https://orcid.org/0000-0002-0041-7151
Figures & data
FIGURE 1. Stratigraphic column of the Calvert Cliffs. Age estimates established on the basis of various biostratigraphic indices and the likelihood that the ∼405 ka orbital eccentricity cycle controlled depositional cyclicity.
FIGURE 2. Map of the northern Chesapeake Bay region of Maryland and Virginia showing the localities incorporated in this study: Calvert Cliffs, Popes Creek, Langley Bluff, and Chancellors Point. Modified from Visaggi and Godfrey (Citation2010).
TABLE 1. The beds as they were grouped for this study, with the inferred time duration for each.
FIGURE 3. Carcharocles spp. teeth, all in labial view. A, CMM-V-4933, C. auriculatus, Eocene, Nanjemoy Formation, Popes Creek, Charles County, Maryland, U.S.A. Collected by W. Counterman. B, CMM-V-5233, C. chubutensis, Miocene, Calvert Formation, Popes Creek, Charles County, Maryland, U.S.A. Collected by J. Osborne. C, CMM-V-818, C. chubutensis, Miocene, Calvert Formation, Popes Creek, Charles County, Maryland, U.S.A. Collected by S. Bentley. D, CMM-V-86, C. chubutensis, Miocene, Calvert Formation, Popes Creek, Charles County, Maryland, U.S.A. Collected by D. Bohaska and N. Riker. E, CMM-V-386, Carcharocles sp., distal lateral cusplet present, mesial one not. Miocene, Calvert Formation, Bed 12, Calvert County, Maryland, U.S.A. Collected by W. Ashby. F, CMM-V-1475, Carcharocles sp., distal lateral cusplet present, mesial one reduced. Miocene, Calvert Cliffs, Calvert County, Maryland, U.S.A. Collected by W. Holliman. G, CMM-V-1469, Carcharocles sp., lateral cusplet presence uncertain. Miocene, Scientists Cliffs, Calvert County, Maryland, U.S.A. Collected by W. Holliman. H, CMM-V-399, C. megalodon, Miocene, Calvert Formation, Bed 12, South of Parkers Creek, Calvert County, Maryland, U.S.A. Collected by W. Ashby. I, CMM-V-4945, C. megalodon, Miocene, Calvert Formation, North of Parkers Creek, Calvert County, Maryland, U.S.A. Collected by J. Nance. J, CMM-V-1304, C. chubutensis, Miocene, Calvert Formation, Popes Creek, Charles County, Maryland, U.S.A. Collected by D. Bohaska. K, CMM-V-92, C. megalodon, Miocene, Calvert Formation, Bed 12, South of Parkers Creek, Calvert County, Maryland, U.S.A. Collected by W. Ashby. L, CMM-V-943, C. megalodon, Miocene, Calvert Formation, Bed 14, Governor Run, Calvert County, Maryland, U.S.A. Collected by M. Gottfried. Scale bar equals 2 cm.
FIGURE 4. Histogram depicting the percentage of cuspleted Carcharocles spp. teeth through time. The width of each bar reflects the time elapsed. The light gray represents percent uncuspleted, and the dark gray represents percent cuspleted. The percent number above each bar (time bin) is the percentage of cuspleted teeth in that sample. The larger number above the percent number is the total tooth sample size available that could be assessed in terms of cusplet presence versus absence (TUC) for each particular group of beds (time bins).
FIGURE 5. Carcharocles chubutensis, USNM 411881, dentition in lingual view from the Pungo River Formation of the Lee Creek Mine in Aurora, North Carolina. Outlines are used to denote missing or broken teeth. Scale bar equals 5 cm.
FIGURE 6. A, crown height (CH) in mm plotted against stratigraphic origin. B, crown height to crown width ratio (CH:CW) plotted against stratigraphic origin. Black circles (left) mark teeth that have lateral cusplets, and open squares (right) indicate teeth without lateral cusplets.
