520
Journal of Paleontology 91(3):512–547
Holotype.—Originally described as Oxyrhina desori by Agassiz (1843, pl. 37, figs. 8–10) from the Miocene of Switzerland. Purdy et al. (2001) recognized one tooth among the syntypes (ETHGI P145) described by Agassiz (1843) as the second upper anterior of Isurus, and named it the lectotype of Isurus oxyrinchus.
Occurrence.—STRI 290145, STRI 300029, STRI 300032, and STRI 430011.
Description.—Moderately large, triangular teeth lacking serrations; with a convex lingual face and flattened labial face. The crown apex is reflexed toward the labial face, and has a sigmoidal or straight profile. The root is robust, lacks a nutrient groove, and has an angled or U-shaped basal margin with pointed or rounded root lobes. Anterolaterally, the crown becomes shorter, increasingly asymmetric, and less noticeably recurved labially; and the root lobes become shorter and more compressed (Kent, 1994; Purdy et al., 2001). Upper teeth differ from lower teeth in having a broader basal root angle and a much weaker sigmoidal profile (Kent, 1994). Isurus oxyrinchus from the Chucunaque Formation ranges from CH = 8.6–15.0mm and CW = 13.3–14.1mm.
Materials.—Seven isolated teeth; upper laterals: UF 281169, UF 281173, and UF 281181; lower laterals: UF 275068, UF 275102, UF 275124, and UF 281172.
Remarks.—Labial recurvature of the apex is considered to be a diagnostic feature (Purdy et al., 2001; Reis, 2005); however, Purdy et al. (2001) noted that this feature is most apparent in upper anterior teeth and may not be present in lateral teeth. Portell et al. (2008) identified six I. oxyrinchus teeth from the Miocene of Carriacou, Grenada, with the largest tooth being a lateral tooth with CH = 13.5mm and CW = 6.6mm. Teeth from the Chucunaque Formation are slightly larger than those from Carriacou. Anterior teeth from the Pungo River Formation range from CH = 27.0–50.0mm and CW = 17.0–29.0mm, whereas anterior teeth from the Yorktown Formation range from CH = 28.0–58.0mm and CW = 11.0–32.0mm (Purdy et al., 2001). Measurements from Purdy et al. (2001) are not directly comparable to those in this study or that of Portell et al. (2008) because they were taken from anterior teeth. Even so, the teeth described by Purdy et al. (2001) represent much larger sharks that those observed in the Chucunaque Formation. Isurus oxyrinchus has also been observed from the Miocene of Brazil (Reis, 2005) and the Pliocene of Angola (Antunes, 1978). Isurus oxyrinchus is not recorded from the Gatun Formation of Panama (Pimiento et al., 2013a). Extant individuals are coastal and oceanic with a cosmopolitan distribution in temperate and tropical seas (Compagno et al., 2005), occurring most frequently from the Caribbean to Argentina (Compagno, 1984). Isurus oxyrinchus is predominantly epipelagic, but has been reported close inshore (Last and Stephens, 1994; Yamada et al., 1995; Mundy, 2005). Direct telemetry data in the North Pacific (Holts and Bedford, 1993), as well as temperature and occurrence data inferred from longline records in the Atlantic (Hoey, 1983), suggest that Isurus oxyrinchus has a preferred temperature range of 14–22°C (Heist et al., 1996). This temperature range
corresponds with the common depth range of 100–150m observed by Bianchi et al. (1999), however Compagno et al. (2005) reported a depth range of 0–500 m.
Family Alopiidae Bonaparte, 1838 Genus Alopias Rafinesque, 1810
Type.—Alopias macrourus Rafinesque, 1810 (Cappetta, 2012).
Alopias superciliosus (Lowe, 1841) Figure 4.17–4.20
Holotype.—Originally described as Alopecias superciliosus by Lowe (1841, p. 39) based on a single young specimen with no mention of its provenance. According to Eschmeyer (1998), the holotype is unknown; however, the type locality is Madeira, eastern Atlantic (Compagno, 2001, p. 83).
Occurrence.—STRI 300032 and STRI 430011.
Description.—Small to moderate-sized, triangular crown that is broad, erect, and lacks serrations. The mesial edge is straight to slightly convex,while the distal edge is straight to slightly concave. The lingual face is convex and the labial face is flat with enameloid extending well onto the root. Flattened root with rounded root lobes, distinct nutrient groove, and obtusely angled basal margin. The moderately broad crown and distally oriented asymmetry indicate a lateral position (Kent, 1994; Purdy et al., 2001). Alopias superciliosus from the Chucunaque Formation has a CH = 4.2–10.3mm and a CW = 6.3–15.4mm.
Materials.—Three isolated teeth; lower lateral: UF 275057, UF 281318, and UF 281319.
Remarks.—Alopias differs from Isurus in having a shorter, broader crown with a concave basal root margin. Alopias superciliosus differs from Alopias cf. A. vulpinus in having a more slender crown, a distinct nutrient groove, and less robust root lobes (Kent, 1994). Alopias superciliosus is an uncommon species, with only three teeth identified from the Chucunaque Formation. Purdy et al. (2001) only described a single anterior tooth from the Pungo River Formation, and Kent (1994) stated that A. superciliosus is uncommonly found in the Calvert Formation of the Chesapeake Bay region. The anterior tooth of Alopias cf. A. superciliosus reported by Purdy et al. (2001) has a height of 13mm and a width of 9mm. Extant individuals in the genus Alopias reach a maximum TL = 6m (Springer and Gold, 1989), although half of the body length is represented by its elongated caudal fin (Kent, 1994). Alopias superciliosus has been reported from the lower Miocene of North Carolina (Case, 1980); the middle Miocene of Parma, Italy (Cigala- Fulgosi, 1983) and Lisbon, Portugal (Antunes, 1970); the late Miocene of Panama (Carrillo-Briceño et al., 2015a); and the Pliocene of Tuscany, Italy (Cigala-Fulgosi, 1988). The extant species has a circumglobal distribution in tropical and temperate seas; occurring in coastal waters over continental shelves, sometimes close inshore in shallow waters, and far from land in open ocean (Compagno, 1984). Alopias superciliosus is a highly migratory species found in oceanic, pelagic, and near
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