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Journal of Paleontology 91(3):512–547
flat with an elongate apron that extends well onto the root. The lingual face is convex with a short uvula that comes to a point. In labial view on the mesial side, the root is narrow, has a slightly concave basal margin, and a large foramen adjacent to the apron. On the distal side, the root is mostly broken off, but appears to have been larger than the mesial side. On the lingual face, there is a slight lingual bulge at the extremity of the uvula, a large infundibulum beneath the uvula, and a depression on the mesial side of the root. Centrophorus sp. from the Chucunaque Formation has a CH = 2.06mm and CW = 2.28mm.
Material.—One isolated tooth; anterolateral: UF 281349.
Remarks.—No teeth from the order Squaliformes were identified fromthe Gatun Formation (Pimiento et al., 2013a); however, they dominate the Piña Sandstone facies of the Chagres Formation (Carrillo-Briceño et al., 2015a). In contrast, only a single tooth from the Chucunaque Formation was identified as belonging to this order. Cappetta (1987, 2012) mentioned that the apron does not extend past the root in Centrophorus; however, that character cannot be addressed with this specimen (Fig. 3.2). Cappetta (1987, p. 53) described Centrophorus as being “not rare in bathyal deposits” in theMiocene of
France.Carrillo-Briceño et al. (2015a) identified 11 teeth as Centrophorus
aff.C.granulosus. Extant Centrophorus granulosus are widespread with occurrences in the Eastern Atlantic,Western Central Atlantic, the Indian Ocean, and the Western Pacific (Compagno, 1984; Last and Stevens, 1994; and Compagno and Niem, 1998); however, it is not known from the Eastern Pacific (White et al., 2013). Extant representatives of the family Centrophoridae most commonly occur at depths of 1000–1500m, however they have been reported at depths as shallow as 50m (Compagno et al., 2005).
Order Lamniformes Berg, 1958 Family Otodontidae Glikman, 1964
Genus Carcharocles Jordan and Hannibal, 1923
Type.—Carcharodon auriculates Blainville, 1818 (Cappetta, 2012).
Carcharocles megalodon (Agassiz, 1835) Figure 4.1–4.5
Holotype.—An upper anterior tooth attributed to Carcharodon megalodon (TE-PLI 18) preserved in the Staatliches Museum für Naturkunde in Karlsruhe, Germany (Purdy et al., 2001). Originally described in Agassiz (1835, pl. 29, figs. 2, 3).
Occurrence.—STRI 290116, STRI 290125, STRI 290139, STRI 290144, STRI 290145, STRI 300029, STRI 300032, STRI 430011, and STRI 430012.
Description.—Large, triangular teeth; broad crown, uniform (or nearly uniform) serrations, convex lingual face with a distinct neck (i.e., bourlette), flat or convex labial face. Robust, thick, and U-shaped root with dispersed foramina; foramina tend to be concentrated at the crown-root contact on the labial face (Fig. 4.1, 4.2). Carcharocles megalodon exhibitsmonognathic and dignathic heterodonty. Upper teeth are broader, especially at the crown apex,
with more convex cutting edges. Lower teeth are narrower with sigmoidal, straight, or concave cutting edges. There is an increasing asymmetry antero-laterally throughout the jaw. Posterior teeth are much smaller than anterior teeth with a more obtuse to nearly straight basal root margin. One specimen, UF 275108, has a reduced lateral cusplet (i.e., a vestigial cusplet; Fig. 4.3–4.5). Carcharocles megalodon from the Chucunaque Formation range from CH = 24.6–88.2mm and CW = 28.6–88.0mm.
Materials.—Sixty isolated teeth; upper anterior: UF 275085, UF 275097, UF 275110, UF 275111, UF 275118, and UF 275132; lower anterior: UF 275129 and UF 275136; upper lateral: UF 275084, UF 275092, UF 275109,UF 275114,UF 275128, andUF 275139; lower lateral: UF 275086, UF 275131, and UF 275134; posterior: UF 275053; indeterminate position: UF 275051–52, UF 275096, UF 275098–99, UF 275107–08, UF 275112–13, UF 275117, UF 275126–27, UF 275130, UF 275133, UF 275135, UF 275137, UF 275138, UF 275148, UF 275151, and UF 275156.
Remarks.—The generic assignment of this species has been highly contested over the last century, with Carcharocles, Megaselachus, Carcharodon, Procarcharodon,and Otodus all being suggested as the most appropriate. A morphometrics study by Nyberg et al. (2006) determined that C. megalodon is not ancestral to Carcharodon carcharias, suggesting it belongs in a separate lineage with Otodus obliquus as the ancestor. Consequently, the oldest alternative generic assignment takes precedence, which is Carcharocles (Jordan and Hannibal, 1923). For a more detailed discussion on this topic see Pimiento et al. (2010). In the Chucunaque Formation, C. megalodon is intermediate in size between that of the Gatun Formation and the Yorktown Formation (Purdy et al., 2001; Pimiento et al., 2013a; Pimiento and Balk, 2015), but more closely aligns with the size range observed in the Gatun Formation, which has been proposed to be a paleonursery for C. megalodon (Pimiento et al., 2010). The lack of lateral cusplets and a broader crown are said to delineate
C.megalodon fromCarcharocles chubutensis,although neither of those characteristics is absolutely definitive (Kent, 1994). Lateral cusplets may still occur in juvenile individuals of C. megalodon (Pimiento et al., 2010), or as vestigial characters in adults (Fig. 4.3–4.5). Carcharocles megalodon had a cosmopoli- tan distribution, occurring in tropical to temperate coastal habitats (Gottfried et al., 1996; Purdy, 1996; Pimiento et al., 2016). Recent studies have calculated the most likely time of extinction of this species to be 2.6 Ma (Pimiento and Clements, 2015). In the region, C. megalodon occurs in both the Caribbean and the Pacific (Longbottom, 1979; De Muizon and DeVries, 1985; Long, 1993; Iturralde-Vinent et al., 1996; Laurito, 1999; Aguilera and Rodrigues de Aguilera, 2001; Donovan and Gunter, 2001; Nieves-Rivera et al., 2003; Portell et al., 2008; Carrillo-Briceño et al., 2015a).
Family Lamnidae Müller and Henle, 1838 Genus Isurus Agassiz, 1843
Type.—Isurus oxyrinchus (Rafinesque, 1810) (Cappetta, 2012).
Isurus oxyrinchus (Rafinesque, 1810) Figure 4.6–4.16
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