524
Journal of Paleontology 91(3):512–547
Remarks.—There is much debate regarding the validity of Galeocerdo aduncus as a distinct species (Gottfried, 1993; Kent, 1994; Purdy et al., 2001; Ward and Bonavia, 2001). It has been suggested that G. aduncus and Physogaleus contortus represent teeth from a single species, with G. aduncus representing upper teeth and P. contortus representing lower teeth (Gottfried, 1993; Kent, 1994). However, the living tiger shark, Galeocerdo cuvier, lacks this marked dignathic heterodonty. Galeocerdo aduncus has a broader crown than Physogaleus contortus, but is narrower than Galeocerdo cuvier. Galeocerdo aduncus lacks the secondary serrations on the distal heel that are diagnostic of G. cuvier and the warped profile that is diagnostic of P. contortus. Galeocerdo aduncus was identified from the Gatun Formation by Gillette (1984), how- ever the original specimens were missing and additional Galeocerdo specimens recovered by Pimiento et al. (2013a) were assigned to Galeocerdo cuvier. Our presumption would be that under greater scrutiny, with a particular focus on the distal cutting edge and the serrations on the distal heel, both G. aduncus and G. cuvier would be present in the Gatun Formation. Because the original holotype of G. aduncus described by Agassiz has since been lost, Purdy et al. (2001) referred to G. aduncus as a nomen dubium and, subsequently, classified the equivalent morphospecies as Galeocerdo sp. Herein, G. aduncus is recognized as a distinct species given the few unique characters discussed above, however, the tooth form of G. aduncus is quite similar to G. cuvier, implying a similar ecological niche. The teeth of G. cuvier are more robust and have a more advanced adaptation toward cutting, which may have given G. cuvier an advantage over G. aduncus.
Galeocerdo cuvier (Peron and Lesueur, 1822) Figure 5.21–5.28
Holotype.—Originally described as Squalus cuvier from the northwest coast of New Holland by Peron and Lesueur (1822).
Occurrence.—STRI 290109, STRI 290116, STRI 290145, STRI 300029, STRI 300032, and STRI 430011.
Description.—Moderately large, robust teeth with a distally angled crown. Weakly convex distal edge with coarse serrations on the heel that are secondarily serrated and fine serrations apical of a deep distal notch; strongly convex mesial edge with serrations that decrease in size around the same height as the distal notch. Root has a concave basal margin, central foramen absent or weakly present. Galeocerdo cuvier from the Chucu- naque Formation has a CH = 3.5–14.8mm and CW = 10.4– 25.1mm.
Materials.—Fifteen isolated teeth; indeterminate position: UF 275045, UF 275060, UF 275062, UF 275082, UF 275095, UF 275105, UF 275120, UF 275145, and UF 281397.
Remarks.—Galeocerdo cuvier differs from Galeocerdo aduncus and Physogaleus contortus in having a broader crown with a more convex mesial edge and a convex distal edge. In profile view, the mesial edge of Galeocerdo cuvier is straight to nearly straight, whereas P. contortus appears to have a twist in the
crown near the apex giving it a weakly sigmoidal appearance (Kent, 1994). Galeocerdo cuvier is an aggressive shark equipped with a cutting-type dentition bearing robust teeth adapted for both slicing and ripping (Frazzetta, 1988), which explains its wide variety of prey options (Kent, 1994). Teeth from the Gatun Formation, CH = 7.4–17.8mm and CW = 14.4–24.5mm (Pimiento et al., 2013a), and from the Yorktown Formation, CH = 13.5–29.1mm and CW = 24.4–33.0mm (Purdy et al., 2001), are larger than those found in the Chucunaque Formation. According to Kent (1994), extant G. cuvier reach lengths up to 7.4 m, but fossil evidence suggests that earlier individuals were likely less than half this length. Galeocerdo cuvier is a highly migratory species with circumglobal distribution in tropical and temperate seas occurring in: Western Atlantic: Massachusetts, USA to Uruguay, including the Gulf of Mexico and the Caribbean; Eastern Atlantic: Iceland to Angola; Indo-Pacific: Red Sea and East Africa to Hawaii and Tahiti, north to southern Japan, south to New Zealand; and Eastern Pacific: southern California, USA to Peru (Garcia, 1994). It has been recognized in a wide variety of habitats, but occurs most frequently at depths less than 140m (Compagno, 1984, 1988; Smith, 1997; Compagno et al., 2005).
Genus Physogaleus Cappetta, 1980 Type.—Trigonodus secundus Winkler, 1876 (Cappetta, 2012).
Physogaleus contortus (Gibbes, 1849) Figure 5.29–5.32
Holotype.—Originally described as Galeocerdo contortus from the Eocene of South Carolina and the Miocene of Virginia by Gibbes (1849, pl. 25, figs. 71–74).
Occurrence.—STRI 290109, STRI 290116, STRI 290145, STRI 300029, STRI 300032, and STRI 430011.
Description.—Moderately large teeth with a slender, distally angled crown. The mesial edge is finely serrated with a warped profile,while the distal edge is notched with fine serrations on the heel and even finer serrations apical of the notch. The root is robust with a U-shaped basal margin and a large lingual protuberance bearing a nutrient groove. Physogaleus contortus from the Chucunaque Formation range fromCH = 6.1–14.9mm and CW = 9.2–17.1mm.
Materials.—Eighteen isolated teeth; indeterminate position: UF 275037, UF 275059, UF 275064, UF 275069, UF 275125, UF 275146, UF 281170, and UF 281171.
Remarks.—Distinguishing features between Physogaleus and Galeocerdo arementioned above, however it is worthwhile to also mention that Physogaleus has finer serrations on the distal heel with a less drastic distal notch and a more pronounced lingual protuberance on the root. The distribution of Physogaleus contortus is difficult to surmise given the confusion that exists regarding its distinction from the genus Galeocerdo (Cappetta, 1980, 1987, 2012; Gillette, 1984; Kent, 1994; Purdy et al., 2001; Ward and Bonavia, 2001) and recent re-assignment to the genus
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