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Journal of Paleontology 91(3):512–547
indicate that the crown becomes increasingly more distally arched posteriorly and the root lobes diminish toward the pos- terior, forming a more horizontal basal margin. This heterodonty was also observed in the Chucunaque Formation (anterior tooth position, Fig. 6.8, 6.9; lateral tooth positions, Fig. 6.10–6.13). Purdy et al. (2001) noted that lower teeth of C. macloti do not bear lateral cusplets. Carcharhinus aff. C. macloti from the Chucunaque Formation range from C = 4.2–6.3mm and CW = 4.2–6.1mm.
Materials.—Ten isolated teeth; upper: UF 275061, UF 281166, UF 281185, and UF 281323–281325.
Remarks.—Carcharhinus macloti is extremely abundant from the Pungo River Formation. Purdy et al. (2001) referred to over 400 teeth in their description, with upper teeth ranging from CH = 5.0–7.3mm and CW = 5.0–9.1mm. Carcharhinus aff. C. macloti is relatively uncommon in the Chucunaque Forma- tion and has not been identified in the Gatun Formation, although this may be an artifact caused by a collection bias given the extremely small size of the teeth. According to Purdy et al. (2001), lower teeth are smaller than upper teeth, symme- trical, and lack the distinctive lateral cusplets. This description aligns well with that of Carcharhinus isodon, and may explain why C. isodon was not recognized from Lee Creek by Purdy et al. (2001) despite the fact that it is recognized as being present in Lee Creek (
www.elasmo.com). Carcharhinus macloti has been reported from the Miocene of Peru (Lambert et al., 2010) and, tentatively, from the middle Eocene of Georgia (Hulbert et al., 1998). Mondal et al. (2009) also reported C. macloti from the Miocene of India, however the specimen imaged in their publication does not seem definitive for C. macloti. Garrick (1985) reported that abundance of lateral cusplets in upper teeth of extant C. macloti vary, but could not ascertain if the variation was attributed to sexual dimorphism or geographic variation. There is little known about extant individuals beyond that they occur in the Indo-West Pacific and Arafura Sea in inshore and offshore waters of continental and insular shelves (Compagno, 1984). Carcharhinus macloti has a demersal habit and typically occurs at depths of 0–170m (Last and Stephens, 1994; Compagno et al., 2005).
Carcharhinus obscurus (Lesueur, 1818) Figure 6.14–6.20
Holotype.—Originally described as Squalus obscurus by Lesueur (1818, p. 223, pl. 9). There is no holotype; however, the type locality is North America (Compagno, 1984).
Occurrence.—STRI 290109, STRI 290113, STRI 290116, STRI 290125, STRI 290145, STRI 300029, STRI 300032, STRI 430011, and STRI 430012.
Description.—Upper teeth are broad and triangular. The mesial edge is apically convex and either straight or concave basally forming a weak notch. The distal edge is significantly notched and is nearly vertical apical of the notch. Serrations are coarser basally and finer apically on both edges, and there is a distal deflection at the crown apex. The root is thick with a transverse
groove and an obtusely angled basal margin. Lower teeth are narrow, have incomplete cutting edges with fine serrations that only comprise the upper third of the crown, a sigmoidal profile, and a distal deflection at the apex. Root is robust, thick, with a transverse groove and an obtusely angled basal margin. Upper teeth can be distinguished from other species of Carcharhinus by the apically convex mesial edge, the distal deflection of the apex, and the vertical distal cutting edge (Purdy et al., 2001). Carcharhinus obscurus from the Chucunaque Formation ranges from: upper CH = 4.7–13.4mm and CW = 8.3–18.0mm; lower CH = 5.6–10.8mm and CW = 6.9–15.2mm.
Materials.—One hundred eighty-four isolated teeth; upper: UF 275040, UF 275123, UF 275155, UF 281144–45, UF 281147; lower: UF 275039, UF 275072, UF 275087, UF 275090, UF 275094, UF 275121, UF 281147–52; inde- terminate position: UF 281146.
Remarks.—Lower teeth can be distinguished fromother species of Carcharhinus and the genus Negaprion by their wider apex with a distal deflection and incomplete cutting edges with fine serrations limited to the upper third of the crown. The description of lower teeth from Carcharhinus egertoni by Kent (1994) is analogous to the description of lower Carcharhinus obscurus teeth herein. Observation of modern C. obscurus dentitions indicates that the lower C. egertoni teeth describe by Kent (1994) are synonymous with lower teeth of C. obscurus (personal communication, G. Hubbell, 2015). Carcharhinus obscurus is the most abundant species identified from the Chucunaque Formation, but is relatively uncommon in the Gatun Formation (Pimiento et al., 2013a). In the middle Miocene Grand Bay Formation of Carriacou, C. obscurus outnumbers other species by more than three to one (Portell et al., 2008). Carrillo-Briceño et al. (2015a) observed C. obscurus as the second most abundant species in the neriticRio Indio facies and as a relatively uncommon species in the bathyal Piña Sandstone facies of the late Miocene Chagres Formation. Teeth from the Chucunaque Formation are larger than those from the Gatun Formation (CH = 7.7–10.1mm and CW = 11.2–16.28mm; Pimiento et al., 2013a), butmuch smaller than theC. obscurus teeth described from the Yorktown Formation (CH = 17.0–22.0mm and CW = 18.0–25.0mm; Purdy et al., 2001). Extant individuals with tooth sizes corresponding to those reported fromtheYorktown Formation are about 3m TL (Purdy et al., 2001), which suggests that C. obscurus from the younger Chucunaque Formation were smaller. Carcharhinus obscurus has a cosmopolitan distribution in themodern tropical and warm temperate seas, commonly occurring on continental and insular shelves, inshore and in oceanic waters (Compagno, 1984; Compagno et al., 2005).Adultsmost commonly occur at depths of 200–400m, while younger individuals can be found in shallower nursery areas (Compagno, 1984; Bass et al., 1986; Compagno et al., 2005).
Carcharhinus plumbeus (Nardo, 1827) Figure 6.21–6.24
Holotype.—Originally described as Squalus plumbeus by Nardo (1827, p. 477). There is no holotype; however, the type locality is the Adriatic Sea (Compagno, 1984).
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