Physogaleus is an extinct genus of requiem shark, which left a fossil record of teeth that are reminiscent of those of Galeocerdo (at least the laterals). In general, the crown is blade-like and distally (weakly or strongly) directed. The mesial cutting-edge continues onto the shoulder and often bears weak serrations. The distal cutting-edge is more upright creating a notch at the distal heel/shoulder. This heel can be strongly serrate with up to four cusplet-like serrations in posterior teeth.

Cappetta (1987) notes that there is strong sexual dimorphism of the lower anterior teeth (the cusps of the male's are laterally compressed), otherwise male and female teeth are of similar design. The basal face of the root can often differentiate upper and lower teeth. In lower teeth, the surface is flat and straight, while in uppers, it is often concave. Positionally, anterior teeth tend to have more erect cusps, few if any distal cusplets, and a stronger lingual root protuberance. In more lateral positions, the cusps become more distally directed, the distal shoulder more serrate and the roots more labio-lingually compressed.

Physogaleus teeth have been reported from Cenozoic deposits of Europe, Africa, Asia and North America. The tooth-design is highly variable amongst tooth-positions and individuals; this has led to the erection of numerous species that have later been synonymized with existing taxa. Represented in the western Atlantic:
 

  • P. secundus (WINKLER 1874). Kent (1994:88) deemed P. secundus as the only species of the Chesapeake's Nanjemoy and Piney Point sediments. At this point, it is only fair to state that I have seen no convincing arguments (by Kent or others) that justify the usage of secundus as a bucket for multiple Physogaleus tooth-designs. For example, within the Nanjemoy, juvenile Physogaleus teeth are represented by two versions which argues against sexual dimorphism as the underlying factor for these variations. Lacking the time and/or expertise to attempt to unravel this matter, I will use "secundus" to refer to the bucket-like treatment of multiple similar but different tooth-designs.

    Case (1994) reported P. tertius (WINKLER 1874) and a new species, P. americanus, from the Paleocene & Early Eocene of Mississippi; the teeth illustrated for these two species are indistinguishable from examples referred to herein as P. "secundus". Müller (1999:52) reported P. tertius (Piney Point Fm) and a new species, P. latecuspidatus (Nanjemoy Fm) from the Eocene of Virginia; again, the illustrated material falls well within the range of P. "secundus" as suggested by Kent. Although scarce, Physogaleus teeth have been found (pers. obs.) in the Aquia Fm (Selandian) of Maryland; these specimens can neither be positively ascribed to nor differentiated from P. "secundus".

    Lutetian and Bartonian sediments of the Castle Hayne formation also include more than one Physogaleus taxon. Case & Borodin (2000) reported Physogaleus sp (fig 47-51) and erected Paragaleus duplinensis (page 28, fig 34, 52, 53) for tooth designs encompassed by "secundus" or Rhizoprionondon (in the case of specimens 50 & 51). In addition, they erected Physogaleus rosehillensis (page 29, fig 54) for a single small lateral tooth with a Rhizoprionodon-like central cusp (see fig. ). Insufficient material is available to either confirm or disprove this assignment based on dentition-design; for now, it will be referred to as "Physogaleus" rosehillensis on the website.

  • P. latus (STORMS 1894) is the Oligocene representative of this genus. Müller (1999:53) was the first to reported this taxon from North America, noting there occurrence in the Old Church Fm of Virginia and the Trent Marls of North Carolina..
  • P. contortus (GIBBES 1849). Based on tooth-design, Ward & Bonavia (2001:138) moved this species from Galeocerdo to Physogaleus. Because the contortus-design is much more similar to Physogaleus, elasmo.com followed this reassignment. They also suggested that contortus be synonymized with Galeocerdo aduncus which would then be attributed to Physogaleus as well. Elasmo.com did not find their arguments sufficient/convincing and does not follow this proposal. P. contortus is generally common in Miocene deposits of Eastern North America.

    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.. 1994. Fossil Fish Remains fron the Late Paleocene Tuscahoma and Early Eocene Bashi Formations of Meridian, Lauderdale County, Mississippi. Palaeontographica Abt. A, 230, pp 97-138.
    Case.G. & Borodin, P., 2000. A Middle Eocene Selachin Fauna from the Castle Hayne Limestone Formation of Duplin County, NC, Munchner Geowiss. Abh.. 39:17-32.
    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. & Grimsley, G., Early Eocene Vertebrates and Plants from the Fisher/Sullivan Site (Nanjemoy Formation) Stafford County, Virginia. Virginia Division of Mineral Resources, Pub 152: 11-37.
    Müller, A. 1999. Ichthyofaunen aus dem atlantischen Tertiär der USA. Leipziger Geowissenschafteb, Leipzig, 9/10: 1-360.
    Ward, D. J. and Bonavia, C. G. 2001. Additions to, and a review of, the Miocene shark and ray fauna of Malta. The Central Mediterranean Naturalist, 3(3) p131-146

     

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