Carcharhinus brachyurus, the Copper shark, is a medium/large-sized (to 3.2m) shark of warm temperate/subtropical waters. It is found in regional pockets along the continental margins of the Indo-Pacific, Atlantic and Mediterranean (no reports from US East coast); close inshore or to depths of 360m. Its diet includes teleosts, cephalopods and small sharks and rays. (Ref. Garrick 1982, Compagno 1984, Compagno et al 2005, and FishBase.org.)

The dentition is cutting-clutching in design with moderately narrow distally inclined uppers and narrow rather upright lowers. Garrick (1982) noted teeth generally number 15-16 per quadrate (plus parasymphyseals)¹. The dentition displays gradational, dignathic, sexual and individual heterodonty; male teeth have narrower cusps and lingually curved crowns (Ref. fig. ).

The upper teeth have broad roots with a well-developed nutrient groove, low shoulders, a short, narrow to moderately broad cusp, fully serrate cutting edge² and are distally directed. Serrations are irregular, may be small to fine and usually become coarser and larger basally (Figs. & ). Shoulders usually transition into the cusp gently, but sometimes display distally, a near notch (Garrick 1982: 175, fig. left). In posterior-most positions, the distal shoulder may appear to bear cusplets (Fig. right). In the accompany tooth-sets (fig. ), the male teeth are much more finely serrate than the female, have a thicker root/crown and are more sigmoidal in profile.

In general, the lower teeth have narrow cusps which are rather erect to weakly inclined with a distal curvature and finely serrate cutting edge; positionally, there are subtle differences. In the above female, the cutting-edge is limited to the main cusp in the first three positions; the cutting edges (& serrations) then move onto the shoulders first distally then mesially. The 13th position actually displays a cusplet-like enlarged serration adjacent to the distal base of the cusp. The male lowers are even narrower and more finely serrate; the shoulders don't reflect a serrate cutting edge until the 8th position.

Lee Creek Perspective

Examples of the Carcharhinus brachyurus tooth-design are abundant in Pungo River tailings. Kent (1994: Fig 11.4.d) included this tooth-design as Carcharhinus priscus (AGASSIZ 1843); common in the Calvert, Choptank and Eastover Formations of the Chesapeake region. Müller (1999: 49, pl 6, fig 10, 11) also included Calvert specimens as C. priscus. Purdy et al (2001: 151, Fig 53a) reported this design as C. brachyurus from Pungo River units 1-5. These authors commented that their specimens (n=500) included no male teeth as described Garrick (1982: 175) or Bass et al (1973: 24) and concluded all the specimens were female. They went on to comment that Corax egertoni (Agassiz 1843, pl 36.6) "is identical to those of the extant C. brachyurus" (we see no clear connection between the two tooth-designs). Prior authors evaluated/described the teeth based on labial/lingual perspective only; including the lateral profile allowed us to recognize two distinct groups -- in the uppers with sigmoidal profiles, the cusp width is narrower (male) than those without.

From the inception of elasmo.com (1996), the "classic" assignments of Miocene Carcharhinus teeth to three paleo-buckets (egertoni, priscus and elongatus) has been reject in favor of establishing relationships with modern taxa. These teeth are usually fairly small (1 to 1.5 cm-class) and closely follow the above description of Recent C. brachyurus individuals; however, serrations are somewhat stronger, particularly on male teeth (when compared with the included recent tooth-set). The accompanying Pungo River reconstruction (Fig ) compares well with the modern female. Male teeth are much less common and a good reconstruction³ could not be attempted; positional assignments are based on the female counterpart.

It is arguable that Carcharhinus brevipinna (Müller & Henle, 1839) is present in the Lee Creek fauna; the accompanying tooth (Fig. left) could represent that species. The serrations are fine and the basal & lateral profiles vary from comparable brachyurus specimens. Definitive examples do not exist to support a different taxon rather than a variation of the brachyurus design-envelope; however, a sub-grouping of teeth can be identified that might represent that taxon. It is interesting to note, these teeth have a different profile than the brachyurus male and are more robust than the female.

Footnotes

References

Bass, A., D'Aubrey, J and Kistnasamy, N., 1973. Sharks of the East Coast of Southern Africa: The Genus Carcharhinus (Carcharhinidae). Investigational Report, Oceanographical Research Institute, 33:1-68.
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 Dec. 2008.
Garrick, J., 1982. Sharks of the Genus Carcharhinus. NOAA Technical Report NMFS Circular 445. 194 pp
Kent, B., 1994. Fossil Sharks of the Chesapeake Region. Egan Rees & Boyer, Maryland. 146 pp.<
Müller, A. 1999. Ichthyofaunen aus dem atlantischen Tertiär der USA. Leipziger Geowissenschafteb, Leipzig, 9/10: 1-360.
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.