teeth, the cusps are narrow and erect; the serrations are minute. The first several files have an incomplete cutting edge which are serrate apically; by the fifth file the cutting edge is complete with apical and shoulder serrations only. In posterior files, the cutting edge may be fully serrate. Symphyseal files number from one to three per jaw; the accompanying example (Fig. ) illustrates what appears to be file-splitting along the lower symphysis.

At Lee Creek, the C. plumbeus upper tooth-design is an uncommon component of upper Pungo River and lower Yorktown (including YT2) sediments. Compared with their modern counterparts, the serrations are less homogeneous; otherwise there appears to be little difference between the Mio-Pliocene and Recent teeth and dentition. Due to relative abundance, lower teeth would be quite scarce and not easily identified with great confidence. A reconstruction of isolated upper teeth (ref Fig. ) supports the argument that these teeth represent a Mio-Pliocene variation of the modern taxon. Purdy et al (2001: 155) reported this tooth-design as present from the upper Pungo River (Unit 4-5) and lower Yorktown (Unit 1) Formation sediments and attributed it to C. plumbeus.

References

Bigelow, H. and W. C. Schroeder 1948. Part 1. Sharks; in Fishes of the western North Atlantic. Sears Foundation for Marine Research, Yale University, New Haven.
Compagno, L.,1984. FAO Species Catalogue, Vol 4, parts 1 & 2 Sharks of the World. United Nations Development Program.
Compagno, L.,1988. Sharks of the Order Carcharhiniformes. Princeton University Press, Princeton, NJ. 486 pp , 35 plates.
Compagno, L,, Dando & M., Fowler, S., 2005. Sharks of the World. Harper Collins, 368 p.
FishBase.org Feb. 2009.
Garrick, J., 1982. Sharks of the Genus Carcharhinus. NOAA Technical Report NMFS Circular 445. 194 pp.
Purdy, R., Schneider, V., Appelgate, S., McLellan, J., Meyer, R. & Slaughter, R., 2001. The Neogene Sharks, Rays, and Bony Fishes from Lee Creek Mine, Aurora, North Carolina. In: Geology and Paleontology of the Lee Creek Mine, North Carolina, III. C. E. Ray & D. J. Bohaska eds. Smithsonian Contributions to Paleobiology, No 90. Smithsonian Institution Press, Washington D.C. pp. 71-202.