Perez et al.—Miocene sharks and rays from Lago Bayano, Panama
Physodon (Leder, 2013). Springer (1964) stated that the type specimen of Physodon muelleri described by Müller and Henle (1841) actually belonged to a male Scoliodon laticaudus, and chose to synonymize the two genera (Cappetta, 1987, 2012). Leder (2013) described Physodon (= Physogaleus) contortus from the Eocene of Crimea; in which he noted similarities with both Galeocerdo and Physogaleus, but overall determined it was unique and, consequently, chose to resurrect the genus Physodon described by Müller and Henle (1841). Cappetta (1980, 1987, 2012) described P. contortus as being a characteristic component of the Miocene deposits of the Gulf Atlantic Coastal Plain that does not occur in Europe; however, Purdy et al. (2001) recognized misidentifications by Storm (1894), Leriche (1927), and Caretto (1972) that actually represent P. contortus from Europe. Physo- galeus contortus from the Gatun Formation range from CH = 10.0–11.1 and CW = 12–15.5mm (Pimiento et al., 2013a) and from the Pungo River Formation range from CH = 12.0– 19.4mm and CW = 12.0–19.5mm (Purdy et al., 2001). Purdy et al. (2001) noted that P. contortus is twice as common as Galeocerdo in the Lee CreekMine, whereas only two specimens of P. contortus were identified from the Gatun Formation (Pimiento et al., 2013a). In the Chucunaque Formation, P. contortus (N = 19) and Galeocerdo (N = 17) have nearly the same abundance. The slender,more delicate crown ofP. contortus indicates a greater reliance on grasping than cutting during feeding, suggesting a different ecological niche than that of Galeocerdo.
Physogaleus sp. Figure 3.14–3.19
Occurrence.—STRI 290109 and YPA105.
Description.—Small teeth, with a triangular shape and a distally arched, labio-lingually compressed crown. The mesial edge is convex or straight; the distal edge is slightly concave to nearly straight. There is a strong distal notch with well-defined lateral cusplets on the distal heel; the mesial heel may or may not bear lateral cusplets. Anterior teeth are more erect and symmetrical than lateral teeth; anterior teeth have a CH:CWratio close to 1:1, whereas lateral teeth have a CH:CW ratio closer to 1:2. Leder (2013) reported similar height:width ratios for Physogaleus tertius teeth of 1:1 to 5:6 for anteriors and 1:2 for the poster- olateral positions. The root has a lingual bulgewith nutrient pores at the crown-root margin and a prominent axial nutrient groove that penetrates the labial face; the labial face is narrow with a smooth, nearly horizontal crown-root margin. Physogaleus sp. from the Chucunaque Formation has a range of CH = 1.61– 3.21mm and CW = 1.81–3.83mm.
Materials.—Fifteen isolated teeth; anterior: UF 281353; upper: UF 281354, UF 281357; lower anterior: UF 281351, UF 281359; indeterminate position: UF 281352, UF 281356, UF 281358, and UF 281360.
Remarks.—Interpretation of Physogaleus and related genera, such as Galeorhinus and Physodon, among others, is highly debated. Cappetta (1987, 2012) suggested that fossils identified as Galeorhinus and Physodon may be male and female
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teeth belonging to the extinct genus Physogaleus. The genus Physogaleus has not yet been reported from Panama, with the exception of Physogaleus contortus, which has since been reassigned to the genus Physodon based on the work of Leder (2013). Galeorhinus cf. G. galeus identified from the Chagres Formation (Carrillo-Briceño et al., 2015a) shares many simila- rities with Physogaleus sp. reported herein; however, they are distinct. Galeorhinus often has a concave mesial apex and convex distal edge, lacks lateral cusplets on the mesial edge, and has robust serrations on the distal heel that rise high up the crown. These teeth are also similar to cf. Iago sp., but differ, especially, in terms of size and the presence of lateral cusplets. Physogaleus sp. is about twice the size of cf. Iago sp. and has well-defined lateral cusplets, although the presence of cusplets may vary depending on the position within the jaw. Physogaleus has been reported from the Eocene of Morocco, West Africa, Egypt, Belgium, Crimea, and Georgia, United States; the Oligocene of Belgium, France, and Hungary; and the Miocene of France (Cappetta, 1987; Leder, 2013).
Genus Carcharhinus Blainville, 1816
Type.—Carcharias melanopterus Quoy and Gaimard, 1824 (Cappetta, 2012)
Carcharhinus falciformis (Bibron, 1841 in Müller and Henle, 1839–1841) Figure 6.1–6.4
Holotype.—Originally described as Carcharias (Prionodon) falciformis by Bibron (1841 in Müller and Henle, 1839–1841, p. 47). The holotype, MNHN 1134, a 528mm female fetus from Cuba, resides in the Museum National d’Histoire Naturelle, Paris, France (Garrick et al., 1964; Compagno, 1984).
Occurrence.—STRI 290109 and STRI 300032.
Description.—Small, triangular teeth; relatively narrow crown, straight mesial edge, concave or angular distal edge, notch on mesial and distal edges marks a transition from coarser basal serrations to finer apical serrations. Thin root with a nutrient groove and a flat or obtusely concave basal margin. Features distinguishing C. falciformis from other Carcharhinus species are its small size, narrow crown with a notch on both cutting edges, and a relatively flat basal root margin. Carcharhinus falciformis from the Chucunaque Formation range from CH = 5.5–6.1mm and CW = 6.5–11.7mm.
Materials.—Four isolated teeth; upper lateral: UF 281160, UF 281161, and UF 281162.
Remarks.—Carcharhinus falciformis is a solitary species (Claro, 1994) and yet, is commonly caught by fisheries (Bonfil et al., 2009). However, this species has a relatively sparse fossil record; Pimiento et al. (2013a) reported three isolated upper teeth from the Gatun Formation and Purdy et al. (2001) referred to five teeth in the USNM collection from the Pungo River Formation. Pimiento et al. (2013a) recorded a range from CH = 5.1–7.2mm and CW = 4.9–6.4mm; whereas Purdy
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